KA6- Metabolic Pathways

Question 1

Metabolic pathways

Answer 1

are integrated and controlled pathways of enzyme-catalysed reactions within a cell.
can have reversible steps, irreversible steps and alternative routes.

Question 2

Reactions within metabolic pathways

Answer 2

can be anabolic or catabolic.
Anabolic reactions build up large molecules from small molecules and require energy.
Catabolic reactions break down large molecules into smaller molecules and release energy.

Question 3

Metabolic pathways are controlled by

Answer 3

the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes

Question 4

The effects of substrate and product concentration on the direction and rate of enzyme reactions

Answer 4

Some metabolic reactions are reversible and the presence of a substrate or the removal of a product will drive a sequence of reactions in a particular direction

Question 5

Control of metabolic pathways through competitive inhibition of enzymes

Answer 5

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

Question 6

Control of metabolic pathways through non-competitive inhibition of enzymes

Answer 6

Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate from binding.
Non-competitive inhibition cannot be reversed by increasing substrate concentration.

Question 7

Control of metabolic pathways through feedback inhibition of enzymes

Answer 7

Feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical concentration.
The end-product then inhibits an earlier enzyme (1), blocking the pathway, and so prevents further synthesis of the end product.
Prevents conversion from first to second