Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis.
Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy. Another familiar fermentation process is alcohol fermentation, which produces ethanol, an alcohol.
The use of alcohol fermentation can be traced back in history for thousands of years. The chemical reactions of alcoholic fermentation are the following Note: CO 2 does not participate in the second reaction :. Alcohol Fermentation : Fermentation of grape juice into wine produces CO2 as a byproduct. Fermentation tanks have valves so that the pressure inside the tanks created by the carbon dioxide produced can be released. The first reaction is catalyzed by pyruvate decarboxylase, a cytoplasmic enzyme, with a coenzyme of thiamine pyrophosphate TPP, derived from vitamin B 1 and also called thiamine.
A carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas. The loss of carbon dioxide reduces the size of the molecule by one carbon, making acetaldehyde. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages. Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions.
Without these pathways, that step would not occur and no ATP would be harvested from the breakdown of glucose. Other fermentation methods also occur in bacteria. Many prokaryotes are facultatively anaerobic.
This means that fewer molecules of ATP can be made. Glucose in human muscle cells is converted to lactic acid during anaerobic respiration:. The lactic acid is a waste product. Some plants, microorganisms and fungi such as yeast can respire anaerobically - it's preferable to release less energy and make less ATP but remain alive. Glucose in yeast cells is converted to carbon dioxide and ethanol , which we refer to simply as 'alcohol':.
This reaction is also called fermentation. This table compares aerobic and anaerobic respiration:. Aerobic and anaerobic respiration Aerobic respiration Respiration using oxygen to break down food molecules is called aerobic respiration.
Anaerobic respiration Most organisms cannot respire without oxygen but some organisms and tissues can continue to respire if the oxygen runs out. Possible Answers:. Correct answer:. Explanation : Aerobic cellular respiration is the process of breaking down glucose to form intermittent electron electron carriers, which eventually donate their electrons to the final electron acceptor, oxygen, at the end of the electron transport chain. Example Question 3 : Understand Aerobic Respiration.
Possible Answers: only produce ATP when oxygen is present. None of these; it depends on the type of prokaryote. Correct answer: None of these; it depends on the type of prokaryote. Explanation : One way to divide prokaryotes is into aerobes and anaerobes.
Example Question 4 : Understand Aerobic Respiration. Possible Answers: Used to produce more glucose. Used to produce oxygen. Correct answer: Used for lactic acid or alcoholic fermentation.
Explanation : If no oxygen is available, anaerobic respiration will occur. Example Question 5 : Understand Aerobic Respiration. Possible Answers: In the presence of.
Correct answer: In the absence of. Example Question 6 : Understand Aerobic Respiration. Possible Answers: Cytosol. Mitochondrial matrix. Correct answer: Cytosol. Copyright Notice. In the presence of oxygen, many more ATP are made. However, some anaerobic organisms that evolved before the atmosphere contained oxygen have survived to the present. Therefore, anaerobic respiration , which takes place without oxygen, must also have advantages.
A major advantage of aerobic respiration is the amount of energy it releases. Without oxygen, organisms can split glucose into just two molecules of pyruvate. This releases only enough energy to make two ATP molecules. With oxygen, organisms can break down glucose all the way to carbon dioxide.
This releases enough energy to produce up to 38 ATP molecules. Thus, aerobic respiration releases much more energy than anaerobic respiration.
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