Basic Science #6: Hemoglobin

Hemoglobin was the first protein that we studied in biochemistry.  I have great fondness for this protein. 

Before I start talking about the chemistry of hemoglobin you should remember a few facts:

*Everybody knows this important protein in our blood. 

*It gives blood the red color because it contains an iron ion. 

*It is essential for binding oxygen and so it gives us energy. 

*Levels of hemoglobin in the blood are measured in any standard blood test. 

*Hemoglobin levels are higher in men than in women and that is one reason why men are usually stronger.

*Hemoglobin levels correlate with the number of red blood cells and levels of iron.  If hemoglobin levels are low it is often caused by iron deficiency anemia.

*The part of the protein that contains iron is called heme.

As I was studying the biology of proteins one fact always amazed me.  My childish impression was that the protein was made once and stayed like that.  But I found out that our cells are continuously making and breaking the proteins according to their need in the machinery of the cell.  If your cell needs the energy it will make more hemoglobin.  While you rest it will break down the protein to its individual amino acids.  And both these processes are very finely controlled.  It is amazing how super intelligent our cells are.

Chemistry of hemoglobin.

Check out this 3D model of hemoglobin:

Hemoglobin is made of 564 amino acids.  Molecular weight of hemoglobin is around 50,000 (For comparison: Oxygen molecule is 16, it fits in a small pocket of hemoglobin.)

Now try to imagine how these 564 amino acids fold in the cell to make the two subunits: a and b. These two subunits then double up to form a tetramer with two of each subunit.  Then the heme is inserted in each of the four subunits for a fully active protein enabling the special function of the hemoglobin - the transfer of the oxygen.  An alteration of any part of this structure of hemoglobin would cause inability to execute its duty of carrying oxygen.

I was really amazed to learn how complex is the structure of such an important basic protein.  The more I learn about the mechanism of action of proteins in our biology I am stunned to see the intricacy of it all.  

To add to the complexity of this we now measure levels of hemoglobin a1c in diabetes patients.  The high level of glucose molecules in the blood causes them to attach to the hemoglobin to form glycated hemoglobin:

I am thankful every day for the way my cells allow me to continue breathing and thinking, running and dancing!