Gas transport - carbon dioxide

Question 1

Which 3 ways is CO2 transported in the blood? Provide percentages.

Answer 1

As dissolved CO2 – 10%

As bicarbonate (HCO3-) – 69%

As carbamino compounds – 21%

Question 2

Carbon dioxide reacts with water to form what?

Answer 2

Carbonic acid – H2CO3

Question 3

Carbonic acid dissociates to form what?

Answer 3

H+ and HCO3-

Question 4

What is the definition of an acid?

Answer 4

Any chemical that can donate H+ (proton)

Question 5

What is the definition of a base?

Answer 5

Any chemical that can accept H+

Question 6

Describe the nature of dissociation of weak acids in solution

Answer 6

Weak acids, such as carbonic acid, only partially dissociate in solution

Question 7

A weak acid with its conjugate base forms what?

Answer 7

A buffer pair

Question 8

What is the normal pH range of blood?

Answer 8

7.35 – 7.45

Question 9

What are the 2 categories of acids in regards to H+ production?

Answer 9

Volatile and non-volatile acids

Question 10

What are volatile acids?

Answer 10

Acids that can easily be converted to gases

Question 11

What are volatile acids excreted by?

Answer 11

Lungs

Question 12

What are non-volatile acids excreted by?

Answer 12

Kidneys

Question 13

The Henderson-Hasselbalch equation allows us to calculate what?

Answer 13

The pH based on measurements of HCO3- and CO2

Question 14

Describe how pH would be restored if too much H+ was produced.

Answer 14

H+ reacts with bicarbonate ions to form CO2. CO2 is breathed out, restoring pH

Question 15

Describe how pH would be restored if concentration of CO2 was too high.

Answer 15

Kidneys excrete less HCO3-, raising HCO3- plasma and restoring pH

Question 16

The reaction between CO2 and H2O is catalysed by which enzyme?

Answer 16

Carbonic anhydrase

Question 17

Where is the carbonic anhydrase enzyme found and not found?

Answer 17

Found in erythrocytes but not in plasma

Question 18

When CO2 reacts with H2O in red blood cells, the reaction is promoted by the removal of the products (H+ and HCO3-). How are they ‘removed’?

Answer 18

H+ is buffered by haemoglobin and HCO3- is transferred to plasma

Question 19

The buffering ability of haemoglobin with H+ ions is enhanced by what?

Answer 19

Deoxygenation

Question 20

What is the Haldane effect?

Answer 20

The ability of deoxygenated haemoglobin to carry more carbon dioxide than in the oxygenated state

Question 21

Describe how the Haldane effect works.

Answer 21

H+ is buffered by haemoglobin. This ability is enhanced when the haemoglobin is deoxygenated, and reduced when haemoglobin is oxygenated. So, deoxygenated haemoglobin can more effectively buffer H+ ions.