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The
Chemistry of Life
Adrian
Whyte and Joanna Johnson, Contributor
ALL
LIVING organisms are made up of chemical
substances. Some of these substances
are very complex and contains the
elements carbon, hydrogen and oxygen,
these are know as organic substances
and they are an important ingredient
in all living things. On the other
hand some of these chemical substances
are simpler and usually lack the element
carbon, these are called inorganic
substances.
Hydrogen,
carbon, oxygen and nitrogen are very
important elements, they make up about
99 % of the mass found in all living
organisms.
The
main types of organic substances are
carbohydrates, fats and proteins.
Carbohydrates:
These include starches and sugars.
Their molecules are made up of the
elements carbon, hydrogen & oxygen
There
are three groups of carbohydrates
1)
Monosaccharides
2)
Disaccharides
3)
Polysaccharides
MONOSACCHARIDES:
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These are simple sugars such as glucose,
galactose
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They are sweet crystalline substances
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They are soluble in water
DISACCHARIDES:
These
are double sugars formed by condensation
(i.e. joining of two simple sugars
by the removal of water)
| See
Diagram 1 |
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Sucrose is made up glucose + fructose
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Maltose or malt sugar is made up of
glucose + glucose
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Lactose is made up glucose + galactose
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They are crystalline and sweet
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They are soluble in water
POLYSACCHARIDES:
These
are multi-sugars formed by joining
many simple sugars.
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Examples of polysaccharides are cellulose,
starch and glycogen.
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Cellulose - found in plant cell walls
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Starch - used as an energy store in
plants (Only found in plant cells.)
provides a food source in animals
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Glycogen - used as an energy store
in animals (Found in Animal cells
especially liver and muscle)
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They are NOT soluble in water
LIPIDS:
fats and oils contain the elements
carbon, hydrogen and oxygen composed
of glycerol and fatty acids (one glycerol
molecule and three fatty acids joined
together). They are insoluble in water
PROTEINS
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Contain the elements carbon, hydrogen
and oxygen as well as nitrogen
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Made up of chains of amino acids arranged
in a precise sequence
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Some are globular and soluble in water.
E.g. enzymes
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Some are fibrous and are insoluble
in water. E.g. Keratin in hair
Q1.
How do organisms obtain these substances?
Q2.
In addition to carbon, oxygen and
hydrogen, plants and animals require
other elements for their growth. Name
five minerals which are essential
for the healthy growth of green plants
and state their
function.
POINTS
TO REMEMBER
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Organic substances must contain both
the elements carbon and hydrogen
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Inorganic substances are required
in small amounts to assist in proper
growth and development .
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NUTRIENTS |
SOURCE |
FUNCTIONS
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Protein
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Beef,
liver, fish, lamb, eggs, poultry,
legumes, Nuts |
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Builds and repairs body tissues.
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Builds antibodies, the blood
components which fight infections.
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Builds enzymes
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| Carbohydrate
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Plantain,
yam, sugar, cereals, bread |
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Primary supply of energy
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Assists in the utilisation of
fats
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Structural purpose as in cellulose
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Fat
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Cheese,
margarine, cream, lard, milk,
vegetable oil, avocado pear, butter |
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Secondary supply of energy after
carbohydrates have been used up
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Aids in the absorption of fat
soluble vitamins
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Protects soft organ by acting
as a shock absorber
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Provides insulation |
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Adrian Whyte and Joanna Johnson
teach Biology at Ardenne High School.
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