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**Glucose made as a byproduct of photosynthetic reactions Harvesting stored energy… Energy stored in organic molecules carbohydrates, fats, proteins Heterotrophs eat food digestive results… raw materials for synthesis fuels for energy controlled release of energy “burning” fuels occurs in series of step-by-step enzyme-controlled reactions Glucose respiration catabolize is the treasure chest glucose to produce ATP glucose + oxygen energy + water + carbon dioxide C6H12O6 + 6O2 ATP + 6H2O + 6CO2 + heat RESPIRATION = making ATP (& some heat) by burning fuels in many small steps ATP ATP O2 CO2 + H2O + ATP (+ heat) glucose enzymes Food digestion = bond breaking & electron movement (energy carrying) Electron movement e NOT alone → move as part of H atom loses e- gains e- p oxidized + + reduced + – H oxidation reduction H oxidation C6H12O6 + 6O2 H e- 6CO2 + 6H2O + ATP reduction Ele- Movement in Respiration Electron carriers move ele- by shuttling H atoms NAD+ NADH (reduced) FAD+2 FADH2 (reduced) NAD+ nicotinamide Vitamin B3 niacin NADH O H C N+ O– O– P reducing power! –O + NH2 H reduction oxidation N+ O– O– P O O– O– P O– O– P adenine –O O ribose sugar O C O phosphates H H carries electrons as a reduced molecule O –O –O NH 4 metabolic stages Anaerobic respiration (NO O2) 1. Glycolysis in cytosol Aerobic respiration (O2) in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 + 6O2 ATP + 6H2O + 6CO2 (+ heat) “glyco – lysis” (splitting sugar) glucose pyruvate 2x 3C 6C Pathway observed in nearly ALL organisms Speculated as one of oldest pathways, most fundamental WHY? Inefficient For every 1 glucose generate only 2 ATP That’s not enough ATP for me! glucose C-C-C-C-C-C 10 reactions convert glucose (6C) to 2 pyruvate (3C) produce: 4 ATP & 2 NADH consumes: 2 ATP NET YIELD: 2 ATP & 2 NADH 2 enzyme 2 enzyme ATP ADP fructose-1,6bP P-C-C-C-C-C-C-P G3P = glyceraldehyde-3-phosphate enzyme enzyme G3P x2 C-C-C-P 2Pi enzyme enzyme enzyme 2H 2 NAD+ 2 G3P x2 P~C-C-C-P 2Pi 4 Pyruvate x2 4 C-C-C ADP ATP Why use excess when its not needed? [ATP] activates/inactivates phosphofructokinase Enzyme used to make 1,6 fructose bisphosphate Allosteric regulation!!! 2 active sites 1. forms 1,6 fructose bisphosphate 2. conformation change, inactivate Is this enough to support life? Not a lot of energy… for 1 billon years+ life on Earth survived this way no O2 = slow growth, slow reproduction only harvest 3.5% of energy stored in glucose more carbons to strip off = more energy to harvest O2 O2 O2 present O2 O2 O2 Onto the Krebs Cycle!!! Double smooth outer membrane highly folded inner membrane membrane cristae intermembrane space fluid-filled between membranes matrix inner fluid-filled space DNA, ribosomes enzymes intermembrane free in matrix & membrane-boundspace outer membrane inner membrane cristae matrix mitochondrial DNA Prepping for Krebs: formation of Acetyl CoA NAD+ Pyruvate C-C-C 2x reduction Coenzyme A Acetyl CoA CO2 C-C oxidation [ Yield = 2C sugar + NADH + CO ] 2 Electron Carriers = Hydrogen Carriers Pyruvate [ enters matrix 2x pyruvate acetyl CoA + CO2 3C 2C 1C NAD 3 step oxidation process releases 2 CO2 reduces 2 NAD+ 2 NADH (moves e-) produces 2 acetyl CoA enters Krebs cycle ] 1937 | 1953 aka in 8 Citric Acid Cycle mitochondrial matrix step pathway each catalyzed by specific enzyme step-wise catabolism of 6C citrate molecule (stripping out the carbons) Appeared later than glycolysis – WHY? Hans Krebs 1900-1981 Count the carbons! pyruvate 3C 2C acetyl CoA 6C 4C This happens twice for each glucose molecule 4C by + and – feedback control by [ATP]!!!** 6C oxidation of sugars CO2 x2 4C **Process regulated 4C citrate 5C 4C CO2 Count the electron carriers! pyruvate 3C 4C acetyl CoA 6C 4C NADH This happens twice for each glucose molecule 2C 6C reduction of electron carriers CO2 x2 4C FADH2 4C NADH 5C 4C ATP citrate CO2 NADH How’s our savings? •Fully oxidized C6H12O6 CO2 •NET YIELD: (4 NADH) x 2 (1 ATP) x 2 (1 FADH2) x 2 8 NADH 2 ATP 2 FADH2 2 ATP Kreb’s cycle 2 ATP Glycolysis Life takes a lot of energy to run, need to extract more energy than 4 ATP! Fun Fact!!! A working muscle recycles over 10 million ATPs per second Proteins built into inner mitochondrial membrane along cristae transport proteins & enzymes In presence of O2 Ele- shuttled (by NADH & FADH2)down ETC pump H+ to create H+ gradient → chemiosmosis!!! yields ~36 ATP from 1 glucose! Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome bc complex Mitochondrial matrix cytochrome c oxidase complex Let’s Follow the Chain… Building proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ H+ C Q e– NADH H e– e– H FADH2 FAD 2H+ + NAD+ NADH dehydrogenase inner mitochondrial membrane cytochrome bc complex 1 O2 H 2O 2 cytochrome c oxidase complex mitochondrial matrix What powers the proton (H+) pumps?… Electrons Flow Downhill Ele- move in steps from carrier to carrier downhill to oxygen each carrier more electronegative controlled oxidation controlled release of energy Set H+ H+ gradient up Allow protons to flow through ATP synthase Synthesize ATP H+ H+ H+ H+ H+ H+ H+ ADP + Pi ATP ADP + Pi CHEMIOSMOSIS!!! H+ Energy Conversion **The Rules: NADH = 3 ATP FADH2 = 2 ATP Glycolysis – 2 NADH 6 ATP Conversion to – 2 NADH 6 ATP Acetyl CoA Krebs ETC cycle - 6 NADH 2 FADH2 34 ATP!!! 18 ATP + 4 ATP = 22 ATP 2 ATP + 2 ATP + ~34 ATP proteins amino acids hydrolysis waste O H H | || C—OH N —C— H | R amino group = Waste, excreted as ammonia, urea, or uric acid glycolysis Krebs cycle 2C sugar = carbon skeleton = enters glycolysis or Krebs cycle fats glycerol + fatty acids hydrolysis glycerol (3C) G3P glycolysis fatty acids 2C acetyl acetyl Krebs groups coA cycle 3C glycerol enters glycolysis as G3P 2C fatty acids enter Krebs cycle as acetyl CoA Digestion carbohydrates, fats & proteins all catabolized through same pathways enter at different points cell extracts energy from every source Why waste? Enough energy? Build stuff!!! points in glycolysis & Krebs cycle used as link to pathways for synthesis run pathways “backwards” have extra fuel, build fat! pyruvate glucose Krebs cycle intermediaries acetyl CoA amino acids fatty acids What happens the absence of oxygen? Pyruvate O2 O2 anaerobic respiration fermentation aerobic respiration mitochondria Krebs cycle Alcohol Fermentation Dead end process ~12% ethanol, kills cells can’t reverse reaction Lactic Acid Fermentation Reversible process if O2 becomes available, lactate converted to pyruvate by the liver recycle NADH Commercial Uses… Bacteria, yeast pyruvate ethanol + CO2 3C NADH 2C NAD+ beer, wine, bread Animals, 1C back to glycolysis some fungi pyruvate lactic acid 3C NADH 3C NAD+back to glycolysis cheese, anaerobic exercise (no O2) ETC ATP Synthase