Key Area 1

Question 1

What is a metabolic pathway?

Answer 1

integrated and controlled pathways of enzyme-catalysed reactions within a cell

Question 2

What is an anabolic reaction?

Answer 2

A reaction which builds up large molecules from small molecules and requires energy

Question 3

What is a catabolic reaction?

Answer 3

A reaction which breaks down large molecules into smaller molecules and releases energy

Question 4

What are metabolic pathways controlled by?

Answer 4

1. The presence or absence of particular enzymes
2. The regulation of the rate of reaction of key enzymes

Question 5

What is induced fit?

Answer 5

When the active site changes shape to better fit the substrate after the substrate binds

Question 6

What does enzyme action do?

Answer 6

Lowers the activation energy for a reaction to proceed

Question 7

Substrate molecules and products have different affinities, why?

Answer 7

The substrate has a high affinity for the active site to allow them to bind to it
the products have a low affinity to allow them to leave the active site

Question 8

What inhibitors control metabolic pathways?

Answer 8

Competitive, non-competitive and feedback

Question 9

Describe the effect of competitive inhibitors on enzymes

Answer 9

Competitive inhibitors bind at the active site preventing the substrate from binding. Competitive inhibitions can be reversed by increasing substrate concentration

Question 10

Describe the effect of non-competitive inhibitors on enzymes

Answer 10

Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate form binding. It can’t be reversed by increasing substrate concentration

Question 11

Why is feedback inhibition need in cells

Answer 11

Feedback inhibition occurs when the end product in the metabolic pathway reaches a critical concentration. The end product then inhibits an earlier enzyme blocking the pathway and so prevents further synthesis of the end product