Protein Function: Oxygen Binding proteins

Question 1

What do many protein functions involve?

Answer 1

the reversible binding of ligands (partner molecules).

Question 2

What is the function of ligands?

Answer 2

bind to specific locations called binding sites whose 3D structure and properties complement those of the ligand (size, shape, hydrophobicity, charge etc.)

Question 3

How could the ligand interactions be described?

Answer 3

specific–> the protein can discriminate between thousands of different molecules it encounters

Question 4

What may ligand binding also involve?

Answer 4

conformational change –> induced fit

Question 5

02 is a _____ molecule and poorly soluble in _______ solution

Answer 5

non polar, aqueous

Question 6

Diffusion of 02 into tissues is ______

Answer 6

inefficient

Question 7

What is Myoglobin?

Answer 7

a simple 02 binding protein of mammalian muscle tissues

Question 8

How is oxygen transported around the body?

Answer 8

via Haemoglobin

Question 9

Describe the Quaternary structure of Haemoglobin

Answer 9

-A tetramer with a a2B2 structure
-a-subunit contains 141 amino acids
-B subunit contains 146 amino acids

Question 10

What does Oxygen binding lead to? What binding behaviour could it be described as?

Answer 10

conformational changes–> allosteric behaviour

Question 11

What does the change in structure do?

Answer 11

the affinity of the molecule for it’s ligand

Question 12

What does this binding break?

Answer 12

a salt bridge

Question 13

What are the 2 states of tetramers?

Answer 13

-Low affinity state
-High affinity state

Question 14

How could the binding curve be described as?

Answer 14

sigmoidal

Question 15

How could the curve also be described? Why?

Answer 15

a hybrid curve reflecting the transition from a low-affinity to a high-affinity state

Question 16

What does co-operative binding render haemoglobin as?

Answer 16

more sensitive to the small changes in P02 between the tissues and the lungs

Question 17

What does this allow?

Answer 17

this allows haemoglobin to bind to oxygen in the lungs (high PO2) and release it in the tissues (low PO2).

Question 18

What does Myoglobin bind to?

Answer 18

O2 readily but becomes saturated at a low PO2

Question 19

Haemoglobin is_____ to take up O2 at first; its affinity____ with O2 uptake

Answer 19

reluctant, increases

Question 20

In the lungs, both proteins would be____ with O2

Answer 20

saturated

Question 21

Carbon dioxide does not bind in the place of_____

Answer 21

oxygen

Question 22

What binds at an extremely high affinity in the place of oxygen?

Answer 22

carbon monoxide

Question 23

Describe the Bohr curve

Answer 23

-Low PH shifts the 02 binding curve
-In muscle high (H+) and CO decrease the affinity of Hb for O2
-In lungs high (O2) drives off bound H+

Question 24

What is 02 binding regulated by?

Answer 24

2,3 bisphosphoglycerate

Question 25

Describe foetal haemoglobin

Answer 25

higher affinity for oxygen so that oxygen can diffuse from mother to child

Question 26

What does the term "allosteric effects" refer to in proteins?

Answer 26

Changes in protein structure that affect ligand affinity, often seen in multi-subunit proteins

Question 27

How does oxygen binding affect haemoglobin's structure?

Answer 27

Oxygen binding induces conformational changes that stabilise the R-state (high affinity).

Question 28

What is the significance of the dissociation constant (Kd)?

Answer 28

Kd reflects the affinity between a protein and its ligand; lower Kd indicates higher affinity.

Question 29

Why is fetal haemoglobin important?

Answer 29

It allows for efficient oxygen transfer from the mother, as fetal lungs are not used for breathing.

Question 30

What is the most common single gene disorder in Black Americans?

Answer 30

Sickle cell anemia, occurring in approximately 1 in 375 individuals.