OCR GCSE Science Biology a and B PAG 4 Suggestion 2

Biology PAG 4: Rates of Enzyme Controlled Reactions

Suggested Activity 2: Investigating the Effect of Temperature on the Activity of Lipase Instructions and answers for teachers & technicians This practical activity is composed of two parts; a teacher/technician section and the learner activity which can be found on page 9. This Practical activity supports OCR GCSE Biology.

When distributing the activity section to the learners either as a printed copy or as a Word file you will need to remove the teacher instructions section.

This is a suggested practical activity that can be used as part of teaching the GCSE (9-1) Gateway Science (A) and Twenty First Century Science (B) specifications.

These are not controlled assessment tasks, and there is no requirement to use these particular activities.

You may modify these activities to suit your learners and centre. Alternative activities are available from, for example, Royal Society of Biology, Royal Society of Chemistry, Institute of Physics, CLEAPSS and publishing companies, or of your own devising.

Further details are available in the specifications (Practical Skills Topics), and in these videos.

OCR recommendations: Before carrying out any experiment or demonstration based on this guidance, it is the responsibility of teachers to ensure that they have undertaken a risk assessment in accordance with their employer’s requirements, making use of up-to-date information and taking account of their own particular circumstances. Any local rules or restrictions issued by the employer must always be followed.

CLEAPSS resources are useful for carrying out risk-assessments: (http://science.cleapss.org.uk).

Centres should trial experiments in advance of giving them to learners. Centres may choose to make adaptations to this practical activity, but should be aware that this may affect the Apparatus and Techniques covered by the learner.

Version 1.1 – December 2017 1 © OCR 2017 Introduction In this activity learners will investigate how the activity of the enzyme lipase changes with temperature. Additionally, in this activity learners will consider how indicators help us to follow chemical reactions.

An enzyme is a biological catalyst. The enzyme lipase specifically targets lipids. Lipase breaks lipids down into fatty acids and glycerol.

Phenolphthalein is a pH indicator, that is pink in an alkaline solution around pH10. In a solution with a pH below pH8, phenolphthalein will turn colourless.

A solution of sodium carbonate and milk, is an alkaline solution. When Phenolphthalein is added to this solution, it will be pink. When lipase is added to this solution, it will begin to break down the lipids in the milk, producing fatty acids. This will lower the pH of the solution, turning the phenolphthalein colourless. The rate at which this reaction occurs will depend on the temperature.

DfE Apparatus and Techniques covered The codes used below match the OCR Practical Activity Learner Record Sheet (Biology / Combined Science) and Trackers (Biology / Combined Science) available online. There is no requirement to use these resources.

1 [1]: Use of appropriate apparatus to make and record a range of measurements accurately, including iv) time, v) temperature and vi) volume of liquids.

2 [2]: Safe use of appropriate heating devices and techniques including the use of ii) a water bath or electric heater

5 [5]: Measurement of rates of reaction by a variety of methods including: iii) colour change of indicator

Aims To investigate how temperature effects the rate of enzyme-controlled reactions

Intended class time 50 - 60 minutes to complete the experiment and draw the graph.

It is recommended that pupils are taught the theory surrounding the practical, particularly knowledge about lipase breaking down lipids into fatty acids, is taught prior to the experiment. This will enable pupils to make sense of what is happening.

Version 1.1 – December 2017 2 © OCR 2017 Links to Specifications: Gateway Describe experiments that can be used to investigate enzymatic reactions.

Explain the mechanism of enzyme action, including factors affecting the rate of enzyme controlled reactions (temperature).

Twenty First Century Enzymes function only in certain conditions, and optimally when conditions are within a narrow range.

Describe practical investigations into the effect of substrate concentration, temperature and pH on the rate of enzyme controlled reactions.

Mathematical Skills covered M1 a) Recognise and use expressions in decimal form, c) use ratios, fractions and percentages

M4 c) Plot two variables from experimental or other data

Gateway working scientifically references covered WS1.2a Scientific theories and explanations to develop hypotheses

WS1.3 Apply the cycle of collecting, presenting and analysing data, including; a) presenting observations and other data using appropriate methods b) Translating data from one form to another e) Interpreting observations and other data f) Presenting reasoned explanations relating data to hypothesis

WS1.4 a) Use scientific vocabulary, terminology and definitions

WS2 a) Carry out experiments b) Make and record observations and measurements using a range of apparatus and methods c) Presenting observations using appropriate methods

Twenty First Century IaS references covered Given contexts use scientific theories and tentative explanations to develop and justify hypotheses and predictions.

Use appropriate scientific vocabulary, terminology and definitions to communicate the rationale for an investigation and the methods used using diagrammatic, graphical, numerical and symbolic forms.

Present observations and other data using appropriate formats.

Version 1.1 – December 2017 3 © OCR 2017 When processing data use SI units where appropriate (e.g. kg, g, mg; km, m, mm; kJ, J) and IUPAC chemical nomenclature unless inappropriate.

When displaying data graphically select an appropriate graphical form, use appropriate axes and scales, plot data points correctly, draw an appropriate line of best fit, and indicate uncertainty (e.g. range bars).

When analysing data identify patterns/trends, use statistics (range and mean) and obtain values from a line on a graph (including gradient, interpolation and extrapolation).

Equipment (all equipment in this section is per group) 4 test tubes 4 test tube bungs A test tube rack 2 10cm3 measuring cylinders 20 cm3 milk 28 cm3 sodium carbonate solution 4 cm3 lipase 2 cm3 syringe Stop clock Access to an ice bath/ tub of ice Access to two water baths (40oC, 70oC) Thermometer

Health and Safety Teachers will need to carry out a suitable risk assessment for each practical. The following may assist you in the preparation of your risk assessment:

 Flame hazard - Keep the phenolphthalein solution away from naked flames.  Splash hazard - Wear eye protection and quickly rinse any splashes of enzyme solution/ phenolphthalein or sodium carbonate from the skin.

Version 1.1 – December 2017 4 © OCR 2017 Method 1. Label 4 test tubes with the temperatures you will be testing (0oC, 20oC, 40oC, 70oC) and place them in a test tube rack.

2. Add 5 drops of phenolphthalein to each of the test tubes.

3. Measure out 5cm3 of milk using a measuring cylinder and add this to each of the four test tubes. 4. Using another measuring cylinder, measure out 7 cm3 of sodium carbonate solution and add this to each test tube. The solution should now be pink. 5. There is; a. An ice bath containing a cold lipase solution (0oC), b. A conical flask containing lipase at room temperature (20oC) c. Two water baths containing hot lipase solution (40oC, 70oC).

Take one of your test tubes over to the corresponding lipase solution you are going to use first.

6. Use a syringe to measure out 1 cm3 of lipase solution and place the lipase solution into the test tube.

7. Place a bung in the test tube and shake for 5 seconds.

8. Remove the bung.

9. Get your stop clock ready.

10. Stand the test tube back in the ice bath, water bath, or in your test tube rack for room temperature (where the lipase came from).

11. Quickly start the stop clock.

12. Stir the contents of the test tube with a glass rod, until the solution loses its pink colour.

13. Stop the clock and note the time in a table of results.

14. Take the temperature of the lipase solution, with the thermometer and note the temperature in a suitable table of results.

15. Calculate the rate of reaction, by 1÷time taken. Note the rate of reaction in a suitable table of results.

Version 1.1 – December 2017 5 © OCR 2017 Technician Notes For this practical the teacher will require for a class of 30 (15 pairs):

 60 test tubes

 60 test tube bungs

 15 test tube racks

 30 10cm3 measuring cylinders

 60cm3 lipase

 An ice bath with test tube racks (0oC),/ tubs of ice, Two water baths (40oC, 70oC).

 4 Bottles of sodium carbonate solution (only 420 cm3 required for the glass in total, splitting across 4 bottles avoids queuing)

 4 beakers of milk (only 300 cm3 required for the glass in total, splitting across 4 bottles avoids queuing)

 15 stop clocks

 15 thermometers

Prior to the experiment, the following should be organised;

 An ice bath containing a cold lipase solution (~ 0oC),

 A conical flask containing lipase at room temperature (~ 20oC)  Two water baths containing a hot lipase solution (~ 40oC, ~ 70oC).

NB/ 1cm3 of lipase will be required for each group, at each temperature. Therefore, each water bath will require a minimum of 15cm3 lipase. A total of 60cm3 lipase will be required, but this will need to be distributed across the four settings.

Version 1.1 – December 2017 6 © OCR 2017 Answers for quiz questions

1. What is the difference between the ‘time taken’ and a ‘rate of reaction’ curve? The graphs show a similar pattern. The time taken shows a decrease, then an increase. The rate of reaction curve shows in increase then a decrease.

2. When fat breaks down, what is produced? Glycerol, fatty acids

3. Use this information to explain why the phenolphthalein changes colour The sodium carbonate is acidic, so turns the Phenolphthalein pink. When the lipase breaks down the fat in the milk, the fatty acids produced increase the acidity of the solution, turning it from pink to clear. 4. What is the effect of temperature on the time taken for lipase to break down the fat in milk? As the temperature increases, the time taken for the lipase to break down the fat decreases until the optimum temperature of 37oC.

Extension 1: Why does the temperature affect the action of lipase in this way? Enzymes work at their fastest rate at an optimum temperature of 37oC. Temperatures higher than this, can denature the enzyme (active site is deformed).

Extension 2: Why is it necessary to break down fat in the digestive system? So it is soluble/so it can be absorbed by the small intestine

Suggested Activity 2: Investigating the Effect of Temperature on the Activity of Lipase Learner Activity

Introduction In this activity, you will investigate how the activity of the enzyme lipase changes with temperature. Additionally, in this you will consider how indicators help us to follow chemical reactions.

An enzyme is a biological catalyst. The enzyme lipase specifically targets lipids. Lipase breaks lipids down into fatty acids and glycerol.

Phenolphthalein is a pH indicator, that is pink in an alkaline solution around pH10. In a solution with a pH below pH8, phenolphthalein will turn colourless.

Aims To investigate how temperature effects the rate of enzyme-controlled reactions.

Version 1.1 – December 2017 9 © OCR 2017 Method 1. Label 4 test tubes with the temperatures you will be testing (0oC, 20oC, 40oC, 70oC) and place them in a test tube rack.

2. Add 5 drops of phenolphthalein to each of the test tubes.

Take one of your test tubes over to the corresponding lipase solution you are going to use first.

6. Use a syringe to measure out 1 cm3 of lipase solution and place the lipase solution into the test tube.

7. Place a bung in the test tube and shake for 5 seconds.

8. Remove the bung.

9. Get your stop clock ready.

10. Stand the test tube back in the ice bath, water bath, or in your test tube rack for room temperature (where the lipase came from).

11. Quickly start the stop clock.

12. Stir the contents of the test tube with a glass rod, until the solution loses its pink colour.

13. Stop the clock and note the time in a table of results.

14. Take the temperature of the lipase solution, with the thermometer and note the temperature in a suitable table of results.

15. Calculate the rate of reaction, by 1÷time taken. Note the rate of reaction in a suitable table of results.

Version 1.1 – December 2017 10 © OCR 2017 Temperature of Lipase Time taken for solution to go Rate of reaction (oC) from pink to colourless (1÷time taken) (mins/secs)

0 20 40 70

Health and Safety

Quiz questions 1. Plot a line graph of temperature against rate of reaction.

2. Plot a line graph of temperature against time taken.

3. What is the difference between a ‘time taken’ and a ‘rate of reaction’ curve for this investigation?

4. When fat breaks down, what is produced?

5. Use this information to explain why the phenolphthalein changes colour.

6. What is the effect of temperature on the time taken for lipase to break down the fat in milk?

Extension 1: Why does the temperature affect the action of lipase in this way?

Extension 2: Why is it necessary to break down fat in the digestive system?

DfE Apparatus and Techniques covered If you are using the OCR Practical Activity Learner Record Sheet (Biology / Combined Science) you may be able to tick off the following skills:

Biology Combined Science 1-iv 1-v 1-vi 1-iv 1-v 1-vi 2-ii 5-iii 2-ii 5-iii