1. Enzymes
Department of Biochemistry
Foundation Module – Phase: 1

2. Energy from breaking bonds in this molecule is used to form ATP
Energy from breaking bonds in this molecule is used to form ATP
Energy
ATP
ADP + Pi
ATP
Energy

3. Energy
The energy in ATP can be used to form bonds in other molecules.
ATP
ADP + Pi
Energy

4. An anabolic reaction
A catabolic reaction
Energy
ATP
ADP + Pi
Energy

5. Substrates (Reactants)
Anabolic Reactions
Products
Energy Supplied
Anabolic reactions consume energy.
Energy Released
Substrates (Reactants)

6. Catabolic Reactions Substrate (Reactant) Energy Supplied
Catabolic reactions release energy.
Energy Released
When bonds are broken, energy is released.

7. Activation Energy Activation Energy Energy Supplied
In either kind of reaction, additional energy must be supplied to start the reaction. This energy is called activation energy.
Energy Released

8. Enzymes Lower Activation Energy
Enzymes lower the amount of activation energy needed for a reaction.
Enzymes Lower Activation Energy
Activation energy without enzyme
Energy Supplied
Activation energy
with enzyme
Energy Released

9. Essential of Enzyme Kinetics
Steady State Theory E E E + + P S S
In steady state, the production and consumption of the transition state proceed at the same rate. So the
concentration of transition state keeps a constant.

10. Relationship between Enzyme Substrate product

11. Introducing the intermediate

12. Effect of Temperature on Enzyme Activity
30   40   50 

13. Effect of Temperature on Enzyme Activity
30   40   50
Increasing the temperature causes more collisions between substrate and enzyme molecules. The rate of reaction therefore increases as the temperature increases.
Arrhenius Effect

14. Enzymes denature when the temperature gets too high. The rate of reaction decreases as the enzyme becomes non functional
30   40   50

15. Effect of pH on Enzyme Activity
Each enzyme has its own optimum pH
Pepsin          Trypsin
Rate of Reaction
 1   2  3  4  5  6  7   8   9 pH

16. S + E ↓ P Product Substrate (mole) Increase Substrate Concentration 11 2 3 4 5 6 7 8 S + E ↓ P 80 60 40 20
Product
(in a fixed period of time)
Substrate (mole)

17. Constant ES Concentration at Steady StateP
Concentration ES E
Reaction Time

18. Enzyme Kinetics When y = 1/2 Vmax , x ([S]) → Km Vmax 1 vo vo 1/2 1/S
- 1 Km 1
Vmax
1/S Km S
Double reciprocal
"Lineweaver Burk plot"
Direct plot

19. Enzyme Kinetics V˳ =Vmax Km=[S] Km Vmax Direct plot 2 Non-competitive
Double reciprocal
Inhibition
Maximum
velocity
Affinity with
substrate

20. Km: Affinity with Substrate
Vmax
If vo = 2
When using different substrate
Km = [S]
Vmax S2 S1 S3
Km  1/ affinity
1/2
S1 S2 S3
Km1 Km2 Km3
Affinity changes

21. Enzyme Inhibition (Mechanism)
Competitive
Non-competitive
Substrate E
Cartoon Guide
Compete for
active site
Inhibitor
Different site
E + S → ES → E + P + I ↓ EI
E + S → ES → E + P
+ +
I I
↓ ↓
IE + S →IES ← ←
Equation  ↑ ↑ ↑
[I] binds to free [E] only,
and competes with [S];
increasing [S] overcomes
Inhibition by [I].
[I] binds to free [E] or [ES]
complex; Increasing [S] can
not overcome [I] inhibition.
Description

22. Questions

23. Q:1 What is shown here? Label A, B and C

24. 1
Q:2
Identify 1 - 5 2 3 5 4

25. Q:3
A similar-shaped molecule is competing with the substrate for active sites.
What is this inhibition?

26. Feedback Inhibition A B C D X X X Q:4 Fill in the blanks
C and D will ……….. because B is needed to produce C and C is needed to produce D.
The amount of B in the cell will …………… if enzyme 1 is inhibited.
A B C D X X X
enzyme 1
enzyme 2
enzyme 3
Enzyme 1 is structured in a way that causes it to interact with D. When the amount of D ………….., enzyme 1 stops functioning.
Feedback Inhibition

27. B C A D
Q:5 Label A, B, C & D

28. Q:6 Identify the two Mechanisms of enzyme actions? ?

29. Q:7 Which point shows the saturating velocity?B C Km s

30. Q:8 a.What is the role of Co2+

31. Q:8 b. Identify A, B and C B A C

32. Q:9
What is the
feature of
Oxygen
that is
seen here

33. A
Q:10 Fill in the blanks
‘A’ shows, the rate of reaction against ………………. or ……………. and
'B' may be the rate of reaction against ………. or ………. B

34. Q:11  Identify the types of inhibitions

36. A:1  ATP
3 phosphate groups
Base (adenine) A
Sugar (ribose)

37. 4 Substrate-Enzyme Complex 5 Products
1 Substrate
2 Active site
3 Enzyme
4 Substrate-Enzyme Complex
5 Products

38. A:3 Competitive Inhibition

39. Feedback Inhibition A:4 A B C D X X X
C and D will decrease because B is needed to produce C and C is needed to produce D.
The amount of B in the cell will decrease if enzyme 1 is inhibited.
A B C D X X X
enzyme 1
enzyme 2
enzyme 3
Enzyme 1 is structured in a way that causes it to interact with D. When the amount of D increases, the enzyme stops functioning.

40. A:5

41. A:6

42. A:7 Saturating velocity = Vmax Km s

43. A:8 a. Co2+ acts as a co-factor

44. A:8 b.

45. A:9
Cooperativity

46. A
A:10
‘A’ shows, rate of reaction against temperature, and B may be rate of reaction against substrate concentration (enzyme concentration is limiting)Or enzyme concentration (substrate concentration is limiting) B

47. A:11