Enzymes

Question 1

What is an Enzyme?

Answer 1

Enzymes are proteins with a specific tertiary structure.

Question 2

What is the active site of an enzyme and what is it’s function?

Answer 2

It is the functional part of the enzyme that binds to the substrate by becoming complementary to the shape of the substrate. This allows the formation of an Enzyme-Substrate Complex (E-S complex).

Question 3

How do enzymes affect the activation energy?

Answer 3

Enzymes lower the activation energy, due to bending bonds, allowing chemical reactions to take place at lower temperatures than they would otherwise occur (e.g. body temperature).

Question 4

Describe the INDUCED FIT model

Answer 4

Enzymes have an active site with a specific shape.
Before the reaction the active site is not complementary to the substrate.
Induced fit causes the active site to change shape and becomes complementary as substrate binds
An enzyme- substrate complex is formed
This stresses and bends the bonds in the substrate which allows the reaction to occur

Question 5

How might a change in the primary structure result in a non-functional enzyme?

Answer 5

A change in amino acid sequence results in different R groups
Results in a change in hydrogen / ionic / disulfide bonds
Which results in a change in the tertiary structure
Which changes the shape of the active site;
Substrate is not complementary to the active site so no enzyme-substrate complexes form.

Question 6

Draw the graph for temp on rate of reaction for enzymes and explain it.

Answer 6

Check ss1.4.2 for graphs.
As temp increases rate of reaction increases
- E and S have more energy
- so there are more collisions
- more E-S complexes formed per second
When temperature exceeds optimum, the rate of reaction decreases
H bonds break so tertiary structure changes so shape of active site changes so less E-S complexes can form.