Respiration160-page3 - In order to obtain sufficient ATP...

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Cell Respiration - 3 Cell Respiration - An Overview of the Processes As with many metabolic processes, cell respiration has a number of stages. Glycolysis The initial stage of glucose metabolism, or cell respiration, is a process called glycolysis, which splits a glucose molecule into two molecules of pyruvate, a 3- carbon compound. Glycolysis occurs in the cytosol of the cell. What follows glycolysis depends on the presence or absence of oxygen and/or the enzymes needed. If oxygen is available and the organism has the enzymes to do aerobic respiration, the pyruvate molecules will be oxidized in the next stages of aerobic respiration. The reactions of aerobic respiration after glycolysis occur in the mitochondria and include the Krebs cycle and the electron transport chain. If oxygen is not available, or if the organism lacks enzymes needed for aerobic respiration, the pyruvate molecules will proceed with fermentations.
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Unformatted text preview: In order to obtain sufficient ATP for survival, most organisms must do aerobic cell respiration. Cellular Respiration - The Pathways Glycolysis - Overview • Glucose is “activated” for the oxidations by two ATP-consuming reactions. Glucose must be "primed", or destabilized, in order to become reactive. • Glucose is then broken into two molecules of the 3-carbon compound, Pyruvate. • In addition: • Two molecules of NADH are produced. • A net of two molecules of ATP are produced. (Four molecules of ATP are produced during glycolysis, but 2 molecules are consumed in activating the glucose.) • Glycolysis always occurs in the cytosol (cytoplasm) of the cell. • Glycolysis is the most widespread metabolic pathway in living organisms, today and evolutionarily. The earliest prokaryotes probably had a glycolysis pathway....
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