Metabolic pathways

Question 1

Summary

Answer 1

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

Metabolic pathways can have reversible steps, irreversible steps and alternative routes.

Question 2

Anabolic reactions

Answer 2

Anabolic reactions build up large molecules from small molecules and require energy.

Question 3

Catabolic reactions

Answer 3

Catabolic reactions break down large molecules into smaller molecules and release energy.

Question 4

Metabolic pathways control

Answer 4

Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes.

Question 5

Induced Fit

Answer 5

Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds.

Question 6

Affinity (First date and break up)

Answer 6

substrate molecule(s) have a high affinity for the active site and the subsequent products have a low affinity allowing them to leave the active site.

Question 7

Activation Energy

Answer 7

(The binding of the enzyme to its substrate also lowers the activation energy of the reaction (amount of energy needed to make a reaction happen).

If an enzyme is present, the amount of energy needed to make a product is lowered. As the products are made, they are no longer specific to the active site (they have a low affinity to the enzyme) and so are released.) Context

You need to understand that when an enzyme binds to a substrate it lowers the activation energy for the reaction. that’s all.

Question 8

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

Answer 8

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 9

Competitive Inhibition

Answer 9

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

Question 10

Non comepetitive inhibition

Answer 10

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 11

Feedback inhibition

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.