2. High energy phosphates &Low energy phosphates: Compound Phosphoenolpyruvate -14.8 Carbamoyl phosphate -12.3 1,3 Bisphosphoglycerate -11.8 Creatine phosphate -10.3 ATP ADP + Pi -7.3 ADP AMP + Pi -6.6 Pyrophosphate -6.6 Glucose 1-phosphate -5.0 Fructose 6 phosphate -3.8 AMP -3.4 Glucose 6 phosphate -3.3 Glycerol 3-phosphate -2.2 Kcal/mol -7.3ATP ADP +Pi
3. Adenosine Triphosphate (ATP)
4. Importance of Adenosine Triphosphate (ATP) ATPservesasthegeneral "freeenergy currency" for virtually all cellular processes. It isadirect sourceof energy for cell motility, muscle contraction, and thespecific transport of substances acrossmembranes. ATPisasourceof phosphateenergy for synthesisof the other nucleosidetriphosphatesviathereaction: ATPisalso an allosteric effector of many enzymes.
5. cytochromes: Protein-bound :- Heme containing carriers Cytochromesconstituteafamily of colored proteinscontaining the Hemeprosthetic group
6. Nature of e- Carriers: Protein-bound carriers :- Iron-sulphurcenters Feion iscoordinated with thesulphursof cysteine residuesand inorgnic sulphur atoms.
7. Nature of e- Carriers: Mobile carriers :- Coenzyme Q CoenzymeQ: small hydrophobic moleculeand theonly onethat isnot apart of protein.
8. Organization of carriers in ETC: Complex I NADH dehydrogenase complex : Largest Respiratory enzyme complex > 40 polypeptide chains Bound FMN At least 7 iron-sulfur centers Electron transfer From NADH to Co Q Blocked by Rotenone and Amytal
9. Complex II SuccinateDehydrogenase: It isapoint of entry of electronsfrom FADH2 produced by theenzymesuccinatedehydrogenasein thecitric acid cycle. FAD asProsthetic group Iron-sulfur proteins Electron transfer From FADH2 to Co Q Thus, both complexesI and II donatetheir electrons to thesameacceptor, coenzymeQ.
10. CoenzymeQ : Benzoquinonelinked to 10 isopreneunits It hastheability to accept electronsin pairsand passthem one at atimethrough asemiquinoneintermediateto Complex III. Thiscycleisreferred to astheQ cycle. Electron transfer From Complex I or II to Complex III Cytochromec : Thissmall mobileprotein accepts e- from Complex III and shuttlesthem to Complex IV
11. Complex III Cytochromeb-c1 complex : It isaDimer Each monomer has: 3 Hemesbound to cytochromes 1 Iron-sulfur protein Electron transfer From Co Q to cytochromec Cytochromec then transferse- to thecomplex IV Blocked by Antimycin A
12. Complex IV Cytochromeoxidasecomplex : Dimer Each monomer has: 13 Different polypeptidechains, including 2 Cytochromesaand a3 and 2 Cu atoms AcceptsoneElectron at atimefrom Cytochromec and passesthem four at atimeto Oxygen Blocked by Cyanide, Azide, and Carbon monoxide
13. Organization of carriers in ETC:
14. Oxidative Phosphorylation Chemical coupling Chemiosmotic hypothesis - proposed by Mitchel - dependent on proton gradient.
15. Chemiosmotic Coupling: 1. Theactivetransport of electronspumpsprotonsout of the mitochondrial matrix into theinter membranespace. 2. An electrochemical gradient of protonsiscreated, outsidethe inner mitochondrial membranethan inside. Theprotonson theoutsidehaveathermodynamic tendency to flow back in. 3. When protonsdo flow back into thematrix, thefreeenergy arising from thegradient (21 kJ/mol of protons) is dissipated, with someof it being used to drivetheATPsynthesis.
16. Chemiosmotic Coupling
17. ATP Synthase: ATPsynthase or F0F1 complex or Complex V Head F1 Stalk F0
18. P:O Ratio TheP:O ratio refersto: thenumber of Inorganic Phosphatemolecules utilized for ATPgeneration for every atom of Oxygen (apair of e-) consumed. .
19. P:O Ratio Electronsentering thesystem at complex I from NADH haveaP/O ratio of about 3/1. Electronsentering thesystem at complex II FADH2'shaveaP/O ratio of about 2/1.
20. ATP Synthesis by ATP Synthase BoyersBinding ChangeMechanism
21. Inhibitors of ETC
22. Inhibitors of ETC: Bind to oneof thecomponentsof ETC and Block the transport of Electrons. At Complex I: Rotenone, Amytal & Piericidin A Between cyt b and c1: Antimycin A & BAL At Complex IV: CO, Cyanide, Azide& H2S
23. Inhibitors of Oxidative Phosphorylation: Uncouplers: 2,4- DNP, FCCP(trifluoro carbonyl cyanidephenyl hydrazone) Thyroxin, FFA Blocksbetween oxidation and phosphorylation Ionophores: Valinomycin, Nigercin altersthepermeability of mitochondrial membrane