1. What are they?
Enzymes
Why do we need them?
Name some examples ?

2. Enzymes Globular proteins that catalyse chemical
reactions in living organisms

3. Enzymes Globular proteins that catalyse chemical
reactions in living organisms
Properties
Specific
Increase rate of the reaction
Unchanged at the end of the reaction

4. Enzymes Need them because... Reactions too slow to maintain life
Can’t increase temperatures/pressure
in cells (fatal)

5. Enzymes Are Proteins The enzyme binds to the substrates
by its active site
The active site is a pocket formed by the folding of the protein
where the substrates bind.

6. Enzymes Are Proteins
The enzyme binds to the substrates by its active site
The active site is a pocket formed by the folding of the protein
where the substrates bind.

7. Active site
The active site involves a small number of key residues that actually bind thesubstrates
The rest of the protein structure is needed to maintain these residues in position

8. Lock and Key

9. Enzyme reactions
enzyme + substrate
enzyme-substrate complex

10. Enzyme reactions
enzyme + substrate
enzyme-substrate complex
E +S ES

11. Enzyme reactions enzyme + substrate enzyme-substrate complex E +S ES
enzyme + product
enzyme-substrate complex ES
E +P

12. How do enzymes work?

13. An Example

14. An Example
Sucrose + H2O
Glucose + Fructose

15. An Example
Substrates
Sucrose + H2O
Glucose + Fructose
Products

16. For a reaction to occur the sucrose
and water would have to collide with
enough energy to break and form bonds
This is the activation energy

17. Sucrose + H2O
Glucose + Fructose + +
Substrates
Products

18. Energy
Progress of reaction

19. Energy
Substrates
Progress of reaction

20. Energy
Substrates
Products
Progress of reaction

21. Energy Progress of reaction High energy intermediate Substrates
Products
Progress of reaction

22. Activation energy Energy Progress of reaction High energy intermediate
Substrates
Products
Progress of reaction

23. = The Activation energy
The minimum amount of energy needed to start the reaction, leading to the formation of a high energy intermediate
= The Activation energy

24. Activation energy Enzymes reduce the height of the energy barrier
High energy
intermediate
Activation energy
Enzymes reduce the
height of the energy
barrier
Energy
Substrates
Products
Progress of reaction

25. How fast an enzyme is working
Enzyme activity
How fast an enzyme is working
Rate of Reaction
Rate of Reaction = Amount of substrate changed (or amount product formed)
in a given period of time.

26. Enzyme activity Temperature pH Four Variables Enzyme Concentration
Substrate Concentration

27. Temperature 5- 40oC Increase in Activity 40oC - denatures
Rate of Reaction 10 20 30 40 50 60
<5oC - inactive

28. Effect of heat on enzyme activty
If you heat the protein above its optimal temperature
bonds break
meaning the protein loses it secondary and tertiary structure

29. ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS
Effect of heat on enzyme activty
Denaturing the protein
ACTIVE SITE CHANGES SHAPE
SO SUBSTRATE NO LONGER FITS
Even if temperature lowered – enzyme can’t regain its correct shape

30. Effect charged residues at activepH
Narrow pH optima
Disrupt Ionic bonds - Structure
Rate of Reaction
Effect charged residues at active
site 1 2 3 4 5 6 7 8 9

31. Enzyme Concentration
Rate of Reaction
Enzyme Concentration

32. Substrate Concentration
Active sites full- maximum turnover
Rate of Reaction
Substrate Concentration

33. What is digestion?
Breaking down large, insoluble molecules into smaller, soluble molecules that can be absorbed through the wall of the small intestine
What breaks down the large molecules?
Digestive enzymes made by specialised cells inside glands

34. Some enzymes are... Amylase Carbohydrates Protease Proteins
Lipase Lipids

35. The enzymes break down... Carbohydrates Simple sugars
Proteins Amino acids
Lipids (fats) Fatty acids + glycerol
Digestion animation

36. What does bile do?
Bile is produced in the liver and stored in the gall bladder.
The enzymes in the small intestine need an alkaline pH to work best, so bile passes into the small intestine and neutralizes acid from the stomach.
Bile also emulsifies fat droplets to increase their surface area

37. Why do you think there is acid in the stomach?
Kills bacteria in food – protects us
Denatures proteins – makes digestion easier
Activates stomach enzymes – these only work in acidic conditions
Ever wondered why PEPSIN (stomach enzyme) doesn’t digest our own stomach?
Pepsin is inactive when first made and is only activated by HCL to start digesting proteins.

38. This powerpoint was kindly donated to www.worldofteaching.com
is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.