CO2 Carriage in Blood and Acid-Base Equilibrium

Question 1

Carbonic anhydrase (true or false):

Contains a zinc atom

Answer 1

True. The zinc atom is an integral part of the enzyme’s function.

Question 2

Carbonic anhydrase (true or false):

Catalyses the conversion of H2CO3 into HCO3- and H+ ions

Answer 2

False. It catalyses CO2 + H2O into H2CO3.

Question 3

Carbonic anhydrase (true or false):

Is abundant in the plasma

Answer 3

False. There is no CA activity in plasma.

Question 4

Carbonic anhydrase (true or false):

Has three isoenzymes

Answer 4

False. There at least 16.

Question 5

Carbonic anhydrase (true or false):

Is limited only by the ability of buffer systems to absorb H+ ions produced

Answer 5

True. It is one of the fastest enzymes known.

Question 6

The Haldane effect:

Is the shift of the Hb dissociation curve in response to changes in PCO2

Answer 6

False. This is the Bohr effect.

Question 7

The Haldane effect:

Is partly caused by increased carbonic anhydrase activity

Answer 7

False. CA has constant activity.

Question 8

The Haldane effect:

Is partly caused by changes in the amount of carbamino carriage of CO2 by Hb

Answer 8

True. This accounts for the majority of the Haldane effect.

Question 9

The Haldane effect:

Is of minor importance in-vivo

Answer 9

False. The effect accounts for much of the difference in CO2 carriage between arterial and venous blood.

Question 10

The Haldane effect:

Involves changes in the dissociation state of histidine residues in the Hb molecule

Answer 10

True. This is the other cause of the Haldane effect.

Question 11

Regarding H+ ions that are produced by the formation of HCO3⁻ within the red blood cell:

They are exported from the red cell in exchange for K+ ions

Answer 11

True.

The HCO3⁻ ions are exported by band 3 protein in exchange for chloride ions.

Question 12

Regarding H+ ions that are produced by the formation of HCO3⁻ within the red blood cell:

They are buffered by haemoglobin

Answer 12

True. Hb has considerable buffering power due to its large number of histidine residues.

Question 13

Regarding H+ ions that are produced by the formation of HCO3⁻ within the red blood cell:

They are buffered by proteins of the glycolytic pathway

Answer 13

False. The buffering potential of intracellular proteins apart from Hb is negligible.

Question 14

Regarding H+ ions that are produced by the formation of HCO3⁻ within the red blood cell:

They are partly responsible for the Bohr effect

Answer 14

True. Changes in the ionization state of histidine residues alters the oxygen affinity of the Hb.

Question 15

Regarding H+ ions that are produced by the formation of HCO3⁻ within the red blood cell:

They are responsible for forming carbamino compounds with Hb

Answer 15

False. Carbamino compounds are formed by a reaction between amino groups and CO2.