Hemoglobin

Hemoglobin

Structure
1. tetramer, made up of two alpha subunits and two beta subunits. each binds a heme
2. subunit has similar structure to myoglobin
Myoglobin
1. made up of alpha helices with connecting loops with heme sitting in a pocket
2. Heme contains iron which can bind to oxygen at one of its six ligand sites
3. only unloads oxygen when levels become unusually low.
Binding of Oxygen
1. four oxygen molecules bind per hemoglobin, one per subunit.
2. binding curve = sigmodial
  1. binding of one oxygen molecule makes it easier for a second to bind
  2. homotrophic positive cooperative effect = affinity of binding of oxygen for the fourth oxygen is 20 fold greater than the affinity for the first oxygen
Allosteric change
1. alpha and beta subunit are more associated with each other than the other two subunits
  1. when oxgen binds, the subunits change their position. this is due to the change of shape of heme when oxygen binds.
    1. When oxygen isnt bound iron doesnt fit in the planar structure but when bound it becomes smaller and can fit
2. this change results in the molecule shifting from low affinity (T) to high affinity (R) state.

Resource summary

	Created by kathrynmoar over 10 years ago