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PinkMonkey Online Study Guide-Biology

5.7 Significance of Respiration

(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 as heat.

(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.



(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 common types.


Table of Contents

5.0 - Introduction
5.1 - Ultrastructure and Functions of Mitochondrion
5.2 - An Overview of Cellular Respiration
5.3 - Glycolysis
5.4 - The T.C.A. Cycle(Tricarboxylic Acid Cycle)
5.5 - Electron Transport Chain
5.6 - Fermentation
5.7 - Significance of Respiration

Chapter 6


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