Session 4

Question 1

What is important about myoglobin?

Answer 1

In muscle
It saturates at low pO2
13.3 kPa and above it is 100% saturated

Question 2

What state of haemoglobin binds O2 well?

Answer 2

Relaxed

Question 3

What state of haemoglobin binds O2 poorly?

Answer 3

Tense

Question 4

At what pO2 is haemoglobin saturated?

Answer 4

8.5 kPa

Question 5

At what pO2 is haemoglobin unsaturated?

Answer 5

1 kPa

Question 6

At what pO2 is haemoglobin half saturated?

Answer 6

3.5-4 kPa

Question 7

What is the pO2 in the lungs?

Answer 7

13.3 kPa so haemoglobin is well saturated

Question 8

What is the oxygen content in normal blood?

Answer 8

2.2 mmol/L and each haemoglobin molecule binds 4 O2 so 8.8 mmol/L actually in blood

Question 9

Approximately, what is tissue pO2?

Answer 9

5 kPa so haemoglobin would be around 65% saturated.Cannot fall below 3 kPa, but the higher the capillary density the lower it can fall

Question 10

How can you calculate the amount of O2 given up at the tissues?

Answer 10

100% saturation of Hb goes to 65% so 35% change. 8.8 mmol/L x 0.35 = 3 mmol/L

Question 11

What effect does pH have on the state of haemoglobin?

Answer 11

Acid - Tense

Alkali - Relaxed

Question 12

How does the pH of tissues aid O2 delivery?

Answer 12

It is lower so haemoglobin becomes tense and dissociates extra O2

Question 13

What effect does temperature have on haemoglobin?

Answer 13

It puts it into its tense state

Question 14

What is maximum unloading?

Answer 14

Haemoglobin becomes very tense and gives up around 70% of O2 due to the higher temperature and lower pH

Question 15

What is O2 reserve?

Answer 15

73% of O2 stays in the blood so if extra O2 needs to be used it can. This is important as muscle activity can increase higher than the cardiac output can safely (So not enough O2 would be able to reach the tissues without O2 reserve)

Question 16

What does CO2 react with in the blood?

Answer 16

Water to make H+ and HCO3-

Reversible reaction and amount reacting depends on the concentration of reactants and products

Question 17

What does dissolved CO2 depend on?

Answer 17

pCO2. So if pCO2 rises, pH will fall. If pCO2 falls, pH will rise

Question 18

What is the other source of HCO3-? (Not CO2)

Answer 18

From NaHCO3. This keeps HCO3- concentration high enough to prevent all CO2 dissolving. Keeps pH alkaline

Question 19

What does H+ from the reaction of CO2 and H2O do?

Answer 19

Bind to haemoglobin (Means there is less space for O2)

Question 20

Why doesn’t the concentration of HCO3- vary much with pCO2?

Answer 20

Because the reactions of CO2 in the red cell are mainly controlled by how much H+ binds to haemoglobin

Question 21

What happens when the body produces acid?

Answer 21

It will react with HCO3- (to buffer) and form CO2 which can be breathed out (prevents a large change in pH)

Question 22

Does more CO2 dissolve in venous blood or arterial blood?

Answer 22

Venous as the pCO2 is higher, but amount of O2 bound effects it as if more O2 is bound, there is less space for CO2

Question 23

What happens when there is extra CO2 in the venous blood?

Answer 23

More is converted to HCO3-
More H+ bind haemoglobin
When reaches lungs, O2 replaces H+ which reacts with HCO3- to make CO2 and is breathed out.
This prevents pH rising as both CO2 and HCO3- rises so ratio is the same

Question 24

What is a Carbamine compound?

Answer 24

CO2 can bind directly to proteins and these contribute to CO2 transport, but not acid/base balance