Page 29 - The Cell in 40 Topics

he level of calcium in the blood is of vital importance for
survival. In the same way that a human being has to breathe
and drink water in order to stay alive, he or she also needs a
particular level of calcium in the blood. When the amount of calcium in the
blood falls below the level required, the individual dies.
Calcium enables our bodies to carry out many vital functions.. For one
thing, in the absence of calcium, blood will not clot—in which event, even a
small wound or cut could prove fatal due to loss of blood. Calcium also
plays an important role in the transmission of nerve signals, enables the
muscles to function, and contributes to bone strength. The body of every
healthy adult contains some 2 kilograms (4 pounds) of calcium. (Figure 17).
Some 99% of this calcium is stored in the skeletal system; the rest is em-
ployed in processes related to metabolism. Only 0.5 grams (0.01 ounces) of
calcium needs to be present in the bloodstream for bodily functions to be
maintained. 2
Let us now consider the following imaginary scenario: A one-liter (33-
ounce) bottle of blood is placed in front of you. You are told that this blood

27