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A Student Guide
The term carbohydrate was applied to the sugars and related organic compounds because many (but not all) fit the
formula CH2O. Deoxyribose (a pentose (5) sugar) is a widely known example of a carbohydrate in which the
hydrogen to oxygen ratio is not 2:1. Other sugars may contain nitrogen or phosphorus in addition to carbon,
hydrogen, and oxygen. In biological systems, sugars are often combined with lipids or proteins, or are stored as
water insoluble polysaccharides. Glucose may be oxidized for energy, converted into fats, or reacted with
nitrogen-containing compounds to produce amino acids. In addition to starch and glycogen, cellulose, gums and
chitin are important polysaccharides.
The lipids are a heterogeneous group of organic compounds classified together because they are insoluble in water
and soluble in organic solvents such as ether, benzene, and acetone. Lipids provide organisms with a concentrated
source of energy, yielding twice as many calories per gram as carbohydrates. Naturally occurring fatty acids are
straight-chained, saturated or unsaturated, and have an even number of carbon atoms. The fatty acids you will
model are typical, except most have longer chains. Other important lipids are the steroids, waxes, and
phospholipids. Cholesterol, a steroid, is associated in occurrence with animal fats, especially the saturated ones.
Lipoproteins are complex compounds formed from lipids and proteins.
Proteins are among the most complex of organic compounds. Proteins differ in the number, kind, and arrangement
of their amino acids; in molecular shape; and in distribution of electrical charge over the molecule. They form
complexes with other organic molecules and are basic functional and structural components of all living systems.
QUESTIONS
1.
If deoxyribose has five carbons but is missing one oxygen what will its chemical formula be? Use the CH 2O
ratio to help you – but be careful!
2. List several functions of carbohydrates in your own words – DO NOT SIMPLY COPY SENTENCES FROM
THE FIRST PARAGRAPH.
3. Why would we call the lipid group HETEROGENEOUS?
4. What will be the difference between fatty acid chains in nature and the models you will be making?
5. Two proteins found in the blood are hemoglobin and myoglobin. Without knowing the chemical formulas,
what differences would you expect to see between these two molecules?