Transport of oxygen in the blood Flashcards
What does oxygen do in the pulmonary capillaries?
Most of it binds to haemaglobin, until haemaglobin is fully saturated
Then it dissolves in the blood, until the pO2 of the blood is equal to the pO2 of the alveoli
What is the equation for the total amount of oxygen in the blood?
Total oxygen = haemaglobin-bound oxygen + dissolved oxygen
Why does most of the oxygen bind to haemaglobin?
Because oxygen has a low solubility coefficient
so it is not very soluble
What does oxygen in the tissue capillaries do?
Oxygen diffuses from the tissue capillaries into the tissue
until the pO2 in the tissue is equal to the pO2 in the tissue capillaries
What is the pO2 in the tissues? Why?
5kPa
Because oxygen diffuses from the tissue into the cells
What is the pO2 in the cells? Why?
3kPa
Because oxygen in the cells is used up in aerobic respiration
What is the minimum pO2 in the tissues? Why?
Higher than 3kPa
Because it needs to be higher than the pO2 in the cells
in order to maintain the partial pressure gradient for diffusion
How many molecules of oxygen can bind to haemaglobin?
Four
one per haem group
What are the different states of haemaglobin?
T state, tense state
R state, relaxed state
What is the tense state of haemaglobin?
Has low affinity for oxygen
What is the relaxed state of haemaglobin?
Has high affinity for oxygen
What promotes the tense state of haemaglobin?
Low pO2
2,3-BPG
CO2, H+
Temperature
How does low pO2 promote the tense state of haemaglobin?
Less oxygen binds to haemaglobin
no conformational change of haemaglobin
remains tense
Where is 2,3-BPG located?
In red blood cells
What promotes the relaxed state of haemaglobin?
High pO2
How does high pO2 promote the relaxed state of haemaglobin?
More oxygen binds to haemaglobin
conformational change of haemaglobin
puts it in relaxed state
Which of the four oxygen molecules that bind to haemaglobin is the hardest to bind? Why?
The first one
because haemaglobin is in its tense state
Once the first oxygen molecule has bound to haemaglobin, how does the difficulty of binding the other oxygen molecules change?
Becomes easier
because haemaglobin undergoes conformational change
is now in its relaxed state
How can the effect of pO2 on oxygen binding to haemaglobin be presented?
Haemaglobin oxygen dissociation curve
What are the axes of the haemaglobin oxygen dissociation curve?
x axis is pO2
y axis is % saturation of haemaglobin
What shape is the haemaglobin oxygen dissociation curve? Why?
Sigmoidal
because the binding of oxygen molecules to haemaglobin becomes easier as more of them bind
What is the pO2 at which haemaglobin is fully saturated?
10 kPa
What is the pO2 at which haemaglobin is half-saturated?
3.5 kPa
How saturated is haemaglobin in the pulmonary capillaries?
Fully saturated
How saturated is haemaglobin in the tissue capillaries?
65%
What is the advantage of haemaglobin only releasing 35% oxygen to tissues when at rest?
When tissues are more metabolically active than at rest
allows for more oxygen to be released
How do carbon dioxide and hydrogen ions and 2,3-BPG and increased temperature affect haemaglobin and oxygen?
Promote tense state of haemaglobin
lower affinity of haemaglobin for oxygen
How do carbon dioxide and hydrogen ions and 2,3-BPG and increased temperature affect haemaglobin releasing oxygen to the tissues?
Releases more oxygen to tissues
How do carbon dioxide and hydrogen ions and 2,3-BPG and increased temperature affect the haemaglobin oxygen dissociation curve?
Cause it to the shift to the right
What is the name of the effect that carbon dioxide and hydrogen ions have on haemaglobin?
Bohr shift
What is the advantage of the Bohr shift?
More metabolically active tissues produce more carbon dioxide and hydrogen ions
recieve more oxygen from haemaglobin to meet their increased demand for oxygen
