Investigation: Modeling Enzyme Activity with Toothpickase - Biology

Investigation:  Modeling Enzyme Activity with Toothpickase - Biology

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In this activity, you will model the action of enzymes breaking down a substrate. Without looking, you will use one hand to break a toothpick in half.

Materials: Toothpicks (50 per team), Colored Toothpicks (25 per team), masking tape, stopwatch (clock)


  • You must break each toothpick one at a time.

  • You may only use one hand.

  • The toothpick must be broken completely in half.

  • Keep your eyes closed so each toothpick is chosen at random.

  • Toothpicks can only be broken once.

1. Spread 50 toothpicks out on the table in a random pile.

2. One person plays the role of the enzyme, while the other keeps time.

3. Break toothpicks for 10 seconds. Stop and record the TOTAL number of toothpicks broken. (Broken toothpicks remain in the pile.)

4. Start timer again, break toothpicks for 20 more seconds (total of 30 seconds). Record.

5. Repeat until you have recorded the total number broken at 60 seconds and 120 seconds.

Part 1: How Fast Does an Enzyme Work Under Normal Conditions?


Total number of broken toothpicks (products)

Amount of substrate remaining (reactants)

Reaction Rate

change in amount of substrate /change in time








Part 2: Competitive Inhibition

Discard any broken toothpicks and add enough new toothpicks to start with 50.

Add 25 colored toothpicks to the pile (total of 75). The colored toothpicks represent substances the enzyme (your fingers) can interact with that are not the substrate. The colored toothpicks will not be counted.


Total number of broken toothpicks (products)

Amount of substrate remaining (reactants)

Reaction Rate

change in amount of substrate /change in time








Part 3: Enzyme Denaturation

Remove any competitive inhibitors (colored toothpicks) and replace substrates for a total of 50 toothpicks.

Enzymes exposed to heat or acidic conditions can become denatured. Their shape changes in a way that interferes with their activity. To model this process, wrap masking tape around your thumb and forefinger and repeat the experiment.


Total number of broken toothpicks (products)

Amount of substrate remaining (reactants)

Reaction Rate

change in amount of substrate /change in time








Data Analysis and Conclusions

  1. Graph the data for parts 1 and 2 on the grid below. Time should be on the X axis and the products on the Y axis. Be sure to label your two lines.
  2. What is the enzyme in this model? What is the substrate?
  3. What happens to the number of products over time (see graph or chart)? What happens to the reactants?
  4. The rate of reaction is determined by dividing the change in amount by the change in time.
    Was the rate of reaction the same across all the time periods? Explain any differences observed.
  5. Predict what would happen if you double the number of toothpicks (substrate).
  6. Predict what would happen if you doubled the amount of enzymes (two people breaking toothpicks).
  7. Predict what would happen if you increased the number of competitive inhibitors in the system.
  8. Enzyme activity can also be altered by noncompetitive inhibition. In this case, a molecule binds to an area that is not the active site, but does change the shape of the active site. Describe how you could model this using the toothpick activity. Use your imagination here!

Investigating Enzyme Structure and Function Through Model-Building and Peer Teaching in an Introductory Biology Course

A foundational knowledge of the relationship between structure and function is critical to understanding how enzymes work. The seemingly invisible nature of these molecular interactions makes it challenging for undergraduate students to conceptualize the dynamic changes that occur during a catalytic cycle. In this Lesson, we describe an interactive, collaborative modeling activity that we use in introductory biology courses to teach students how enzymes catalyze chemical reactions. First, the students imagine a fictitious enzyme and its associated reaction, and use modeling compound to demonstrate the progression of the reaction while focusing on the three-dimensional shape of active site and substrate in facilitating this catalysis. Second, they then select one of four types of enzymatic regulation (competitive inhibition, allosteric inhibition, allosteric activation, or feedback inhibitions) to incorporate into their model. They then demonstrate these reactions to groups of peers. This student-centered approach uses active learning and peer instruction to provide students with prompt feedback to strengthen their understanding of the inter-relatedness of structure and function. This modeling activity concludes with student reflection and discussion, and student learning is assessed with exam questions.

Directions: Break as many toothpicks as you can in 60 seconds. Your partner will act as anon-competitive inhibitor by making the enzyme change its shape without interacting with the active site. Have your partner record how many toothpicks are broken in 10 second intervals up to 60 seconds in Table 3. When done, switch roles.

13. How does non-competitive inhibitor affect how many toothpicks are broken by toothpick-ase?

14. What represents the non-competitive inhibitors? Why are these called non-competitive?

Graph your data from Part 1-3 and connect the dots to make lines. Do this on a computer and make each trial a different color. Finally, answer the questions that correlate to each part of the lab and include these answers with the graphs.

Investigation: Modeling Enzyme Activity with Toothpickase - Biology

The following websites will be extremely valuable to you throughout the duration of this class.

  • All podcasts can by found at the this website:
  • Click on the title of the podcast that matches the title on the review worksheet
  • Plant Taxonomy
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                                      • Calvin Cycle Notes:
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                                      • Enzyme Activity (Toothpickase) Lab
                                      • Enzyme Notes:
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                                      • Finish Enzyme Notes
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                                                                      Experiments on Enzyme Activity | Biochemistry

                                                                      Benzidine solution, razor, thin sections of actively growing root (or germinating seeds or germinating pollen grains), phosphate buffer, hydrogen peroxide (1%), ammonium chloride (5%), starch paste.

                                                                      Method, observations and results:

                                                                      1. Cut thin sections of fast-growing roots or germinating seeds or take some pollen grains and put the material in phosphate buffer at pH 7.0. Now transfer the material in the incubation mixture [made of 5% benzidine saturated solution + 5 ml hydrogen peroxide (1%) and 1 ml ammonium chloride (5%)]. Incubate the entire mixture at room temperature for 5 minutes and observe. Dark-blue colour appears. This is due to the presence of the enzyme peroxidase.

                                                                      2. Make a paste of starch, immerse in it the provided material like actively growing roots or germinating pollen grains and test for sugar. Positive test of sugar indicates that starch has transformed into sugars, and this further confirms the presence of enzyme amylase in the studied plant material.

                                                                      2. Experiment to demonstrate that heat destroys activity of enzyme but not that of a catalyst:

                                                                      Four test tubes, manganese dioxide (MnO2), water, beaker, spirit lamp, piece of fresh liver or potato, hydrogen peroxide, boiled and cooled piece of liver or potato, boiled and cooled manganese dioxide solution.

                                                                      Pour 2 ml of H2O2 solution is each of the four test tubes. Add a pinch of manga­nesedioxde in the first test tube, pre-boiled and cooled 1 ml of manganese dioxide solution in the second, small piece of fresh liver or potato in third and pre-boiled and cooled piece of liver or potato in the fourth.

                                                                      All the test tubes are kept at room temperature if it is summer and warm water (kept at about 38°C) if it is winter. Oxygen bubbles are found to come out of solution in the first three test tubes but not in the fourth one.

                                                                      Manganese dioxide is a catalyst that helps to break hydrogen peroxide into water and oxygen. The catalyst is not affected by heat as it is clear from evolution of oxygen in the second test tube.

                                                                      Fresh liver or potato contains enzymes peroxidase and catalase that help in evolving oxygen from hydrogen peroxide. The enzymes are functional at room temperature (test tube three) but heating destroys their activity (test tube four). Therefore, heat kills enzyme activity but has little effect on the activity of a catalyst.

                                                                      (i) Test tubes must be thoroughly washed with water before use.

                                                                      (ii) Do not perform the experiment without warm water if it is cold outside,

                                                                      (iii) Keep the temperature of warm water to about 38″C. Do not allow it to go beyond 50°C.

                                                                      (iv) Use fresh potato slice or liver piece.

                                                                      3. Experiment to prove that enzymes are specific in their activity:


                                                                      Four test tubes, one percent starch solution, one percent sucrose solution, saliva, Bennedict’s or Fehling’s solution, spirit lamp.

                                                                      Take four test tubes. Pour 1 ml of 1% starch solution in the first, 1 ml of 1% sucrose solution in the second, 1 ml each of 1% starch solution and saliva in the third, and 1 ml each of 1% sucrose solution and saliva in the fourth. Keep all the test tubes undisturbed for one hour at room temperature if it is summer and in warm water (about 38°C) if winter.

                                                                      Afterwards pour 3 ml of Bennedict’s or Fehling’s solution (having cupric ions) in each of the test tube. Heat the test tube to boiling for about 2 minutes and observe. There is no change of colour in first and second test tubes. The fourth test tube also does not show any change in colour. However, in the third test tube, the blue colour of Bennedict’s or Fehling’s solution gets changed to yellowish or reddish precipitate.

                                                                      The change of colour from blue to yellowish or reddish precipitate is caused by conversion of cupric ions of Bennedict’s or Fehling’s solution into cuprous oxide.

                                                                      This occurs in the presence of reducing sugars. Both sucrose and starch are non-reducing in nature as is found by the absence of colour change in test tube one and two. In test tube four having sucrose and saliva there is no enzyme activity since colour change is absent.

                                                                      However, test tube three having starch and saliva (containing enzyme salivary amylase) reducing sugars are produced as is clear from change of colour. Therefore, the enzyme, salivary amylase, present in saliva catalyses hydrolysis of starch but not sucrose which is a common disaccha­ride.

                                                                      (i) Test tubes must be thoroughly washed and dried

                                                                      (ii) The water in which the solutions are to be kept must not be very hot.

                                                                      (iii) In winter warm water must be taken,

                                                                      (iv) Before the collection of saliva, mouth must be washed thoroughly with distilled water,

                                                                      (v) Swill the rinsed mouth with 7-10 cc of distilled water for 1 minute and then collect the same, as water containing saliva,

                                                                      (vi) While heating the solution should not be allowed to bump violently.

                                                                      4. Experiment to demonstrate the activity of the enzyme amylase extracted from the germinating barley or pea seeds:

                                                                      Starch powder, iodine solution, germinating barley or pea seeds, distilled water, test tubes, mortar, pestle, filter paper, and funnel.

                                                                      1. Take a little amount of ordinary starch and make a thin paste of it in about 50 ml boiling water. Allow it to cool down.

                                                                      2. Take about 5 gm. of germinating seeds of barely or pea. In case of pea seedlings, remove their cotyledons. Ground the cotyledons along with distilled water in the mortar, and filter the contents through a funnel.

                                                                      3. Pour the starch solution in two test tubes and mark them as ‘A’ and ‘B’.

                                                                      4. Add a few drops of iodine solution in tube ‘A’ and observe the colour change.

                                                                      5. Add the filterate of the crushed cotyledons or endosperm of barely in tube ‘B’.

                                                                      6. Keep both the tubes at a warm place (about 35°- 40°C) for about 30 minutes.

                                                                      In test tube ‘A’, the contents turn blue in colour. In test tube ‘B’, the contents show reddish- brown colour. After about 15 minutes, if iodine solution is added, it shows no positive test for starch in tube ‘B’. However, if a few drops of Fehling’s solution are added in tube ‘B’, a brick-red precipitate appears.

                                                                      Formation of blue colour in tube ‘A’ confirms the test of starch. In tube ‘B’, formation of reddish-brown colour is due to the fact that addition of seed extract supplied the enzyme amylase which partially hydrolysed the starch into maltose (a 12-carbon sugar). After about 30 minutes, the entire starch in tube ‘B’ gets completely hydrolysed into hexose sugar.

                                                                      Due to this the iodine solution gives negative test for starch. Formation of reddish-brown colour after the addition of Fehling’s solution confirms the presence of hexose sugar. It is a reducing sugar, and a product of hydrolysis of starch made of amylase and amylopectin.

                                                                      The enzyme amylase is present in the germinating barley or pea seeds. It is released during the crushing process. Amylase is actually an enzyme which catalyzes the breakdown of starch into monosaccharide units.

                                                                      5. Experiment to study the enzyme activity of diastase in germinating seeds of barley and to study the influence of pH and temperature:

                                                                      The enzyme diastase acts on starch and converts it to hexose sugar.

                                                                      Germinating barley seeds, mortar, water, muslin cloth, centrifuge, measuring flask, iodine solution prepared in potassium iodide), starch solution, test tubes, beaker, enzyme extract, pipette, Benedict’s solution, buffer solutions of known pH, diastase solution, water baths (7), stop watch.

                                                                      Preparation of Required Solutions:

                                                                      It is prepared by adding 2 gm. of soluble starch in 50 ml of boiling water.

                                                                      Add 6.95 gm. of monobasic sodium phosphate (0.2 M) in 250 ml of distilled water and use it as buffer solution A.

                                                                      (c) Buffer solution B:

                                                                      Dissolve 17.92 mg of dibasic sodium phosphate (Na2HPO4.12H2O) in 250 ml of water to get 0.2 M buffer solution B.

                                                                      (d) Iodine solution (1 %):

                                                                      Mix 1 gm. iodine and 2 gm. KI in 300 ml water and use it as iodine solution.

                                                                      Method and observations:

                                                                      1. Take 10 gm. of germinating barley seeds and 20 ml of water and grind them in mortar.

                                                                      2. Filter the above mixture through muslin cloth, centrifuge the filtrate at low speed, take the supernatant liquid in a measuring flask and make up the volume of the enzyme extract upto 100 ml.

                                                                      3. Take six test tubes and put 1 ml iodine solution (1 %) in each of them. Also add 20 ml water in each of them.

                                                                      4. In a separate test tube take 1 ml of 1% iodine solution and 20 ml water and add 1 ml starch solution. This will work as a control.

                                                                      5. Take 10 ml of starch solution in a beaker, add 1ml enzyme extract and shake it well.

                                                                      6. This starch diastase mixture is now called digestion mixture. Pipette out 1ml of this digestion mixture and add it in each of the six test tubes containing iodine solution and observe. Colour starts disappearing. Note the time of disappearance of colour.

                                                                      7. After about 10 minutes of digestion, take out 1ml of digestion mixture into a test tube, and now test for sugar by Benedict’s reagent. Sugar test is positive.

                                                                      This shows that activity of the enzyme diastase has transformed the starch into sugar. This further confirms the enzyme activity of diastase in germinating seeds of barley.

                                                                      Take 9 test tubes and in each of them take 5ml of buffer solution of known pH like 5.0,5.5, 6.0,6.5,7.0,7.5,8.0,8.5,9.0. In each test tube, add 5 ml of starch solution (1%). Now add 1 ml of diastase solution in each of the test tubes and note the time of addition. Shake the contents thoroughly and mix them well.

                                                                      Now pipette 1 ml of the reaction mixture every 5 minutes into separate test tubes containing 1ml of iodine solution and 20 ml of water. Take a graph paper and plot the time taken in minutes for complete hydrolysis (as shown by complete disappearance of colour of iodine) against the pH. Time of disappearance of colour is different in different pH, and this shows the influence of pH on enzyme activity.

                                                                      Effect of temperature:

                                                                      Take seven water baths and maintain them at seven different temperatures like 100°C, 80°C, 60°C, 40°C, 20°C, 10°C and 0°C. Take seven test tubes and in each of them add 5 ml of soluble starch (1 %) maintained at pH7 and put them in seven different water baths maintained at different temperatures.

                                                                      Note the time when contents in different test tubes attain the temperature of their respective water baths and now add 1 ml of diastase solution in each test tube. Shake the test tubes well, wait for 5 minutes and add in each test tube 1 ml mixture of 1 ml iodine solution and 20 ml water. Wait for some time, note the time taken for disappearance of iodine colour against each temperature and plot the time on graph paper.

                                                                      6. Experiment to demonstrate the activity of peroxidase in plant material:

                                                                      Potato tuber, test tube, muslin cloth, hydrogen peroxide (3%), pyrogallol solution (1%).

                                                                      1. Macerate 5 gm. of potato tuber, squeeze it through a muslin cloth, and take 3 ml of the potato extract in a test tube.

                                                                      2. Put 1% solution of pyrogallol (a phenolic compound) in the test tube containing potato extracts and add 3 drops of hydrogen peroxide (3%) and observe.

                                                                      Change in colour takes place.

                                                                      This change in colour shows the presence of peroxidase activity in the extract of potato tuber.

                                                                      7. Experiment to demonstrate the pH change inhibits in enzyme activity:

                                                                      Two test tubes. 1% starch solution, saliva, dilute HCI, beaker, water, spirit lamp, iodine solution (I + KI).

                                                                      Pour 2 ml of starch solution in each of the two test tubes. Add 1 ml of fresh saliva in each. A few drops of dilute hydrochloric acid are added to one of the test tubes to make its solution acidic. Both the test tubes are kept for one hour at room temperature if it is summer or in warm water (about 38°C) if it is winter.

                                                                      After one hour both the test tubes are tested for starch by pouring 1 to 2 drops of iodine solution. Test tube one shows negative starch test while test tube two (acidified) develops blue colour showing the presence of starch.

                                                                      In test tube one, pH is nearly that of saliva. The salivary amylase contained in saliva is functional and causes hydrolysis of starch because starch test is negative.

                                                                      In test tube two appearance of blue colour indicates that the starch has not been hydrolysed by enzyme present in saliva. The only difference in two test tubes is that the solution of the second test tube has been acidified. Therefore, change in pH inhibits enzyme activity.

                                                                      (i) Test tubes must be thoroughly washed and dried,

                                                                      (ii) Before the collection of saliva mouth must be washed and any acidic or alkaline food must not be taken,

                                                                      (iii) Warm water must be used in winter,

                                                                      (iv) Care must be taken that there is no contamination of first test tube by the HCI which is being used for second test tube.

                                                                      2018 (B12)

                                                                      – Final Project – (make sure the video will play on the school computer! – bring on USB or email)
                                                                      – Final Project due: June 17th!

                                                                      Tuesday, June 11th

                                                                      – Final Project – (see rubric)
                                                                      – Final Project due: June 13th/17th?

                                                                      Friday, June 7th

                                                                      – Final Project – start VIDEO! (see rubric)
                                                                      – Final Project due: June 13th/17th?

                                                                      Wednesday, June 5th

                                                                      – Final Project research (see rubric)
                                                                      – Final Project due: June 13th/17th?

                                                                      Monday, June 3rd

                                                                      – Final Project research (see rubric)
                                                                      – Final Project due: June 13th/17th?

                                                                      Thursday, May 30th

                                                                      – Wellness Week: 5 minutes of mindful breathing!
                                                                      – Reproductive Structures Competition
                                                                      – Final Project topic selection
                                                                      Sample Video:

                                                                      – Final Project due: June 13th/17th?

                                                                      Tuesday, May 28th

                                                                      Quiz: Respiratory System
                                                                      – Practice mindful breathing!

                                                                      Friday, May 24th

                                                                      Urinary System
                                                                      Lab: Kidney Dissection
                                                                      Review: Respiratory System
                                                                      – Respiration Quiz next class!

                                                                      Wednesday, May 22nd

                                                                      Review: Kahoot

                                                                      – Urinary System intro worksheet
                                                                      – Read pg. 304-307
                                                                      – Respiration Quiz next Tuesday, May 28th

                                                                      Thursday, May 16th

                                                                      – Demo: Measuring Vital Capacity with a homemade Spirometer
                                                                      – Notes: Internal & External Respiration (Gas Exchange) in detail
                                                                      – Read p. 292-293
                                                                      – Make a comic or flow chart showing the process of gas exhange

                                                                      Tuesday, May 14th

                                                                      – Lab: Breathing Rate
                                                                      – Read p. 288-291
                                                                      – Do p. 300 “Studying the Concepts” #2,3,4

                                                                      Friday, May 10th

                                                                      – Capillary-Tissue Fluid Exchange
                                                                      – Gas Exchange
                                                                      – Respiratory System: Structure vs. Function
                                                                      – complete handout if not done
                                                                      – Read p. 255, p. 284 – 287

                                                                      Wednesday, May 8th

                                                                      Quiz: Cardiovascular System

                                                                      Monday, May 6th

                                                                      Group Presentations: Cardiovascular System Disorders
                                                                      Article: Colours of Blood & Hemoglobin
                                                                      Review WS (key posted)
                                                                      – go through Learning Goals checklist to study
                                                                      – Read Chapter 13
                                                                      – Quiz: Wednesday, May 8th

                                                                      Thursday, May 2nd

                                                                      Activity: Blood Typing Game

                                                                      – go through Learning Goals checklist to study
                                                                      – Read Chapter 13
                                                                      – Quiz: Wednesday, May 8th

                                                                      Tuesday, Apr. 30th

                                                                      – Recap: Heart Dissection
                                                                      – Types of Vessels (see online Class Notebook, Worksheet, & Textbook)
                                                                      – Systemic vs. Pulmonary Circuits
                                                                      – Blood Pressure & Blood Velocity vs. Cross-sectional Area
                                                                      – WS: Components of Blood
                                                                      – Read Chapter 13
                                                                      – Quiz: Wednesday, May 8th

                                                                      Thursday, Apr. 25th

                                                                      – Lab: Sheep Heart Dissection (hand in completed lab q’s)

                                                                      – WS: Blood Vessels / Heart Review
                                                                      – Read pg. 240-241, 248 in textbook (13.1 & 13.3)

                                                                      Tuesday, Apr. 23rd

                                                                      – Parts of the Heart (see online Class Notebook for notes & q’s)
                                                                      – Video: Blood Flow through the Heart
                                                                      – Heartbeat & the Cardiac Cycle (see online Class Notebook)

                                                                      – Activity: Heart Rate & Blood Pressure
                                                                      – WS: Heart Rate, Cardiac Cycle & Blood Pressure
                                                                      – Read pg. 242-245 in textbook (13.2)

                                                                      Wednesday, Apr. 17th

                                                                      – Quiz: Digestion
                                                                      – WS: Heart Colouring & labelling
                                                                      – Read pg. 242-243 in textbook

                                                                      Monday, Apr. 15th

                                                                      – Sort: Mechanical vs. Chemical Digestion
                                                                      – Team Task: Digestion Application Q’s
                                                                      – Review: Practice Test
                                                                      Animation: Digestion Overview

                                                                      – ANSWER KEYS POSTED!
                                                                      – Digestion Quiz next class! (includes Homeostasis/Regulating Blood Sugar)

                                                                      Thursday, Apr. 11th

                                                                      – Review: Digestion Vocab Picture Clues
                                                                      – Notes: Digestion (part 2)
                                                                      – Activity: draw & label parts of digestive system OR
                                                                      – complete Notes page using Enzyme table on p. 225
                                                                      – worksheet (optional chart & labeling)
                                                                      – Digestion Quiz next Wed! (includes Homeostasis)

                                                                      Tuesday, Apr. 9th

                                                                      – Review: Types of tissues
                                                                      – Notes: Digestion (part 1)
                                                                      – Activity: Saliva & Crackers
                                                                      – worksheet (chart & labeling)
                                                                      – Digestion Quiz next Wed! (includes Homeostasis)

                                                                      Friday, Apr. 5th

                                                                      – Review: Homeostasis worksheet
                                                                      – Quiz returned (Enzymes & Metabolism)
                                                                      – Self-Notes: Human Organization package (p.194-211)
                                                                      – finish Human Org. Notes
                                                                      – read and go over Digestion colouring handout

                                                                      Wednesday, Apr. 3rd

                                                                      – Positive Feedback (amplifies) vs. Negative Feedback (inhibits)
                                                                      – Homeostasis Temperature Lab
                                                                      – Homeostasis worksheet (try both sides)

                                                                      Monday, Apr. 1st

                                                                      – Read 11.5 Homeostasis (p.208-209)
                                                                      – Complete the 4 Learning Goals on Homeostasis
                                                                      – Copy Figure 11.12 from the textbook & the 2 additional graphs in online notebook, read Regulation of Body Temperature (pg. 205)

                                                                      Thursday, Mar. 14th

                                                                      Animation: Activation Energy & Enzymes
                                                                      – Quick Review
                                                                      – Quiz: Metabolism & Enzymes

                                                                      Tuesday, Mar. 12th

                                                                      – Pre-Lab Check
                                                                      – Lab: Enzyme Activity (Catalase & Hydrogen Peroxide)
                                                                      – complete Conclusion for Lab (criteria in Class Notebook)
                                                                      – Review handout
                                                                      – Enzymes Quiz next day (can use class notes package, review handout from today, and one page of OWN notes) – you will get 30-40mins to review at the beginning of class

                                                                      Friday, Mar. 8th

                                                                      – Activity Recap: “Toothpickase” KEY posted
                                                                      – Notes: Metabolism & Enzymes (part 2)
                                                                      – Worksheet: Enzyme Reaction Rates (KEY POSTED)
                                                                      – Pre-Lab: MUST BE COMPLETED FOR NEXT DAY!!
                                                                      – Quiz: open notebook next Thursday (Read 6.2 + 6.3 to prepare)

                                                                      Wednesday, Mar. 6th

                                                                      – Notes: Metabolism & Enzymes (part 1)
                                                                      – Activity: “Toothpickase” (modelling enzyme activity)
                                                                      – complete questions from “Toothpickase” activity
                                                                      – complete Enzymes handout from last class if not done (KEY posted)
                                                                      – Open-notebook Quiz next Thursday! (last day before break)

                                                                      Monday, Mar. 4th

                                                                      – COMPASS survey
                                                                      – Inquiry Sharing
                                                                      – Enzymes handout (KEY POSTED)

                                                                      Thursday, Feb. 28th

                                                                      – DNA/Mutations/Biotech Mini Inquiry (remember to record sources!)
                                                                      – Inquiry project due Monday! (be ready to share your project in small groups)

                                                                      Tuesday, Feb. 26th

                                                                      – DNA/Mutations/Biotech Mini Inquiry (remember to record sources!)
                                                                      – Inquiry project due next Monday!

                                                                      Thursday, Feb. 21st

                                                                      – Quiz: Protein Synthesis & Mutations
                                                                      – begin researching for inquiry project (due Mon, Mar. 4th)

                                                                      Tuesday, Feb. 19th

                                                                      – Powerpoint: Simple vs. Complex Questions
                                                                      – Sample Article & Question Development (Microplastics in Human Feces)
                                                                      – Group Activity: developing complex questions using Bloom’s Taxonomy
                                                                      – Protein Synthesis & Mutations Quiz NEXT CLASS!
                                                                      – Review worksheet (KEY posted)
                                                                      – Develop a refined complex Q for inquiry project (in pairs ok)
                                                                      – Mini-Inquiry due: Monday, March 4th

                                                                      Thursday, Feb. 14th

                                                                      – Hand in Mutations assignment

                                                                      – DNA Mini-Inquiry: Part 1 (Research background Info & Brainstorm Q’s)
                                                                      – complete “Brainstorm” handout (make sure you have some questions!)
                                                                      – Protein Synthesis & Mutations Quizzie next Thursday!

                                                                      Friday, Feb. 8th

                                                                      – Notes: Genetic Mutations
                                                                      – complete “Investigation” assignment (the one with the cow) – in pairs ok

                                                                      Wednesday, Feb. 6th

                                                                      – finish BOTH protein synthesis worksheets (#1 & #2) – KEYS POSTED

                                                                      Monday, Feb. 4th

                                                                      – HW Check
                                                                      – Notes: Protein Synthesis
                                                                      – Group Activity: Foosbah (from genes to proteins & traits)
                                                                      Drag & Drop Protein Synthesis
                                                                      Transcribe & Translate a Gene
                                                                      Protein Synthesis
                                                                      – Read p.510-516 and complete the rest of the definitions from last day’s handout

                                                                      Thursday, Jan. 31st

                                                                      – Review: Proteins Vocab
                                                                      – Notes: Proteins Review & worksheet
                                                                      – Notes: RNA
                                                                      – Worksheet: Introduction to Protein Synthesis
                                                                      – Read p.510-516 and complete at least half of the definitions

                                                                      Tuesday, Jan. 29th

                                                                      – DNA Replication Project Share?

                                                                      – DNA Replication Quiz
                                                                      – preview next section 25.2: Gene Expression (Protein Synthesis) p.510-516

                                                                      Thursday, Jan. 24th

                                                                      – Telomeres article:
                                                                      Are Telomeres the Key to Aging and Cancer?
                                                                      – complete Telomeres worksheet
                                                                      – DNA Replication Quiz next class (refer to Learning Goals/Review worksheet)

                                                                      Tuesday, Jan. 22nd

                                                                      – Discovery of DNA Double Helix
                                                                      – Project: DNA Replication Model & Animation
                                                                      – DNA Replication Animation due Thursday, Jan. 24th
                                                                      – Quiz Tuesday, Jan. 29th

                                                                      Friday, Jan. 18th

                                                                      – Project: DNA Replication Model & Animation (videotaping should be done today! Make sure to include required vocabulary!)
                                                                      – DNA Replication Animation due Thursday, Jan. 24th

                                                                      Wednesday, Jan. 16th

                                                                      – Project: DNA Replication Model & Animation (practice manipulating your model to show the steps of replication)

                                                                      Monday, Jan. 14th

                                                                      – Notes: DNA Review + Replication
                                                                      – Project: DNA Replication Model & Animation (cut and paste together 40 nucleotides)

                                                                      Thursday, Jan. 10th

                                                                      – DNA Review (read pg. 40-41, 506-508 and complete handout)
                                                                      – DNA Replication Flowchart (read pg. 509 and complete handout)
                                                                      – complete Biology Careers Exploration if not yet done
                                                                      – handouts from today if not done

                                                                      Tuesday, Jan. 8th

                                                                      – Biology Careers Exploration (on Office 365) due Friday, Jan. 11th

                                                                      Friday, Dec. 21st

                                                                      – Fad Diet Presentations
                                                                      – hand in audience participation handout
                                                                      *HAVE A FANTASTIC WINTER HOLIDAY!*

                                                                      Wednesday, Dec. 19th

                                                                      – Fad Diet Presentations + Audience Participation handout

                                                                      Monday, Dec. 17th

                                                                      – Fad Diet Project
                                                                      – Fad Diet presentations: Wed, Dec. 19th

                                                                      Thursday, Dec. 13th

                                                                      – Ch.2 Organic Molecules Test
                                                                      – Fad Diet Project
                                                                      – Fad Diet presentations: Wed, Dec. 19th

                                                                      Tuesday, Dec. 11th

                                                                      – Hydrogenated Fats (Cis vs. Trans)
                                                                      – Learning Goals + Review handout for Organic Molecules
                                                                      – Fad Diet Research project
                                                                      – Biomolecules Test: Thursday, Dec. 13th
                                                                      – Fad Diet presentations: Wed, Dec. 19th

                                                                      Friday, Dec. 7th

                                                                      Wednesday, Dec. 5th

                                                                      – hand in Proteins & Lipids lab data (table + conclusion)
                                                                      – complete Intro to Organic Molecules worksheet “AFTER” section (handout from before we started the unit)
                                                                      – Review Q’s: Lipids & Nucleic Acids
                                                                      – Biological Molecules Test: Thursday, Dec. 13th

                                                                      Monday, Dec. 3rd

                                                                      – Writing a good conclusion (sample conclusion & peer edit)
                                                                      – Notes: Nucleic Acids
                                                                      – Results Data Table & Conclusion for Proteins/Lipids Test (due next class)
                                                                      – Complete the questions following Nucleic Acids notes

                                                                      Thursday, Nov. 29th

                                                                      – Lab: Testing for Proteins & Lipids
                                                                      – write a Conclusion for the lab
                                                                      – Read Section 2.8 on Nucleic Acids (p.40-41)

                                                                      Tuesday, Nov. 27th

                                                                      – Hand in Protein Profile assignment
                                                                      – Notes: Lipids

                                                                      – WS: Lipids Q’s & Identification
                                                                      – complete Lipids questions (KEY POSTED)
                                                                      – complete Carbs/Proteins Review (KEY POSTED)

                                                                      Thursday, Nov. 22nd

                                                                      – Video: Protein Structure & Folding

                                                                      – Activity: Pipecleaner Proteins continued (answer key posted)
                                                                      – Assignment: Protein Profile (choose a SPECIFIC protein)
                                                                      – Review: Carb’s & Proteins Q’s
                                                                      – Protein Profile due next class
                                                                      – keep working on review WS (answers posted soon)

                                                                      Tuesday, Nov. 20th

                                                                      – Hand in: Carbohydrates Lab
                                                                      – Review: Carbohydrates Q’s
                                                                      – Debrief: last day’s List-Group-Label Activity (Cheesy Science)
                                                                      – Notes: Proteins
                                                                      – Activity: Pipecleaner Proteins (continue next class)
                                                                      – Read Proteins handout & Text section 2.7

                                                                      Friday, November 16th

                                                                      – Quiz: Water, Acids, Bases
                                                                      – Hand in Carbohydrates Lab

                                                                      – Activity: Cheesy Science Article
                                                                      – Read Section 2.7 on Proteins
                                                                      – complete Carbohydrate lab if still not done

                                                                      Wednesday, November 14th

                                                                      – Lab: Glucose Test (Part 2)
                                                                      – Learning Goals WS: Water, Acids, Bases
                                                                      – Quiz next class (Water, Acids, Bases)
                                                                      – complete Carbohydrates Lab
                                                                      – keep working on Carbohydrates worksheet

                                                                      Friday, November 9th

                                                                      – review Water & Acids/Bases worksheet
                                                                      – Demo: blowing CO2 into a basic solution
                                                                      – Notes: Organic Biochemical Molecules
                                                                      – Powerpoint: Carbohydrates
                                                                      – Lab: Starch Test (Part 1)
                                                                      – Carbohydrates worksheet (complete table on first page using textbook)
                                                                      – Water & Acids/Bases Quiz next Friday, Nov. 16th

                                                                      Wednesday, Nov. 7th

                                                                      – Importance of Water:

                                                                      – I AM Rant (peer feedback & presentation)
                                                                      – Review handout: 2.3 Water Properties + Annotate Article
                                                                      – Intro to Organic Molecules (complete the “BEFORE” column)

                                                                      Monday, Nov. 5th

                                                                      – Hand in Acid/Base/Buffer Lab
                                                                      – Ch.4 Membrane Test returned
                                                                      – Review: Water Stations Activity

                                                                      – I am Water/Acid/Base “RANT”!

                                                                      – Review handout: 2.3 Water Properties (complete by Friday)

                                                                      Thursday, Nov. 1st

                                                                      – Notes: Acidic & Basic Solutions
                                                                      – Lab: Acids, Bases and pH
                                                                      – complete discussion questions for lab and a very thoughtful conclusion!

                                                                      Tuesday, Oct. 30th

                                                                      – Notes: Structure & Properties of Water
                                                                      – Stations Activity
                                                                      – complete Water Stations Activity handout
                                                                      – Read pg. 26-30
                                                                      – Read Acid-Base Lab (be ready to complete next class)

                                                                      Friday, Oct. 26th

                                                                      – Ch. 4 Quest (Membrane Transport)
                                                                      – Read pg. 26-30 (Properties of Water)

                                                                      Wednesday, Oct. 24th

                                                                      – Tonicity in the real world
                                                                      – Review worksheets
                                                                      – Check out animation links below
                                                                      – Video Crash Course:

                                                                      Monday, Oct. 22nd

                                                                      – hand in Osmosis Lab
                                                                      – Notes: Active Transport & Endocytosis/Exocytosis
                                                                      – complete Active Transport & Endocytosis/Exocytosis worksheets
                                                                      – Review worksheet
                                                                      – Ch.4 (Membrane) Quiz Friday

                                                                      Animation: Phagocytosis (Endocytosis) & Exocytosis
                                                                      Animation: How the Sodium-Potassium Pump Works (Active Transport)
                                                                      Animation: How Facilitated Diffusion Works
                                                                      Animation: How Diffusion Works
                                                                      Animation: How Osmosis Works

                                                                      Wednesday, Oct. 17th

                                                                      – finish Osmosis Lab
                                                                      – completed lab due next class (complete sentences)
                                                                      – Ch.4 (Membrane) Quiz Fri, Oct. 26th
                                                                      – work on any incomplete handouts

                                                                      Monday, Oct. 15th

                                                                      – Notes: Passive Transport & Tonicity
                                                                      – Revisit last day’s mini-lab (Evidence of Diffusion/Osmosis)
                                                                      – Demo: Naked Egg & Potato
                                                                      – Osmosis (Dialysis Tubing) Lab set-up
                                                                      – complete drawings on the back of “Osmosis Demos” worksheet
                                                                      – Transport Across Membrane Quiz Friday, Oct. 26th

                                                                      Thursday, Oct. 11th

                                                                      – Powerpoint Notes: Review + Permeability & Diffusion/Osmosis
                                                                      – Perfume + dye demo
                                                                      – Mini-Lab: Investigating Evidence of Diffusion & Osmosis
                                                                      – read 4.2 & 4.3
                                                                      – think about questions in lab
                                                                      – complete Diffusion & Osmosis worksheet
                                                                      – try to fill in notes worksheet (Permeability of Plasma Membrane) –> will go over together next class

                                                                      Tuesday, Oct. 9th

                                                                      – Powerpoint Notes: Transport Across the Membrane
                                                                      – Group Activity: Building a Fluid Mosaic Model
                                                                      – Worksheets: Role of Membranes in Cells, Plasma Membrane Structure & Function
                                                                      – Read Ch.4 (pg.68-72)
                                                                      – complete the 2 worksheets

                                                                      Thursday, Oct. 4th

                                                                      – HW Check! –> answers posted in Class Notebook
                                                                      – Investigating Cells (Office 365)
                                                                      – Cell Quiz returned
                                                                      – Investigating Cells online assignment due by next class

                                                                      Tuesday, Oct. 2nd

                                                                      – Cell Structures Quiz
                                                                      – Cell Size Investigation worksheet
                                                                      – complete & read Cell Size worksheet
                                                                      – read pg.48 in text

                                                                      Online Quizzes for Review:

                                                                      Friday, Sept. 28th

                                                                      – hand in Microscope/Cells lab
                                                                      – Notes: Powering the Cell
                                                                      – Cell Types & Cell Structures/Function/Identification Quiz next Tuesday
                                                                      – more practice: Ch.3 (pg.64-64) #5,6,8,9 M/C #2-11

                                                                      Wednesday, Sept. 26th

                                                                      – complete Microscope Lab from last class
                                                                      – Energy Flow in Living Things (read and colour or label)
                                                                      – Cell Types & Cell Structures/Function/Identification Quiz next Tuesday
                                                                      – Cell Review WS

                                                                      Monday, Sept. 24th

                                                                      – Rules for Scientific Drawings & Calculating Actual Size/Drawing Mag.
                                                                      – Microscope Lab (Cell Types & Scientific Drawings)
                                                                      – Cell Types & Cell Structures/Function/Identification Quiz next Tuesday
                                                                      – read over the lab and notes from today

                                                                      Wednesday, Sept. 19th

                                                                      – The Endomembrane System + Plasma (Cell) Membrane
                                                                      – Cell Analogies (group activity)
                                                                      – Prokaryotic vs. Eukaryotic Cells
                                                                      – complete worksheet on Prokaryotic vs. Eukaryotic Cells / Labelling Micrograph

                                                                      Monday, Sept. 17th

                                                                      – Science in the News assignment from last class due today!
                                                                      – Characteristics of Living Things worksheet (pg.7-12)
                                                                      – Cell Structures (worksheet, simulation, videos)
                                                                      Cell Simulation
                                                                      Cell Structures Video
                                                                      Lysosomes Animation
                                                                      Cell Size & Scale Simulation
                                                                      Scale of the Universe Simulation
                                                                      – finish Characteristics of Living Things worksheet
                                                                      – finish Cell Structures worksheet (use pg.49-63 or online sources – KEY POSTED)

                                                                      Thursday, Sept. 13th

                                                                      – Sign out “Cheetah” textbook
                                                                      – How to use Office 365 for assignments
                                                                      – Science in the News: Southern Resident Orcas Assignment
                                                                      – complete Science in the News Assignment (on Office 365, or email me, or print it out)
                                                                      – Check answers for the Scientific Method booklet online in the Class Notebook

                                                                      Tuesday, Sept. 11th

                                                                      – Scientific Method Review

                                                                      – finish booklet (check answers in notebook)

                                                                      Friday, Sept. 7th

                                                                      – Course Outline Quiz
                                                                      – Biology Stations Ice Breaker

                                                                      Wed, Sept. 5th

                                                                      – Introductions & Stations Activity
                                                                      – Course Outline

                                                                      UMUC Biology 102/103 Lab 4: Enzymes Answer Key

                                                                      This contains 100% correct material for UMUC Biology 102/103 LAB04. However, this is an Answer Key, which means, you should put it in your own words. Here is a sample for the Pre lab questions answered:

                                                                      1. How could you test to see if an enzyme was completely saturated during an experiment? (2 pts)

                                                                      To test this, you’d simply see if the reaction was still taking place. If the enzyme was completely depleted, the reaction could no longer occur.

                                                                      2. List three conditions that would alter the activity of an enzyme. Be specific with your explanation. (2 pts)

                                                                      Temperature, salinity, and acidity are three conditions that affect enzyme activity. Specific examples include:

                                                                      Adding a salt packet to an enzyme would alter its activity–salt ions are often necessary for optimal enzyme activity, so too much or too little salt will slow down the rate.

                                                                      Enzyme activity increases with increasing temperature, until it becomes hot enough to denature the protein (enzymes are proteins), then the activity would cease.

                                                                      Enzymes have an optimum pH where they function the best. Higher or lower pH than the optimum slows the rate of activity.

                                                                      3. Take a look around your house and identify household products that work by means of an enzyme. Name the products, and indicate how you know they work with an enzyme. (2 pts)

                                                                      Some examples include: contact lens cleaner (protease), dish soap (amylase), cheese

                                                                      (rennin), meat (papain), and starch products (amylase).

                                                                      The rest of the questions that are answered:

                                                                      Experiment 1: Enzymes In Food

                                                                      Data Tables and Post-Lab Assessment

                                                                      Table 1: Substance vs. Starch Presence

                                                                      Negative Control: Student Must Select

                                                                      1. What were your controls for this experiment? What did they demonstrate? Why was saliva included in this experiment?

                                                                      2. What is the function of amylase? What does amylase do to starch?

                                                                      3. Which of the foods that you tested contained amylase? Which did not? What experimental evidence supports your claim?

                                                                      4. Saliva does not contain amylase until babies are two months old. How could this affect an infant’s digestive requirements?

                                                                      5. There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. Research to determine what this enzyme is called. What substrate does it act on? Where in the body does it become activated, and why?

                                                                      6. Digestive enzymes in the gut include proteases, which digest proteins. Why don’t these enzymes digest the stomach and small intestine, which are partially composed of protein?

                                                                      Experiment 2: Effect of Temperature on Enzyme Activity

                                                                      Data Tables and Post-Lab Assessment

                                                                      Table 2: Balloon Circumference vs. Temperature

                                                                      Balloon Circumference (Uninflated cm)

                                                                      Balloon Circumference (Inflated cm)

                                                                      1. What reaction is being catalyzed in this experiment?

                                                                      2. What is the enzyme in this experiment? What is the substrate?

                                                                      3. What is the independent variable in this experiment? What is the dependent variable?

                                                                      4. How does the temperature affect enzyme function? Use evidence from your data to support your answer.

                                                                      5. Draw a graph of balloon diameter vs. temperature. What is the correlation?

                                                                      6. Is there a negative control in this experiment? If yes, identify the control. If no, suggest how you could revise the experiment to include a negative control.

                                                                      7. In general, how would an increase in substrate alter enzyme activity? Draw a graph to illustrate this relationship.

                                                                      8. Design an experiment to determine the optimal temperature for enzyme function, complete with controls. Where would you find the enzymes for this experiment? What substrate would you use?

                                                                      Links and Resources

                                                                      Enzyme Action

                                                                      This interactive provides information on enzymes and enzyme action, with links to both metabolic and industrial processes. The animations are colourful, simple and clear. It includes useful animations which illustrate the lock and key model of enzyme action. Students see how temperature and pH influence the enzyme's active site and therefore the rate of reaction.

                                                                      There is also a glossary (key words) which students can refer to this could be used as the beginning of a glossary for this topic, with students adding all the words that are required.

                                                                      Students could work in mixed ability pairs and complete each section of this website, answering the questions at the end of each section and also the six question auto marked test.

                                                                      The application can be installed on your school laptops or VLE.

                                                                      Using enzymes to make creme eggs

                                                                      This video demonstrates how to make soft-centred chocolates, using enzymes. Students could carry out this practical and if undertaken in a food safe environment, using food materials and following a scrupulous hygiene regime, produce chocolates that could be eaten.

                                                                      This practical/demonstration provides a "real-world" application of the use of enzymes, which will be of interest to many students (chocolate!). It would be a good practical to complete at the start of this topic or as a reward at the end of the topic if students can demonstrate appropriate knowledge and understanding of enzyme action.

                                                                      Upgrading Whey

                                                                      This practical activity is a good demonstration of the use of immobilised enzymes in biotechnology. The materials give a method for producing whey from milk. Students then use immobilised enzymes to produce glucose from the &lsquowaste&rsquo whey. This part of the procedure is fairly straight forward and requires students to follow a set of instructions. They immobilise the enzyme lactase in alginate beads which are placed inside a syringe barrel. As the whey is run over the beads, glucose is produced.

                                                                      Students use a glucose test strip to measure the amount of glucose produced. Before their use, test strips can be cut in two along their length to double the number of tests. Once students have shown that glucose is produced, they can be challenged to optimise the process to see how to get the greatest yield of glucose.

                                                                      Factors that could be investigated include:

                                                                      &bull Temperature of the syringe &lsquoreaction vessel.&rsquo

                                                                      &bull Flow rate of whey solution.

                                                                      &bull Pressure inside the syringe.

                                                                      &bull Longevity of the immobilised enzyme.

                                                                      &bull Effects of storage on the activity of the enzyme beads.

                                                                      Depending on time available, students can work in groups and present results to the class, to model how a research group would work. This is the type of activity that would be undertaken in industry where laboratory processes are scaled up to full production size.

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                                                                      Practical Work for Learning

                                                                      Class practical

                                                                      Measure the time taken for amylase to completely break down starch, by withdrawing samples at 10 second intervals and noting the time at which the solution no longer gives a blue-black colour with iodine solution (but the iodine solution remains orange). Use buffers to provide solutions at different pHs. Calculate the rate of this enzyme controlled reaction by calculating 1÷ time.

                                                                      Lesson organisation

                                                                      This procedure is simple enough for individuals to carry out if you have enough dimple tiles. If you choose to investigate five pHs, then groups of five students could complete the investigation by working together and pooling results.

                                                                      Apparatus and Chemicals

                                                                      For each group of students:

                                                                      Syringes, 5 cm 3 , 2 (1 for starch, 1 for amylase)

                                                                      Iodine solution in a dropper bottle (Note 4)

                                                                      Test tube, 1 for each pH to be tested

                                                                      Dimple tile or white tiles

                                                                      For the class – set up by technician/ teacher:

                                                                      Amylase 1% (or 0.5%) (Note 1)

                                                                      Starch 1% (or 0.5%) (Note 2)

                                                                      Buffer solutions covering a range of pH, each with a labelled syringe/ plastic pipette (Note 3)

                                                                      Health & Safety and Technical notes

                                                                      Amylase solution and iodine solution are low hazard once made up. Wear eye protection when handling iodine solution.
                                                                      Hazards of buffers may vary. See CLEAPSS Recipe card or supplier’s information and see Note 3.

                                                                      1 Amylase (See CLEAPSS Hazcard and Recipe card) The powdered enzyme is HARMFUL, but solutions less than 1% are LOW HAZARD. It is wise to test, well in advance, the activity of the stored enzyme at its usual working concentration to check that substrates are broken down at an appropriate rate. Enzymes may degrade in storage and this allows time to adjust concentrations or to obtain fresh stocks. Amylase will slowly lose activity, so it is best to make up a fresh batch for each lesson batches may vary in activity and results collected on different days will not be comparable. The optimum temperature for your enzyme will be listed on the supplier’s label.

                                                                      Using saliva: the CLEAPSS Laboratory Handbook provides guidance on precautions to take (including hygiene precautions) in order to use saliva safely as a source of amylase. This has the advantage of being cheaper, not requiring technicians to make up fresh solutions each lesson, it is directly interesting to students, and salivary amylase is reliable. It also provides an opportunity to teach good hygiene precautions – including ensuring that students use only their own saliva samples (provide small beakers to spit into) that students are responsible for rinsing their own equipment and that all contaminated glassware is placed in a bowl or bucket of sodium chlorate(I) before technicians wash up.

                                                                      2 Starch suspension – make fresh. Make a cream of 5 g soluble starch in cold water. Pour into 500 cm 3 of boiling water and stir well. Boil until you have a clear solution. Do not use modified starch.

                                                                      3 Buffers: (See CLEAPSS Recipe card) If you make universal buffer it will contain sodium hydroxide at approximately 0.25 M, and should be labelled IRRITANT. Refer to other relevant Hazcards if you choose to make other buffers, or to supplier’s information if you purchase buffer solutions/ tablets. (Note 1)

                                                                      4 Iodine solution (See CLEAPSS Hazcard and Recipe card). A 0.01 M solution is suitable for starch testing. Make this by 10-fold dilution of 0.1 M solution. Once made, the solution is a low hazard but may stain skin or clothing if spilled.

                                                                      Ethical issues

                                                                      There are no ethical issues associated with this procedure.


                                                                      SAFETY: All solutions once made up are low hazard. Wear eye protection, as iodine may irritate eyes.


                                                                      a Check the speed of the reaction with the suggested volumes of reactants to be used – 2 cm 3 of starch: 2 cm 3 of amylase: 1 cm 3 of buffer at pH 6. Ideally the reaction should take about 60 seconds at this pH: this is the usual optimum for amylase (see note 1). If the reaction is too fast, either reduce the enzyme volume or increase the starch volume. If the reaction is too slow, increase the enzyme volume or concentration or reduce the starch volume or concentration.


                                                                      b Place single drops of iodine solution in rows on the tile.

                                                                      c Label a test tube with the pH to be tested.

                                                                      d Use the syringe to place 2 cm 3 of amylase into the test tube.

                                                                      e Add 1 cm 3 of buffer solution to the test tube using a syringe.

                                                                      f Use another syringe to add 2 cm 3 of starch to the amylase/ buffer solution, start the stop clock and leave it on throughout the test. Mix using a plastic pipette.

                                                                      g After 10 seconds, use the plastic pipette to place one drop of the mixture on the first drop of iodine. The iodine solution should turn blue-black. If the iodine solution remains orange the reaction is going too fast and the starch has already been broken down. Squirt the rest of the solution in the pipette back into the test tube.

                                                                      h Wait another 10 seconds. Then remove a second drop of the mixture to add to the next drop of iodine.

                                                                      i Repeat step h until the iodine solution and the amylase/ buffer/ starch mixture remain orange.

                                                                      j You could prepare a control drop for comparison with the test drops. What should this contain?

                                                                      k Count how many iodine drops you have used, each one equalling 10 seconds of reaction time.

                                                                      l Repeat the whole procedure with another of the pH buffers to be used, or pool the class results.

                                                                      m Consider collecting repeat data if there is time.

                                                                      n Plot a graph of time taken to break down starch against pH, or calculate the rate of reaction and plot rate against pH.

                                                                      Teaching notes

                                                                      This is a straightforward practical giving reliable, unambiguous results. The main errors will be in the order of mixing the enzyme/ substrate/ buffer, or a delay in sampling so that the reaction time is under-estimated or rate is over-estimated. Temperature variation affects enzyme activity, so results collected on different days are not comparable.

                                                                      Health and safety checked, September 2008


                                                                      Download the student sheet Investigating the effect of pH on amylase activity (72 KB) with questions and answers.

                                                                      Web links

                                                                      A clear and thorough presentation of information about enzymes as chemical catalysts and the factors affecting their activity.

                                                                      (Website accessed October 2011)

                                                                      © 2019, Royal Society of Biology, 1 Naoroji Street, London WC1X 0GB Registered Charity No. 277981, Incorporated by Royal Charter

                                                                      Watch the video: Toothpickase Lab Demo (May 2022).