Carbon dioxide transport

Question 1

What are the three main ways CO2 is transported in the blood?

Answer 1

• HCO3- (69%)
• Carbamino compounts (21%)
• Dissolved CO2 (10%)

Question 2

How do you work out pH?

Answer 2

Log10[H+]

Question 3

What are the sources of H+ in the body?

Answer 3

Volatile acids - From aerobic metabolism & CO2 production from tissues

Non-volatile acids - From other metabolic processes

Question 4

How are volatile acids and non-volatile acids excreted?

Answer 4

Volatile acids - via lungs

Non-volatile acids - via kidneys

Question 5

What is the Henderson-Hasselbalch equation?

Answer 5

pH = pK + log10([HCO3-]/[CO2])

Question 6

What is the physiological buffer system?

Answer 6

Kidneys can alter bicarbonate levels & lungs can alter CO2 levels.
One system can compensate for the other.

Question 7

How is H+ buffered by Hb?

Answer 7

Via histadine residue on globin

Question 8

What reaction does carbonic anhydrase catalyse in erythrocytes?

Answer 8

CO2 + H2O ↔ H+ + HCO3-

Question 9

How does HCO3- leave the cell?

Answer 9

In exchange for Cl- (Chloride/Hamburger shift) - this is why HCO3- is the main transport of CO2 in blood

Question 10

What are carbamino compounds?

Answer 10

CO2 reacts with protein amino groups, especially Hb.

This forms carbaminohaemoglobin - low o2 affinity

Question 11

What is the typical O2 saturation of venous blood?

Answer 11

70%