Metabolic Pathways

Question 1

What do we call integrated and controlled pathways of enzyme-catalysed reactions in a cell?

Answer 1

Metabolic pathways

Question 2

What is metabolism?

Answer 2

All the chemical reactions that take place within an organism

Question 3

Tell me 2 things about anabolic reactions.

Answer 3

1. build up larger molecules from smaller molecules

2. Require energy

Question 4

If a step within a metabolic pathway is one-way is is described as…

Answer 4

irreversible

Question 5

If a product can be converted back into a substrate within a pathway, it is described as…?

Answer 5

reversible

Question 6

With the induced fit model, what is it that changes shape?

Answer 6

The active site of the enzyme

Question 7

There isn’t always one way to get to the same end product. If there is a different pathway, what do we call it?

Answer 7

An alternative route

Question 8

Tell me 2 things about a catabolic reaction.

Answer 8

1. Breaks down larger molecules into smaller molecules

2. Releases energy

Question 9

‘Lock and Key’ in Nat 5 was a lie!!! What is a better model for how an enzyme works?

Answer 9

induced fit model

Question 10

State 3 functions of proteins embedded within the cell membrane.

Answer 10

1. Protein pores (diffusion)
2. Protein pumps (active transport)
3. Enzymes

Question 11

If there is a mutation to a gene that controls the production of an enzyme, how would that affect the concentration of substrate and product?

Answer 11

Substrate would probably increase

Product would probably decrease (enzyme not present to carry out the reaction)

Question 12

What does the term affinity mean?

Answer 12

an attraction

Question 13

What is the affinity between an enzyme and its substrate.

Answer 13

High

Question 14

What is the affinity between an enzyme and its product.

Answer 14

Low

Question 15

What do we call the energy required to initiate a reaction?

Answer 15

Activation energy

Question 16

How does an enzyme affect the activation energy for a reaction?

Answer 16

It lowers the activation energy

Question 17

State the 3 roles of the active site.

Answer 17

1. It orientates reactants and is a binding site for reactants (high affinity for substrates)
2. It decreases the activation energy
3. It releases products with low affinity

Question 18

State 5 factors that can affect enzyme activity.

Answer 18

1. temperature
2. pH
3. Enzyme concentration
4. substrate concentration
5. end product inhibition

Question 19

Describe how increasing substrate concentration affects the rate of a reaction (2)

Answer 19

As the substrate concentration increases initially the rate of reaction increases and then rate of reaction levels out and remains the same.

Question 20

Explain why continually increasing the substrate concentration does not continually increase the rate of reaction.

Answer 20

The enzymes reach saturation point - all the enzyme active sites are occupied.

Question 21

In end product inhibition, what does the end product inhibit?

Answer 21

An enzyme at the start of the metabolic pathway

Question 22

What is end product inhibition also known as?

Answer 22

Feedback inhibition

Question 23

When does feedback inhibition take place?

Answer 23

When the end product reaches a critical concentration.

Question 24

It the concentration of the end product decreases to below the critical concentration, what happens?

Answer 24

The enzyme at the start of the metabolic pathway is no longer inhibited.

Question 25

What do we call substances that prevent enzyme activity?

Answer 25

inhibitors

Question 26

Where does a competitive inhibitor join onto an enzyme?

Answer 26

active site

Question 27

Why is a competitive inhibitor able to join to the active site of an enzyme?

Answer 27

It has a similar shape to the substrate

Question 28

What is the result of the competitive inhibitor attaching to the active site?

Answer 28

It blocks the active site so no enzyme-substrate complex can be produced so the reaction rate is reduced

Question 29

Why is a competitive inhibitor described an a reversible reaction?

Answer 29

When the inhibitor is released from the active site, the substrate can once again interact with the enzyme

Question 30

How can you reduce the effect of a competitive inhibitor?

Answer 30

Increase the concentration of substrate, there is more chance of the substrate winning the competition and combining with the active site

Question 31

Where does a non-competitive inhibitor join to an enzyme?

Answer 31

The allosteric site, somewhere else on the enzyme

NOT the active site

Question 32

Why does a non-competitive inhibitor joining to the allosteric site affect the rate of a reaction?

Answer 32

It causes the active site of the enzyme to alter its shape, no longer complementary to the substrate

Question 33

How does increasing the concentration of substrate affect a non-competitive inhibitor?

Answer 33

It doesn’t

Question 34

Why is a non-competitive inhibitor described as reversible?

Answer 34

Once the inhibitor is released, the active site is restored to its original shape