Lecture 17: O2 and CO2 transport

Question 1

O2 is carried around in the blood in what two forms?

Which way is more effective?

Answer 1

1. Dissolved in O2
   - very ineffective
   - 0.03 ml of O2 per litre of blood
2. Combined with haemoglobin
   - O2 forms an easily REVERSIBLE combination wi Hb to give oxyHb

Question 2

What is the O2 saturation of Hb in:
Arterial blood
and
Venous blood
What is the O2 saturation for P50?

Answer 2

Arterial blood: PaO2 = 100mmHg - 97%
Venous blood: PvO2 = 40mmHg - 75%

P50 = when Hb is 50% saturated = 25mmHg

Question 3

The relationship btw PO2 saturation is:

Answer 3

SIGMOIDAL

Question 4

What does the upper flat part of the oxygen dissociation curve tell us?

Answer 4

Tells us that moderate changes in PO2 only have small effects on the % saturation and therefore the amount of O2 carried by arterial blood

Question 5

What does the steep part of the of the oxygen dissociation curve at lower PO2 tell us?

Answer 5

Tells us that small changes in PO2 result in large changes in the amounts of O2 bound to haemoglobin
- which help withs loading of Hb in lungs AND unloading of O2 to the tissues

Question 6

What is the O2 content of arterial blood?

What is the O2 content of venous blood?

What is O2 capacity?

What is O2 content?

Answer 6

O2 content of arterial = 200 ml O2/litre blood
O2 content of venous = 150ml O2 /litre blood

O2 capacity : the maximal amount of O2 that can be combined with Hb
= 1.34 x amount of Hb
O2 content: How much O2 is the blood carrying
= O2 capacity x saturation ( +dissolved)

Question 7

What happens when there is a LEFT ward shift in the dissociation curve?

What happens when there is a RIGHT shift in the dissociation curve?

Answer 7

Leftward shift means more Loading of O2 in Lungs

Right ward shift means more Release(unloading) of O2 in tissues

Question 8

The Bohr effect:

What happens when there is a right shift in the curve?

Answer 8

RELEAESE of O2 in TISSUES
- Increased PCO2
- Increased H+
- Increased temperature
- Increased 2,3 DPG which increases with exercise, high altitude and sever lung diseases
- when you exercise you release - you make lots of CO2 - off load O2 - deliver / release O2 to tissues
If you have high CO2 = unload more O2

Question 9

The Bohr effect:

What happens when there is a left shift in the curve?

Answer 9

LOAD O2 in the lUNGS

• Decreased PCO2
• Hb “picks up” O2 which is what you want in the lungs

Question 10

In what 3 ways is CO2 transported in the blood?

Answer 10

1. Dissolved in plasma - 20x more soluble than O2 = 10%
2. A bicarbonate = 70%
3. Combined with proteins to form carbamino compounds = 20% - are compound from by the combination of CO2 with a terminal anime group in blood proteins e.g haemoglobin

Binding CO2 to haemoglobin is easier when Hb is NOT bound to O2

Question 11

What is the Haldane effect?

Answer 11

Haldane effect: unload O2 = load more CO2

• deoxygenation of blood increased CO2 carriage
• remove O2 from tissue —-> more CO2 can be carried (removed)