1

ENZYMEENZYME

2

Lesson 1

Learning Objective1.Define enzymes as proteins that function as biological

catalysts.Outline Enzyme Metabolic reaction Enzyme structure Substrate and product

3

Enzyme

A protein that can speed up the rate of metabolic reaction without itself being

changed at the end of the reaction.

It is also known as biological catalyst.

4

Examples of Enzymes

Carbohydrase

Lipase

Protease

Catalase

Amylase

Starch Phosphorylase

Enzymes are commonly named by “-ase” ending

5

Metabolic reaction refers to all the chemical reactions within a living organism

Metabolic Reaction

METABOLISM = ANABOLISM + CATABOLISMMETABOLISM = ANABOLISM + CATABOLISM

'Build up' reaction 'Break down' reaction

6

Ana & The Cat

7

Ana & The Cat

8

Examples of Catabolic Reaction

Proteins Amino acids

Starch Maltose

Fats Fatty acids + Glycerol

Protease

Amylase

Lipase

9

Examples of Anabolic Reaction

Glucose Starch

Starch phosphorylase

10

Enzyme is Important

Many metabolic reactions are controlled by enzyme. Enzyme is vital in maintaining the normal functioning in

an organism. It is more important than the air you breath, the water

you drink and the food you eat. Without enzyme, reactions would be so slow they

could not occur properly. This may result in death.

11

Roles of Enzyme

Enzymes have roles in

Digestion Germination of seeds Photosynthesis Etc.

12

Enzyme structure

13

Enzyme structure

14

Enzyme structureEnzyme is a protein.

It has a very specific shape. It has a 'dent' This 'dent' is called the active site This active site is exactly the right shape and size for

the substrate to fit in.

15

Substrate and product

A chemical reaction always involve changing one substance into another.

Substrate is a substance which is present at the start of a reaction

Product is a substance which is present at the end of a reaction

Amylase

Starch Maltose

16

Group Discussion:

1.Based on the definition of enzyme, explain why enzymes can be reused over and over again?

2.Digestion and photosynthesis are two of the many reactions that are catalysed by enzymes. Are they catabolic or anabolic reactions? Explain.

17

Lesson 2

Learning Objective1.Explain enzyme action in terms of of the 'lock

and key' hypothesis.Outline Active site and substrate Lock and key hypothesis

18

Active Site and Substrate

Each enzyme has its own active site which has exactly the right shape and size for the substrate to fit in.

Enzyme is very specific.

19

Substrate

Enzyme

ZYX

A CB

20

Lock and Key Hypothesis

The reaction between enzyme and substrate is called the lock and key hypothesis.

Substrate Enzyme

21

Lock and Key Hypothesis

LEKS

Lock = EnzymeKey = Substrate

22

Lock and Key Hypothesis

23

Lock and Key Hypothesis

Substrate binds with enzyme at the active site

Stage 1:

24

Lock and Key Hypothesis

Enzyme-substrate complex is formed.At this stage, enzyme breaks down the substrate.

Stage 2:

25

Lock and Key Hypothesis

Products are formed and they leave the enzyme.Enzyme is ready to bind with another substrate.

Stage 3:

26

Lock and Key Hypothesis

Catabolic reaction

27

Group Activity

• 1 group – 4 or 5 students• Design a lock and key hypothesis for an

anabolic reaction on a piece of paper.– Label the enzyme, active site, substrate,

enzyme-substrate complex and product.– Write a brief explanation for each stage.

28

Anabolic reaction

Lock and Key Hypothesis

Substrates bind with enzyme at the active

site

Enzyme – substrate complex is formed.

At this stage, enzyme combines the

substrates together.

Product is formed andit leaves the enzyme.

Enzyme is ready to bind with another

substrate

29

Past Year Question

30

Past Year Question

31

Past Year QuestionThe figure below shows, in order, four stages in which an enzyme-

controlled chemical reaction may occur.

a) Identify M, N, O and P

b) By referring to the figure, explain why only a small amount of enzyme is needed to catalyse a reaction involving many molecules.

32

Lesson 3

Learning Objective1.Investigate and describe the effect of

temperature and of pH on enzyme activity.Outline Characteristics of enzyme

– Enzymes are temperature-sensitive.– Enzymes are pH-sensitive.

33

Characteristics of Enzymes

Enzymes are Very specific

Enzymes areproteins

Enzymes are catalysts

Enzymes are affected by..

Enzymeconcentration

SubstrateconcentrationpHTemperature

34

Enzyme is temperature-sensitive

35

Enzyme is temperature-sensitive• Enzymes have an optimum temperature at which they function

very effectively.

• At low temperatures, enzymes are inactive.

• As the temperature increases, the rate of reaction increases.

– Enzymes gain kinetic energy– They move faster and collide more with substrates, forming

enzyme-substrate complex.• Beyond the optimum temperature, the enzyme activity decreases

as the enzyme is denatured.

– Very high temperature changes the structure of the active site.

– Substrate cannot fit into active site.– No enzyme-substrate complex formed.

36

Enzyme is temperature-sensitive

37

Enzyme is pH-sensitive

• Enzymes are affected by the acidity or alkalinity of solutions.

• Some work best in acidic environment (eg pepsin)

• Some work best in alkaline environment (intestinal enzymes eg lipase)

• Extreme changes in pH can denature the enzymes.

38

Enzyme is pH-sensitive

Enzyme Optimum pH

Amylase 7

Enzyme in stomach, eg. pepsin

2

Enzyme in intestine,eg. lipase

8

39

Enzyme is pH-sensitive

40

Group Activity

• Find a partner• Draw a graph showing the effect of pH on the

activity of the following enzymes:– Amylase– Pepsin (in stomach)– Lipase (in intestine)

41

Past Year Question

42

Past Year QuestionThe diagrams represent an enzyme molecule and its substrate. Which

diagram shows these molecules after they are heated to 100ºC?

43

Past Year Question

44

Lesson 4

Outline Characteristics of enzyme

– Enzymes are affected by • substrate concentration• enzyme concentration.

45

Substrate Concentration

46

Substrate Concentration

• As the substrate concentration increases, the speed of enzyme reaction also increases.

• But, there comes a time when any more increase in the substrate concentration does not increase the speed of enzyme reaction.

Why?

47

Substrate Concentration

• At low substrate concentrations, collisions between enzymes and substrates are infrequent and reaction proceeds slowly.

substrate enzymes

48

Substrate Concentration

• As the substrate concentration increases, the rate of reaction initially increases because collisions between enzymes and substrates become more frequent.

substrate enzymes

49

Substrate Concentration

• What do you think happen if there is a further increase in substrate concentration?

substrate enzymes

50

Group ActivityDraw a graph showing the effect of enzyme

concentration on enzyme activity.

Think of how many enzyme-substrate complex formed when there is less/more enzyme

molecules present.

51

Substrate Concentration

• What do you think happen if there is a further increase in substrate concentration?

substrate enzymes

52

Lesson 4

Outline Enzymes in germinating seed

53

Enzymes in Germinating Seed

Germination is the growing of young plant.

54

Enzymes in Germinating Seed

• Germination begins with water absorption.• Water activates the enzymes in the seed.• Enzymes digest the food stored in the seed into

smaller soluble substances.Complex food Enzyme Digested food

Starch Carbohydrase Simple sugars

Proteins Protease Amino acids

Oils Lipase Fatty acids and glycerol

55

Past Year Question