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AP Biology John D. O’Bryant School of Mathematics and Science October 25, 2012 AP Biology Agenda Do Now: HW Review Outlining: Concept 9.5 Cellular Respiration: Lecture/Discussion Quiz AP Biology 1. A deficiency of a citric acid cycle enzyme in both mitochondria and the cytosol of some tissues (e.g. blood lymphocytes) results in severe neurological abnormalities in newborns. The disease is characterized by excretion in the urine of abnormally high amounts of a-ketoglutarate, succinate, and fumarate. What enzyme deficiency would lead to these symptoms? (Or at least tell me the substrate and the product of the particular citric acid cycle step involved.) Propose a possible way to solve this deficiency. AP Biology 2 . Fluoroacetate, prepared commercially for rat control, is also produced by a South African plant. After entering the cell, fluoroacetate is converted to fluoroacetyl-CoA in a reaction catalyzed by the enzyme acetate thiokinase. The toxic effect of fluoroacetate was studied in an experiment using intact isolated rat heart. After the heart was perfused (supplied with) with 0.22 mM fluoroacetate, the measured rate of glucose uptake and glycolysis decreased, and glucose 6-phosphate and fructose 6-phosphate accumulated. Examination of the citric acid cycle intermediates revealed that their concentrations were below normal, except for citrate, with a concentration 10 times higher than normal. a) Where did the block in the in the citric acid cycle occur? What caused citrate to accumulate and the other cycle intermediates to be depleted? b) Fluoroacetyl CoA is enzymatically transformed in the citric acid cycle. The transformed product is very similar to citrate. Why does this product block the citric acid cycle? How might the effect of the transformed product be overcome? c) Why is fluoroacetic acid poisoning fatal? AP Biology 3. Explain why one NADH molecule is worth 3 ATP's. 4. Explain why one FADH2 molecule is worth 2 ATP's. 5. A total of 36 (or 38) molecules of ATP are derived from a glucose molecule via glycolysis followed by aerobic respiration. Describe where these ATP molecules come from. AP Biology Cellular Respiration Stage 1: Glycolysis AP Biology 2007-2008 But can’t stop there! G3P DHAP NAD+ raw materials products Pi + NADH NAD NADH Pi 1,3-BPG NAD+ Pi + NADH NAD 1,3-BPG NADH 7 ADP Glycolysis 6 Pi ADP ATP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH 8 Going to run out of NAD+ 9 H2O without regenerating NAD+, energy production would stop! Phosphoenolpyruvate (PEP) another molecule must accept HADP 10 from NADH ATP so AP Biology NAD+ is freed up for another round Pyruvate H2O Phosphoenolpyruvate (PEP) ADP ATP Pyruvate How is NADH recycled to NAD+? Another molecule must accept H from NADH H2O O2 recycle NADH with oxygen without oxygen aerobic respiration anaerobic respiration “fermentation” pyruvate NAD+ NADH acetyl-CoA CO2 NADH NAD+ lactate acetaldehyde NADH NAD+ lactic acid fermentation which path you use depends on AP Biology who you are… Krebs cycle ethanol alcohol fermentation Fermentation (anaerobic) Bacteria, yeast pyruvate ethanol + CO2 3C NADH 2C NAD+ beer, wine, bread 1C back to glycolysis Animals, some fungi pyruvate lactic acid 3C NADH AP Biology 3C NAD+back to glycolysis cheese, anaerobic exercise (no O2) Alcohol Fermentation pyruvate ethanol + CO2 3C NADH 2C NAD+ back to glycolysis Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction Count the carbons! AP Biology 1C bacteria yeast recycle NADH Lactic Acid Fermentation pyruvate lactic acid 3C NADH 3C NAD+ back to glycolysis Reversible process once O2 is available, lactate is converted back to pyruvate by the liver Count the carbons! AP Biology O2 animals some fungi recycle NADH Pyruvate is a branching point Pyruvate O2 O2 fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration AP Biology Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle AP Biology 2006-2007 Cellular respiration AP Biology Cellular Respiration Stage 4: Electron Transport Chain AP Biology 2006-2007 Cellular respiration AP Biology Electron Transport Chain Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome bc complex Mitochondrial matrix AP Biology cytochrome c oxidase complex Remember the Electron Carriers? Glycolysis glucose Krebs cycle G3P 2 NADH Time to break open the piggybank! AP Biology 8 NADH 2 FADH2 Electron Transport Chain Building proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ C e– NADH H FADH2 NAD+ NADH dehydrogenase inner mitochondrial membrane e– Q AP Biology H+ e– H FAD 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex mitochondrial matrix What powers the proton (H+) pumps?… Stripping H from Electron Carriers Electron carriers pass electrons & H+ to ETC H cleaved off NADH & FADH2 electrons stripped from H atoms H+ (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ETC) flowing electrons = energy to do work transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space H+ + H H+ TA-DA!! Moving electrons do the work! + H H+ H+ + H+ H+ H + H+ H H+ C e– NADH AP Biology + H H+ Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ cytochrome bc complex + 1 2 O2 H2O cytochrome c oxidase complex ADP + Pi ATP H+ But what “pulls” the electrons down the ETC? H 2O O2 AP Biology electrons flow downhill to O2 oxidative phosphorylation Electrons flow downhill Electrons move in steps from carrier to carrier downhill to oxygen each carrier more electronegative controlled oxidation controlled release of energy make ATP instead of fire! AP Biology “proton-motive” force We did it! Set up a H+ H+ H+ H+ gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + Pi ATP Are we there yet? AP Biology H+ H+ H+ H+ H+ ADP + Pi ATP H+ Chemiosmosis The diffusion of ions across a membrane build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP Chemiosmosis links the Electron Transport Chain to ATP synthesis So that’s the point! AP Biology 1961 | 1978 Peter Mitchell Proposed chemiosmotic hypothesis revolutionary idea at the time proton motive force 1920-1992 AP Biology 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 AP Biology H+ ATP ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase Cellular respiration 2 ATP AP Biology + 2 ATP + ~36 ATP Summary of cellular respiration C6H12O6 + 6O2 6CO2 + 6H2O + ~40 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 else is produced that is not listed in this equation? Why do we breathe? AP Biology Taking it beyond… What is the final electron acceptor in H+ H+ H+ C Electron Transport Chain? e– NADH O2 Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex So what happens if O2 unavailable? ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H AP Biology ATP production ceases cells run out of energy and you die! What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 Do Now (Quiz) 1. Which H+ ion has just passed through the inner mitochondrial membrane by diffusion? A) hydrogen ion A B) hydrogen ion B C) hydrogen ion C D) hydrogen ion D E) hydrogen ion E AP Biology Do Now (Quiz) As a scientist employed by the FDA, you've been asked to sit on a panel to evaluate a pharmaceutical company's application for approval of a new weight loss drug called Fat Away. The company has submitted a report summarizing the results of their animal and human testing. In the report, it was noted that Fat Away works by affecting the electron transport chain. It decreases the synthesis of ATP by making the mitochondrial membrane permeable to H+ which allows H+ to leak from the mitochondrial matrix to the intermembrane space. This effect leads to weight loss. AP Biology Do Now (Quiz) 2. Fat Away prevents ATP from being made by A) blocking access of H+ to ATP synthetase. B) glycolysis from occurring. C) preventing the conversion of NADH to NAD+. D) lowering body temperature. E) slowing down the Krebs cycle. AP Biology Do Now (Quiz) 3. To obtain energy from starch and glycogen, the body must begin by A) hydrolyzing the starch to glucose and the glycogen to amino acids. B) hydrolyzing both starch and glycogen to glucose. C) converting both starch and glycogen to fatty acids. D) removing nitrogen atoms from both molecules. E) removing one glucose at a time with a condensation reaction. AP Biology Do Now (Quiz) 4. Which of the following statements regarding glycolysis is false? A) Glycolysis is considered to be an ancient metabolic system because it does not require oxygen. B) Glycolysis is considered to be an ancient metabolic system because it is not located in a membrane-bound organelle. C) Glycolysis is considered to be an ancient metabolic system because it occurs universally. D) Glycolysis is considered to be an ancient metabolic system because it is the most efficient metabolic pathway for ATP synthesis. E) Glycolysis is considered to be an ancient metabolic system because glucose is the universal substrate for glycolysis. AP Biology Do Now (Quiz) 5. A child is born with a rare disease in which mitochondria are missing from skeletal muscle cells. However, the muscles still function. Physicians find that A) the muscles contain large amounts of lactate following even mild physical exercise. B) the muscles contain large amounts of carbon dioxide following even mild physical exercise. C) the muscles require extremely high levels of oxygen to function. D) the muscle cells cannot split glucose to pyruvate. E) the muscles require extremely large amounts of carbon dioxide to function. AP Biology Do Now (Quiz) 6. Which kind of metabolic poison would most directly interfere with glycolysis? A) an agent that reacts with oxygen and depletes its concentration in the cell B) an agent that binds to pyruvate and inactivates it C) an agent that closely mimics the structure of glucose but is not metabolized D) an agent that reacts with NADH and oxidizes it to NAD+ E) an agent that blocks the passage of electrons along the electron transport chain AP Biology Do Now (Quiz) 7. How does pyruvate enter the mitochondrion? A) active transport B) diffusion C) facilitated diffusion D) through a channel E) through a pore AP Biology Lab: Alcoholic Fermentation in Yeast AP Biology Lorenzo’s Oil AP Biology