1. IB Enzyme practical

2. Factors affecting Enzymes
Temperature pH
Substrate concentration
Enzyme concentration

3. The best way to understand temperature, pH and substrate concentration effects is through paying with this game.... and here's another....

4. Factors which affect enzyme activity 1: Temperature
From: GCSE Bitesize:

5. The effect of temperature
For most human enzymes the optimum temperature is about 37°C
Many are a lot lower. For example, cold water fish can die at 30°C since many of their enzymes denature
Many plant enzymes have optimal temperature of 28 – 30 C
A few bacteria in hot springs have enzymes that can withstand very high temperatures up to 100°C
Most enzymes are fully denatured at 70°C

6. Factors which affect enzyme activity 2: pH
Optimum pH values
Enzyme activity
Trypsin
Pepsin pH 1 3 5 7 9 11

7. The effect of pH The pH of a solution affects the shape of an enzyme
At non-ideal pH values, the active site is distorted and the substrate molecules will no longer fit
Extreme pH levels will produce denaturation
Many enzymes have pH values which are NOT neutral (pH = 7): e.g. pepson, trypsin in the stomach and gut

8. Denaturation
Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function. Enzymes (and other proteins) can be denatured by heat, pH changes, or certain chemicals NB: Denaturation is not the same as ‘killing’ – proteins and enzymes are not living things, so can’t be killed!

9. What does ‘enzyme denaturation’ mean?

10. Factors which affect enzyme activity 3: Substrate and enzyme concentration
From:
August 26th 2012

11. Substrate concentration: Enzymic reactions
Reaction velocity
Substrate concentration
Vmax

12. Celebrity enzymes
Amylase
Pepsin
Pectinase
Catalase

13. Amylase
all about amylase...
amylase digestion

14. Pepsin
All about pepsin
pepsin working in the stomach

15. Pectinase
Pectinase is widely used to increase the yield in fruit juice extraction, and also to make juice clear rather than cloudy
Pectinase breaks down the pectin chains in the middle lamellae connecting fruit cells
Pectinases and amylases can both break down these insoluble polysaccharide compounds within fruit cells, releasing soluble sugars which clarify the juice producing a clearer, sweeter product.

16. Catalase Better, stronger, faster
A biological enzyme present in all living cells exposed to oxygen
‘Extremely high turnover number’
Catalase instantaneously degrades hydrogen peroxide into water and oxygen

17. What does hydrogen peroxide do in the body?
H2O2 is a strong oxidising agent produced as a by-product of metabolism
Can damage cells – can break DNA, cell membrane, proteins and lipids

18. When do we use hydrogen peroxide commercially?
Bleach
stain remover
Wound treatment (?)

19. Where is Hydrogen peroxide located?

20. Your Research Challenge
Investigate the effect of yeast (saccharomyces cerevesiae) catalase enzyme concentration on) the rate if breakdown of hydrogen peroxide using quantitative methods p. 44 of your IGCSE book

21. What is the hypothesis you are going to test?
Research Question: Does catalase concentration affect the rate at which catalase breaks down H2O2? What is the hypothesis you are going to test? Quantitative experiment How can we measure the rate at which catalase breaks down H2O2?

22. Does enzyme concentration affect the rate at which catalase breaks down H2O2?
Working Observation

23. Experimental Design
Working Observation: As enzyme concentration increases, the rate of breakdown of H2O2 by catalase should increase
(Null hypothesis: a change in enzyme concentration has no effect on the rate of H2O2 decomposition by catalase does not change)
(Alternative hypothesis: enzyme concentration is directly related to the rate of H2O2 decomposition by catalase )

24. Quantitative experiment
How can we measure the rate at which catalase breaks down H2O2?
Quantity of oxygen produced over a set time (volume, %, pressure)

25. Starting questions
What apparatus and other materials will you need for your experiment?

26. A few starting questions:
How exactly will you ‘measure’ the reaction between H2O2 and catalase??

27. How exactly will we ‘measure’ the reaction between H2O2 and catalase?
We will measure the rate of reaction between catalase and hydrogen peroxide indirectly by measuring the pressure change in a closed chamber, using a Vernier Gas pressure probe

28. Data Collection

29. Uncontrolled variables
Catalase experiment
Dependent Variable
Independent Variable
Controlled variables
Uncontrolled variables

30. Uncontrolled variables
Catalase experiment
Dependent Variable
Gas pressure produced by in closed chamber
Independent Variable
Catalase concentration %
Controlled variables pH
Temperature
Substrate concentration
Uncontrolled variables
Human error – timing and measurement

31. Starting questions:
3. Can you think of other factors that may affect enzyme activity?
Substrate concentration
Temperature pH
Human error

32. Starting Questions…
How will we record our data?
“Results table?

33. …and a few questions about study design…
Which concentrations should we test? – and why?
Do you want this to be a controlled experiment? What will be the control group?
How many test groups should we have?
How many times will you repeat each test?
How will we prepare our stock catalase solutions?

34. Predictions/ Conclusions
Make a prediction about your conclusions.
Do you expect to find support for your hypothesis?
Why or Why not?