Page 13 - Biology Form Two

Biology for Secondary Schools

When proteins are consumed, they are
broken down into amino acids that are
absorbed into the bloodstream and used
by the body to produce its own proteins.
For example, the haemoglobin found
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in the red blood cells is one of the
body proteins. Haemoglobin enables
red blood cells to transport oxygen in

our bodies. Other examples of body Figure 1.4: Sources of lipids
proteins include antibodies which
provide body immunity and enzymes Functions of lipids
that are involved in food digestion. In Lipids are a source of energy. They
addition, many hormones are protein provide more energy than all other food
in nature. They control and regulate substances. Each gram of lipid provides
various processes in the body. nine kilocalories (kcal) of energy.
They are important components of cell
Lipids membranes. Fat deposits surround and
They are organic compounds made of protect body organs such as the heart
carbon, hydrogen, and oxygen. They are and kidneys. Stores of fat in the adipose
insoluble in water but soluble in organic tissue under the skin help to regulate
solvents such as ether and benzene. The body temperature by insulating the
main forms of dietary lipids are fats and body against loss of heat. Fat-soluble
oils. Fats are solid at room temperature vitamins are also stored in fatty tissues.
while oils are liquid at room temperature. Essential fatty acids are important for
Lipids are made up of fatty acids and the formation of substances that help to
glycerol. Fatty acids can be essential or control blood pressure and activate the
non-essential. Essential fatty acids are body’s immune response.
obtained from foods eaten while non-
essential fatty acids can be made by the Carbohydrates
body. The body can not produce essential
fatty acids. It is, therefore, important Carbohydrates are organic compounds
to eat foods that contain essential fatty made up of small repeating units called
acids. Examples of such foods are oily monosaccharides. The small repeating
fish, nuts, avocados, oil, and seeds such units form bond with each other to make
as sunflower and sesame, as shown in a larger molecule. Monosaccharides are
Figure 1.4. mainly made up of carbon, hydrogen,
and oxygen. Carbohydrates are sugar

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