Regulation Of Protein Function

Question 1

What are the ways to regulate enzyme activities in the short term?

Answer 1

Substrate product concentration
Change in enzyme conformation:
- allosteric regulation
- covalent modification
- proteolytic cleavage

Question 2

What are the ways to regulate enzyme activity in the long term?

Answer 2

Change in rate of protein synthesis

Change in rate of protein degradation

Question 3

What are isoenzymes?

Answer 3

Different forms of the same enzyme that have different kinetic properties

Question 4

What is product inhibition?

Answer 4

Accumulation of product of reaction inhibits forward reaction
E.g. glucose-6-phosphate inhibits hexokinase activity

Question 5

How is the graph for allosteric enzymes different to simple enzymes?

Answer 5

Allosteric show a sigmoid relationship between rate and substrate concentration, simples show rectangular hyperbola

Question 6

What do allosteric activators do?

Answer 6

Increase the proportion of enzyme in R state (high affinity)

Question 7

What do allosteric inhibitors do?

Answer 7

Increase the proportion of enzyme in T state (low affinity)

Question 8

Why is protein phosphorylation (covalent modification) so effective?

Answer 8

Adds 2 negative charges
A phosphoryl group can make H bonds
Rate of phosphorylation/dephosphorylation can be adjusted
Links energy status of cell to metabolism through ATP
Allow for amplification effects