Chemical Forums
Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: orgo814 on April 18, 2015, 03:55:26 PM
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I'm a little confused on this. Learning how skeletal muscle can utilize glucose for ATP, both anaerobic and aerobic. I know glycolysis in itself is an anaerobic process and that once continues into CAC and ETC you need oxygen as final electron acceptor to synthesize ATP through oxidative phosphorylation. So what do they mean by glycolysis can be both aerobic and anaerobic? Apparently in the brain its strictly aerobic but aren't ATP produced in that process without presence of oxygen?
If someone can clarify this a little for me that would be great. Thanks.
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Glycolosis is an anerobic process, in vertebrate muscle cells, or simpler organisms. The process produces ATP, and also reduces NAD+ to NADPH (and others.) NAD+ can be regenerated from NADPH by the electron transport chain, that uses oxygen as the terminal electron acceptor, reducing it to water. That part is aerobic. The Krebs cycle produces CO2 as well as NADPH and friends, and I assume vertebrates need to breathe to get rid of CO2, but its not aerobic per se. NAD can be regenerated in muscle cells by forming lactic acid or in say, yeast by forming CO2 and ethanol, both from the terminal product of glycolosis, pyruvate. All this is to regenerate NAD+ so more fermentation can happen, not to make energy.
I always assumed vertebrate brains can't rely on glycolosyisn alone because the cells energy needs are high, but someone will correct me soon if there's a biochemical explanation for a missing metabolic pathway in brain cells.
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As a generalization tissues that work continuously, such as brain and heart muscle, work aerobically. Tissues that change how much they work, such as skeletal muscle, can work aerobically or anaerobically. The advantage to being able to work anaerobically for short bursts of activity is said to be speed.
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It's true. There are both aerobic and anaerobic glycolisis. Aerobic glycolisis uses oxygen, which is a good energy-transfer molecule--molecule because its diatomic. Anaerobic glycolisis uses ATP in place of oxygen. One cycle of aerobic glycolisis produces 20 ATP. A cycle of anaerobic glycolisis produces 2 ATP. Cyanide would be much less deadly if it did not bind almost irreversibly to hemoglobin (instead of oxygen), depriving cells of oxygen for aerobic glycolisis, and forcing them to use anaerobic glycolisis. This produces too little fuel to counteract the acid buildup from ATP-fuelled glycolisis. So, what condition, in terms of body PH, causes death by cyanide?
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The main site of toxicity of cyanide is cytochrome c oxidase, which is present in smaller amounts than hemoglobin Cyanide binds to a heme group. One treatment for cyanide poisoning is to produce a small amount of methemoglobin by oxidizing hemoglobin. The methemoglobin binds cyanide. Apparently one can afford to sacrifice a small amount of hemoglobin in this way. http://en.wikipedia.org/wiki/Methemoglobin
Glycolysis is glycolysis, and no oxygen is directly involved. What is different is the fate of the pyruvate and the NADH, which are some of the products of glycolysis. In aerobic catabolism, the fate of pyruvate is complete oxidation to carbon dioxide, with transfer of the electrons ultimately to oxygen.