MadSci Network: Biochemistry |
Dear Nancy, Your confusion between the experiment that you performed, that is, decalcifying a chicken bone and the brittleness of bone in an individual who is suffering from osteoporosis is understandable. Unfortunately when people talk about osteoporosis, they concentrate on just calcium rather than the actual problem. When you placed the chicken bone in vinegar and removed calcium you simulated a condition known as "osteomalacia," where not enough calcium is deposited in the forming bone (in kids the same condition is known as "rickets," it is only in adults that it is called osteomalacia). People suffering from osteomalacia have bones that do not have enough calcium in them and the bones begin to bend, especially the long bones of the leg, under the weight of the body. Individuals who have osteoporosis have a different problem, namely, they lose bone tissue, not just calcium. Technically, their bones do not become more brittle. Instead they have thinner bones than they should for their body mass and thus they are more likely to break. However, if you take a piece of osteoporotic bone and a piece of normal bone, the bone composition (% of inorganic substances and % of organic substances) will be the same as for normal bone. However, for the same volume of bone tissue, the bone mass will be less. What I am trying to say is this: assume that you take one of the vertebrae from the individual before osteoporosis sets in and weigh that vertebra and measure its density. Then put it back in where you found it and wait a few decades until after osteoporosis has set in. Then take out the same vertebra, you'll find that now it weighs less and has less density. But, biochemically its composition will not have changed. I hope this helps. Les Gartner, Ph.D. Department of Anatomy, Dental School University of Maryland at Baltimore lgartner@umaryland.edu
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