Oxygen In Blood

Question 0

Draw an oxygen-haemoglobin dissociation curve, label the axes correctly and indicate the normal values of alveolar pO2 and capillary pO2 in a typical tissue

Answer 0

Sigmoidal shape (oxygen bound vs pO2) 
Alveolar pO2 = 13.3kPa
Capillary pO2 = 8.8mmol/L
Tissue pO2 = 5kPa

Question 1

State the solubility of oxygen in bodily fluids

Answer 1

Oxygen is not very soluble in water

Oxygen is soluble in body fluids due to reversible reaction with haem

Question 2

List the properties of the Hb molecule which facilitates the transport of oxygen in the blood

Answer 2

Very reversible reaction 
Tetramer (2a, 2B) 
Each subunit = haem + globin 
Haemoglobin has two states - tense/relaxed
Tense = low affinity 
Relaxed = high affinity

Question 3

Draw the effects on the Hb dissociation curve of a fall in pH and a rise in temperature

Answer 3

Bohr shift (to right) in low pH (acid) and high temperature
Hb is more tense in these conditions
Less oxygen is bound, more is given up at tissues

Question 4

Estimate the rate of delivery of oxygen to the tissues at different capillary pO2s and pHs

Answer 4

Low pO2 and pH = increased delivery of oxygen

Question 5

State the factors influencing the diffusion of gasses across the alveolar membrane

Answer 5

Diffusion distance
Gradient
Rate of blood/gas flow

Question 6

Describe in outline how the transfer factor (‘diffusion capacity’) of the lungs may be determined

Answer 6

CO transfer measures diffusion conductance
CO has a high affinity for Hb so pCO is decreased
CO from alveolar blood limited by diffusion capacity of lung