Anaerobic glycolysis is the transformation of
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
to
lactate when limited amounts of
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
(O
2) are available.
Anaerobic glycolysis is only an effective means of energy production during short, intense exercise,
providing energy for a period ranging from 10 seconds to 2 minutes. This is much faster than aerobic metabolism. The anaerobic glycolysis (lactic acid) system is dominant from about 10–30 seconds during a maximal effort. It replenishes very quickly over this period and produces 2
ATP molecules per glucose molecule,
or about 5% of glucose's energy potential (38 ATP molecules).
The speed at which ATP is produced is about 100 times that of
oxidative phosphorylation.
Anaerobic glycolysis is thought to have been the primary means of energy production in earlier organisms before oxygen was at high concentration in the atmosphere and thus would represent a more ancient form of energy production in cells.
In mammals, lactate can be transformed by the
liver
The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
back into glucose using the
Cori cycle
The Cori cycle (also known as the lactic acid cycle), named after its discoverers, Carl Ferdinand Cori and Gerty Cori, is a metabolic pathway in which lactate, produced by anaerobic glycolysis in muscles, is transported to the liver and convert ...
.
Fates of pyruvate under anaerobic conditions:
# Pyruvate is the terminal electron acceptor in lactic acid fermentation
When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, NAD+ is regenerated from NADH by reduction of pyruvate to lactate.
Lactate is converted to pyruvate by the enzyme
lactate dehydrogenase
Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells. LDH catalyzes the conversion of lactate to pyruvate and back, as it converts NAD+ to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one ...
.
The standard free energy change of the reaction is -25.1 kJ/mol.
# Ethanol fermentation
Yeast and other anaerobic microorganisms convert glucose to ethanol and rather than pyruvate. Pyruvate is first converted to acetaldehyde by enzyme pyruvate decarboxylase in the presence of Thiamine pyrophosphate and Mg++. Carbon-dioxide is released during this reaction. Acetaldehyde is then converted to ethanol by the enzyme alcohol dehydrogenase. NADH is oxidized to NAD+ during this reaction.
See also
*
Aerobic glycolysis Aerobic fermentation or aerobic glycolysis is a metabolic process by which cells metabolize sugars via fermentation in the presence of oxygen and occurs through the repression of normal respiratory metabolism. It is referred to as the Crabtree effec ...
*
Lactate shuttle hypothesis
*
Lactic acidosis
Lactic acidosis is a medical condition characterized by a build-up of lactate (especially -lactate) in the body, with formation of an excessively low pH in the bloodstream. It is a form of metabolic acidosis, in which excessive acid accumulates d ...
References
{{DEFAULTSORT:Anaerobic Glycolysis
Chemical reactions