BASIC BIOLOGY & METHODS of SCIENCE

Introduces fundamental biological mechan-
isms that are basic to an understanding of
how organisms live and function. Presents
some of the fundamental intellectual, phys-
ical & conceptual tools of scientific study.

CHEMISTRY FOR BIOLOGISTS
Reviews basic concepts in chemistry of importance to biological scientists. 20 slides and guide.
EPSS-0945S SLIDES
$42.50

GENERAL CHEMISTRY FOR BIOLOGY Slides order #SS-0945S............$42.50

Modern biology has become increasingly concerned with investigating under-
lying mechanisms of living systems. Purely descriptive approaches are no longer
adequate. This program reviews some of the basic concepts of chemical structures and
bonds that are most helpful to an understanding of modern biology. 20 frames and guide.
(Filmstrip order SS 0945F........$15.00.)

CONTENT SAMPLE: 15. Phospholipids and steroids are two more types of lipids with
important biological roles.

Phospholipids are similar to fats in having a glycerol backbone and fatty acid side-
branches, except that one of the fatty acid molecules is here replaced by a group containing
phosphorus and nitrogen. The nitrogen group is charged and this polarity renders that end of the
phospholipid molecule soluble in water; the other nonpolar end is water insoluble. Phospholipids
are prevalent in cell membranes where their insolublility aids in the regulation of cellular water
content. Phospholipids also participate in blood clotting.

Steroids are complex molecules that are often classified with lipids; they too are insoluble
in water but soluble in ether. The structures of steroids are very different from those of other
lipids, however. Instead of an alcohol backbone with fatty acid sidechains, steroids are composed
of four interlocking carbon rings. To this basic configuration are attached various side groups
which give different steroids their specific properties. Some vitamins and hormones are steroids.
Ergosterol, for example, is a steroid in the skin that forms vitamin D when exposed to ultraviolet
radiation. The male and female sex hormones (testosterone and estrogen respectively) are also
steroids. So is cholesterol, an important constituent of cell membranes and bile.
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