Oxygen dissociation curve

Question 1

After the first oxygen molecule binds to haemoglobin, the haemoglobin protein changes shape, or conformation, making it easier

Answer 1

for the next haemoglobin molecules to bind; this speeds up binding of the remaining oxygen molecules and explains the steeper part of the curve in the middle of the graph
The shape change of haemoglobin leading to easier oxygen binding is known as cooperative binding

Question 1

Due to the shape of the haemoglobin molecule it is difficult for the first oxygen molecule to bind to haemoglobin; this means that binding of the first oxygen occurs

Answer 1

slowly, explaining the relatively shallow curve at the bottom left corner of the graph

Question 2

As the haemoglobin molecule approaches saturation it takes longer for the fourth oxygen molecule to bind due to

Answer 2

the shortage of remaining binding sites, explaining the levelling off of the curve in the top right corner of the graph

Question 3

When the curve is read from left to right, it provides information about the rate at which haemoglobin binds to oxygen at different partial pressures of oxygen

At low pO2, in the bottom left corner of the graph, oxygen binds slowly to haemoglobin; this means

Answer 3

that haemoglobin cannot pick up oxygen and become saturated as blood passes through the body’s oxygen-depleted tissues

Question 4

Haemoglobin has a low affinity for oxygen at……………….. so saturation %

Answer 4

low po2

Question 5

At medium pO2, in the central region of the graph, oxygen binds more easily to haemoglobin and saturation increases quickly; at this point on the graph a small increase in

Answer 5

a small increase in pO2 causes a large increase in haemoglobin saturation

Question 6

At high pO2, in the top right corner of the graph, oxygen binds easily to haemoglobin; this means that haemoglobin ……………..

Answer 6

can pick up oxygen and become saturated as blood passes through the lungs