Question

Biochem question

1. List positive and negative effectors for oxygen binding to hemoglobin.

2.List the structural changes that occur when oxygen binds to the heme group in Mb, and in Hb

Answer 1

1. Hemoglobin consists of four subunits. Each heme unit contains iron in the +2 oxidation state in the centre. Each heme is capable of binding with one oxygen molecule.

The addition of oxygen is by a mechanism called allosteric addition. Basically, hemoglobin is a protein which has primary, secondary, tertiary and quaternary structures. Once oxygen binds to a heme, the oxidation state of iron changes from +2 to +3. The overall process causes a change in the quarternary structure of the heme. This makes it more conducive for the oxygen to bind to the adjacent heme in the hemoglobin molecule. So, the binding of oxygen takes place in 4 steps, not at once. Each step makes it easier for the next oxygen molecule to bind with the heme.

Negative factors are                                                                                                                                                         i) Oxygen concentration should be moderately good. Otherwise, the oxygen will not bind with hemoglobin.                             ii) Some gases like Carbon Monoxide has a much higher affinity for hemoglobin than oxygen. That is why exposure to such gases in the lack of fresh air leads to poisoning sometimes even death.