16).
Function of
Carbohydrates:
Carbohydrates participate in a wide
range of functions.
- They are the most abundant dietary
source of energy (4 cal/g) for all organisms. About 60% of the
total energy requirement of man is provided by the breakdown of
carbohydrates.
- Carbohydrates play a key role in
the metabolism of amino acids and fatty acids.
- Carbohydrates serve as an important
structural material in some animals and in all plants, where they
constitute the cellulose frame work. Monsaccharides are important
constituents of nucleic acids, co- enzymes, Flavoproteins etc.
Heparin prevents the clotting of blood. Chondroition sulphates are
found in cornea, cartilage tendons, skin, heart valves and saliva.
Glycosides are components of steroid hormones.
- Some carbohydrates are essential
for normal oxidation of fats.
- Carbohydrates are utilized as raw
materials for several industries.
Ex: paper, plastic, textiles, alcohol etc.
17).
Functions of
Lipids:
- Lipids provide food of high caloric
value (1 gram fat produces about 9.3 kilo calories of heat)
- These serve as the structural
components of cellular membranes.
- These serve as intra cellular
storage deposits of metabolic fuel.
- Many enzymes require lipid
molecules for maximal activation.
- Adrenal corticoid, sex hormones and
vitamin D2 are synthesized from lipid derivatives.
- Much of the lipid of mammals is
located sub cutaneously and acts as an insulator against excessive
heat loss to the environment.
- As compounds of the inner
mitochondrial membrane, lipids (Phospolipids) participate in
electron transport chain.
- Edible oils extracted from many
seeds are used in cooking
- Myelin sheath around nerve fibers
take part in insulation
- Phospholipids play an important
role in the absorption and transportation of fatty acids.
- Lipids act as a solvent for fat
soluble vitamins A, D and E.
- In animals the fat produce a shock
absorbing cushion around eyeballs, gonads, kidneys and other vital
organs.
18).
Functions of proteins:
Proteins are indispensable for life and perform a number of
funcitons
- Proteins primarily serve as structural proteins by contributing
towards the building of cell organelles, tissue protective
coverings etc. Exapmles of structural proteins are myosin of
muscles, keratin of skin and hair in mammals and collagen of
connective tissue.
- The most important class of proteins are the enzymes. They
catalyze different kinds of chemical reactions. Most enzymes are
characterized by a high degree of specificity, i.e, they will
catalyze one particular reaction but not another and require an
optimum pH and temperature to work.
- Many hormones are proteins and play important role in metabolic
reactions.
- Ex. Insulin, oxytocin etc.
- The blood contains a number of proteins with different
functions.
- Serum albumins-Control the osmotic pressure and the pH of
- the blood
- Fibrinogen- play important role in blood coagulation
- Haemoglobin –transport oxygen from the lungs to all
tissues
- of the body
- Immunoglobulins of the blood plasma (β-and Y-globulins) in
mammals and other animals act as antibodies that neutralize the
harmful effects of such foreign agents as viruses, bacteria and
cells from other organisms.
- Proteins like actin and myosin are directly involved in the
contraction of muscles through which the mechanical work is
performed
- Proteins of our food serve as a source of the aminoacids. These
essential amino acids are readily synthesized in plants and in some
animals and are ingested as proteins by man.
- The visual purple pigment, rhodopsin is made up of retinene (an
aldehyde derivative of vitamin A) and a protein opsin.
Melanin, the pigment of skin, hair
and choroid layer of eye is derived from the amino acid
tyrosine.