Gas Transport

Question 1

How is oxygen carried in the blood?

Answer 1

Dissolved in plasma

Attached to haemoglobin

Question 2

What is oxygen proportional do if its dissolved in plasma?

Answer 2

Partial pressure

Question 3

if oxygen dissolves in plasma and its PO2 is 100mmHg, how much oxygen will there be?

Answer 3

0.3ml/100ml

Question 4

What is formed when all four binding sites on haemoglobin have been filled?

Answer 4

Oxyhaemoglobin

Question 5

Describe the oxygen-haemoglobin dissociation curve?

Answer 5

Sigmoidal

As one oxygen binds, it causes a conformational change making it easier for the next to bind

Question 6

What happens if the partial pressure changes at the steep lower part of the oxygen dissociation curve?

Answer 6

Large amounts of oxygen can be extracted for a small drop in PO2

Question 7

What happens if the partial pressure changes at the plateau at the upper end of the oxygen dissociation curve?

Answer 7

If PO2 falls, saturation is not greatly altered so at altitude the O2 supply is still usually adequate

Question 8

How does PO2 change in the lungs after inspiration?

Answer 8

Goes from 40mmHg to 100mmHg so Hb essentially is fully saturates

Question 9

How does PO2 change at the tissues?

Answer 9

PO2 has fallen by more than half, but the Hb is still around 75% saturated

Question 10

What things shift haemoglobin saturation to the right?

Answer 10

Increase in;

Temperature

Hydrogen ions

CO2

2,3-bisphosphoglycerate

Question 11

Why is an increase in temperature good?

Answer 11

Modifies haemoglobin structure so that it has less of an affinity for oxygen

This means warmed up muscles release O2 faster and a good reason to race-prep

Question 12

How does an increase in CO2 move to Hb saturation curve to the right?

Answer 12

Increased CO2 leads to an increase in hydrogen ions which weaken the Hb-O2 interaction- called the Bohr Effect

Question 13

When does the Hb saturation curve switch to the right?

Answer 13

At the lungs

Question 14

What does the amount of oxygen carried in the blood equal?

Answer 14

Amount carried by haemoglobin + amount dissolved

Question 15

How do you calculate amount carried by Hb?

Answer 15

Concentration in the blood multiplied by the maximum oxygen carrying capacity multipled by % saturation of Hb

Question 16

How much haemoglobin is there in 100ml of blood?

Answer 16

15g

Question 17

What is the total amount of oxygen carried in the blood?

Answer 17

20ml O2/100ml

Or 200ml of O2/litre

Question 18

How can carbon dioxide be transported in the blood?

Answer 18

Dissolved in plasma

Bound to haemoglobin

As bicarbonate

Question 19

How much of carbon dioxide is transported in plasma?

Answer 19

7-10%

Question 20

How much of carbon dioxide is transported by haemoglobin?

Answer 20

10-20%

Question 21

What does carbon dioxide bind to on haemoglobin molecule?

Answer 21

Amino acids

Question 22

what is the Haldane effect?

Answer 22

Deoxygenation of Hb increases its ability to bind CO2 and vice versa in the lungs, oxygenation of Hb releases CO2 into plasma for transport into alveoli

Question 23

What percentage of haemoglobin is found in bicarbonate form?

Answer 23

70-80%

Question 24

what happens when CO2 dissolves in water?

Answer 24

Produces carbonic acid, this degrades quickly into hydrogen ion and bicarbonate

Bicarbonate diffuses down concentration gradient into plasma

hydrogen ions bind the haemoglobin

Chloride ions move into RBC to maintain electrical balance

Process reversed in the lungs, HCO3 moves back into RBC (chloride moves ut), reacts with H+ to form carbonic acid which is rapidly reacted by carbonic nhydrase to orm CO2 and water. CO2 diffuses into alveoli space.

Question 25

What is the function of carbonic anhydrase?

Answer 25

Producing carbonic acid from CO2 and water

Question 26

What is haemoglobin’s new name once CO2 binds?

Answer 26

Carbaminohaemoglobin

Question 27

How do you calculate the pH of blood?

Answer 27

pK add the log( conc of bicarbonate/ conc of CO2)

Question 28

What is the pK used to calculate the pH of blood?

Answer 28

6.1

Question 29

What happens if ventilation decreases for too long?

Answer 29

CO2 increases

pH falls

Bicarbonate increases

Causing respiratory acidosis

Question 30

What happens if the patient hyperventilates?

Answer 30

Patient blows off more CO2

pH rises

Levels of bicarbonate fall

Respiratory alkalosis