Metabolism and Survival

Question 1

What is metabolism?

Answer 1

Metabolism is the total of all integrated controlled enzyme catalysed reactions that occur within a cell.

Question 2

What are metabolic pathways?

Answer 2

Metabolic pathways are integrated and controlled pathways of enzyme-catalysed reactions within a cell. They are controlled by the presence and absence of particular enzymes and the regulation of the rate of reaction of key enzymes. Metabolic pathways can have reversible steps, irreversible steps and alternative routes.

Question 3

What are the two different types of reactions within metabolic pathways?

Answer 3

Catabolic
Anabolic

Question 4

What are catabolic reactions?

Answer 4

The breakdown of complex molecules to simpler ones.
They release energy (ATP).

Question 5

What are anabolic reactions?

Answer 5

The biosynthesis of complex molecules from simpler molecules.
They require energy (ATP).

Question 6

What are the different types of membrane proteins?

Answer 6

Protein pores
Protein pumps
Enzymes in membrane

Question 7

What are protein pores?

Answer 7

Larger molecules need a channel pore to cross the membrane by diffusion.
This is passive so no ATP is required.

Question 8

What are protein pumps?

Answer 8

Transport specific ions by active transport.
This requires ATP.

Question 9

What are enzymes in the membrane?

Answer 9

Biological catalysts found in phospholipid membrane that speed up reactions but are not used up e.g. ATP synthase.

Question 10

What are enzymes?

Answer 10

Enzymes are molecules that speed up reactions as they lower the activation energy required to form products from reactants.

Question 11

What is induced fit?

Answer 11

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

Question 12

What are the steps of induced fit?

Answer 12

Substrate has high affinity for active site with the shape of the active site ensuring the correct orientation of the reactions.

Active site ensures correct orientation of substrate.

Chemical bonds in substrate weakened lowering the activation energy.

Products are released as they have a low affinity (enzyme reused as active site returns to original shape).

Question 13

What are the factors affecting enzyme activity

Answer 13

Substrate concentration
Product concentration
pH
Temperature

Question 14

What are inhibitors?

Answer 14

Molecules that decrease the rate of an enzyme controlled reaction.

Question 15

What are the different types of inhibitors?

Answer 15

Competitive inhibitors
Non-competitive inhibitors
Feedback inhibition

Question 16

What are competitive inhibitors?

Answer 16

A molecule that binds to the active site of an enzyme preventing the substrate from binding. This is a temporary blockage.

This can be reversed by increasing substrate concentration.

Question 17

What are non-competitive inhibitors?

Answer 17

A molecule that binds away from the active site but changes the shape of the active site preventing substrate from binding. This is a more permanent blockage.

This cannot be reversed by increasing substrate concentration.

Question 18

What is feedback inhibition?

Answer 18

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.