(c) Fats and Oils (Lipids) : Fats and their
derivatives are collectively called lipids. Fats are the compounds
of fatty acids and glycerol. They are composed of C, H and O but
there is less oxygen than in carbohydrates.
There are mainly three types of lipids, namely
the simple lipids such as fats and waxes, the
compound lipids such as phospholipids and glycolipids and
the derived lipids such as steroids which include
cholesterol, sex hormones like estrogen, androgen, etc.
Fats are highly concentrated energy foods
which produce 9.5 Kcal of energy per gram, more than twice produced
by carbohydrates. They are obtained from butter, cream, oil, nuts,
Importance of lipids in metabolism : Fats
are used in the growth of living bodies. They mainly serve as compact
fuel molecules because they yield more energy per unit weight
than any other food substance. Fats also serve as reserve food.
In animals living in cold regions, fats form an insulating coating
within the body. In the case of animals like camels living in deserts,
oxidation of fats yields metabolic water which enables the animal
to remain without ingesting water for several days.
(d) Vitamins : These are organic food factors
which are essential for healthy and well balanced growth of the
body. Small amounts of vitamins are sufficient for the normal functioning
of the body, as they are usually recycled in the bodyo. If vitamins
are not taken in sufficient quantities, it may lead to various "deficiency
diseases" as shown in the table below.
Vitamins are not synthesized by animals but obtained
directly or indirectly from plants. Vitamins are A, B-complex, C,
D, E and K of which B-complex and C are water soluble while
A, D, E and K, are fat-soluble.
(e) Minerals : These are necessary for the
body to perform its normal functions. About 4% of our body weight
is formed by minerals. Fresh fruits and green vegetables are rich
in minerals. A few important minerals needed for our body functions
are given below:
(i) Calcium and Phosphorus: They are
essential for the development of bones and teeth. Besides, calcium
is also useful in clotting of blood and phosphorus is necessary
in the formation of energy rich molecule called ATP.
(ii) Iron: It is essential for the formation
of red pigment hemoglobin of blood. Deficiency of iron causes anemia.
(iii) Iodine: It is necessary for the
proper functioning of the thyroid gland. A deficiency of iodine
leads to simple goiter.
(iv) Potassium and Sodium: These are
the main constituents of body fluids, nerve cells and blood plasma,
and are often ingested in mineral forms.
(v) Magnesium: This is useful in the
activation of many enzymes.