Transport Of O₂

Question 1

Haemoglobin

Answer 1

carries 4 oxygen molecules
protein
4 sub units
4 polypeptide chains
haem (non-protein) group in each = iron ion Fe²⁺
iron ion has high affinity (attraction to oxygen)

Question 2

haemoglobin ___________ curve is _ shaped.

___ is plotted against ___

Answer 2

dissociation
S
pO₂
% saturation with O₂

Question 3

use what key words when talking about haemoglobin and oxygen?

Answer 3

associates/dissociates with

binds with

Question 4

how is the concentration of oxygen measured?

Answer 4

by relative pressure it contributes to mixture of gases
this is the partial pressure of oxygen or pO₂ also called oxygen tension
units kPa

Question 5

What is the partial pressure of oxygen (pO₂)?

Answer 5

the relative pressure that it contributes to a mixture of gases

Question 6

What is oxygen tension?

Answer 6

partial pressure of oxygen

Question 7

What happens at low oxygen tension?

Answer 7

Haemoglobin doesn’t readily associate with oxygen because the haem group is in the middle so oxygen molecules can’t reach it. So there is a low saturation level of haemoglobin at low oxygen tensions.

Question 8

What happens when oxygen tension rises?

Answer 8

The diffusion gradient into haemoglobin molecules increases.
When the first O₂ associates, a conformational change in haemoglobin occurs, then it easily allows more O₂ to bind. This causes the steepness of the curve as pO₂ rises.

Question 9

What happens at high oxygen tension?

Answer 9

as approaches 100% saturation of haemoglobin, the curve levels off

Question 10

_____ in lungs is _________, and ______ in ____ is _______ to _________

Answer 10

oxygen tension
high to produce close to 100% saturation
oxygen tension
tissues
low
cause oxygen to dissociate from oxyhaemoglobin

Question 11

Fetal haemoglobin has a ___________ so the curve ___________.
This is because ______________.
In the placenta _______________.

Answer 11

higher affinity for oxygen

for haemoglobin dissociation, is to the left of the adult haemoglobin curve (is steeper so associates more easily to oxygen as low pO₂)

fetal haemoglobin must be able to associate with oxygen in an environment where oxygen tension is low enough to make adult haemoglobin dissociate with oxygen.

pO₂ is low, fetal H will absorb O₂ from surrounding tissues making pO₂ even lower, so O₂ diffuses from mother’s blood fluid to placenta, reducing pO₂ in mother’s blood. This makes maternal haemoglobin release more oxygen.