Oxygen transport in the blood

Question 1

What is Henry’s law of partial pressures?

Answer 1

The amount of a given gas dissolved in a given type and volume of liquid at a constant temperature is proportional to the partial pressure of the gas in equilibrium with the liquid

Question 2

How is most (98.5%) oxygen transported in the body?

Answer 2

Bound to haemoglobin

Question 3

What is contained in a molecule of haemoglobin?

Answer 3

2 alpha and 2 beta subunits each containing a haem group, each of which can bind reversibly to one molecule of oxygen

Question 4

In what saturation level is haemoglobin at, at low pO2?

Answer 4

Low saturation

Question 5

In what saturation level is haemoglobin, at high pO2?

Answer 5

High saturation

Question 6

What does the saturation - Blood pO2 graph look like?

Answer 6

Question 7

What is the equation for Oxygen delivery index (DO2I)?

Answer 7

DO2I = Oxygen content of arterial blood (CaO2) x cardiac index (CI)

Question 8

What is mean by cardiac index?

Answer 8

A measurement that related cardiac output to body surface area

Question 9

What is the normal range of cardiac index?

Answer 9

2.4 - 4.2 L/min/m^2

Question 10

How much oxygen, in ml, can one gram of haemoglobin carry?

Answer 10

1.34 ml

Question 11

What is the calculation for Oxygen content of arterial blood (CaO2)?

Answer 11

CaO2 = 1.34 x [Hb] x % saturated Hb (SaO2)

Question 12

What are some examples of conditions that can affect oxygen delivery to tissue?

Answer 12

Respiratory failure - Lowers pO2
Heart failure - Lowers CI
Anaemia - Lowers [Hb]

Question 13

What causes the sigmoid shape of the oxygen dissociation graph?

Answer 13

The binding of 1 molecule of O2, increases the haemoglobin affinity to bind to other O2 molecules causing the steeper slope

The flat upper part of the sigmoid means that a moderate fall in pO2 will not affect oxygen loading

A steep lower part of the sigmoid means that only a small drop in pO2 is required for Hb to dissociate

Question 14

What occurs as a result of Bohr shift to the right?

Answer 14

This means that O2 is released at higher pO2 levels, do it decreases the affinity of Hb for oxygen

Question 15

What are some examples of factors that can cause a Bohr shift to the right?

Answer 15

pCO2
[H+]
Temperature
2,3-Biphosphoglycerate (A product of glycolysis which binds to haemoglobin and further decreases affinity)

Question 16

What does a molecule of foetal haemoglobin contain?

Answer 16

2 alpha and 2 gamma subunits which interact less with 2,3-biphosphoglycerate

Question 17

What are the advantages of foetal haemoglobin?

Answer 17

It interacts less with 2,3-biphosphoglycerate
This means it has a higher affinity for O2 compared to adult haemoglobin
This allows O2 to transfer from the mother to the foetus, even if the pO2 is low

Question 18

Where is myoglobin found?

Answer 18

In cardiac and skeletal muscle

Question 19

How many subunits does myoglobin contain?

Answer 19

1 haem group

Question 20

What is the function of myoglobin and why?

Answer 20

Myoglobin releases O2 at very low pO2 and provides short term storage for O2 in anaerobic conditions

Question 21

What does myoglobin in the blood suggest?

Answer 21

Muscle damage

Question 22

What does the oxygen dissociation curve for myoglobin look like?

Answer 22