Electron transport chain terminal oxidation oxidation phosphorylation

Electron transport chain terminal oxidation oxidation phosphorylation

1. Electron Transport Chain Terminal Oxidation Oxidative Phosphorylation

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

3. Five complex proteins involved Complex I to Complex V Electron transport through electron carriers NAD+, FAD+, CoQ and cytochromes ( cyt . b, cyt . c, cyt . a and cyt . a3) Oxidation of Coenzymes & energy is released Energy utilized for phosphorylation (ADP + Pi ------- ATP) - Phosphorylation By Oxidation called as Oxidative Phosphorylation

4. 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. 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.

5. IM space Complex I Complex II Complex III Complex IV Complex V NADH Dehydrogenase U Q Succinate De h y d r o g e n a s e Cytochrome bc1 complex Cytochrome c Oxidase ATP Synthase Cyt c M a t r i x OM of MC

6. Electron Transport in ETS NADH Dehydrogenase Succinate De h y d r og e n as e Cyt. b Cyt.c1 C y t .c Cyt. a Cyt.a3 e - UQ NADH e - FADH 2 O 2 e - e - e - e - e - e -

7. NAD H NA D O 2 H 2 O F M N U Q Cyt bc 1 Cyt c Cyt a 3 ATP S y n t h as e H + H + H + AD P + Pi A TP IM of MC M a t r i x OM of MC IM space e -

8. Respiration – Energy Budgeting Glycolysis = 2 ATP & 2 NADH 2 + (2 X 3 ) = 8 ATP = 2 NADH = 2 X 3 = 6 ATP Link Reaction Kreb Cycle = 6NADH, 2FADH 2 and 2ATP 6 X 3 + 2 X 2 + 2 = 18 + 4 + 2 = 24 ATP Total = 3 8 ATP

9. Pathway Substrate-Level Phosphorylation Oxidative Phosphorylation Total ATP Glycolysis 2 2 NADH (= 6 ATP) 8 Link Reaction 2 NADH (= 6 ATP) 6 Krebs Cycle 2 6 NADH (= 18 ATP) 2 FADH 2 (= 4 ATP) 24 Total 4 32 3 8 Net ATP production per glucose molecule in respiration

10. Oxidative Phosphorylation Photophosphorylation It occurs during Respiration It occurs during Photosynthesis Found inside of Mitochondria Found inside of Chloroplast Process occurs IM of MC Occurs in Thylakoid membrane Oxygen is needed Oxygen is not required ETS made up of Cytochromes ETS made up of PS I & PS II Electron donor is NADH Electron donor is water Electron acceptor is O 2 Electron acceptor is NADP Produced ATP molecules are used for different metabolic reactions Produced ATP molecules are used for CO 2 fixation in dark reaction

11. Respiratory Quotient (R.Q.) The ratio between volume of CO 2 released and volume of O 2 consumed in respiration The value of RQ depends upon the nature of the respiratory substrate (the organic food matter oxidized in respiration) and its oxidation R.Q. = Volume of CO 2 released Volume of O 2 consumed

12. 1. R.Q. for Carbohydrate – Complete oxidation (Aerobic) C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O R.Q. = 6 6 = 1 2. R.Q. for Carbohydrate – Incomplete oxidation (Anaerobic) C 6 H 12 O 6 2 CO 2 + 2 C 2 H 5 OH R.Q. = 2 = ∞

13. 3 . R.Q. for Protein or Fat – More O 2 is required C 16 H 32 O 2 + 11 O 2 C 12 H 22 O 11 + 4 CO 2 + 5 H 2 O R.Q. = 4 1 1 = 0.36 (Less than 1) 4. R.Q. for Organic Acid– Require less O 2 C 4 H 6 O 5 + 3 O 2 4 CO 2 + 3 H 2 O R.Q. = 4 3 = 1.33 (More than one)

14. Types of Respiration Aerobic Respiration Anaerobic Respiration (Fermentation) Alcohol Fermentation Lactic acid fermentation

15. Aerobic & Anaerobic Respiration G lu c os e Pyruvic acid TCA cycle 34 ATP 36 A T P 2 ATP Lactic Acid P D C E t h a nol NADH NAD Acetaldehyde NADH ADH NAD Aerobic Re s p ir a t i o n L D H Anaerobic Re s p ir a t i o n 2 ATP O 2 ET S