Lactic Acid

(noun)

A byproduct of anaerobic respiration which strongly contributes to muscle fatigue.

Related Terms

Examples of Lactic Acid in the following topics:

  • Muscle Fatigue

    • Pyruvate is continually processed into lactic acid.
    • With pyruvate accumulation, lactic acid production is also increased.
    • This lactic acid accumulation in the muscle tissue reduces the pH, making it more acidic and producing the stinging feeling in muscles when exercising.
    • Lactic acid is transported to the liver where it can be stored prior to conversion to glucose in the presence of oxygen via the Cori Cycle.
    • The amount of oxygen required to restore the lactic acid balance is often referred to as the oxygen debt.

  • Fermentation Without Substrate-Level Phosphorylation

    • Homolactic fermentation is the production of lactic acid from pyruvate; alcoholic fermentation is the conversion of pyruvate into ethanol and carbon dioxide; and heterolactic fermentation is the production of lactic acid as well as other acids and alcohols.
    • Sugars are the most common substrate of fermentation, and typical examples of fermentation products are ethanol, lactic acid, lactose, and hydrogen.
    • Fermentation occurs in mammalian muscle during periods of intense exercise where oxygen supply becomes limited, resulting in the creation of lactic acid.
    • Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or to fatty acids through acetyl-CoA.
    • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactic acid when oxygen is lacking (fermentation).

  • Anaerobic Cellular Respiration

    • Some examples include alcohol fermentation in yeast and lactic acid fermentation in mammals.
    • The chemical reactions of lactic acid fermentation are the following:
    • 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.
    • It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas.
    • Lactic acid fermentation is common in muscle cells that have run out of oxygen.

  • Microbes and Dairy Products

    • Lactic acid fermentation is performed most often by lactic acid bacteria.
    • Some lactic acid bacteria can produce agents with antimicrobial properties.
    • Sometimes other lactic acid bacteria are added as well.
    • It consists of milk proteins and fat together with lactic acid bacteria.
    • Lactic acid bacteria have been researched for medicinal health benefits.

  • Non-Spore-Forming Firmicutes

    • These bacteria, usually found in decomposing plants and lactic products, produce lactic acid as the major metabolic end-product of carbohydrate fermentation.
    • Furthermore, lactic acid and other metabolic products contribute to the organoleptic and textural profile of a food item.
    • This aspect partially enables LAB to outcompete other bacteria in natural fermentation, as they can withstand the increased acidity from organic acid production (e.g., lactic acid).
    • Intracellular redox balance is maintained through the oxidation of NADH, concomitant with pyruvate reduction to lactic acid.
    • Discuss the role of non-spore forming Firmicutes in industrial applications, specifically lactic acid bacteria (LAB)

  • Muscle Metabolism

    • Pyruvate is continually processed into lactic acid.
    • With pyruvate accumulation, the amount of lactic acid produced is also increased.
    • This lactic acid accumulation in the muscle tissue reduces the pH, making it more acidic and producing the stinging feeling in muscles when exercising.
    • While the pyruvate generated through glycolysis can accumulate to form lactic acid, it can also be used to generate further molecules of ATP.
    • Cellular respiration is limited by oxygen availability, so lactic acid can still build up if pyruvate in the Krebs Cycle is insufficient.

  • Stereoisomers Part II

    • For example, lactic acid (a C3H6O3 carboxylic acid) was found in sour milk as well as in the blood and muscle fluids of animals.

  • Fermented Foods

    • Fermentation is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using microorganisms.
    • Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions.
    • Fermentation is also employed in the leavening of bread (CO2 produced by yeast activity); in preservation techniques to produce lactic acid in sour foods such as sauerkraut, dry sausages, kimchi, and yogurt; and in the pickling of foods with vinegar (acetic acid).
    • Preservation of substantial amounts of food through lactic acid, alcohol, acetic acid, and alkaline fermentations.
    • Biological enrichment of food substrates with protein, essential amino acids, essential fatty acids, and vitamins.

  • Pyruvic Acid and Metabolism

    • Pyruvic acid (CH3COCOOH) is an organic acid, a ketone, and the simplest of the alpha-keto acids.
    • Pyruvic acid (CH3COCOOH; is an organic acid, a ketone, and the simplest of the alpha-keto acids.
    • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration); when oxygen is lacking, it ferments to produce lactic acid.
    • The cycle is also known as the citric acid cycle or tri-carboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions.
    • Pyruvic acid supplies energy to living cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactic acid when oxygen is lacking (fermentation).

  • Clostridial and Propionic Acid Fermentation

    • Acetogenesis is a biological reaction wherein volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen.
    • Acetic acid is equally a co-metabolite of the organic substrates' fermentation (sugars, glycerol, lactic acid, etc.) by diverse groups of microorganisms which produce different acids: Propionic bacteria (propionate + acetate), Clostridium (butyrate + acetate), Enterobacteria (acetate + lactate), Hetero-fermentative bacteria (acetate, propionate, butyrate, valerate, etc.)
    • Acidogenesis is a biological reaction wherein simple monomers are converted into volatile fatty acids.
    • Acetogenes is a biological reaction wherein volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen .
    • Acetic acid is equally a co-metabolite of the organic substrates' fermentation (sugars, glycerol, lactic acid, etc.) by diverse groups of microorganisms, which produce different acids: