Gas transport in the blood 2

Question 1

Where must oxygen from the lungs be transported?

Answer 1

To the tissues for cellular use

Question 2

Where must CO2 produced by cellular mechanisms be transported?

Answer 2

To the lungs for removal from the body

Question 3

What are the 3 means of CO2 transport in blood?

Answer 3

• Solution (10%)
• As bicarbonate (60%)
• As carbamino compounds (30%)

Question 4

What is the main transport mechanism of CO2 in the blood?

Answer 4

As bicarbonate (60%)

Question 5

What is Henry’s Law?

Answer 5

The amount of a gas dissolved in a liquid (e.g. blood) at a constant
temperature is:
proportional to the partial pressure of the gas in equilibrium with the liquid

Question 6

How is sufficient CO2 transported in blood despite having a much lower partial pressure than oxygen?

Answer 6

Carbon dioxide about 20 times more soluble than oxygen

Question 7

What proportion of CO2 is carried in solution?

Answer 7

10%

Question 8

How is bicarbonate formed in the blood?

Answer 8

CO2 reacts with H20 in the presence of carbonic anhydrase to form carbonic acid, which then dissociated to form H+ and HCO3-

Question 9

What can H2CO3 dissociate into?

Answer 9

CO2 and H20
Or
H+ and HCO3-

Question 10

What is the catalyst in the following reaction:

CO2 + H2O –> H2CO3

Answer 10

Carbonic anhydrase

Question 11

How does CO2 diffuse from the tissues into blood cells in capillaries?

Answer 11

Via partial pressure gradient

Question 12

What reaction occurs once CO2 is inside red blood cells?

Answer 12

It will react with water in the presence of carbonic anhydride, leading to formation of bicarbonate

Question 13

How does bicarbonate enter plasma?

Answer 13

Chloride shift - bicarbonate eneters plasma in exchange for chloride

Question 14

What reaction occurs once HCO3- is inside the blood plasma?

Answer 14

It will dissociate into H+ and CO2, which will react with haemoglobin

Question 15

What are carbamino compounds?

Answer 15

Carbamino compounds are formed by combination of CO2 with terminal amine groups in blood proteins

Question 16

What is the most common terminal amine group CO2 combines with?

Answer 16

Globin of haemoglobin to give carbamino-haemoglobin

Question 17

Does the reaction of Hb with CO2 require a catalyst?

Answer 17

No, rapid even without enzyme

Question 18

How is the affinity of Hb for CO2 increased?

Answer 18

If Hb liberates oxygen to become deoxygenated

Question 19

What is the Haldane Effect?

Answer 19

Removing O2 from Hb increases
the ability of Hb to pick-up CO2 and
CO2 generated H+

Question 20

What does he Haldane Effect work in synchrony with?

Answer 20

The Bohr Effect

Question 21

What does the synchrony of the Bohr Effect and Haldane Effect facilitate?

Answer 21

O2 liberation and uptake of CO2 & CO2 generated H+ at tissues

Question 22

What does the Bohr Effect facilitate?

Answer 22

The Bohr Effect Facilitates the Removal of O2 from haemoglobin at tissue level by shifting the O2-Hb dissociation curve to the right

Question 23

What shifts the CO2 dissociation curve to the right?

Answer 23

Oxygen

Question 24

What happens to Hb at the lungs?

Answer 24

It picks up O2

Question 25

What does oxygen binding to Hb mean for affinity of Hb for CO2 and H+?

Answer 25

This weaken its ability to bind CO2 and H+

Question 26

A 65- year old woman life-long smoker with COPD, emphysema and shortness of breath. What are the reasons for shortness of breath?

Answer 26

• Loss of elastic recoil (hyperinflation of lungs)

* Dynamic airway compression (more resistance in the airways, lower pressure gradient upstream)

Question 27

A 65- year old woman life-long smoker with COPD, emphysema and shortness of breath. What are the possible change in lung volumes and capacities?

Answer 27

• Increased Residual Volume (RV) due to hyperinflation - normal lungs are resonant to percussion, hyperinflated lungs are hyperresonant to percussion
• Increased Functional Residual Capacity (FRC)

Question 28

A 65- year old woman life-long smoker with COPD, emphysema and shortness of breath. How is blood oxygenation affected?

Answer 28

• Emphysema will reduce the surface area for gas exchange as it destroys alveoli, patient may have a low PO2
• In fibrosis, oxygenation will decrease as pulmonary compliance decreases (lungs are stiffer, thicker alveolar membrane that affects diffusion of oxygen)