Electron transfer chain

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1. Assignment Topic:
ELECTRON TRANSFER CHAIN
Submitted To :
Sir Rameez Hussain sb.
Submitted By :
Muhammad Usman BAGF14E256
Subject:
BOT-502 Advance Botany


UNIVERSITY COLLEGE OF AGRICULTURE
UNIVERSITY OF SARGODHA

2. ELECTRON TRANSFER CHAIN
DISCOVERY
 In 1961, an American biochemist, Albert Lehninger, discovered that the citric acid cycle
and the electron-transfer chain of enzymes (where 1 NADH makes 3 ATPs) are located
within each cell’s mitochondria.
 And each cell has many mitochondrion power plants that produce an energy output which
can be measured.
IMPORTANCE
 These are the mechanism by which NADH plus H
+
and FADH2 are used to generate
ATP
INTRODUCTION
 ETC is the 4
th
and final stage of aerobic respiration.
 Through ETC, the E needed for the cellular activities is released in the form of ATP.
 ETC is an O2 dependent process which occurs in the inner mitochondrial membrane.
 Respiration is the oxidative breakdown of organic compound to release energy.
 Organic compounds:


LIPIDS PROTEINS CARBOHYDRATES
 Main aim of these various metabolic reactions is to produce ATP.
 But how is ATP produced?
Electron Transport
• This is the final common pathway in aerobic cells by which electrons derived from various
substrates are transferred to oxygen.
• ETC is series of highly organized oxidation-reduction enzymes.
• As the electrons reach the proton pumping channels, their energy drives the transport of
protons out across the membrane, leading to the synthesis of ATP

3. Enzymes
• NADH – Nicotinamide Adenine Dinucleotide
• FADH – Flavin Adenine Dinucleotide
• CoEnzyme Q
• Cytochrome C
LOCATION OF ETC
 ETC is localized in Mitochondria.
 MC are the centres for metabolic oxidative reactions to generate reduced coenzymes
(NADH and FADH2) which in turn, are utilized in ETC to liberate E in the form of ATP.
 Hence, MC is regarded as Power House of the Cell.













Reaction of ETC
• After Glycolysis and Krebs Cycle, we are left with 10 NADH and 2 FADH₂

4. • These will undergo oxidation – losing of electrons
• 1a. At enzyme complex I, NADH is oxidized to NAD+ and e- are transferred between
different proteins in this cluster, then to coenzyme Q (CoQ or Ubiquinone). Protons are
pumped.
• NADH NAD⁺ + H⁺ + 2e⁻
• 1b. FADH2 is oxidized (transfers its e-) to the CoQ at enzyme complex II. The reduced
CoQ joins the rest of the “chain”.
• 2. The reduced CoQ travels to enzyme complex III where the e- are transferred between
proteins and then to cytochrome c. Protons are pumped.
• 2e⁻ Coenzyme Q Cytochrome C 2e⁻
• 3. Cytochrome c travels to the enzyme complex IV where the e- are transferred between
proteins and then to O2 to form water. More protons are pumped.
• 2e⁻ + H⁺ + ½O₂ H₂O
• The H+ ions that have been pumped into the intermembrane space can only get back into
the matrix through ATP Synthase. The energy released as H+ flow back to the matrix is
coupled with the formation of ATP:
• ADP + Pi → ATP + H2O (oxidative phosphorylation1)