(1) It is the energy releasing and supplying
process in all living organisms.
(2) It converts food energy into metabolically
usable forms of chemical energy.
(3) Respiration releases energy in a controlled
and step-wise manner as a result of which most of the released energy
is properly utilized for the cellular activities (e.g. metabolism,
cell division, growth, etc.) Only a small part of energy is lost
(4) In other words, respiration conserves
energy very efficiently. Out of the total 673 Kcal energy released
per molecule of glucose, 456 Kcal is conserved as 38 ATP molecules.
(5) Various intermediate products of glycolysis
and Kreb’s cycle are used for biosynthesis of other complex organic
compounds in cell metabolism.
(6) Carbon dioxide, required for photosynthesis
by green plants, is replenished by carbon dioxide released in respiration.
Similarly, oxygen required for respiration is replenished by oxygen
released in photosynthesis. Thus, photosynthesis and respiration
are complementary to each other and together help to maintain the
balance of oxygen and carbon dioxide in nature.
(7) Fermentation, which is a type of anaerobic
respiration, is helpful in the industrial production of various
useful products such as alcohol, antibiotics, vitamins, organic
acids, bakery and dairy products, tanned leather, etc.
SUMMARY - RESPIRATION
(1) It is a characteristic process of every
living cell. (2) It is an intracellular oxidation of organic
compounds with release of carbon dioxide and energy. (3) In
respiration, substrate is enzymatically broken down in a step-wise
manner. (4) Phase-I is glycolysis (EMP pathway). It is completed
in cell cytoplasm. These reaction involves further breakdown
of pyruvic acid to form the end products of respiration. (6)
Pyruvic acid metabolism can be aerobic or it can be anaerobic.
(7) Phase-II of aerobic respiration is completed in mitochondria.
The oxidation of substrate is complete and end products are
6CO2, 6H2O and 38 ATP for every molecule
of glucose. (8) Phase-II of anaerobic respiration is completed
in cytoplasm only. The end products are ethyl alcohol, carbon
dioxide and energy. (9) Fermentation is an anaerobic respiration.
It is commonly found in saprophytic microorganisms like bacteria
and fungi. End products are sometimes very useful. Alcoholic
fermentation and lactic acid fermentation are the two most