12 BIOLOGY BOTANY Mechanism of Respiration - Electron Transport Chain
12th botany neet school

Mechanism of Respiration – Electron Transport Chain

Mechanism of Respiration – Electron transport chain

Mechanism of Respiration – Electron Transport Chain

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Electron transport system (ETS) is a chain of electron carriers
consisting of NAD+, FAD+, CoQ and cytochromes (cyt. b, cyt. c, cyt. a
and cyt. a3).

The glucose molecule is completely oxidized by the end of
the citric acid cycle.

But, energy is not released, unless NADH2 and FADH2 are oxidized through electron transport system.

Transfer of electrons and protons from NADH2 and FADH2 to oxygen through a series of components like flavoprotein, cytochrome is called electron transport chain.

This process leads to coupling of electrons to form high-energy
phosphate bonds in the form of ATP from ADP is called oxidative

The electron transport components are arranged in the
inner membrane of mitochondria.

According to modern concept, the electron carriers in the electron
transport system are arranged in four complexes – complex I, complex II,
complex III and complex IV.

When NAD+ is a primary acceptor of electrons, the electrons are transported from complex I to II, II to III and then to complex IV. When electrons are transported from one complex to next complex, an ATP is produced.

Thus, one molecule of NADH2 generates three ATPs. When FAD+ is a primary acceptor of electrons, the electrons are transported from complex II to III and then to complex IV.

Thus, one molecule of FADH2 generates two ATPs.

The molecular oxygen forms the terminal constituent of the electron
transport system.

It is the ultimate recipient of electrons and picks up the protons from the substrate to form water.

Mechanism of Respiration - Electron Transport Chain

Energy yield

Complete oxidation of one glucose molecule yields a net gain of 38ATP.

Out of 38ATP molecules, 4ATP are obtained by direct substrate level
phosphorylation, 30ATP through oxidation of NADH2 and 4ATP through
oxidation of FADH2.

Since, a large number of ATP molecules are produced in the mitochondria, they are called the ‘power houses of the cell’.energy yield 12 std notes

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For more information about Electron Transport Chain click here

Other links 

Plant tissue culture – origin and techniques

Plant physiology – photosynthesis and its significance

Site of photosynthesis and Mechanism of photosynthesis

Electron transport system and photophosphorylation types

Dark reaction

C3 and C4 pathways

Photorespiration or C2 cycle

Factors affecting photosynthesis

Test tube and funnel experiment, Ganong’s light screen experiment

Mode of nutrition – Autotrophic, Heterotrophic


Mechanism of Respiration – Glycolysis

Mechanism of Respiration – Oxidative decarboxylation , Krebs cycle

Ganong’s respiroscope, Pentose phosphate pathway

Anaerobic respiration, Respiratory quotient, Compensation point, Kuhne’s fermentation tube experiment

Plant growth and Measurement of plant growth

Phytohormones Auxins

Phytohormones Gibberellins

Phytohormones Cytokinin, Ethylene, Abscisic Acid, Growth Inhibitors – Physiological Effects

Photoperiodism and vernalization, Phytochromes and flowering


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