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Name: Denise
Status: Other
Grade:  Other
Location: IN
Country: United States
Date: December 2006

How does hemoglobin carry oxygen to cells?

Hemoglobin is a metalloprotein (a protein that contains a metal) which is very important in oxygen transport. Hemoglobin has four parts (subunits) to it, each with an iron atom bound. Each iron atom can be oxidized by binding a molecule of oxygen, and each time this happens the protein changes shape so that it can bind more oxygen molecules more effectively, this is known as cooperativity.

If the hemoglobin is an environment that is low in oxygen it won't bind much oxygen, but as a result of cooperativity if the hemoglobin is around a lot of oxygen it will bind the oxygen very well. This way hemoglobin is used by the body to take oxygen from the lungs (where there is a lot of it) to places like our muscles (which are low in oxygen).

Ethan Greenblatt
Ph.D. Candidate
Stanford Department of Chemistry

Each hemoglobin molecule contains four iron atoms each of which can reversibly bind an Oxygen molecule.

Ron Baker, Ph.D

Hi Denise

Here's the basics of how our red blood cells function in taking oxygen from our lungs to our functioning tissues.

To start, it is important for the cells in our body to have a constant supply of oxygen. These cells need oxygen to make energy in the form of ATP. The cells make this energy mainly by breaking down sugars (glucose is the sugar most preferred by our cells) and extracting the energy from it. This usable energy is stored within the chemical bonds of a molecule called ATP. Without oxygen our cells can make only a fraction of the ATP that we need. Without ATP our cells cannot carry out their functions and cannot survive, they quickly become damaged and die. If this happens, WE become tired, sick and aren't able to survive. So we really need a good way to assure that the tissues in our body get the oxygen that it needs!

More about ATP and it's importance later.

So now we know how important oxygen is to our bodies - but there is one problem - oxygen does not dissolve in our blood very well. This is where hemoglobin comes in.

Red Blood cells (also known as erythrocytes) serve many functions in our body. One of the main jobs of the erythrocyte is to carry oxygen to our working tissues. Erythrocytes are the red blood cells that are dissolved in our blood.

Erythrocytes contain a protein called hemoglobin. Hemoglobin contains four "pockets" if you can use your imagination. In the middle of each pocket is a molecule of iron. It is this iron that is responsible for the oxygen carrying capabilities of hemoglobin and our red blood cells.

In our lungs, the concentration of oxygen is high. Oxygen enters the red blood cells and binds to the iron within the hemoglobin molecules. It is the binding of oxygen to the iron inside hemoglobin that enables our blood to carry enough oxygen to our cells so they can keep working.

From our lungs, this oxygen rich blood goes to our hearts, where it is pumped out into our bodies through the biggest artery in our body, the aorta. Our aorta branches into many other arteries that deliver this blood, which contains all of that fresh oxygen bound to its hemoglobin - to our brain, muscles, organs and other tissues. Once it reaches these working tissues, it drops off some if it's oxygen so these cells can use it to make ATP. Because the oxygen concentration is low at these places, it can come off of the hemoglobin. It will then pick up carbon dioxide - which is produced by working tissues as a waste product of making ATP - and once again return to our lungs where it will drop off the carbon dioxide (which we will breath out) and pick up some more fresh oxygen (which we breath in).

Hopefully this helps. These are very cool and complex processes. There are many other factors to think about when it comes to all of these processes that I described above. I hope you find them interesting and this raises more questions and furthers your study of them.

Physiology, science and medicine can be very fascinating!

Stephen A. Sardino Jr.
Pennsylvania State University - College of Medicine

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