THE RED BLOOD CELLS
The red blood cells form a major part of the blood. It is shaped like a doughnut except that it does not have a hole. There is a slight depression on the centre of the cell. The red blood cells are very important to you. No one can survive without them.
The most honourable duty of red blood cells is to carry oxygen gas around the body. Although they do carry a little carbon dioxide sometimes, most of this unwanted gas is transported by the
How does a red blood cell carry oxygen? Within a red blood cell, there is a red pigment, known as as haemoglobin. Each haemoglobin has 4 iron (hemes) and proteins ( globins).
The 4 hemes are each attach to 1globin, which is a polypeptide chain.
As the red blood cell arrives at the lungs, one oxygen molecule is attached to one iron molecule in the cell. Loaded with the oxygen molecules, the pigment is now known as the oxy-haemoglobin. The cell
has a bright red colour at this stage.
When the blood goes around the body, the red blood cells have to unload all these oxygen molecules at places where they are
needed, such as at muscle cells carrying out respiration.
In the lungs, there's a high concentration of oxygen, relatively low temperature, and less acidic. In such a condition, a red blood cell automatically absorbs oxygen.
In the tissues, where respiration is carried out, it's relatively warmer, lower in oxygen concentration and is likely to be more acidic due to a higher concentration of carbon dioxide. Here, the cell is more likely to lose the oxygen. Without any oxygen molecules in the cell, it appears dull red. The pigment inside the cell is now called deoxyhaemoglobin. And the cell is quickly transported back to the lungs to be reloaded with oxygen.
red blood cell has well-adapted features to help it carry out this tiresome task:
- the cell has no nucleus. All other
cells are born with a nucleus, but not the red blood cell. Without
the large structure in the cell, it can carry more oxygen. But
because without this nucleus, it cannot reproduce and will die eventually.
A red blood cell's life span is about 3-4 months. After that, it
will be sent to the liver to be destroyed. The iron is used to
produce new red blood cells. The cycle goes on this way..
- The red blood cell does not have mitochondria and other organelles present in a normal cell. Mitochondria
generate energy for a cell to carry out activities, and since
a red blood cell doesn't have any, it depends on anaerobic respiration. It is another kind of respiration that is carried out without oxygen.
This is so that the cell does not use up any of the oxygen it is
carrying, or else other tissues will be starved of oxygen. If
the red blood cell uses up the oxygen it is carrying, it would be like a pizza delivery man eating up all the pizzas he's delivering.
ęCopyright TQ Team 25896, 1999. The Circulatory System- Online Learning.