1. M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar

2.  Bio-energitics is the study of energy changes [ release or utilization ] in biochemical reactions.  Reactions where energy is released are called exergonic reactions.  Reactions where energy is utilized are called endergonic reactions.

3.  Free energy [G]  Gibb's change in free energy [ G] negative positive zero  Standard free energy [ G o ]  Enthalpy [ H]  Entropy [ S]

4.  Free energy [G] denotes the fraction total energy in the system available to do the work.  Gibbs change in free energy [ G] It is the portion of free energy that is useful to do the work.  Standard free energy change [ G 0 ] is the free energy change under standard conditions [ pH 7 and 1M\ L concentration]

5. Gibbs Change in free energy [ G ] predicts whether a reaction is favorable or not predicts whether a reaction is favorable or not and the energy available to do work. and the energy available to do work. 1. exergonic reactions ; negative 1. exergonic reactions ; negative 2.endergonic reactions ; positive 2.endergonic reactions ; positive 3.equilibrium reactions ; zero 3.equilibrium reactions ; zero

6. Enthalpy [H] is the measure of the change in the heat content of the system i.e. energy released or absorbed. Entropy [S] It is the fraction of enthalpy that is not available to do the work. it denotes the randomness of the products and reactants.

7.  A biochemical reaction depends on the change in free energy, Enthalpy, and Entropy. G = H - T S [T= absolute temperature in Kelvin]

8.  ATP is the energy currency of the cell  ATP on hydrolysis yields -7.3 Kcal ATP ADP + Pi - 7.3 Kcal  ATP is utilized for Active transport Nerve conduction Muscle contraction synthetic reactions

9. 1.Pyro-phosphates -------------- ATP 2.Acyl phosphates -------------- 1,3-BPG 3.Enol phosphates -------------- PEP 4.phosphoguanides ------------- creatine –P 5.Thio - esters ------------- Acyl-co A the high energy bond in these compounds is called as Acid –anhydride bond

10.  phopho enol pyruvate [-14.8Kcal]  phospho creatine  1,3-BPG  SAM  ATP - 7.3Kcal  ADP  G-1-P  F-6-P  G-6-P [-3.3Kcal]

11.  The electrons flow uni directionally from one carrier to the other in ETC.  The carriers are reduced when they accept the electrons and get oxidized when they donate to the other carrier.  the reduced and oxidized forms of the same carrier are referred as redox pairs.  Redox potential is the tendency of the redox pair to donate or accept electrons.  electrons always flow from negative to positive redox potential.

12. REDOX PAIRS REDOX POTENTIAL 1. NADH\NAD -0.32 2. FADH\FAD -0.12 3. H 2 O\O 2 +0.82 The ETC is arranged in the increasing order of their redox potentials.

13.  All the enzymes of biological oxidation belongs to the major class of oxido-reductases. They are classified as follows 1.Oxidases 2.Oxygenases 3.Hydroperoxidases 4.dehydrogenases

14. Class Oxido reductases: 1.OxidasesEg: Cytochrome oxidase 2.Oxygenases Mono-oxygenasesEg: Cyt P 450 DioxygenasesEg: Tryptophan dioxygenases 3.Hydroperoxidases PeroxidasesEg: Glutathione peroxidase Catalases 4.Dehydrogenases AerobicEg: Xanthine oxidase Anaerobic: a.NAD linked b.FAD linked c.FMN linked

15. 1.Oxidases ; these enzymes catalyze the removal of hydrogen from the substrates. Oxygen acts as acceptor of hydrogen forming water. E.g. cytochrome -oxidase,MAO A H 2 +1\2 O 2 ---------- A + H 2 O

16. 2.Oxygenases 1. Mono-oxygenases [ mixed function oxidase] incorporates one oxygen atom into the substrate other is reduced to water. E.g. cyt-P 450, tyrosine hydroxylase etc. A-H + O 2 + BH 2 AOH + H 2 O +B 2. di-oxygenases incorporate both oxygen atoms into the substrate. E.g. Tryptophan dioxygenase A H + O 2 AOOH

17. 3. Hydroperoxidases act on H 2 O 2. 1. peroxidase ; glutathione peroxidase AH 2 +H 2 O 2 ---------2H 2 O + A 2.catalase; 2H 2 O 2 ----------------2H 2 O +O 2

18. 4.Dehydrogenases Catalyze the removal of hydrogen from the substrate. Based on the type of H 2 acceptor they are classified as follows 1. aerobic dehydrogenases oxygen is the acceptor of hydrogen. 2. anaerobic dehydrogenases coenzymes act as acceptors of hydrogen NAD + linked dehydrogenases NADP + linked dehydrogenases FAD- linked dehydrogenases

19.  Aerobic dehydrogenases These are flavoproteins and the product formed is mostly hydrogen peroxide AH 2 + O 2 -------------A + H 2 O 2 E.g. xanthine oxidase, glucose oxidase etc

20.  Anaerobic dehydrogenases hydrogen acceptor s are co-enzymes. When the substrate is oxidized the co- enzyme is reduced AH 2 + B ----------------A + BH 2

21. Transport of electrons from reduced substrates to O 2 is called as ETC. Site: Inner mitochondrial membrane Components: 1.Nicotinamide nucleotides [NADH + H + / NAD + ] 2.Flavo-proteins [FADH 2 / FAD+]. 3.Ubiquinone: CoQ. 4. Cytochromes: b, c 1, c, a, a 3.

22. ETC components are arranged in four complexes in the increasing order of their redox potentials from -4.2 for (NADH + H + ) to +0.82 for O 2. Complex I: NADH + H + ----- CoQ reductase. II: Succinate ----- CoQ reductase. III: Co-Q ------- Cyt C reductase. IV: Cytochrome oxidase.

24. ATPsynthase[ v ]

25. ATP synthase – Complex 5  Integral protein in the inner mitochondrial membrane.  It has two units F 0 & F 1.  F 0 acts as a protein channel.  F 1 has ATP synthase activity.

27. 1.Nicotinamide nucleotides [NADH + H + and NAD + ] 2. flavo-proteins [ FADH 2 and FAD + ]

28. 3. Co- Q [ubiquinone]

29. 4. cytochromes

30.  P;O ratio is the number of P atoms utilized To synthesize ATP for one atom of O 2 oxidized P;O ratio for NADH + H + is ‘3’ [three sites of ATP synthesis] P;O ratio for FADH 2 is ‘2’ [two sites of ATP synthesis]

31. 1. Chemical coupling: Generation of ATP at substrate level. 2. Conformational coupling: Conformational changes in the molecules in mitochondrial membrane leads to ATP generation. 3. Chemi -osmotic theory: The proton gradient generated during electron transfer is utilized for ATP synthesis.

33. Site specific : 1. NADH + H + to CoQ; 1.Rotenone 2.piericidin 3. amylobarbital 2. Cyt b to Cyt c 1 1. Antimycin 2. BAL. 3. Cyt a 3 to O 2 1. HCN 2. H 2 S 3. CO.

34. Uncouplers: 2,3 dinitrophenol, 2,3 dinitrocresol Physiological uncouplers: Large doses of 1. Unconjugated bilirubin, 2. Thyroxine 3. Aspirin 4. Long chain fatty acids. 1. Oligomycin : Blocks ATP synthase activity. 2.Atractyloside : Block the proton flow into the mitochondrial matrix.