Protein Function

Question 1

What part of haemoglobin does oxygen bind to?

Answer 1

Haem group

Question 2

What makes up an oxygenated haem group?

Answer 2

Protoporphyrin ring
Iron atom
A histidine residue
Oxygen

Question 3

How many amino acids make up a molecule of haemoglobin?

Answer 3

153

Question 4

When myoglobin binding to oxygen is plotted on a graph at different partial pressures of oxygen, what shape is the graph?

Answer 4

Hyperbolic

Question 5

How many and what types of sub-units is haemoglobin made up of?

Answer 5

4 subunits, 2a and 2B

Question 6

How many oxygen molecules can 1 sub-unit of haemoglobin bind to?

Answer 6

1

Question 7

In theT state, does haemoglobin have a high or low affinity for oxygen?

Answer 7

Low

Question 8

How does haemoglobin promote stabilisation when oxygen binding occurs?

Answer 8

The molecule of haemoglobin twists after every oxygen addition so it makes it easier to bind more oxygen to it.

Question 9

If haemoglobin oxygen binding was plotted on a graph, what shape would the graph show?

Answer 9

Sigmoidal, S-shaped

Question 10

What effect does BPG have on haemoglobin’s affinity for oxygen?

Answer 10

Decreases

Question 11

When are levels of BPG high in the body?

Answer 11

Eg. high altitudes

Question 12

Name 2 other molecules apart from BPG that can regulation haemoglobin’s affinity for oxygen

Answer 12

H+ and C02

Question 13

What is the Bohr Effect?

Answer 13

Metabolically active cells produce lots of H+ and C02 creating a low partial pressure. H+ and C02 bind to haemoglobin to lower the affinity for oxygen so oxygen is released. The Bohr Effect ensures that delivery of O2 is coupled to demand.

Question 14

How does carbon monoxide cause death?

Answer 14

CO binds to haemoglobin 250x more readily than oxygen so cannot be displaced. It also makes the haemoglobin molecule unable to release the oxygen molecules it is bound to. Oxygen transport is blocked.

Question 15

How can haemoglobin be used as a long term marker for diabetes?

Answer 15

Glycosylation of haemoglobin A forms HbA1c. This can be measured to see the control of sugars in the long-term

Question 16

What is special about foetal haemoglobin?

Answer 16

It has a higher affinity for oxygen than maternal blood so oxygen is transferred from the mother’s blood to the foetal blood.

Question 17

What mutation causes Sickle Cell Anaemia?

Answer 17

Glutamate to Valine (in a B-globin molecule)

Question 18

What are Thalassaemias?

Answer 18

A group of genetic disorders where there is an imbalance between the number of a and B globin chains

Question 19

When do a-thalassaemias present?

Answer 19

Before birth

Question 20

Why is a transport protein needed to transport oxygen in the blood?

Answer 20

Oxygen is non-polar so does not dissolve or diffuse well in water