Question

What is the structure of hemoglobin and how is oxygen bound to it?

Answer 1

Answer:

The correct answer would be "Hemoglobin is made of four protein subunits. Within each subunit, is a heme group made of nitrogen and iron. The heme groups bind to oxygen".

Hemoglobin is a protein exists in quaternary structure. It has four sub-units namely 2 alpha subunits and 2  beta subunits. The structure is denoted as α₂β₂.  

The subunits are bound together with the help of hydrogen bonds, salt bridges, and hydrophobic interactions.

Each subunit consists of a protein chain and a prosthetic group termed as heme which consists of iron ion and a porphyrin ring. The iron and the four nitrogen atoms lie in one plane in the center of the ring.

This iron serves as the oxygen binding site in the hemoglobin.

Answer 2

The last option is correct about the structure of hemoglobin. Hemoglobin is made of four subunits. Each subunit contains a polypeptide chain called globin and a heme group. So there are 4 polypeptide chains (globin chains), two of which are called alpha chains and the other two are beta chains. Each polypeptide chain is associated with a heme group which has iron at the center. It is the oxygen binding site.

So 1 hemoglobin molecule - has 4 heme groups (each heme group binds to an oxygen molecule)

Thus 1 hemoglobin molecule - can carry 4 oxygen molecules.