Re: Explain the reason human red blood cells are clear in the center and why...

Well, your source is correct, but there's another reason why red blood cells have a doughnut shape too--it helps them flow through blood vessels well. When a person has Sickle Cell Anemia, their blood cells are shaped like sickles, and they stick to one another. This keeps them from flowing through blood vessels and they can't do their job. The big issue here is that the person's immune system attacks the sickle cells to get rid of them, and the body cannot replace them quickly enough. Okay, now for the shape of blood cells. A blood cell's job is to carry oxygen. That's what hemoglobin does: it's a protein with iron atoms in the middle that can associate with oxygen and carry it through the bloodstram. Things like the blood's pH, oxygen and carbon dioxide concentrations affect the oxygen carrying capacity of blood. So, why the shape? Think about it this way: if you're moving everything from your bedroom to another room in the house, and you have a cart to help you, are you going to want to use a small cart or a large one that has lots of space for your stuff? The large one, right? It's the same in a blood cell. If a blood cell is round, the amount of hemoglobin that has access to oxygen is less than if there's a depression in the middle. Try this: take a balloon with a large-ish opening and stretch it over a faucet. Fill the balloon half to 2/3 of the way full with water. Tie a knot at the end. Look at your balloon and imaging that it's a red blood cell. If this balloon's swimming around your blood, and it's in your lung trying to get oxygen, what part of the liquid inside is going to have the most access to the air being transfered to it in the lung? The liquid at the periphery of the balloon, right? So, how could you increase the amount of oxygen that this cell picked up? You could shape it so that there was more liquid at the periphery, correct? How would you do this? Take your balloon and pinch it in the middle so that it has a doughnut shape. Do you notice that the balloon is easier to see through in the middle with this shape? This explains the explanation your found in one way. But can you also see that now you not only have liquid in the periphery as you did before, but the thinness of the balloon in the middle gives more liquid in the center access to the air around it, so the cell can carry more oxygen. You find this kind of thing all over the body--the cell needs to increase its surface area, so it generates folds or all kinds of funky shape changes to accomodate that need. Look at mitochondria in the cell--all those little folds, called christae, make your mitochonria power houses for your cell. If you have more questions or need more information, just send another email. Sources: http://www.kidshealth.org/kid/health_problems/blood/sickle_cell.html http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=1236400&pageindex=1 http://www.anapsid.org/cnd/diagnosis/redcells.html http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=red+blood+cell+shape+AND+mcb%5Bbook%5D+AND+106746%5Buid%5D&rid=mcb.section.5117#5130