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

What is the definition of a strong acid?

Answer 6

An acid which completely dissociates in solution

E.g. Hydrochloric acid becomes H+ and Cl-

Question 7

A weak acid with its conjugate base forms what?

Answer 7

A buffer pair

Question 8

What is the average pH of blood?

Answer 8

7.4

Question 9

Acidity in the body can come from which 2 types of acids?

Answer 9

Volatile acids
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 is used to calculate what?

What 2 things are used to calculate it?

Answer 13

pH

Bicarbonate + 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 carbonic anhydrase present and not present?

Answer 17

Present - red blood cells

Not present - blood plasma

Question 18

When CO2 reacts with H2O in red blood cells, how are the products (H+ and HCO3-) removed?

Answer 18

H+ is buffered by haemoglobin

HCO3- is transferred to plasma

Question 19

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

Answer 19

Deoxygenation

Question 20

What is the Haldane effect?

Answer 20

Giving up O2 increases the uptake of CO2 by haemoglobin

Question 21

What is the partial pressure value of oxygen in arterial blood?

Answer 21

13.3 kPa

Question 22

What is the partial pressure value of CO2 in arterial blood?

Answer 22

5.3 kPa

Question 23

What is the partial pressure value of oxygen in venous blood?

Answer 23

6 kPa

Question 24

What is the partial pressure value of CO2 in venous blood?

Answer 24

6.5 kPa

Question 25

What is the definition of a weak acid?

Answer 25

An acid which only partially dissociates in solution E.g. H2CO3 becomes H+ and HCO3

Question 26

Why does the reaction between CO2 and H2O occur more rapidly in red blood cells compared to plasma?

Answer 26

Carbonic anhydrase is not present in plasma, but it is present in red blood cells

Question 27

How does HCO3- leave red blood cells?

Answer 27

Cl- HCO3 - exchanger (antiporter)

Question 28

What is the main carbamino compound?

Answer 28

Carbamino haemoglobin

Question 29

Which part of haemoglobin does CO2 bind with to form carbamino haemoglobin?

Answer 29

NH2 group