Some Additional Material on Oxygen Carriage in the Blood

Question 1

Is the arterial partial pressure of O2 the same as the arterial O2 concentration?

Answer 1

No

Question 2

What does the partial pressure of oxygen refer to?

Answer 2

It refers purely to oxygen in solution in the plasma.

Question 3

What determines partial pressure of oxygen?

Answer 3

Oxygen solubility and the partial pressure of oxygen in the gaseous phase that is driving that oxygen into solution.

Question 4

What is the relationship of the partial pressure of the alveoli and the partial pressure in solution at equilibrium?

Answer 4

They are the same.

Question 5

How do you calculate the partial pressure of oxygen (oxygen tension)?

Answer 5

Solubility of oxygen in water: eg. 0.03 l/mmHg
Volume of plasma: 3ml

Oxygen tension: 3/0.03 = 100mmHg

Question 6

Why is partial pressure not the same as concentration?

Answer 6

It depends on the form that the molecule is in (there are many more molecules of oxygen in gas than there are in solution.)

Question 7

Do gases travel in the gaseous phase in plasma?

Answer 7

No

Question 8

How many ml of oxygen bind to each gram of haemoglobin?

Answer 8

1.34 ml

Question 9

What are the four types of haemoglobin?

Answer 9

• 92% of haemoglobin is HbA
• The remaining 8% is made up of HbA2 (gamma chains are replaced with beta chains), HbF (beta chains are replaced with gamma chains) and glycosylated Hb (Hb1, Hb2, Hb3).

Question 10

What is the important function of glycosylated Hb?

Answer 10

It is really important in the monitoring of blood glucose in diabetes because haemoglobin becomes glycosylated when it is exposed to high levels of glucose. Clinicians will look at the patients glycosylated haemoglobin levels, in order to get a picture of how well that patient has been able to control the blood levels over a three month period. (Red blood cells only live for three months)

Question 11

What is myoglobin?

Answer 11

It is carrying molecule but it is only found in skeletal and cardiac muscle.

Question 12

Do you find myoglobin the blood?

Answer 12

No

Question 13

When do you find myoglobin in the blood?

Answer 13

During extensive muscle damage.

Question 14

How many polypeptide chains does myoglobin have?

Answer 14

One

Question 15

What has a higher affinity for oxygen: Myoglobin and foetal haemoglobin or adult haemoglobin?

Answer 15

Myoglobin and foetal haemoglobin.

Question 16

What is the percentage saturated of oxygen in adult haemoglobin, foetal haemoglobin and myoglobin?

Answer 16

Adult Haemoglobin - 65%
Foetal Haemoglobin - 80%
Myoglobin - 90%

Question 17

What does the high affinity of foetal haemoglobin allow?

Answer 17

It allows a foetus to be able to extract oxygen from the mother blood

Question 18

What does the high affinity of myoglobin allow?

Answer 18

It allows muscles to extract oxygen from the blood.

Question 19

What is hypoxia?

Answer 19

The inadequate supply of oxygen to tissues.

Question 20

What are the five types of hypoxia?

Answer 20

1. Hypoxaemic Hypoxia
2. Anaemic Hypoxia
3. Stagnat hypoxia
4. Histotoxic hypoxia
5. metabolic hypoxia

Question 21

What is hypoxaemic hypoxia?

Answer 21

Reduction in oxygen diffusion at the lungs due to pathology or decrease in oxygen partial pressure.

Question 22

What is the most common type of hypoxia?

Answer 22

Hypoxaemic hypoxia

Question 23

What is anaemic hypoxia?

Answer 23

Reduction in the oxygen carrying capacity of the blood. (red blood cell loss/ iron deficiency)

Question 24

What is stagnant hypoxia?

Answer 24

heart disease results in ineffcient pumping of the blood to the lungs and around the body.

Question 25

What is histotoxic hypoxia?

Answer 25

poisoning prevents the cells utilising the oxygen that is delivered to them. e.g carbon monoxide, cyanide

Question 26

What is metabolic hypoxia?

Answer 26

Oxygen delivery to the tissues does not meet the increased oxygen demand by the tissues.