7.014 Handout Biochemistry V-VI 1 MIT Department of Biology7.014 Introductory Biology, Spring 20057.014 Glycolysis Reactions Handout ONote: for simplicity, H's are shown as stars (*). O-P = P O-12 3456 CH2OH O OH OH OH OH H O HHOHH OHC C C C C Cglucose OH OH ATP H OH ADP O OH OH OH O P glucose-6-phosphate C C C C C C OH HO O OH OH O P fructose-6-phosphate C C C C CC OH ADP ATP P O O OH OH O P P OCH2 H OHO CH2O P fructose 1,6-di phosphate C C C C CC H OH OH split at this bond OH H 12 3 4 56 P O O H OH O P dihydroxyacetone H C C C H + OC C C H glyceraldehyde-3-phosphatephosphate H OH HH H + (2 molecules of g3p,3 2 1 therefore next reactions are doubled)OH O PO C C C H glyceraldehyde-3-phosphate H H H 2H O C Note: E = enzyme H C O H + (glyceraldehydeglyceraldehyde-3-phosphate H S EH C O P H H O H C S E H C O HH C O P H These reactions happen twice for each glucose. NAD+ NADH + H+ O C S E H C O HH C O P H Pi (enzyme is released H S Eunchanged = catalyst) O C O P 1,3 diphosphoglycerate H C O H H C O P H ADP ATP O O-C 3-phosphoglyceric acid H C O H H C O P H 3-phosphate dehydrogenase) side chain of cysteine in protein transient intermediate (substrate is covalently bound to enzyme) transient intermediate 3These reactions happen twice for each glucose. O C O-3-phosphoglyceric acid H C O H H C O P H O C O-2-phosphoglyceric acid H C O P H C O H H O O C C C O-P H H H2O phospho-enol-pyruvate (PEP) ATP ADP C O C O H "keto" form: more stable (low energy) "enol" form: less stable (high energy) O O-C pyruvate C O H C H This reaction recyclesthe NADH in human muscle cells when O2is low or absent.NADH + H+ NAD+ H O or (Thiamine – a B-vitamin O- is required for this step)C H C O H O C OH C H H+ NADH + HThis reaction recyclesNADH in yeast (andsome bacteria) when O2 is absent.+ NAD+ O HCO H lactate H C H H C H H C H HH ethanol 4ATP & ADP ATP ADP NH2 N HH O N N N HH CH2 O-O-O-O-A P O O P O P O O O Pi OH OH R NAD = N icotinamide Adenine DinucleotideNAD+ & NADH N C O NH2 H H H H nicotinamide: a vitamin for humans (a.k.a. niacin) but not for yeast or E. coli H HO H C NH2 AA -H N H+ 2 e + H+ R NAD+ reduced to NADH R RR (another molecule is oxidized) P P P P NADH oxidized to NAD+ NAD+ (another molecule is reduced) NADH 5Photosynthesis & Electron Transport Photosynthesis: Cyclic Photophosphorylation 2 e-H+ out in H+ light Chl Chl Generates H+ gradient (used for ATP synthesis) only. PS I Non-cyclic Photophosphorylation Chl Chl light 2 e-Chl 2 e-light PS II Chl PS I2 e-H2O H+ in out H+Generates H+ gradient (used for ATP synthesis) and NADPH. NADP+ NADPH + H+ O2 6Respiration Electron Transport H+ out in H+ H+ in out H+ H+ out in H+ H+ out in H+ O2 H2O 2 e-NADH + H+ NAD+ NADH from glycolysis & Krebs' Cycle is recycled using O2 and generating H+ gradient (used for ATP synthesis). ATP Synthesis from H+ Gradient (H+ gradient is generated by electron transport in photosynthesis & respiration) H+ - driven ATP synthetase (proton ATPase) ATPADP + Pi H+H+ electron-transfer-driven proton pump 2 e-+ 2 H+ 2 e-+ 2 H+ low [H+] high [H+] membrane
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