The Essentials of Biochemistry
By Prof. Liwayway Memije-Cruz
Biochemistry is the branch of science that explores
the chemical processes within and related to living
organisms. It is a laboratory based science that
brings together biology and chemistry. By using
chemical knowledge and techniques, biochemists
can understand and solve biological problems.
hydrated carbons; examples
are glucose (C6 H12O6) and
ribose (C5H10O5). They
provide an easy and ready to
use source of food.
Monosaccharides are commonly referred to
as simple sugars.
Glucose – blood sugar which is the universal
Fructose - converted to glucose for used by
Ribose - form part of the structure of nucleic
Disaccharides are referred to as double sugars.
Some of the important disaccharides in the diet
Sucrose (glucose-fructose), which is cane
Lactose (glucose-galactose) found in milk.
Maltose (glucose-glucose) malt sugar.
Disaccharides must be broken down (digested)
to monosaccharide to be absorbed from the
digestive tract in to the blood.
Polysaccharide, which literally means
much sugar, is a polymer of linked
Starch is the storage polysaccharide
formed by plants as starchy foods like
grains and root vegetables (potatoes and
Glycogen is found in animal tissues like
in the muscles and the liver.
Lipids: The most abundant lipids in the
Lipids are organic compounds
composed of carbon, hydrogen and
oxygen. They are a large and diverse
group of organic compounds composed
of fatty acids and glycerol. They may be
solid or liquid. Most of them are
insoluble in water but readily dissolve in
other lipids, and in organic solvents like
alcohol, ether and acetone.
1. Neutral Fats (triglycerides)
They represent the body’s most abundant and
concentrated sources of usable energy. They are stored
chiefly in fat deposits beneath the skin and around
body organs where they help insulate the body and
protect deeper body tissues from heat loss and bumps.
They are modified lipid containing phosphorous. Their
presence in cellular membrane allow cells to be
selective about what may enter or leave. They are found
in the brain and the nervous tissue where they help to
form insulating white matter.
3. Steroids. They are specific groups of chemical substances.
They include certain hormones and cholesterol.
Cholesterol – the basis of all body steroids. Found in all
membranes, and abundant in the brain.
Bile salts - breakdown product of cholesterol that is released
by the liver into the digestive tract where they aid in fat
digestion and absorption.
Vitamin D – produced in the skin on exposure to ultra violet
radiation from modified cholesterol. Necessary for normal
body growth and function.
Sex hormones –produced from cholesterol, which include
estrogen and progesterone that are vital for normal
reproductive function. Lack of sex hormones may results to
Adrenal cortical hormones – composed of cortisol, a long-
term antistress hormone necessary for life and aldosterone
that helps regulate salts and water balance in the body fluids
by the targeting the kidneys.
OTHER LIPOID SUBSTANCES INCLUDE:
Vitamin A - found in orange – pigmented vegetables (carrots)
and fruits (tomatoes) and part of the photoreception pigments
involved in vision.
Vitamin E - found in wheat germ and green leafy vegetables that
promote wound healing and contribute to fertility. It may help to
neutralize free radicals and believed to the involved in triggering
some types of blood.
Vitamin K - made available largely by the action of intestinal
bacteria, it is also present in a wide variety of food and is
necessary for proper blood clotting.
Prostaglandin derivatives of fatty acids found in cell membranes,
which stimulate uterine contraction, regulate blood pressure and
control stomach secretion and motility of the gastrointestinal
Proteins are complex nitrogenous substances
that are accounted for over 50% of the organic
matter in the body. Amino Acids are small
molecules that are the building blocks of
proteins. 20 common types of amino acids are
found in the body. The amino acids released
through protein digestion are absorbed and used
to build the body’s proteins. Of the common
amino acids, eight are essential amino acids. Our
body cannot build these molecules; they should
be obtained from the diet.
– Transport proteins carry iron,
cholesterol and other substances in the
body. Example is hemoglobin, which
helps in the transport of oxygen in the
– Contractile proteins are involved in
cell division and sperm propulsion.
Actin and myosin are substances
essential for muscle contraction and
– Catalyst is essential for every
biochemical reaction in the body.
A catalyst is a substance that increases the rate of a
chemical reaction without becoming part of the product
or being changed itself.