Haemoglobin and Oxygen Transport

Question 1

Composition of air?

Answer 1

78% Nitrogen

21% Oxygen

Question 2

As altitude increases kPa **

Answer 2

Decreases

Question 3

Partial pressure of a dissolved gas is equal to what?

Answer 3

The air it equilibrates with
*Overlooks fact that gases have different solubilities in different liquids. Example CO2 is 25 times more soluble in water than Oxygen.

Question 4

How is alveolar air different to atmospheric air?

Answer 4

Has a lower PAO2 of 14kPa and a higher PACO2 of 5kPa

Question 5

Tidal volume is small relative to?

Answer 5

Residual lung capacity

Question 6

What is functional residual capacity?

Answer 6

Air remaining in lungs after exhaling.

*2L when breathing normally

Question 7

Number of polypeptide chains in Haemoglobin (HbA) and their make up?

Answer 7

4 polypeptide chains. 2 are Alpha chains and 2 are Beta chains.

Question 8

How many binding sites in Hb?

Answer 8

4 and also there are 4 Iron atoms

Question 9

Structural difference between HbA and HbF?

Answer 9

HbF has Alpha, Delta and Gamma chains because it needs to compete with the mother for oxygen

Question 10

What is O2 content?

Answer 10

How much O2 is present in a certain volume of blood including plasma.
*Normally 190-200ml/L

Question 11

What is O2 Saturation?

Answer 11

Percentage of Hb binding sites which are occupied by O2.

Question 12

Anaemic people have a lower RBC count and so less Hb. This means that…

Answer 12

O2 content will be low even though saturation and PaO2 are normal.

Question 13

What is Hypoxia?

Answer 13

PaO2 of 9/10kPa which means Oxygen is not reaching tissues.

Question 14

What is Cyanosis and why does it occur?

Answer 14

Cyanosis = Blue discolouration of skin.

Due to excessive concentration of deoxy Hb. If 5g/100ml present in blood then colour becomes noticeable.

Question 15

Central Cyanosis vs Peripheral Cyanosis

Answer 15

Central = Bluish under tongue and lips. Failure of oxygenation due to circulatory or ventilation problems.
Peripheral = Bluish at fingertips only. Due to slow flow through peripheral tissue from vasoconstriction.

Question 16

Why are anaemic patients less likely to get Central Cyanosis?

Answer 16

They have an overall lower concentration of Hb which means saturation is high and occurs faster so there is a lower concentration of deoxy Hb.

Question 17

What is Polycythaemia?

Answer 17

Patient has abnormally high concentration of Hb due to a high RBC count and therefore has high O2 content.

Question 18

Why are Polycythaemic patients more likely to present with Central Cyanosis?

Answer 18

High RBC count means a lower saturation.

Question 19

What causes the O2 Dissociation curve to shift to the left?

*What does a left shift mean?

Answer 19

Lower CO2
Lower 2,3-DPG
Higher pH
Lower Temperature
*Left shift = Saturation at lower PaO2 because it has a higher affinity for Oxygen.

Question 20

What causes the O2 Dissociation curve to shift to the right?

*What does a right shift mean?

Answer 20

Higher CO2
Higher 2,3-DPH
Lower pH
Higher Temperature

*Right shift = Saturation at higher PaO2 because it has a lower affinity for Oxygen. Therefore easily released to tissue.

Question 21

What is myoglobin?

Answer 21

Found in hardworking muscles. Used as a back up system to haemoglobin. Made up of a single polypeptide chain and a single ahem group.