Topic 1: Metabolic Pathways

Question 1

What is metabolism?

Answer 1

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

Question 2

What is anabolism?

Answer 2

A process that builds up large molecules from smaller molecules - requires energy

Question 3

What is catabolism?

Answer 3

The breakdown of large molecules into smaller molecules - releases energy

Question 4

What is the cell membrane structure?

Answer 4

A phospholipid bilayer with embedded proteins

Question 5

What do you membrane proteins include?

Answer 5

Pores (diffusion and osmosis)
Pumps (active transport)
enzymes (catalyse reactions at membrane)

Question 6

What are metabolic pathways controlled by?

Answer 6

Presence or absence of a particular enzyme

Question 7

How else can metabolic pathways be controlled by?

Answer 7

The regulation of the rate of reaction of key enzymes

Question 8

What does the affinity of substrate molecules for the active site determine?

Answer 8

The rate of reaction

Question 9

What is induced fit?

Answer 9

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

Question 10

What is the role of the active site?

Answer 10

1. It orientates the reactants so that they are aligned correctly relative to one another
2. It lowers the activation energy of the transition state
3. It releases the products as they have a low affinity for the active site

Question 11

What affinity to the substrate molecules have for the active site?

Answer 11

Substrate molecules have a high affinity for the active site

Question 12

What affinity do the product molecules have for the active site?

Answer 12

The product molecules have low affinity for the active site, allowing them to leave

Question 13

What effect can the presence or absence of the substrate have on a metabolic reaction?

Answer 13

It can drive a sequence of reactions in a particular direction

Question 14

Why are genes for some enzymes continuously expressed?

Answer 14

So enzymes are always present in the cell and must be controlled through the regulation of the rates of reaction

Question 15

How are metabolic pathways controlled?

Answer 15

Competitive, non-competitive and feedback inhibition of enzymes

Question 16

What is a competitive inhibitor?

Answer 16

They resemble the substrate and bind up the active site preventing the desired substrate from binding

Question 17

How can competitive inhibition be reversed?

Answer 17

By increasing the desired substrate concentration

Question 18

What is a non-competitive inhibitor?

Answer 18

They bind away from the active site but change the shape of the active site preventing the desired substrate from binding

Question 19

Can non-competitive inhibition be reversed?

Answer 19

Non-competitive inhibition cannot be reversed by increasing the substrate concentration

Question 20

What is feedback inhibition?

Answer 20

It’s when the end product in the metabolic pathway reaches a Critical concentration

Question 21

What happens to the end product in feedback inhibition?

Answer 21

The end product inhibits an earlier enzyme to block the pathway so prevents further synthesis of the end product