1. Respiratory chain and oxidative phosphorylation 1

2. Respiratory chain (RCH) a) is located in a mitochondrion b) includes enzymes integrated in the inner mitochondrial membrane c) needs oxygen (O2) for its function 2

3. Impermeable to ions and most other compounds In inner membrane knobs mitochondrion the mitochondrion contained the enzymes responsible for electron transport and oxidative phosphorylation

4. Electron Transport (Respiratory) Chain  Electrons carried by reduced coenzymes (NADH or FADH2) are passed sequentially through a chain of proteins and coenzymes (so called electron transport chain)to O2.  Electron transport along the chain generates a proton electrochemical gradient and this is used to produce ATP 4

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6. Enzymes of the RCH a) can transfer either H or electrons b) are called Complex I, II, III and IV 6 --------------------------------------------------------------------------------- ------------ The Four Electron Transport Complexes in the Inner Mitochondrial Membrane Respiratory Chain --------------------------------------------------------------------------------- ------------- (a) Complex I NADH-CoQ reductase ………  G = - 16.6 kcal/mol ( ATP ) (b) Complex II Succinate CoQ reductase ….  G = - 1.6 kcal/mol ( no ATP ) (c) Complex III CoQ- Cytochrome c reductase,  G = - 10.1 kcal/mol ( ATP ) (d) Complex IV Cytochrome c oxidase…………  G = -19.8 kcal/mol ( ATP )

7. The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 proton = H + electron = e -

8. Nicotinamide coenzymes: NAD + Always a 2-electron reaction transferring 2 e - and 2 H +

9. The flavin coenzymes / flavoproteins FAD Always a 2-electron reaction transferring 2 e - and 2 H +

10. Ubiquinone QCoenzyme QCoQ Other names and abbreviations: Most often n = 10 Free CoQ can undergo a 2 e  oxidation/reduction: Q + 2 e  + 2 H +  QH 2.

11.  Coenzyme Q (CoQ, Q or ubiquinone) is lipid- soluble. It dissolves in the hydrocarbon core of a membrane.  the only electron carrier not bound to a protein.  it can accept/donate 1 or 2 e -. Q can mediate e - transfer between 2 e - that transfer and 1 e - carriers

12. Cytochromes proteins that accept electrons from QH 2 or FeS Ultimately transfers the electrons to oxygen

13. Cytochromes are electron carriers containing hemes. Hemes in the 3 classes of cytochrome (a, b, c) differ in substituents on the porphyrin ring. Cytochrome c is a small, water-soluble protein. Cytochromes

14. Electron Transport (Respiratory) Chain The transfer of electrons is not directly to oxygen but through coenzymes. a) Complex I transfers H + into an intermembrane space b) Coenzyme Q accepts e- from both Complex I and Complex II c) Complex IV transfers electrones to oxygen d) oxygen is reduced to H 2 O 14

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16. The function of the RCH 1) is to regenerate NAD + from NADH 2) is to regenerate FAD from FADH 2 3) oxygen is reduced to H2O 4) is to finish oxidation of energy substrates and conserve their energy in a form of ATP 16

17. Oxidative Phosphorylation  Coupling of the electron transport in RCH with phosphorylation of ADP to form ATP. a) needs proton gradient on the inner mitochondrial membrane by RCH b) is catalyzed by ATP synthase 17

18. On the the Inner Mitochondrial Membrane (IMM), the ATP Synthase Uses the Proton Gradient Generated by Electron Transport of the Respiratory Chain to Synthesize ATP Electron transport chain

19. ATP yield from oxidative phosphorylation accounts for approximately 85% of the maximal 38 ATP generated in complete oxidation of glucose to CO2. a) 1 NADH 3ATP b) 1 FADH 2ATP 19

20. Glycogen  Glycogen is the main storage form of carbohydrates in animals. It is present mainly in liver and muscle.  In the liver, glycogen can compose up to 8% of the fresh weight (100–120 g in an adult) soon after a meal. Only the glycogen stored in the liver can be made accessible to other organs.  In the muscles, glycogen is found in a much lower concentration (1% to 2% of the muscle mass.

21. Glycogen is a polymer of glucose residues linked by  α-1:4 glycosidic bonds, mainly  α-1:6 glycosidic bonds, at branch points. - Glycogen branches contain about 8 -12 glucose residues.

22. Glycogenesis  It is the formation of glycogen in muscle and liver  Its site in the cytoplasm of every cells mainly liver and muscle

23. Glycogen synthesis

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25. Glycogen synthesis 3-Glycogen synthase enzyme in presence of pre-existing glycogen primer (glycogenin) will add glucose mol. from UDP-G by forming α l :4 glucosidic link. 4- When the chain has been lengthened, the branching enzyme transfers a part of the α1:4 chain to a neighbouring chain to form an α l :6 glucosidic link. Thus establishing the branching points in the molecule. The branches grow by further addition of 1:4 glucosyl units. 5- The key regulatory enzyme is glycogen synthase which present in 2 forms: - Active (dephosphorylated form) - Inactive (phosphorylated form)

26. Glycogenolysis It is the breakdown of glycogen into glucose in liver and lactic acid in muscles. Glycogen Phosphorylase catalyzes phosphorolytic cleavage of the α(1  4) glycosidic linkages of glycogen, releasing glucose-1- phosphate as reaction product. Glycogen (n) + P i  Glycogen (n–1) + glucose-1-phosphate

27. Glycogenolysis G-1-P is converted into G-6-P by the action of phosphoglucomutase. In liver, G-6-P is hydrolyzed by the action of G-6- phosphatase free glucose (diffuse from liver cell to blood stream) In muscle, G-6-P by glycolysis lactic acid because absence of G-6-phosphatase

28. Glycogenolysis The key regulatory enzyme of glycogenolysis is phosphorylase enzymes which present 2 forms. - Active (Phosphorylated form) - Inactive (Dephosphorylated form) = Debranching enzyme is hydrolytic enzyme acts on α1 6 glycosidic link giving free glucose. = Muscle glycogen is to provide muscle with glucose during contraction.. = Liver glycogen is to maintain blood glucose between meals. = After 12 -18 hr fasting, liver glycogen whereas muscle glycogen is not affected otherwise after prolonged exercise.

29. 29 Pathway of Glycogenesis and Glycogenolsis in the liver

30. Difference between muscle and liver glycogen Muscle glycogenLiver glycogen More in amountMore in concentrationAmount Glucose onlyGlucose and other precursorsSource Give lactic acidGive blood glucoseHydrolysis Not affectedConverted into blood glucoseStarvation Insulin Adrenalin Thyroxine Glucagon Insulin Adrenaline Thyroxine Glucagon Effect of Hormones