Lecture 8 - Cooperativity and allostery

Question 1

If we have a protein with one binding site for a ligand, the number of ligands bound per site depends on

Answer 1

1. Ligand concentration in solution
2. Binding constant, K

Question 2

The number of ligands bound per site is called the

Answer 2

fractional saturation (ϴ)

Question 3

A binding curve for a ligand and a protein with more than one binding site is _______ shape.

Answer 3

sigmoidal

Question 4

A binding curve for a ligand and a protein with one binding site is _______ shape.

Answer 4

hyperbolic

Question 5

Cooperative binding

Answer 5

The binding of one ligand to one site increases its affinity to the next site

Question 6

Cooperative binding is a property of _______ proteins

Answer 6

multisubunit

Question 7

For cooperative binding, the first binding step corresponds to a(n) ______ in Gibbs energy

Answer 7

increase

Question 8

Cooperativity is the key mechanism for

Answer 8

allosteric regulation

Question 9

Allosteric regulation is

Answer 9

the regulation of an enzyme or protein by binding an effector molecule to a site other than the enzyme’s active site

Question 10

Allosteric sites allow effectors to bind to the protein, resulting in a

Answer 10

conformational change

Question 11

Allosteric activators are

Answer 11

effectors that enhance the protein’s activity

Question 12

Allosteric inhibitors

Answer 12

effectors that decrease the protein’s activity

Question 13

The approach to saturation is controlled only by the

Answer 13

binding constant K

Question 14

Hemoglobin role

Answer 14

transport O2 from lungs to tissues

Question 15

Myoglobin role

Answer 15

O2 storage protein

Question 16

For Hill equation, n>1 is

Answer 16

positively cooperative binding

Question 17

For Hill equations, n<1 is

Answer 17

negatively cooperative binding

Question 18

For Hill equations, n=1 is

Answer 18

noncooperative binding

Question 19

In positively cooperative binding, once the ligand molecule is bound to the enzyme, its

Answer 19

affinity for other ligand molecules increases

Question 20

In negatively cooperative binding, once the ligand is bound to the enzyme, its

Answer 20

affinity for other ligand molecules decreases

Question 21

In noncooperative binding, the affinity of the enzyme for a ligand molecule

Answer 21

is not dependent on whether or not other ligand molecules are already bound

Question 22

The two models to describe how ligand binding at one site influences ligand-binding affinity at another identical site

Answer 22

1. symmetry model
2. sequential model

Question 23

Oligomer

Answer 23

a polymer whose molecules consist of relatively few repeating units

Question 24

In the symmetry model, protomers can exist in what states

Answer 24

T and R

Question 25

In the symmetry model, the ligand can bind to

Answer 25

both the T and R states

Question 26

In the symmetry model, the molecular symmetry of the protein must be

Answer 26

conserved during conformational changes

Question 27

In the symmetry model, no oligomers contain both

Answer 27

T and R states

Question 28

The ______ model allows for a more flexible interaction between a ligand and protein than the symmetry model does.

Answer 28

induced-fit

Question 29

The sequential model of cooperativity is based on the

Answer 29

induced-fit model

Question 30

The two states, T and R, stand for what?

Answer 30

tense (or taught), and relaxed

Question 31

In the sequential model, when a subunit binds oxygen, that subunit changes from the

Answer 31

T state to the R state

Question 32

In the sequential model, oligomers can contain

Answer 32

both T and R states

Question 33

In the sequential model, the most likely states are

Answer 33

the totally empty and the fully bound states

Question 34

In positive cooperativity, the binding of a ligand to one subunit

Answer 34

increases the ligand affinity of another subunit

Question 35

In negative cooperativity, the binding of a ligand (inhibitor) to one subunit

Answer 35

decreases the ligand affinity of another subunit

Question 36

The essence of the sequential model is that the protein’s ligand binding affinity

Answer 36

varies with the number of bound ligands