Page 14 - Biology Form Two

Biology for Secondary Schools

molecules found in certain foods and in the liver. The glycogen is stored
drinks. Sources of carbohydrates include in the liver and muscles, while fats
maize, sweet potatoes, sugarcane, are stored as fat deposits in the lower
bananas, cassava, fruits, and yams, as abdomen, around kidneys, and under
shown in Figure 1.5. the skin. Glycogen acts as a source of
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energy when there is short supply of
carbohydrates in the body. In the muscles
and liver, glycogen is broken down to

glucose for provision of energy when
required, for example, during a vigorous
physical activity. Also, carbohydrates
combine with proteins and lipids to

form glycoproteins and glycolipids,
Figure 1.5: Sources of carbohydrates respectively, which are important
components of cell membranes.
Functions of carbohydrates
Carbohydrates are a major source of Vitamins
energy in the body. In an ideal situation, Vitamins are complex organic
we should get two-thirds of our energy micronutrients that are essential for
from carbohydrates. They are broken body growth and survival. Animals need

down into glucose which acts as fuel vitamins for proper body functioning and
metabolism. Vitamins can be grouped
for the body. Each gram of carbohydrate into two categories, which are water-
produces four kilocalories (kcal) of soluble and fat-soluble vitamins.
energy in the body to be used by the
cells to perform work. Carbohydrates are Fat-soluble vitamins can be stored in
also essential for the proper functioning the body. Vitamins A, D, E and K are
of the nervous system, heart, and examples of fat-soluble vitamins.

kidneys. In addition, carbohydrates Water-soluble vitamins are not stored in
form genetic materials, which are DNA the body. Vitamins B and C are water-
(Deoxyribonucleic Acid) and RNA soluble. Vitamin B is of various forms
(Ribonucleic Acid) in the cells. namely, vitamin B , B , B , B , B and
1 2 3 6 9
Excess carbohydrates in the body are B . These can be easily destroyed by
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converted into either glycogen or fats heat.

8 Student’s Book - Form Two

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BIOLOGY FORM 2 NEW.indd 8 05/10/2024 15:36:18