1. Unit 1 – Cell Biology
Topic 4 - Enzymes

2. From the last topic you should remember that the code held in the order of DNA bases is used to produce proteins
This section focuses on a particular group of proteins called Enzymes

3. What you need to know...
-What are enzymes?
-Where are enzymes found?
-What kind of reactions do enzymes help take place?
-What biotechnology industries are enzymes used in?

4. Enzymes allow chemical reactions to occur within cells at low temperatures (eg 370C)
3 cell processes this includes are Respiration, Photosynthesis and Digestion

5. Enzymes are molecules which speed up chemical reactions, without being changed in the process
Enzymes are found in every cell and are made of proteins.
Enzymes can build-up and break-down molecules.

6. Enzyme
Substrate (what the enzyme acts on)
Product (What is produced from the reaction)

7. Amylase
An enzyme found in your saliva.
It helps the breakdown of a large molecule called starch into small sugar molecules

8. The amylase is involved in the reaction but is not used up

9. Experiment
Set up the following:-
Test tube
5ml Starch solution + 0.5ml Amylase

10. Dimple tile
Add 2 drops of the starch and amylase mixture to each dimple

11. Test 1 dimple each minute for the presence of starch using 1 drop of Iodine
Iodine turns blue/black in the presence of starch

12. When all the starch has been broken down add 10 drops of Benedicts reagent to the test tube and place the tube in a waterbath at 700C
Benedicts reagent turns brick red/orange if sugar is presence

13. Results
Iodine – over a short time the iodine no longer turns black – the amylase has broken down all the starch
Benedicts – The starch and amylase mixture turns orange with the benedicts reagent – The amylase has produced the sugar Maltose

15. Enzymes have a shape which is complementary to the substance it is helping react. (Their shapes match)
This is why enzymes are specific, their shape only matches to one substrate
Eg. Amylase only breaks down starch
Pepsin only breaks down protein

16. As well as breaking down molecules, some enzymes can help build up bigger molecules from smaller ones. We call these synthesis reactions.

17. Phosphorylase
An enzyme found in plants which builds up starch from small glucose molecules
It can be extracted from potatoes as long as all the potato starch is removed

18. Phosphorylase
Glucose-1-phosphate
Starch

19. Experiment
Dimple tile
Row 1
Row 2
Row 3

20. Add the following to the dimples in each row
Row 1 – 2 drops potato extract + 2 drops glucose-1-phosphate
Row 2 – 2 drops potato extract + 2 drops water
Row 3 – 2 drops water + 2 drops glucose-1-phosphate

21. Test the first dimple in each row with Iodine (has starch been produced?)
Repeat every 5 minutes for the second, third and fourth dimple

22. Results
Shade in the dimple if iodine turns black
Row 1
Row 2
Row 3

23. Conclusion
The starch is only produced when the substrate (Glucose-1-phosphate) and the enzyme phosphorylase (from the potato extract) are present

24. Effect of temperature on Enzymes
Most enzymes work best at body temperature (370C)
Above this temperature, the heat affects the enzyme and its shape is permanently changed – it is denatured

25. A denatured enzyme no longer fits its substrate – the enzyme doesn’t work

26. Experiment
Pineapple contains an enzyme Bromelain which breaks down proteins
Tinned pineapple is heat treated to destroy microbes which might make the pineapple go off
Gelatine is a protein found in jelly which makes the liquid jelly set

27. Set up 2 petri dishes, one labelled fresh and one labelled tinned
Add enough jelly to each dish to cover the base
Add a segment of fresh or tinned pineapple to the appropriate labelled dish

28. Leave to set overnight

29. Results
Fresh pineapple contains the enzyme which breaks down the gelatine and the jelly does not set
Tinned pineapple allows the jelly to set as the enzyme breaking down the gelatine is destroyed

30. Enzymes in industry
Enzymes can be added to washing powders to help break down biological stains such as grass, blood, food stains etc on clothes
These are Biological detergents
They work best at low temperatures, around C

31. Experiment
Photo film has a plastic base layer and a light sensitive layer held on by a protein glue

32. Setup as follows:-
Tube A
Tube B
20ml Non-Bio detergent
20ml Bio detergent
Place both tubes into warm water for 30 minutes

33. Results
The Biological detergent contained enzymes which broke down the protein glue and separated the light sensitive layer from the plastic

34. Cheese making also uses an enzyme called Rennet
It causes milk to clot, giving solid curds to make cheese and liquid whey.
It is obtained from the stomachs of calves or from genetically engineered bacteria

35. Check test questions
1 – Name the biological substance which speeds up chemical reactions in cells but isn’t use up in the process

36. 2 – What term refers to the fact that enzymes only act on one substrate eg. Enzymes are __________
3 – What enzyme breaks down starch molecules into smaller sugars?

37. 4 – What physical property of an enzyme means that it can only work on one substrate?
5 – Why do enzymes in washing detergents help to save money? (Problem solving)

38. Check test questions
1 – Name the biological substance which speeds up chemical reactions in cells but isn’t use up in the process
Enzymes

39. 2 – What term refers to the fact that enzymes only act on one substrate eg. Enzymes are __________
Specific
3 – What enzyme breaks down starch molecules into smaller sugars?
Amylase

40. 4 – What physical property of an enzyme means that it can only work on one substrate?
Their shape
5 – Why do enzymes in washing detergents help to save money? (Problem solving)
They work at low temperatures – don’t have to use energy to heat water up as much