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A short revision

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All About EnzymesActivation Energy Lock & Key

Saturation Effect of pH Effect of Temperature

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A Catabolic Example

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reactant 1

+

reactant 2

products

e

n

e

r

g

y

Activation

energy

Course of reactionNext

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reactant 1

+

reactant 2

products

e

n

e

r

g

y

enzyme

present

+

enzyme+

enzyme

Course of reactionMenu

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Enzyme Substrate

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Lock and Key HypothesisLock and Key Hypothesis

Enzymes are 3-D molecules. They have a shape (surface configuration).

Has active sites

depressions in

molecule

of complementary shape

reactions are

catalysed after

formation

substrate

released as

products

unchanged enzyme

free to bind to

another substrate

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very inactive atvery low

temperatures

enzymes and

reactants has

very low

kinetic energy,less collisions,

less reactions

X

2X

temp. increases,

enzyme activity

decreases until

enzyme is denatured

Denaturationenzymes 3D shape

altered by high heator chemicals.

Enzyme becomes

less soluble and

coagulated.

Active sites lost.Substrate cannot fit

into active sites.

Cannot act as catalyst

Enzyme most active

at this temp. Rate of

reaction is maximum.as temp. increases, enzymeactivity increases. Every 10

degrees increase in temp.enzyme rate doubles

Enzymes and reactants have

more kinetic energy, collide

more frequently, more

reactions occur

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pH of solutions can affect enzyme activity.

Extremely LOW

and HIGH pH

causes

denaturation ofenzymes.

as pH increases,

enzyme activity

increases

At this pH, enzyme activity is maximum.

This is called optimum pH.

Different enzymes have different optimum

pH.

Enzyme activity

decreases as pH

increases after optimum

pH

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Effect of substrate & enzymeEffect of substrate & enzyme

concentration on rate of reactionconcentration on rate of reaction

Enzymes not

saturated.

Substrate

concentrationincreases, more

effective collisions

with enzymes, more

reactions catalysed.

Rate of reactionincreases with

substrate

concentration

All enzymes are saturated, no free

enzymes to act on higher amount ofsubstrates.

Enzyme concentration = limiting

factor

At all times,

all enzymes are acting on

substrates.

No free enzymes.

Maximum rate of reaction for this

concentration of enzymes

Higher enzyme concentration.

More enzymes in solution.

More substrates that can beacted on and more products

formed per unit time.

Rate increases significantly.

However, will still reach a plateauwhen all enzymes are being

used.

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