CHAPTER 9 4 metabolic pathways 1 Glycolysis few ATP produced via substrate level phosphorylation In cytoplasm a b Glucose gets oxidized broken down to pyruvate c Occurs with or without oxygen d 2 phases i Energy investment phase 1 Use 2 atp 2 Kinase enzymes that transfer phosphate groups 3 Isomerase enzyme catalyzes reversible reaction 4 Fructose 6 phosphate to fructose 1 6 bisphosphate extreme energy very unstable Key step in glycolysis regulation allosteric inhibition or stimulation by binding to Phosphofructokinase 5 G3P glyceraldehyde 3 phosphate to Dihydroxyacetone phosphate DHAP back and forth ii Energy payoff phase 1 4 ATP formed 2 Dehydrogenase enzyme that removes hydrogens to NAD 3 G3P turned into 2 NADH 4 Phosphoglycerokinase transfers phosphate groups and produces ATP via substrate level phosphorylation 5 Ends with pyruvate e Net i Glucose 2 pyruvate 2H2O ii 4 ATP formed 2 ATP used 2atp iii 2 NAD 4e 4H 2NADH 2H f Cancer cells favor glycolysis 2 Breakdown of pyruvate to an acetyl group releasing CO2 a Pyruvate oxidation turns to Acetyl CoA i Per molecule of pyruvate 1CO2 1NADH 1acetyl CoA which consists of 2 carbons from pyruvate attached to coenzyme A In mitochondria matrix b c No atp produced d Pyruvate O2 aerobic e Pyruvate goes into mitochondria via transport protein f g Coenzyme A comes in forms Acetyl CoA Loses CO2 gives electron to NAD to form NADH H first CO2 coming out 3 Citric acid cycle krebs cycle few ATP produced via substrate level phosphorylation In the matrix of mitochondria a Acetyl coa proceeds to the citric acid cycle b c Releases 2 co2 d Reduces 3 NAD to 3 NADH Produces 1 ATP e Reduces 1 FAD to FADH2 f g Regenerate oxaloacetate h Cycle turns TWICE for each original glucose molecule BECAUSE 2 PYRUVATE WERE FORMED YEILDING 2 ACETYL COA i Products of cycle PER GLUCOSE MOLEUCLE are 4 CO2 2 ATP 6 NADH and 2 i NADH and FADH go to the electron transport chain FADH2 running total 4 Oxidative phosphorylation a ETC Inner membrane of mitochondria i ii High energy e passed from NADH and FADH2 DOWN AN E TRANSPORT CHAIN OR ETC of increasing electronegativity until they reach O2 the final electron acceptor iii The reduced oxygen then picks up protons from solution to become H2O iv Massive amounts of energy released during this v NAD and FAD regenerated back in oxidized form 1 Q CoQ not protein mobile electron carrier 2 Cyt c mobile electron carrier vi Electronegativity increases DOWN the hill toward O2 vii NADH dumps HIGHER ENERGY LEVEL FADH2 dumps LOWER ENERGY LEVEL b Chemiosmosis term used for ATP production tied to an electrochemical H gradient across a membrane i ATP synthase 1 Protons flow back into the matrix through ATP synthase 2 Energy dissipated through this process is used to synthesize ATP 3 Membrane bound enzyme that uses energy of the proton gradient to synthesize ATP from ADP Pi ii pH of INTERMEMBRANE SPACE low iii pH of MATRIX high iv Proton pump electrogenic pump i About 30 or 32 ATP PER GLUCOSE ii 3 ATP per NADH or 2 ATP per FADH2 c Net totals 1 10H moved by 1 NADH and 8H by 1 FADH2 to the intermembrane space 2 4H 1 ATP so 2 5 ATP per NADH and 1 5 ATP per FADH2 ANAEROBIC 1 Other e acceptors a E coli uses nitrate b Methanogens use CO2 which is reduced to CH4 Sulfur bacteria use SO4 c d Some are obligate anaerobes cannot survive in oxygen e Some are facultative anaerobes yeast and many bacteria 2 sulfate i In prokaryotes ETC is in the plasma membrane and respiration reactions occur in the cytoplasm prok Don t contain membrane bound organelles 2 Alcohol fermentation yeast baking etc a Purpose is to regenerate NAD so glycolysis can continue i Glycolysis 2 pyruvate ii 2 pyruvate 2 CO2 2 acetaldehyde final e acceptor iii 2 acetaldehyde 2 ethanol 3 Lactic acid fermentation muscle cells some fungi and bacteria yogurt and cheese a Mammalian cells can ferment temporarily i Glycolysis 2 pyruvate final e acceptor ii 2 pyruvate 2 lactate iii NO RELEASE OF CO2 respiration controlled by feedback inhibition If your body has enough ATP then the process stops and excess food molecules are stored as glycogen or FAT PROTEINS FATS 1 DEAMINATION 2 Can enter at glycolysis Acetyl CoA or citric acid cycle 1 BETA OXIDATION 2 Can enter at glycolysis or straight to Acetyl CoA Evolved over time don t know the exact stages A hypothetical timeline 1 ability to store chemical energy in ATP 2 evolution of glycolysis 3 anaerobic photosynthesis using H2S 4 use of H2O in photosynthesis not H2S 5 evolution of nitrogen fixation 6 aerobic respiration evolved most recently
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