Question

What is the origin of the lactate or lactic acid?

Answer 1

Robergs et al. identified that the discovery of lactic acid was in 1789 by Carl Wilhelm Sheele, a Swedish chemist. Sheele isolated an acid in sour milk samples. This origin of acid in milk led to the naming = lactic‘, which means relating to milk. Continuing with their historical account, Robergs et al. noted that by 1810 chemists had verified the presence of lactic acid in other organic tissues such as in meat and in blood. In 1833, the actual chemical formula for lactic acid was determined. The molecular formula of lactic acid is C3H6O3

By 1869, scientists observed different isomers (atomic compounds with different energy states) of lactic acid along with its formation in fermentation reactions. Fermentation is an enzyme-driven chemical change in an organic (has carbon) compound whereby the substance is split into simpler compounds. Since lactic acid is a naturally occurring molecule, originally detected in food products (and with a mild acidic taste), it has and continues to be used to acidify some foods and beverages as well as function as a food preservative.

The prevailing understanding regarding lactic acidosis in humans can be attributed to some early researchers of skeletal muscle biochemistry during exercise. Two noted original researchers were Otto Meyerhoff and Archibald V. Hill, who in 1922 both received a Nobel Prize for their research in the energy capabilities of carbohydrate metabolism in skeletal muscle. Robergs and colleagues (2004) point out that it was Meyerhoff who suggested that lactic acid was a side reaction to glycolysis (splitting of sugar) in the absence of oxygen. They continue that the research of Hill and Meyerhoff solidified the acceptance of lactic acid production and acidosis into the mindset of academics in physiology and biochemistry, although this was primarily based from their (incomplete) observations of cell metabolism at that time. Robergs states, ―...it is easy to comprehend how the Nobel prize 52 quality of work of Hill and Meyerhoff was proof enough to the scientific world at that time for the interpretation that lactate production and acidosis were cause-and-effect.

LACTATE PRODUCTION

The citric acid cycle — also known as the Tricarboxylic acid cycle (TCA cycle), or the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation 53 of acetate derived from carbohydrates, fats and proteins into carbon dioxide and chemical energy in the form of adenosine triphosphate (ATP). Also, the cycle provides precursors of certain amino acids as well as the reducing agent NADH that is used in numerous other biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically.

Lactate production occurs whenever the rate of pyruvate production from glycolysis exceeds glucose oxidation by the mitochondria. Therefore, for increased lactate production to be important physiologically, mitochondrial glucose oxidation must decrease under conditions known to result in increased gluconeogenesis.

During power exercises such as sprinting, running, cycling when the rate of demand for energy is high, glucose is broken down and oxidized to pyruvate, and lactate is produced from the pyruvate faster than the tissues can remove it, so lactate concentration begins to rise. Once the production of lactate has occurred it regenerates NAD+, which is used up in the creation of pyruvate from glucose, and this ensures that energy production is maintained and exercise can continue