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Blood lactate

Lactic acid
Skeletal formula of L-lactic acid
L-Lactic acid
Ball-and-stick model of L-lactic acid
Names
Preferred IUPAC name
2-Hydroxypropanoic acid
Other names
Lactic acid
Milk acid
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.000.017
E number E270 (preservatives)
UNII
Properties
C3H6O3
Molar mass 90.08 g·mol−1
Melting point 53°C
Boiling point 122 °C (252 °F; 395 K) @ 15 mmHg
Acidity (pKa) 3.86, 15.1
Thermochemistry
1361.9 kJ/mol, 325.5 kcal/mol, 15.1 kJ/g, 3.61 kcal/g
Pharmacology
G01AD01 (WHO) QP53AG02 (WHO)
Hazards
GHS pictograms GHS-pictogram-acid.svg
H315, H318
P280, P305+351+338
Related compounds
Other anions
lactate
acetic acid
glycolic acid
propionic acid
3-hydroxypropanoic acid
malonic acid
butyric acid
hydroxybutyric acid
Related compounds
1-propanol
2-propanol
propionaldehyde
acrolein
sodium lactate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Lactic acid is an organic compound with the formula CH3CH(OH)COOH. In its solid state, it is white and water-soluble. In its liquid state, it is colorless. It is produced both naturally and synthetically. With a hydroxyl group adjacent to the carboxyl group, lactic acid is classified as an alpha-hydroxy acid (AHA). In the form of its conjugate base called lactate, it plays a role in several biochemical processes.

In solution, it can ionize a proton from the carboxyl group, producing the lactate ion CH
3
CH(OH)CO
2
. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid deprotonates ten times more easily than acetic acid does. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.

Lactic acid is chiral, consisting of 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. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid.

Lactic acid is hygroscopic. DL-lactic acid is miscible with water and with ethanol above its melting point which is around 17 or 18 °C. D-lactic acid and L-lactic acid have a higher melting point.

In animals, L-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate 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 lactate is usually 1–2 mmol/L at rest, but can rise to over 20 mmol/L during intense exertion and as high as 25 mmol/L afterward.


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