<unk>  (IUPAC systematic name: 2-hydroxypropanoic acid), also known as milk acid, is a chemical compound that plays a role in several biochemical processes.  It was first isolated in 1780 by a Swedish chemist, Carl Wilhelm Scheele, and is a carboxylic acid with a chemical formula of C3H6O3. It has a hydroxyl group adjacent to the carboxyl group, making it an alpha hydroxy acid (AHA).  In solution, it can lose a proton from the acidic group, producing the<unk> ctate ion CH3CH(OH)COO−. It is miscible with water or ethanol, and is hygroscopic.<unk>  is chiral and has two optical isomers. One is known as L-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is D-(-)-lactic acid or (R)-lactic acid.  L-(+)-Lactic acid is the biologically important isomer.
In animals, L-lactate is constantly produced from pyruvate via the enzyme<unk> ctate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise.  It does not increase in concentration until the rate of<unk> ctate production exceeds the rate of<unk> ctate removal which is governed by a number of factors including: monocarboxylate transporters, concentration and isoform of LDH and oxidative capacity of tissues. The concentration of blood<unk> ctate is usually 1-2 mmol/L at rest, but can rise to over 20 mmol/L during intense exertion.
Industrially,<unk>  fermentation is performed by<unk> ctobacillus bacteria, among others. These bacteria can operate in the mouth; the acid they produce is responsible for the tooth decay known as caries.
In medicine,<unk> ctate is one of the main components of Ringer's<unk> ctate or<unk> ctated Ringer's solution (Compound Sodium<unk> ctate or Hartmann's Solution in the UK). This intravenous fluid consists of sodium and potassium cations, with<unk> ctate and chloride anions, in solution with distilled water in concentration so as to be isotonic compared to human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or a burn injury.
Lactic acid
Glycerin
Fructose
Muconic acid
Cholesterol
Meconic acid
D-Galacturonic acid
Uric acid