1. Respiratory chain and oxidative phosphorylation +
Glycogenesis and Glycogenolysis

2. Respiratory chain (RCH)
is located in a mitochondrion
needs oxygen (O2) for its function

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

4. Electron Transport (Respiratory) Chain
Electron transport chain (ETC) or respiratory chain (RC)
functions to oxidize NADH and FADH that arise from different metabolic pathways carried out on nutrients, leading to release of energy(exergonic).
Part of the released E is used for the synthesis of ATP (oxidative phosphorylation).

5. Components Of The Electron Transport Chain:
can transfer either H or electrons
are called Complex I, II, III and IV
The Four Electron Transport Complexes in the Inner Mitochondrial Membrane Respiratory Chain
(a) Complex I NADH-CoQ reductase (ATP)
(b) Complex II Succinate CoQ reductase (no ATP)
(c) Complex III CoQ- Cytochrome C reductase, (ATP)
(d) Complex IV Cytochrome C oxidase (ATP)

6. the only electron carrier not bound to a protein. 2.Cytochrome c
Two small electron carriers are also needed to link these large complexes, they are:
1.Coenzyme Q (CoQ or ubiquinone)
the only electron carrier not bound to a protein.
2.Cytochrome c
Cytochromes are electron carriers containing hemes .
Cytochrome c is a small, water-soluble protein.

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

8. Operation of the Electron Transport (Respiratory) Chain
The transfer of electrons is not directly to oxygen but through coenzymes.
Complex I transfers H+ into an intermembrane space
Coenzyme Q accepts e- from both Complex I and Complex II
Complex IV transfers electrones to oxygen
oxygen is reduced to H2O

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

11. The function of the RCH is to regenerate NAD+ from NADH
is to regenerate FAD from FADH2
oxygen is reduced to H2O
is to finish oxidation of energy substrates and conserve their energy in a form of ATP

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

14. Mechanism of Oxidative Phosphorylation
1- During the ETC (located at the inner mitochondrial membrane) , H+ are released into the intermembrane space (outside inner mitochondrial membrane). 2- The inner mitochondrial membrane is impermeable to H+, which accumulate outside the membrane.

15. 3- An electrochemical gradient is creating across the membrane
3- An electrochemical gradient is creating across the membrane. An electrical gradient (with more positive charges on the outside of the membrane than on the inside ) and chemical gradient or pH gradient (the outside of the membrane is at lower pH than the inside).
4- This H+ gradient is used by the ATP synthase complex to make ATP via oxidative phosphorylation.

18. On the the Inner Mitochondrial Membrane, 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.
1 NADH ATP
1 FADH ATP

20. Glycogenesis and Glycogenolysis
Glycogen metabolism
Glycogenesis and Glycogenolysis

21. Glycogen
Glycogen is the main storage form of carbohydrates in animals. It is present mainly in liver and muscle.
The total quantity of muscle glycogen is more than liver glycogen, because of the large muscle mass.
The glycogen is present in the cytoplasm of the cell, because all the enzymes related to glycogen metabolism are cytoplasmic.

22. Function of glycogen:
The function of liver glycogen is to maintain the blood glucose concentration (acts as a glucose buffer).
The function of muscle glycogen is to serve as a fuel reserve for synthesis of ATP during muscle contraction (as energy store).

23. α-1:4 glycosidic bonds, mainly
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 glucose residues.

24. Glycogen synthesis (glycogenesis)
Glycogen is synthesized from D-glucose in muscle and liver.
Its site in the cytoplasm of every cells mainly liver and muscle

25. Steps of Glycogen synthesis (glycogenesis):
1-Activation of glucose:
UDP-glucose (the active form of glucose) is formed from glucose 1-phosphate and UTP (Uridine triphosphate) by UDP-glucose pyrophosphorylase.
UDP-glucose is the source of all glucosyl residues that are added to the growing glycogen molecule.

27. 3- Glycogen synthase: Activated glucose units, UDP-glucose, are sequentially added by glycogen synthase to glycogen primer molecule(short linear glucose polymer). The glycogen synthase can add glucose units in only 1,4-linkages.
Glycogen primer (n) + UDP-glucose ---- Glycogen (n+1) + UDP.

28. Glycogen synthesis
4- Branching enzyme: 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.

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

30. Glycogenolysis 2)- Debranching enzyme is hydrolytic enzyme acts on
α1 - 6 glycosidic link giving free glucose.
3)- G-1-P is converted into G-6-P by the action of phosphoglucomutase.
In liver, G-6-P is hydrolysed 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

31. The rate limiting enzymes controlling glycogen metabolism are:
1. Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis.
2. Glycogen synthase catalyzes the rate-limiting step in glycogenesis.

32. Glycogenolysis
Muscle glycogen functions to provide muscle with glucose during contraction. .
Liver glycogen functions to maintain blood glucose between meals.
After hr fasting, liver glycogen whereas muscle glycogen is after prolonged exercise.

33. Difference between muscle and liver glycogen
Muscle glycogen
Liver glycogen
More -
Amount
Glucose only
Glucose and other precursors
Source
Give lactic acid
Give blood glucose
Hydrolysis
Not affected
Converted into blood glucose
Starvation
Depleted first
Depleted later on
Muscular exercise