Haemoglobin & Myoglobin and Oxygen Transport

Question 1

What are the main differences between myoglobin and haemoglobin?

Answer 1

Myoglobin –> carries and stores oxygen in muscle cells. Haemoglobin –> carries oxygen in the blood

Question 2

Describe haem

Answer 2

Fe bound to 4 N ring, Fe can make 2 more bonds to oxygen, 1 oxygen binds each haem group

Question 3

How many subunits does haemoglobin have vs myoglobin?

Answer 3

4 vs 1

Question 4

What is the T and R state?

Answer 4

undergoes change when O2 binds, T STATE (low affinity) –> R STATE (high affinity)

Question 5

Describe cooperative binding

Answer 5

O2 binding = conformational change = increases affinity for O2 = stabilisation of R State. 1st O2 = low affinity, by 4th O2 = high affinity

Question 6

Describe the myoglobin haemoglobin graph

Answer 6

Myoglobin affinity for oxygen = higher, Hb affinity for oxygen = lower

Shift curve to let = higher affinity, Shift curve to the right = lower affinity

Hb lower affinity than myoglobin in tissues means it will give the oxygen away. Higher affinity in the lungs means it will readily bind oxygen

Question 7

How does BPG (bisphosphoglycerate) regulated oxygen binding?

Answer 7

lowers affinity

people at higher altitudes = higher BPG = lower affinity = more dissociation of oxygen to tissue

Question 8

How does CO2 and H+ regulate oxygen binding?

Answer 8

bind Hb = lowers affinity = oxygen gets released to counteract acidic environment = BOHR EFFECT - ensure delivery of O2 to meet demand

Question 9

How does carbon monoxide effect the blood?

Answer 9

poison, blocks oxygen transport, binds 250x more readily, fatal when COHb is >50%

Question 10

What are the Hb variants?

Answer 10

Adult: HbA (can glycosylate to HbA1c)
HbF (foetal, higher affinity than HbA)
HbA2

Question 11

Describe sickle cell

Answer 11

Single BP mutation: Glu for Val = hydrophobic AA residues on surface = try and hide = joins to another Hb = tetramer, masks valine = clustering – LONG POLYMER. Sickled cells = more prone to lyse

Question 12

What is thalassaemia?

Answer 12

Imbalance between number of α and β globin chains

Question 13

What are the thalassaemia types?

Answer 13

β –> decreased/absent, chromosome 11 each has 1 gene, 1 lost = minor, 2 lost = major.

α –> decreased/absent, chromosome 16 each has 2 genes, 1 lost = silent carrier, 2 lost = mild, 3 lost = HbH disease clinically severe, 4 lost = hydrops fetalis usually fatal (fluid in 2 foetal compartments)

Question 14

describe Hb structure

Answer 14

4 polypeptide chains = 2 alpha chains, 2 beta chains

Question 15

why does foetal Hb exist?

Answer 15

higher affinity for O2 than HbA, transfer of O2 from mother Hb to foetal blood supply