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Download Chapter 9. Cellular Respiration STAGE 1: Glycolysis
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Unit 3 Topic 3 Cellular respiration C6H12O6 + 6O2 --> 6CO2 +6H2O The Big Picture Cellular respiration Cellular Respiration Stage 1: Glycolysis Glycolysis Breaking down glucose “glyco – lysis” (splitting sugar) glucose pyruvate 2x 3C 6C Occurs in the cytoplasm A little ATP energy is harvested, but it’s inefficient generate only 2 ATP for every 1 glucose That’s not enough ATP for me! Overview 10 reactions convert glucose (6C) to 2 pyruvate (3C) produces: 4 ATP & 2 NADH consumes: 2 ATP net yield: 2 ATP & 2 NADH Substrate-level phosphorylation Substrate-level phosphorylation Products of glycolysis move on to stage 2 Cellular Respiration Stage 2: Pyruvate "grooming" & the Krebs Cycle Cellular respiration Mitochondria — Structure Double membrane energy harvesting organelle smooth outer membrane highly folded inner membrane intermembrane space fluid-filled space between membranes matrix inner fluid-filled space DNA, ribosomes enzymes free in matrix & membrane-bound outer intermembrane membrane inner space membrane cristae matrix What cells would have a lot of mitochondria? mitochondrial DNA This happens twice for each glucose molecule Electron Carriers = Hydrogen Carriers H+ Krebs cycle produces large quantities of electron carriers NADH FADH2 go to Electron Transport Chain! H+ H+ H+ + H+ H H+ H+ ADP + Pi ATP H+ Cellular Respiration Stage 3: Electron Transport Chain Cellular respiration ATP payoff! Electron Transport Chain series of proteins built into inner mitochondrial membrane transport of electrons down ETC pumps H+ across the membrane to create H+ gradient just like in the light reactions, the gradient powers ATP synthase O2 Electron Transport Chain Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome Mitochondrial matrix cytochrome Remember the Electron Carriers? Glycolysis 2 NADH Time to break open the piggybank! Krebs cycle 8 NADH 2 FADH2 Electron Transport Chain NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ H+ C 2e– Q 2e– NADH H FADH2 NAD+ NADH dehydrogenase inner mitochondrial membrane 2e– H FAD 2H+ + cytochrome 1 2 O2 H2O cytochrome mitochondrial matrix What powers the proton (H+) pumps?… Electronegativity! H 2O O2 electrons are “pulled” to O2 oxidative phosphorylation Cellular respiration 2 ATP + 2 ATP + 34 ATP Summary of cellular respiration C6H12O6 + 6O2 6CO2 + 6H2O +~34-38 ATP Where did the glucose come from? Where did the O2 come from? Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the ATP come from? What is recycled for use again? Why do we breathe? Taking it beyond… What is the final electron acceptor in Electron Transport Chain? O2 So what happens if O2 unavailable? ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H ATP production ceases cells run out of energy Anaerobic respiration Making ATP without oxygen All cells carry out glycolysis: prokaryotes and eukaryotes. Eukaryotes and many prokaryotes also carry out oxidative phosphorylation (remember this requires oxygen). How can some bacteria carry out aerobic respiration if they don't have mitochondria? FUN FACT: many bacteria have ETC’s in their cell membranes. A net of 2 ATP is generated in glycolysis. NAD+ must be present available for this process. For aerobic organisms this is not a problem, NAD+ is regenerated during oxidative phosphorylation (ETC). Fermentation is the pathway that some prokaryotes always have to take (obligate anaerobes). This pathway is also used by prokaryotes and yeasts that are facultative anaerobes. Fermentation is also used by your own muscles when you are working out strenuously and gas exchange is not happening fast enough to replenish ATP through oxidative phosphorylation. Fermentation (anaerobic) Alcohol fermentation Bacteria (prokaryotes), yeast (eukaryotes) wine, bread Lactic acid fermentation Animals, some fungi (eukaryotes) cheese, anaerobic exercise (no O2) Alcohol fermentation recycle NADH NADH is recycled back to NAD+ when pyruvate is converted to ethanol. Alcohol is released into the organism's environment as waste. Fun fact: Bubbles in beer and champagne are CO2 released in the conversion of pyruvate to alcohol. recycle NADH NADH is recycled back to NAD+ when pyruvate is converted to lactate (enzymecatalyzed) Once O2 is available, lactate is converted back to pyruvate by the liver Cells can then resume aerobic respiration using pyruvate (starts Stage 2). Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-CoA 1. Electrons are harvested and carried to the transport system. NADH Krebs cycle e- e- FADH2 e- 2. Electrons provide energy to pump protons across the membrane. e- H2O 3. Oxygen joins with protons to form water. 1 O 2 +2 2H+ O2 H+ CO2 ATP Mitochondrial matrix H+ ATP ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase QuickTime™ and a H.264 decompressor are needed to see this picture. QuickTime™ and a H.264 decompressor are needed to see this picture. Catalyst: Answer all of the following questions in your notebook. What are the products of pyruvate grooming for 1 molecule of glucose? What are the products of the citric acid cycle for 1 molecule of glucose? After glycolysis, pyruvate grooming, and the citric acid cycle, what are your net products? What is phosphorylation? What is substrate-level phosphorylation? What is the main goal for stages 1-3? Catalyst: Answer all of the following questions in your notebook What is the summary equation for cellular respiration? If oxidation is a loss of electrons (in the form of hydrogen atoms) and reduction is the gain of electrons (in the form of hydrogen atoms), what is oxidized during cellular respiration? what is reduced during cellular respiration? How does glucose get to your cells for cellular respiration? What is the point of cellular respiration? What are the net molecular products of glycolysis?