Haemoglobin and Gas Transport

Question 1

What is the main carrier for oxygen in the blood?

Answer 1

Haemoglobin

Question 2

How is most of CO2 transported in the blood?

Answer 2

In solution in plasma

Question 3

Do gases travel in gaseous phase when in plasma and why?

Answer 3

No as bubbles in the blood would cause an air embolism

Question 4

How much arterial O2 is extracted by peripheral tissues at rest?

Answer 4

25%

Question 5

What is the main determinant of the degree to which haemoglobin is saturated with oxygen?

Answer 5

Partial pressure of oxygen in arterial blood

Question 6

What are the 4 forms of haemoglobin in red blood cells?

Answer 6

HbA
HbA2
HbF
glycoisated Hb

Question 7

What is the most common form of haemoglobin?

Answer 7

HbA (makes up 92%)

Question 8

What is HbF?

Answer 8

Foetal haemoglobin

Question 9

What is the reserve capacity of haemoglobin for oxygen and normal venous PO2?

Answer 9

75%

Question 10

Does HbF have a higher or lower affinity than HbA and why?

Answer 10

Higher affinity to allow O2 extraction from maternal blood

Question 11

What is the definition of anaemia in relation to O2 carrying capacity of the blood?

Answer 11

Any condition where O2 carrying capacity of the blood is compromised

Question 12

During anaemia what happens to PaO2 and total blood O2?

Answer 12

PaO2 is normal

Total blood O2 is low

Question 13

Are red blood cells able to be fully saturated with O2 in anaemia and why?

Answer 13

Yes as PaO2 is normal

Question 14

What effect does acidosis and alkolisis have on haemoglobin’s affinity for O2?

Answer 14

Acidosis - decreases affinity

Alkalosis - increases affinity

Question 15

What effect does increasing the PCO2 have on haemoglobin’s affinity for O2?

Answer 15

As PCO2 increases, affinity decreases

Question 16

What effect does increasing the temperature have on haemoglobin’s affinity for O2?

Answer 16

As temperature increases, affinity decreases

Question 17

What effect does adding 2,3-DPG have on haemoglobin’s affinity for O2?

Answer 17

As 2,3-DPG is added, affinity decreases

Question 18

What effect does carbon monoxide have on haemoglobin?

Answer 18

It binds to haemoglobin with 250 times greater affinity than O2 causing it to competitively inhibit O2

Question 19

What are 6 symptoms of carbon monoxide poisoning?

Answer 19

Hypoxia
Anaemia
Nausea
Headaches
Cherry red skin
Mucous membranes

Question 20

What are 2 of the possible consequences of carbon monoxide poisoning?

Answer 20

Brain damage

Death

Question 21

What are the 3 outcomes when CO2 diffuses from the tissues into the blood?

Answer 21

70% combines with water in the erythrocytes to form carbonic acid
23% combines in the erythrocytes with deoxyhemoglobin to form carbamino compounds
7% remains dissolved in plasma and erythrocytes

Question 22

What effect does hypoventilation have on respiratory pH and why?

Answer 22

Hypoventilation causes CO2 retention leading to respiratory acidosis

Question 23

What effect does hyperventilation have on respiratory pH and why?

Answer 23

Hyperventilation blows off more CO2 leading to respiratory alkalosis