Oxygen transport

Haemoglobin structure

• 4 subunits that all contain a haem group.

• haem contains iron which is binding site for oxygen.

• binds with oxygen to form icy haemoglobin

Positive cooperative binding

once oxygen to ones subunit, it becomes easier to bind to the remaining subunits as they go through conformational change

Affinity

how strongly oxygen is bound to haemoglobin.

• Low partial pressure=lower affinity so oxygen releases (tissues)

• High partial pressure=increase affinity. (strongly bound to haemoglobin)

Partial pressure

“oxygen concentration”

in tissue, oxygen concentration is lower.

In lungs, oxygen concentration is higher.

Oxygen dissociation curve

shows that at lower partial pressures (4kPa) only 25% saturation so only one haem can bind (low affinity)

But as partial pressure increases, affinity increases and saturation is around 75% (2 more haem bind)

Graph up = lungs

Graph down = releasing to tissues/muscles.

Fetal haemoglobin

shift to the left, as they have higher affinity because little oxygen would be transferred.

higher affinity allows fetals to obtain oxygen from mothers blood at placenta.