Week 4 - Oxygen In The Blood

Question 1

What is the alveolar partial pressure of oxygen?

Answer 1

13.3kpa

Question 2

If partial pressure of oxygen is 13.3kpa then haemoglobin is saturated. Therefore how would you calculate the oxygen content of the blood?

Answer 2

Hb conc in blood is 2.2mmol. Each Hb binds one molecule therefore = 8.8mmol.l-1

Question 3

How low can po2 get in the tissues?

Answer 3

Tissue po2 must be high enough to still drive diffusion in to the cells. Therefore cannot be below 3kpa. However the higher the cap density the lower the po2 can fall as doesn’t have so far to diffuse eg metabolically active tissue like the heart

Question 4

Explain the Bohr shift

Answer 4

Shifts curve to the the right. Therefore allowing the haemoglobin to dissociate from the bound oxygen at higher partial pressures of oxygen. Eg acid conditions promote the tense state.

Question 5

What are the effects of 23bpg

Answer 5

Shifts curve to the right therefore releasing oxygen at lower partial pressures in the tissues. Levels of 23bpg rise with anaemia or altitude.

Question 6

Why does a dissociation curve of myoglobin plateau?

Answer 6

Saturates the limit supply of myoglobin