Haemoglobin and Gas Transport

Question 1

How much oxygen is dissolved per litre of plasma?

Answer 1

3ml

Question 2

Haemoglobin in red blood cells increases the oxygen carrying capacity to what?

Answer 2

200 ml/L

Question 3

Arterial pressure of oxygen is determined by what two factors?

Answer 3

Oxygen solubility

Partial pressure of oxygen that is driving oxygen into solution

Question 4

Gases travel in solution in the plasma. If they traveled in the gaseous phase, it would lead to what?

Answer 4

Air embolism (fatal)

Question 5

Oxygen delivery to the tissues can be calculated using what equation?

Answer 5

Oxygen delivery to tissues =
Arterial O2 Content (ml/L)
x Cardiac Output (L/min)

Question 6

What is the O2 demand of normal, resting tissues?

Answer 6

250ml/min

Question 7

What is normal cardiac output?

Answer 7

5L/min

Question 8

What percentage of arterial oxygen is extracted by peripheral tissues at rest?

Answer 8

25%

Question 9

What volume of oxygen binds to each gram of Haemoglobin?

Answer 9

1.34ml

Question 10

What percentage of haemoglobin is in the form HbA?

Answer 10

92%

Question 11

What is the difference between HbA and HbA2?

Answer 11

Alpha chains replace beta

Question 12

Haemoglobin in the form HbF is formed when beta chains are replaced by what chains?

Answer 12

Gamma

Question 13

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

Answer 13

Partial pressure of oxygen in arterial blood

Question 14

Oxygen is moved out of the alveoli down a partial pressure gradient until what?

Answer 14

The haemoglobin becomes saturated with oxygen

Question 15

Within how many seconds of contact with the alveoli is saturation complete?

Answer 15

0.25 seconds

Question 16

What is the normal systemic arterial PO2?

Answer 16

100 mmHg

Question 17

At normal venous PO2, what is the reserve capacity?

Answer 17

75%

Question 18

Do Foetal Haemoglobin and Myoglobin have a higher or lower affinity for oxygen than HbA?

Answer 18

Higher

Question 19

Where is myoglobin found?

Answer 19

Muscle (particularly concentrated in oxidative muscle)

Question 20

What do the higher affinities of myoglobin and foetal haemoglobin (compared to HbA) allow them to do?

Answer 20

Extract more oxygen
Myoglobin from skeletal muscle
Foetal Haemoglobin from the maternal blood

Question 21

How is Anaemia defined?

Answer 21

Any condition where the oxygen carrying capacity of the blood is compromised

Question 22

Is it possible for red blood cells to be fully saturated with oxygen in anaemia?

Answer 22

Yes

Question 23

Why is it possible for red blood cells to be fully saturated with oxygen in anaemia?

Answer 23

As PaO2 is normal - there is no problem with ventilation or diffusion so alveolar volume and diffusion should be normal (exception is iron deficiency anaemia)

Question 24

Why is there a low oxygen content in anaemia?

Answer 24

Due to a low haemoglobin content as red blood cells are missing/not being synthesised properly due to anaemia

Question 25

What factors would decrease the affinity of haemoglobin for oxygen?

Answer 25

Decreased pH Increased PCO2 Increased temperature Increased binding of DPG

Question 26

What cells synthesise DPG?

Answer 26

The erythrocytes

Question 27

Under what circumstances would the binding of DPG increase?

Answer 27

Inadequate oxygen supply

Question 28

What does DPG help to maintain?

Answer 28

Oxygen release in the tissues

Question 29

How is carbon monoxide formed?

Answer 29

From incomplete combustion of carbon fuel

Question 30

Carbon monoxide binds to haemoglobin to form what?

Answer 30

Carboxyhaemoglobin

Question 31

Carbon monoxide's affinity for haemoglobin is how many times greater than that of oxygen?

Answer 31

250

Question 32

What is the typical, physical symptom of carbon monoxide poisoning?

Answer 32

Cherry red skin, mucous membranes and nail beds

Question 33

What affect would CO poisoning have on respiration rate?

Answer 33

No affect - respiration rate is unaffected due to normal arterial PCO2

Question 34

The treatment for CO poisoning is administering 100% oxygen, why is this treatment difficult?

Answer 34

Haemoglobin is already 98% saturated with oxygen, so providing pure oxygen can only increase this by 2%

Question 35

What are the 5 main types of Hypoxia?

Answer 35

``` Hypoxic Anaemic Ischaemic Histoxic Metabolic ```

Question 36

What is the most common type of hypoxia?

Answer 36

Hypoxic hypoxia

Question 37

What is hypoxia?

Answer 37

A deficiency/inadequacy in the volume of oxygen reaching the tissues

Question 38

The reduction in O2 diffusion at the lungs in hypoxic hypoxia is due to what?

Answer 38

Decreased atmospheric PO2 or tissue pathology

Question 39

Heart disease results in the inefficient pumping of blood to the lungs and around the body, what type of hypoxia does this cause?

Answer 39

Ischaemic

Question 40

What type of hypoxia may be found in an unfit person exercising?

Answer 40

Metabolic

Question 41

What is anaemic hypoxia?

Answer 41

A reduction in oxygen carrying capacity of blood due to anaemia

Question 42

What type of hypoxia is found when CO poisoning prevents cells from utilising oxygen delivered to them?

Answer 42

Histoxic

Question 43

When CO2 molecules diffuse from tissue to the blood, what percentage remains dissolved in plasma and erythrocytes?

Answer 43

7%

Question 44

70% of CO2 which remains in the plasma and erythrocytes after diffusion combines with water to form what?

Answer 44

Carbonic acid

Question 45

Carbonic acid dissociates to yield what?

Answer 45

Bicarbonate and H+ ions

Question 46

Normally, pH is stable because all CO2 produced is eliminated where?

Answer 46

In expired air

Question 47

CO2 retention leading to increased [H]+ will cause what?

Answer 47

Respiratory acidosis

Question 48

Blowing off more CO2 leading to decreased [H]+ will cause what?

Answer 48

Respiratory alkalosis

Question 49

Is respiratory alkalosis found in hypo or hyper-ventilation?

Answer 49

Hyperventilation

Question 50

Is respiratory acidosis found in hypo or hyper-ventilation?

Answer 50

Hypoventilation