Enzyme regulation of metabolsim

Question 1

The Rate Limiting step is the ____ reaction in the pathway

Answer 1

Slowest reaction

Question 2

Which molecule is usually the rate limiting step?

Answer 2

First unique enzyme in a pathway

In a branched pathway this will occur after a branch so products can be made independently of each other

Question 3

The enzyme in a pathway with the lowest Vmax means what?

Answer 3

Rate limiting step

Question 4

State the equation for finding Mass action ratios?

Answer 4

MAR= [products]/[reactants]

(Different to Keq as here you are finding the R:S ratio within a cell

Question 5

What does MAR=Keq mean?

Answer 5

reaction close to equilibrium

Question 6

What does MAR< Keq mean?

Answer 6

Rection is rate limiting

Question 7

On a graph of [% of unsaturation] and enzyme type what does the lines crossing over indicate?

Answer 7

Regulatory step

Question 8

In glycolysis what are the limiting steps?

Answer 8

Hexokinase

Phosphofructokinase 1

Question 9

What are 3 reasons why we need to control metabolism?

Answer 9

Ensure a given metabolic pathway is active when its product is needed
Ensure competing pathways arent simultaneously active
Ensure Co-ordinated activity in multiple related pathways

Question 10

What is a futile cycle?

Answer 10

wo metabolic pathways run simultaneously in opposite directions and have no overall effect other than to dissipate energy in the form of heat.

Question 11

Name 3 types of enzyme regulation

Answer 11

1) Intrinsic control by metabolites:
Allosterism/inhibitors
2) Fast extrinsic control via hormones: covalent modification
3) Slow Extrinsic Control via hormones - gene expression

Question 12

Explain how Intrinsic control by metabolites works

Answer 12

Product inhibits its own production eg G-6-P

Or Allosterism- the change in the affinity for binding of a ligand or substrate that is caused by the binding of another ligand away from the active site.
Effectively changing charges on molecules

Question 13

Link ADP and ATP to metabolism

Answer 13

ATP inhibits

ADP/AMP activates

Question 14

What can hormones alter relating to enzymes?

Answer 14

Activity of Enzymes- short lived effect of a rapid de/phosphorylation
Number of enzymes- longer lived slow via gene expression changes

Question 15

Describe how phosphorylation controls enzyme regulation

Answer 15

PHOSPHORYLATION OVERRIDES ALLOSTERISM

It causes conformational change and activation/inactivation

Question 16

How many phosphorylation sites are there in
In muscle and
In liver?

Answer 16

Phosphorylation sites:
In muscle:9
In liver:7

Question 17

Name the alleosteric regulators in muscle and the liver

Answer 17

In muscle:
+ AMP
- ATP, G-6-P

In liver:
- Glucose

Question 18

Slides 15, ETC DO THE RECORDNG WHEN IT POPS UP

Answer 18

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