Transport of O2 and CO2 in the blood

Question 1

Why does efficient transport of oxygen in the blood require a carrier?

Answer 1

Oxygen has a very low solubility in water

Question 2

Why does Hb allow 4x more oxygen to be transported than we need at rest?

Answer 2

To allow an overshoot during exercise

Question 3

What subunits make up Hb?

Answer 3

2 alpha and 2 beta subunits

Question 4

What is the difference in structure of foetal Hb and what effect does this have?

Answer 4

Foetal Hb contains 2 gamma instead of 2 beta subunits. This causes it to have a higher affinity fro oxygen - so can bind oxygen at lower partial pressure

Question 5

What happens to the affinity for oxygen in sickle cell anaemia?

Answer 5

Hb in the RBCs have a lower affinity for oxygen so cannot bind as well - needs a higher partial pressure

Question 6

Why are sickle cells classified as less stress resistant than healthy RBCs?

Answer 6

They are more venerable to deformation during passage through the capillaries to are degraded much quicker

Question 7

What affect do sex hormones have on Hb concentration?

Answer 7

Oestrogen causes vasodilation

Androgens cause vasoconstriction

Question 8

What affect does vasoconstriction have on Hb concentration?

Answer 8

Reduced blood flow, so there is a need to increase the carrying capacity of oxygen so Hb content is increased.

Question 9

What affect does vasoconstriction have on Hb concentration?

Answer 9

Increased blood flow reduces the need to increase the carrying capacity of oxygen so Hb content is decreased

Question 10

Where on Hb does oxygen bind?

Answer 10

To the harm group via Fe atom

Question 11

Where on Hb does CO2 bind?

Answer 11

N-terminus

Question 12

Why is CO toxic?

Answer 12

CO and O2 compete for the same binding site and CO outcompetes O2 and binds irreversibly so O2 cannot eb transported

Question 13

Why is it a sigmoidal curve?

Answer 13

The binding of the 1st oxygen is hard but this causes a conformational change that helps the next ones bind.
When the limit is nearly reached very little additional binding occurs so the curve flattens out (even with a large increase in partial pressure)

Question 14

What is the effect of shifting the curve to the right?

When might this occur?

Answer 14

Decreased affinity for oxygen
Needs higher partial pressure to bind.
Occurs when increasing CO2 concentration

Question 15

Why does an increase in CO2 decrease Hb affinity for oxygen? What is this called?

Answer 15

More CO2 means more H2CO3, so more H+ so Hb undergoes a conformational change and can’t bind oxygen as well. Bohr effect

Question 16

What is the effect of increasing temperature on the oxygen dissociation curve?

Answer 16

Shifts to the right

Lower affinity for oxygen as it denatures Hb

Question 17

When and where is 2,3DPG produced

Answer 17

In erythrocytes during glycolysis (anaerobic respiration)

When O2 concentration is low

Question 18

What is the affect of 2,3 DPG on oxygen and the dissociation curve?

Answer 18

It promotes the release of oxygen from Hb because oxygen concentration is low this shifts the curve to the right so less oxygen binds.

Question 19

Why does foetal Hb need a higher affinity for oxygen?

Answer 19

It competes with the mothers supply of oxygen

Question 20

Why does foetal Hb have a higher affinity for oxygen structurally?

Answer 20

It has a lower affinity for 2,3 DPG so it cannot promote the release of oxygen

Question 21

What enzyme is involved in the transport of CO2?

Answer 21

Carbonic anhydrase

Question 22

How is CO2 transporter in the blood in proportions?

Answer 22

23% bound to Hb
7% free in the blood
70% as carbonic acid

Question 23

What is chloride shift?

Answer 23

H+ and HCO3- produced from carbonic acid.
H+ is buffered by Hb
HCO2- transported to plasma and replaced by Cl- to maintain neural charge