5. Haemoglobin and non-retinol binding

Question 1

what is the advantage of foetal Hb having a higher affinity than adult Hb

Answer 1

allows maternal Hb to dissociate oxygen in the placenta and the foetal Hb can bind this readily

Question 2

explain what happens to the oxygen dissociation curve at higher temperatures

Answer 2

the curve shifts to the right, increasing release of oxygen.

this is because at higher temperatures more tissues are active.

Question 3

what happens to the structure when Hb shifts from a deoxygenated to oxygenated state

Answer 3

the void existing between the beta chains decreases in distance

Question 4

what happens to 2,3 BPG during the shift to the oxygenated state

Answer 4

it sits in this void in the deoxygenated state, it cannot fit in the oxygenated state

Question 5

what state is deoxyhaemoglibin in

Answer 5

tense state

Question 6

describe the structure of the tense state (deoxyhaemoglobin)

Answer 6

• constrained by hydrophobic bonds and 8 electrostatic bonds
• Iron bonded to proximal his F8
• Iron is above porphyrin ring
• penultimate tyr residues bond to a val

Question 7

what happens to the porphyrin ring when oxygen binds

Answer 7

oxygen binds to iron -> this pulls iron closer to the porphyrin plane

8 electrostatic bonds break

tyrosine residues pop out of binding with valines - this destabilises the tense state

the alpha-1 beta-1 subunits rotate and beta subunits move closer, the void narrows, BPG can no longer bind

Question 8

what is another name for retinol

Answer 8

vitamin A

Question 9

what transports vitamin A to vitamin-A dependent tissues

Answer 9

retinol binding protein

Question 10

describe the structure of retinol binding protein

Answer 10

• barrel structure
• beta-domain protein
• retinol binding site is lined with hydrophobic residues

Question 11

what is retinol stored as in the liver

Answer 11

retinol palmitate

Question 12

name 2 functions of vitamin A

Answer 12

• anti-oxidant
• steroid hormone
• night vision