S4.1 CO2 In The Blood

Question 1

What reaction occurs to CO2 in plasma?

Answer 1

CO2 reacts with water to form carbonic acid (H2CO3) which then quickly dissociates into H+ and HCO3-

CO2 + H2O……H+ + HCO3-

Question 2

What is the role of carbonic anhydrase?

Answer 2

Speeds up the reaction of CO2 and H2O

Question 3

How does pCO2 and [HCO3-] determine pH and what can change their concentrations?

Answer 3

pH is determined by the ratio of [HCO3-]:pCO2. pCO2 can be changed by ventilation, HCO3- by rbc production and kidneys.

Question 4

Summarise how HCO3- is produced by RBC

Answer 4

CO2 + H2O……H+ + HCO3-

The H+ binds to Hb inside the RBC, the HCO3- leaves the RBC via the chloride bicarbonate exchanger.
Kidneys then control HCO3- concentration

Question 5

What is the role of HCO3- in blood?

Answer 5

Buffers extra acid that make CO2 upon reaction, so HCO3- decreases, CO2 is removed by breathing and pH changes are minimised.

Question 6

In what forms is CO2 transported?

Answer 6

3 forms: Dissolved CO2, HCO3-, carbamino compounds

Only 8% of CO2 is transported as a waste product, the rest is used as part of the pH buffering system.