Environmental biochemistry : U.Satayanarayana & U. Chakrapani :Biochemistry

f nvironment constitutes the non-living (air,
Lwater, land, energy etc.) as well as the living
(biological and social) systems surrounding man.
Environmental biochemistry primarily deals with
the metabolic (biochemical) responses and
adaptations in man (or other organisms) due to
the environmental factors.
A healthy environment is required for a
healthy life which is however, not really possible
or practicable. This is mainly because of the
atmospheric (climatic) changes and
environmental pollution.
Environmental biochemistry is a very vast
subject. The basic concepts regarding the
atmospheric changes and environmental
oollution on humans are dealt with here.
The climatic changes include cold, heat etc. .
The body makes every effort to maintain its
normal temperature (despite cold and
surroundings) for optimal physiological
biochemical functions.
EXPOSURE TO COLD
Short-term exposure to cold causes shivering
(mainly due to skeletal muscle) to produce extra
heat. Heat is generated by the hydrolysis of ATP'
tw,+. g,,:t:t; j,i+'r e "t: 94 r:li:*s;ie
Chronic exposure to cold results in non-
shivering phase which is characterized by
several metabol ic adaPtations.
heat
and
Energy metabolism : Heat generation by a
process called chemical thermogenesis occurs
in non-shivering phase. The foodstuffs undergo
oxidation to generate heat at the expense of
growth and other anabolic processes.
Elevation in BMR, and increased intake oi
foods are observed.
Lipid metabolism : Stored fat (triacylglycerol)
in the adipose tissue is mobilized to supplyfree fatty acids for oxidation and production of
energy. Brown edipose tissue, particularly in
neonatal life, significantly contributes to
thermogenesis.
. Hormonal changes : Thyroxine, a hormone
closely associated with energy metabolism, is
elevated. Further, corticosteroids are increased
on exoosure to cold.
EXPOSURE TO HEAT
There is a continuous generation of heat by
the body due to the ongoing biochemical
processes, referred to as metabolic heat. This
heat has to be exchanged with the environment
to maintain a constant body temperature. On
exposure to heat in surroundings, as happens in
sLrmmer, the body is subjected to an
uncomfortable situation (since temperature of the
surroundings is much higher than that of the
body). However, heat is still lost from the body
through sweating and evaporation. Normally, the
body (thermoregulation) gets acclimatized to
higher temperature within 3-5 days.
Heat stroke : lt is characterized by the failure
of the heat regulatory system (thermoregulation)
of the body. The manifestations of heat stroke
include high body temperature, convulsions,
partial (some times total) loss of consciousness.
In extreme cases, heat stroke may cause
irreversible damage to brain. The treatment for
the heat stroke involves rapid cooling of the
body.
The milder form of heat stroke is referred to
as heat syncope. Although the body temperature
is not raised much in this condition, the blood
pressure falls and the person may collapse
suddenly. Heat syncope is easily reversible.
Environmental pollution may be regarded as
the addition of extraneous (foreign) materials to
air, water or land which adversely affects the
quality of life. Pollution may be caused by
physical, chemical or biological processes.
The term pollutant refers to a substance
which increases in quantity due to human
activity and adversely affects the environment
(e.9. carbon monoxide, sulfur dioxide, lead). A
substance which is not present in nature but
released during human activity is the
contaminant (e.g. methyl isocyanate, DDT,
malathion). A contaminant however, is regarded
as a pollutant when it exerts detrimental effects.
Environmental pollution may be considered in
different ways-industrial pollution; agricultural
pollution; pollution due to gaseous wastes, liquid
wastes and solid wastes.