7.1 - Haemoglobin

Describe what haemoglobin is and its function. (2)

• Protein found in red blood cells

• Binds to oxygen and carries it around the body

Describe the structure of haemoglobin (2)

• Quaternary structure with 4 polypeptide chains

• Contains 4 haem groups

What occurs in the capillaries in the lungs? (3)

• There is a high concentration of O2

• So haemoglobin binds to oxygen via oxygen loading or association

• Forms oxyhaemoglobin

How many oxygen molecules can one hemoglobin molecule carry?

4 oxygen molecules (one per haem group)

What occurs after body has transported oxyhaemoglobin to capillaries in body tissues? State what this process is called. (3)

• Low O2 concentration

• Haemoglobin releases oxygen so cells can use it for respiration; oxygen unloading/dissociation

• Blood returns to lungs and cycle starts again

What does haemoglobin saturation with oxygen depend on? (1)

the oxygen concentration, or partial pressure of oxygen (pO₂)

The units of partial pressure are…?

Kilopascal (kPa)

What is an oxygen dissociation curve?

It is a graph that shows us how the % saturation of haemoglobin with oxygen depends on the partial pressure of O2.

How does a higher pO₂ affect haemoglobin saturation?

Haemoglobin has a high affinity for oxygen and binds with it (e.g. in the lungs).

How does a lower pO₂ affect haemoglobin saturation?

Haemoglobin has a low affinity for oxygen and releases it (e.g. at respiring body cells).

What does the cooperative nature of oxygen binding mean? (2)

• When haemoglobin binds with one oxygen, it changes shape so it becomes easier to bind another oxygen.

• When haemoglobin is mostly saturated with oxygen, it is harder for more oxygen to bind.

How does fetal haemoglobin differ from adult haemoglobin? (3)

• Fetal haemoglobin has a higher affinity for oxygen as it must obtain oxygen from the mother’s blood

• Allowing O2 to dissociate from the mother’s haemoglobin and associate with fetal haemoglobin instead

• Ensuring fetus gets enough O2 to survive whilst it develops.

How does haemoglobin differ across different species? (2)

• Animal at high altitude/inactive: O2 pressure lower so haemoglobin has higher affinity for oxygen & O2 binds to it more easily

• Animal at low altitude/active: O2 pressure higher so haemoglobin has lower affinity for oxygen to ensure O2 dissociates to respiring cells quickly.

What does the Bohr effect describe?

How haemoglobin has a lower affinity for oxygen when CO2 is present.