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Stages of Cellular Respiration and Fermentation There are three that occur continuously Question The break down of glucose is called 1. A. B. C. D. Hydrolysis Cytolysis Dehydration synthesis glycolysis Question 2. The resulting products of glycolysis include A. B. C. D. Sugar ATP ADP water Question 3. NAD and FAD molecules move the following throughout the cell A. B. C. D. Electrons Hydrogens Energy All of the above Question 4. The organic product of glycolysis is a molecule containing ___ carbon atoms called pyruvic acid A. B. C. D. One Two Three Four Question 5. Pyruvic acid is formed in the cells _____. A. B. C. D. Matrix Stroma Cytoplasm Membrane Question 6. After grooming pyruvic acid enters into the second stage of aerobic cellular respiration aka ___. A. B. C. D. Krebs Cycle Electron Transport chain Substrate level phosphorylation Chemiosmosis Question 7. The Krebs cycle takes place in the ___of the mitochondria. A. B. C. D. Inter-membrane space Outer membrane Inner membrane Matrix Question 8. The products of the Krebs cycle include A. B. C. D. ATP NADH and FADH2 CO2 All of the above Question 9. Chemiosmosis generates more ATP than glycolysis because of the presence of A. B. C. D. The electron transport chain Oxygen ATP synthase All of the above Question 10. Glycolysis is an ___ process A. B. Aerobic Anaerobic Overview First two (Glycolysis and Krebs) are exergonic Break down glucose and other organic fuels Glycolysis occurs in the cytoplasm Begins respiration by breaking glucose into 2 molecules of pyruvic acid Krebs Cycle occurs in the mitochondria Completes breakdown of glucose by decomposing a pyruvic acid derivative into Carbon Dioxide The cell makes a small amount of ATP during these two stages The main function of these two stages is to provide electrons to the third stage of respiration 3rd Stage is the Electron Transport Chain Obtains electrons from NADH(the reduced form of NAD), as well as from FADH2 (the reduced form of FAD) This process stores energy that ATP Synthase uses to make most of the cell’s ATP by chemiosmosis Overview of Respiration Glycolysis: Harvesting Chemical Energy “splitting of sugar” Universal energy-harvesting process- all living cells (an ancient process) Begins with a single molecule of sugar Ends with two molecules of pyruvic acid 6-Carbon sugar Each has 3-Carbon sugar As the reaction occurs it releases two molecules of ATP by substrate-level phosphorylation and reduces two molecules of NAD to NADH Thus, banking energy in ATP and NADH Glycolysis Breakdown Between glucose and the pyruvic acids there are intermediates. Each chemical step leads to the next in succession Starting materials: glucose (fuel), ADP and inorganic phosphate, and NAD Along with a little ATP- thus the cell must expend a little energy to start glycolysis Plus a few needed enzymes Glycolysis continued… 2 sets of stages First is preparatory and consumes energy ATP energy(2 molecules) is used to split glucose into two smaller ones Second is energy yielding. Because there are two pyruvic acids, all of these stages occur in duplicate. NADH is produced along with the oxidation of sugar, and 4 ATP are produced. Thus, the net gain of ATP during Glycolysis is 2 ATP per molecule of glucose Accounts for 5% of the energy that a cell can harvest from a molecule of glucose NADH in 2 set of stages account for an additional 16% of potential ATP Most organisms need a lot more energy than that! Glycolysis Details of Glycolysis Pyruvic Acids get “groomed” for the Krebs Cycle Pyruvic acid diffuses through cytoplasm into the mitochondria It is oxidized while NAD+ is reduced to NADH A carbon atom is removed/released as CO2 Coenzyme A (from B vitamin) joins with the 2-Carbon molecule remaining to form acetyl coenzyme A (acetyl CoA) Fuel molecule for the Krebs cycle For each molecule of glucose that entered glycolysis, two molecules of acetyl-CoA enter the Krebs Cycle Preparation for Krebs Krebs Cycle Coenzyme A helps the acetyl enter into the Krebs cycle and then splits and is recycled Only the 2-C acetyl enters Each step is catalyzed by a specific enzyme Disassembles acetyl CoA Strips its electrons Casts off 2 Carbons as CO2 per acetyl fragment that enters into the Krebs cycle Krebs Cycle Continued… Each turn of the cycle yields one molecule of ATP by substrate level phosphorylation Also yields 3 NADH molecules and one molecule of FADH2 molecule Since there are two acetyl CoA molecules per glucose molecule, the actual yield is: 2ATP, 6 NADH, and 2FADH2 By this point, the cell has gained a total of 4 ATP, 10 NADH and 2 FADH2 To actually use all of this energy, the cell must transfer all of the energy in the NADH and FADH2 to ATP Krebs Cycle . Chemiosmosis powers most ATP production Final stage: ETC and ATP synthesis by chemiosmosis With chemiosmosis, the spatial arrangement of membrane bound proteins makes it possible for mitochondria to use chemical energy to create a H+ gradient Can then use energy stored in the gradient to drive ATP synthesis Chemiosmosis in the Membrane The how, where, and why ETC of cellular respiration is in the inner membranes of the mitochondria. Cristae (folds of the membrane) extend its surface area. Many copies of ETC and many ATP synthase complexes Can produce many ATP simultaneously Pathway of electrons: NADHETC O2 Each oxygen atom combines with 2 electrons and 2 hydrogens to form H2O ( one of the final products of cellular respiration) All carriers bind and release electrons in redox reactions. What happens when redox occurs? Use energy released from electrons to move H+ across the membrane from the matrix into the inner membrane space. The resulting H+ gradient stores potential energy Poised to produce a LOT of ATP ATP Synthase provides the channel to allow H+ ions through Contains the enzyme necessary to catalyze the phosphorylation of ADP to ATP As H+ ions pass through, they drive ATP synthesis Finally Via Chemiosmosis, the cell can couple the exergonic reactions of the ETC to the endergonic formation of ATP. The total net yield of ATP per glucose molecule has a maximum of 38. This can be interfered with, ie. Certain poisons or toxins Without O2, chemiosmosis cannot occur. What then??? ATP Yield Poisons that can block the ETC Anaerobic alternatives Some organisms, like yeast and bacteria can survive without oxygen. They use only the 2 ATP generated from glycolysis But how can they replenish the NAD+ from its reduced form Use Fermentation! Types of Fermentation Alcoholic Fermentation Can convert pyruvic acids to CO2 and ethyl alcohol Yeasts release alcoholic wastes into the environment, but die if the alcohol becomes too concentrated Lactic Acid Fermentation Produces lactic acid when NADH is oxidized No CO2 is produced Used in dairy industry- cheese and yogurt If you get a “stitch” it can be broken down by liver to end muscle cramp Fermentation Oxygen-lacking conditions Strict Anaerobes Require anaerobic conditions Oxygen is poisonous Facultative anaerobes (E.coli) can make ATP by fermentation or chemiosmosis depending upon conditions Cells use all kinds of organic food sources Also use food for biosynthesis But where does all of this food come from? Photosynthesis Time to reverse the reaction!