Practical 1 - A-Level Biology coursework PDF

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A-Level Biology coursework ...

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Polina Lobacheva November 27th, 2018 Y12 AS Level Biology Mrs. Carr Group Partners: Shareef Jarkas, Nicholas Warren Required practical 1: Identifying the ways in which temperature affects the rate of lipase Aim: The aim of this experiment is to investigate the effect of temperature on the rate of lipase. Introduction Enzymes are globular proteins that act as biological catalysts, meaning they increase the rate of reactions, lower the activation level and can be reused. The active site on the enzyme is complementary to its substrate in shape. A substrate is a molecule formed by the reaction of the products. Only specific substrates fit into an enzyme’s active site. When enzymes and substrate bind, they make an enzyme-substrate complex, which is where the product is formed and then released. As temperature increases, the number of successful collisions between the enzyme and the substrate molecule increases as well. However, temperature is also a limiting factor because when temperature reaches a certain degree, enzymes are no longer t capable of working properly and in turn, denature. This means that the active site loses its shape and is no longer able to bind with substrates, therefore there will be a decrease in enzyme activity1. Phenolphthalein will be used as an indicator and will go from 10 to 8.3 at which it turns colourless. Hypothesis As the temperature increases, the time taken for the solution with lipase to turn colourless decreases. This will continue until the temperature reaches a certain point after which the curve of the graph will curve the opposite direction. Risk Assessment Hazard 1 (BBC Bitesize, 2018).

Risk2

Control

Ethanol

Highly flammable

Wear eye protection and make sure

Sodium carbonate

Irritant

room is ventilated Wear eye protection and avoid skin

(low hazard) Glassware

Cut yourself with sharp

contact Safety goggles should be worn

Beakers

edges Can burn yourself

Wear eye protection and thermal

Irritant, health hazard,

protection gloves Wearing disposable gloves and wear

corrosive

eye protection

Enzyme (lipase)

Method

1. Label a test tube with the temperature in Celsius (10, 20, 30, 40, 50, 60) to be investigated. 2. Add 5 drops of phenolphthalein to the test tube. 3. Measure out 5 cm3 of milk using a measuring cylinder (or syringe) and add this to the test tube. 4. Measure out 7 cm3 of sodium carbonate solution using another measuring cylinder (or syringe) and add this to the test tube. The solution should be pink. 5. Place a thermometer in the test tube. Take care as the equipment could topple over. 6. Place the test tube in a water bath and leave until the contents reach the same temperature as the water bath. 7. Remove the thermometer from the test tube and replace it with a glass rod. 8. Use the 2 cm3 syringe to measure out 1 cm3 of lipase from the beaker in the water bath for the temperature you are investigating. 9. Add the lipase to the test tube and start the stopwatch. 10. Stir the contents of the test tube until the solution loses its pink colour. 11. Stop the clock/watch and note the time in a suitable table of results.

Results 2 (CLEAPSS)

Temperature (°C) 10 20 30 40 50 60 Graph

Time (seconds) Trial 1 397 299 229 279 410 No change

Trial 2 420 286 255 260 440

Average 408.5 292.5 242 269.5 425

On the left is a graph of how temperature affects enzymes. As you can see, enzymes have an optimum temperature at which they work their best. At high temperatures, enzymes denature and are incapable of working. By looking at my graph above, it demonstrates how it takes the shorter amount of time to react at about 30°C3. Conclusion My hypothesis proves to be correct, which is supported by the graph above. From the graph, it can be seen that as the temperature increases the time taken for lipase to turn colourless decreases. The curve decreased until 30°C and then it started rising up again. This shows that the 3 (Evolvingsciences.com, 2018).

lipase enzyme’s optimum temperature is at 30°C as it takes the shortest time to react. As the temperature rises, the kinetic energy of the molecules increases so they undergo more successful collisions. This means that the substrate collides with the active sites more often. However, the enzymes stop working when the temperature gets too high and changes the shape of the active site, hence eventually causing the enzyme to denature. Milk contains fats, and lipase breaks those fats down into fatty acids and glycerol. Lipases are enzymes which catalyse the hydrolysis of triglyceride to give di- and mono- glycerides, glycerol and free fatty acids4. Before lipase can digest fat, bile, an emulsifier, it must break the fat down into smaller units. Evaluation Overall, the experiment went as planned, however there are many areas for improvement. It was very difficult to keep stirring, because our wrists got tired and so the stirring became less effective as time went on. A solution for this would be to get an automatic whisker thin enough to stir the solution inside the test tube. Throughout this experiment we controlled the temperature, by placing the test tubes in water baths and bringing them up to according temperatures. However, the temperatures kept decreasing, when my group was stirring the solutions, and it proved to be very difficult to keep it constant, which I believe might have affected the results of this experiment. This was one of the difficult aspects of the experiment to control. To solve this, next time I would use an electric water bath. There were no major anomalies that affected the curve of the graph. If someone were to repeat this experiment they would get roughly the same results. The majority of the results I obtained are precise as they’re close to the mean value.

4 (Diet and Health.net, 2018).

The following results are taken from another group that conducted a similar investigation. As you can see, the graph on the right matches the results I obtained. The only difference is that the y-axis is labelled as the rate of lipase activity instead of time but it’s the same idea. To create my graph to visually represent my findings, I decided to use Google Sheets. This was challenging as I have not worked with Google Sheets before and it took me a few hours to figure out how to use it. Eventually, I was able to create a graph that represents my data well. References BBC Bitesize. (2018). BBC Bitesize - GCSE Biology (Single Science) - Enzymes and digestion (CCEA) - Revision 2. [online] Available at: https://www.bbc.com/bitesize/guides/zwnstv4/revision/2 [Accessed 23 Nov. 2018]. Bitesize. (2018). Enzymes and digestion (CCEA). [online] Available at: http://www.citethisforme.com/cite/website/autocite [Accessed 23 Nov. 2018]. Evolvingsciences.com. (2018). Graphs and Factors. [online] Available at: https://www.evolvingsciences.com/Graphs%20and%20Factors%20.html [Accessed 26 Nov. 2018]. Cleapss.org.uk. n.d. CLEAPSS. [online] Available at: [Accessed 10 April 2020]. Diet and Health.net. (2018). How Lipases Helps Break Down Fats - Diet and Health.net. [online] Available at: https://www.diet-and-health.net/Supplements/Lipase.html [Accessed 27 Nov. 2018]. Lawrence, l. (2018). lipase enzyme reaction. [online] Issuu. Available at:

https://issuu.com/lawrencekokwingkhong/docs/gina_internal_assessment_design_2__lipase_activit [Accessed 27 Nov. 2018]....