Chapter 8 HARVESTING ENERGY FROM FOOD GLYCOLYSIS AND CELLULAR RESPIRATION Glycolysis and Cellular Respiration Fig 8 1 We break down glucose to CO2 and energy C6H12O6 6 O2 6 CO2 6 H2O Energy ATP heat Mitochondria Powerhouses for the cell Produce the cell s ATP Mitochondria malfunctions can have serious consequences for an individual s health More than 100 genetic mitochondrial disorders have been identified and all lead to energy shortage muscle weakness and chronic fatigue Cellular respiration is a cumulative function of glycolysis the Krebs cycle and electron transport Three metabolic stages of cellular respiration 1 Glycolysis 2 Krebs cycle a k a Citric Acid Cycle 3 Electron transport chain and oxidative phosphorylation Glycolysis harvests chemical energy by breaking down glucose to pyruvate Glyco sugar Lysis to break apart Glycolysis is a catabolic pathway during which a six carbon glucose is split into two three carbon sugars which are then rearranged by a stepwise process that produces two pyruvic acid molecules Glycolysis Occurs in the cytoplasm Partially oxidizes glucose C6 in two pyruvic acid C3 molecules Glucose goes in 2 pyruvic acids come out overall 2 ATP s are produced cytoplasm 2 ATP C C C C C C glucose Glycolysis C2 C C pyruvate A multi step pathway that takes place C in the cytoplasm Splits glucose to pyruvate Occurs with or without O2 The reactions of glycolysis occur in two phases 1 Glucose activation phase 2 Energy harvest phase 2 ATP 2 ADP C C C C C C glucose C C C C C C fructose bisphosphate Glucose activation Fig 8 3 uses cellular ATP to phosphorylate adds a phosphate group to the glycolysis intermediates costs two ATP molecules per glucose Fig 8 3 2 ATP 2 ADP 4 ADP 4 ATP C C C C C C glucose C C C C C C 2 C C C G3P fructose bisphosphate Glucose activation 2 C C C pyruvate 2 NAD 2 NADH Energy harvest produces ATP yields 4 ATP molecules per glucose 2 molecules of NADH per glucose Glycolysis is distinct from cellular respiration because Glycolysis does not produce ATP Glycolysis utilizes oxygen Glycolysis does not occur in the The products of glycolysis do not enter the mitochondria mitochondria Fermentation see fig 8 8 If there is no oxygen present then the pyruvic acid molecules from glycolysis go through fermentation anaerobic takes place without O2 No ATP production results in the partial degradation of sugars regenerates NAD Two types of fermentation The two most common products of pyruvate reduction are either ethanol or lactic acid 1 Alcohol fermentation 2 Lactic acid fermentation Glycolysis followed by alcoholic fermentation regeneration 2 NAD 2 NADH 2 NADH 2 NAD C C C C C C C2 C C 2 C C 2 C glucose glycolysis fermentation pyruvate ethanol CO2 2 ADP 2 ATP Fig 8 8 Glycolysis followed by lactate fermentation regeneration 2 NAD 2 NADH 2 NADH 2 NAD C C C C C C C2 C C 2 C C C glucose glycolysis fermentation pyruvate lactate 2 ADP 2 ATP Fig 8 8 How can glycolysis continue producing energy when oxygen is not present Fermentation regenerates the NAD needed for glycolysis by allowing pyruvate to accept electrons and H from NADH Fermentation regenerates the ATP needed for glycolysis by allowing pyruvate to accept phosphates from ADP formation Fermentation produces oxygen allowing the organism to make more energy in cellular respiration Fermentation keeps oxygen which is poisonous from entering the cell How is champagne different from wine Fig 8 10 How is champagne different from wine Both are the result of alcohol fermentation Yeast is allowed to consume the sugars in grapes Alcohol is produced in the process With wine this process is completed BEFORE being bottled up With champagne the fermentation process occurs INSIDE the champagne bottle This produces CO2 bubbles which pressurize inside the bottle This is why the cork flies off when you open it You help a friend move and the next day your arms and legs are sore What caused the soreness Your overworked muscles did not get enough CO2 and switched to fermentation which builds up lactate Your overworked muscles did not get enough CO2 and switched to glycolysis which builds up lactate Your overworked muscles did not get enough O2 and switched to fermentation which builds up lactate Your overworked muscles did not get enough O2 and switched to glycolysis which builds up lactate If there is NO oxygen around then fermentation occurs following glycolysis If there IS oxygen around the pyruvic acid molecules from glycolysis go to the bridge reaction followed by the Kreb s cycle in cellular respiration ATP production results in the complete breakdown of sugars C C C C C C glucose cytoplasm Glycolysis C2 C C pyruvate C 2 CO2 2 ATP 2 C C C lactate or 2 2 C C C CO2 ethanol 4 C CO2 Fermentation Cellular respiration C C 2 acetyl CoA The reaction that connects glycolysis to the Krebs cycle is the bridge reaction which converts pyruvic acid to acetyl CoA Formation of acetyl CoA coenzyme A C CO2 C C C pyruvate C C CoA acetyl CoA NAD NADH 1 Removal of CO2 C Formation of acetyl CoA coenzyme A C CO2 C C C pyruvate C C CoA acetyl CoA NAD NADH 2 Production of NADH from NAD Two molecules of C NADH per glucose molecule Formation of acetyl CoA coenzyme A C CO2 C C C pyruvate C C CoA acetyl CoA NAD NADH 3 Attachment of coenzyme A a k a CoA to C form acetyl CoA Kreb s Cycle Occurs in the mitochondrial matrix the innermost part of the mitochondria Completes the breakdown of glucose that glycolysis started Fig 8 4 The products of glycolysis and the Kreb s cycle NADH and FADH2 a small amount of ATP generated 3 NADH 3 NAD FAD FADH2 coenzyme A C C CoA acetyl CoA Krebs cycle 2 C CO2 ADP ATP Fig 8 5 3 3 NAD NADH FAD FADH2 coenzyme A C C CoA acetyl CoA Krebs cycle 2 C CO2 ADP ATP Fig 8 5 3 3 NAD NADH FAD FADH2 coenzyme A C C CoA acetyl CoA Krebs cycle 2 C CO2 ADP ATP Fig 8 5 3 3 NAD NADH FAD FADH2 coenzyme A C C CoA acetyl CoA Krebs cycle 2 C CO2 ADP ATP Fig 8 5 Formation of acetyl CoA 3 NADH 3 NAD coenzyme A C CO2 coenzyme A FAD FADH2 C C C pyruvate NAD NADH C C CoA acetyl CoA Krebs cycle 2 C CO2 ADP ATP Fig 8 5 Formation of acetyl CoA 3 NADH 3 NAD coenzyme A C CO2 coenzyme A C C C pyruvate NAD NADH C C CoA acetyl CoA Krebs cycle 2 C CO2 Fig 8 5 FAD FADH2 ATP ADP CO2 3 NADH FADH2 4 1 ATP 1 Formation of acetyl CoA 3 NADH 3 NAD coenzyme A C CO2 coenzyme A C C C pyruvate NAD NADH C C CoA acetyl CoA Krebs cycle 2 C CO2 Fig 8 5 FAD FADH2 ADP ATP NADH FADH2 ATP CO2 4 …
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