Glycolysis

Glycolysis - Glycolysis the Universal Process Nine reactions each catalyzed by a specific enzyme makeup the process we call glycolysis ALL

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Glycolysis, the Universal Process Nine reactions, each catalyzed by a specific enzyme, makeup the process we call glycolysis . ALL organisms have glycolysis occurring in their cytoplasm . At steps 1 and 3 ATP is converted into ADP, inputting energy into the reaction as well as attaching a phosphate to the glucose. At steps 6 and 9 ADP is converted into the higher energy ATP. At step 5 NAD + is converted into NADH + H + . The process works on glucose, a 6-C, until step 4 splits the 6-C into two 3-C compounds. The end of the glycolysis process yields two pyruvate acid (3-C) molecules, and a net gain of 2 ATP and two NADH per glucose. Graphic summary of the glycolysis process. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates.
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Anaerobic Pathways Under anaerobic conditions, the absence of oxygen, pyruvate can be routed by the organism into one of three pathways: lactic acid fermentation, alcohol fermentation, or cellular (anaerobic) respiration. Humans cannot ferment alcohol in their own bodies, we lack the genetic information to do so. These biochemical pathways, with their myriad reactions catalyzed by reaction-specific enzymes all under genetic control, are extremely complex. We will only skim the surface at this time and in this course. Alcohol fermentation is the formation of alcohol from sugar. Yeast, when under anaerobic conditions, convert glucose to pyruvate via the glycolysis pathways, then go one step farther, converting pyruvate into ethanol, a C-2 compound. Fermentation of ethanol. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates.
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Many organisms will also ferment pyruvate into, other chemicals, such as lactic acid. Humans ferment lactic acid in muscles where oxygen becomes depleted, resulting in localized anaerobic conditions. This lactic acid causes the muscle stiffness couch-potatoes feel after beginning exercise programs. The stiffness goes away after a few days since the cessation of strenuous activity allows aerobic conditions to return to the muscle, and the lactic acid can be converted into ATP via the normal aerobic respiration pathways. Fermentation of lactate (lactic acid). Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission. Aerobic Respiration When oxygen is present (aerobic conditions), most organisms will undergo two more steps, Kreb's Cycle , and Electron Transport , to produce their ATP. In eukaryotes, these processes occur in the mitochondria, while in prokaryotes they occur in the cytoplasm.
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Overview of the cellular respiration processes. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates. Acetyl Co-A: The Transition Reaction
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This note was uploaded on 05/23/2011 for the course BIO 101 taught by Professor Lanno during the Spring '08 term at Ohio State.

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Glycolysis - Glycolysis the Universal Process Nine reactions each catalyzed by a specific enzyme makeup the process we call glycolysis ALL

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