1m- Ligand binding changes the conformation of a protein

Question 1

What is a ligand?

Answer 1

A substance that can bind to a protein

Question 2

R groups are not involved in protein folding but can allow what ?

Answer 2

Binding to ligands

Question 3

What will a binding site have for its ligand?

Answer 3

A complementary shape and chemistry to the ligand

Question 4

What happens to a protein-binding site as a ligand binds, and what does this cause?

Answer 4

The conformation of the protein changes, this causes a functional change in the protein

Question 5

What do allosteric interactions occur between?

Answer 5

Spatially distinct sites

Question 6

What does the binding of a substrate molecule to one active site of an allosteric enzyme cause to happen, and why is this of biological importance?

Answer 6

The affinity of the other active sites for binding of subsequent substrate molecules increases, this is of biological importance because the activity of allosteric enzymes can vary greatly with small changes in substrate concentration

Question 7

What do many allosteric proteins consist of?

Answer 7

Multiple subunits (have quarternary structure)

Question 8

What do allosteric proteins with multiple subunits show when binding?

Answer 8

They show co-operativity in binding, in which changes in binding at one subunit alter the affinity of the remaining subunits

Question 9

Allosteric enzymes contain a second type of site, what is this called?

Answer 9

An allosteric site

Question 10

What do modulators do?

Answer 10

Regulate the activity of the enzyme when they bind to the allosteric site

Question 11

What happens following the binding of a modulator to an enzyme?

Answer 11

The conformation of the enzyme changes and this alters the affinity of the active for the substate

Question 12

What is the difference between positive and negative modulators?

Answer 12

Positive modulators increase the enzymes affinity for the substrate, whereas negative modulators reduce the enzymes affinity

Question 13

What is an example of co-operativity?

Answer 13

The binding and release of oxygen in haemoglobin, changes in binding of oxygen at one subunit alter the affinity of the remaining subunits for oxygen

Question 14

What can lower the affinity of haemoglobin for oxygen and why is this important?

Answer 14

A decrease in pH or an increase in temperature lower the affinity of haemoglobin for oxygen, this will reduce the binding of oxygen to haemoglobin promoting increased oxygen delivery to tissue