Haemoglobin And Myoglobin

Question 1

What is the structure of haem?

Answer 1

An iron atom attached to four nitrogen atoms

Question 2

What amino acid is haem bound to?

Answer 2

Histidine

Question 3

How many 02 molecules can bind to one haem group?

Answer 3

One

Question 4

What has better affinity for O2, myoglobin or haemoglobin?

Answer 4

Myoglobin

Question 5

What is the molecular structure of haemoglobin?

Answer 5

Two polypeptide chains, each with an essential haem group.

4 haem containing subunits, 2 beta 2 alpha, of which each can carry one 02 molecule.

Question 6

What is the difference between T and R state?

Answer 6

T state = low affinity

R state = high affinity.

Question 7

What happens to the 02 affinity of haemoglobin once one 02 molecule is bound?

Answer 7

With no oxygen, low affinity.
However once one oxygen bind, haemoglobin changes conformation to a more relaxed state, and affinity for more O2 increases.

Question 8

What is the meaning of a sigmoidal curve on a graph measuring O2 affinity?

Answer 8

Low affinity at the start, then affinity increases dramatically until max is reduced (full saturation).

Question 9

Is O2 affinity higher in the lungs or the tissues? How does this aid with O2 transport around the body?

Answer 9

High affinity in the lungs to pick up O2

Low affinity in the tissues to drop off O2

Question 10

What does BPG (1,2,3-bisphosphoglycerate) do to oxygen affinity?

Answer 10

Decreases it

Question 11

Geographically, where does BPG concentration increase?

Answer 11

In high altitudes

Question 12

What does exercise have on oxygen affinity and why?

Answer 12

When we exercise, we produce more H+ and C02, reduces ph of the tissue (more acidic).
C02 and H+ can both bind to haemoglobin. Therefore 02 affinity is decreased, and C02/H+ affinity is increased, so that 02 can be dropped off at the tissues to feed working muscles and poisonous C02 can be taken up to the lungs for elimination.

Question 13

What effect does carbon monoxide have on the body? Can it be reversed?

Answer 13

Carbon monoxide (COHb) combines ferromyobin with ferrohaemoglobin and blocks 02 transport, giving way for C02 binding.
C02 binds 250x more than 02, so can be fatal.
Binds very tightly - can only be reversed if the patient is put in an oxygen chamber.

Question 14

What is HbF?

Answer 14

Foetal haemoglobin

Question 15

What does HbF have a higher 02 affinity than normal Hb?

Answer 15

Because if needs to take some 02 supply off mother for development.

Question 16

What is sickle cell anaemia?

Answer 16

A inherited blood disorder.
A single nucleotide change (missense) from Glutamate (hydrophilic) to Valine (hydrophilic).
This causes a hydrophobic pocket in the middle of the cell, making it a moon shape rather than rounded.
It’s abnormal shape makes it inflexible and unable to get through some blood vessels.

Question 17

What is Thalasseamia?

Answer 17

A blood disorder where there is an imbalance between the alpha and beta globin chains.
Beta thalasseamias - decreased beta globins chains, alpha chains unable to for a stable tetramer
Alpha thalassemias - decreased alpha globins, beta globins have high affinity for 02 which means it can’t drop it off at the tissue.