Everything about Lactic Acid totally explained
| Section2 =
}}
Lactic acid (
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 C
3H
6O
3. 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
lactate ion CH
3CH(OH)COO
−. It is miscible with water or ethanol, and is
hygroscopic.
Lactic acid 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 lactate dehydrogenase (LDH) in a process of
fermentation during normal
metabolism and
exercise. It doesn't 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.
Industrially,
lactic acid fermentation is performed by
Lactobacillus 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, lactate is one of the main components of Ringer's lactate or
lactated Ringer's solution (
Compound Sodium Lactate or
Hartmann's Solution in the UK). This
intravenous fluid consists of
sodium and
potassium cations, with lactate 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.
Exercise and lactate
During power-intensive exercises such as sprinting, when the rate of demand for energy is high, lactate is produced faster than the ability of the tissues to remove it and lactate concentration begins to rise. This is a beneficial process since the regeneration of
NAD+ ensures that energy production is maintained and exercise can continue. The increased lactate produced can be removed in a number of ways including
Contrary to popular belief, this increased concentration of lactate doesn't directly cause
acidosis, nor is it responsible for
delayed onset muscle soreness. This is because lactate itself isn't capable of releasing a
proton, and secondly, the acidic form of lactate, lactic acid, can't be formed under normal circumstances in human tissues. Analysis of the glycolytic pathway in humans indicates that there are not enough hydrogen ions present in the glycolytic intermediates to produce lactic or any other acid.
The
acidosis that's associated with increases in lactate concentration during heavy exercise arises from a separate reaction. When
ATP is
hydrolysed, a hydrogen ion is released. ATP-derived hydrogen ions are primarily responsible for the decrease in pH. During intense exercise,
aerobic metabolism can't produce ATP quickly enough to supply the demands of the muscle. As a result,
anaerobic metabolism becomes the dominant energy producing pathway as it can form ATP at high rates. Due to the large amounts of ATP being produced and hydrolysed in a short period of time, the
buffering systems of the tissues are overcome, causing pH to fall and creating a state of acidosis, a natural process which facilitates the easier dissociation of
Oxyhaemoglobin and allows easier transfer of oxygen from the blood. This may be one factor, among many, that contributes to the acute muscular discomfort experienced shortly after intense exercise.
The effect of lactate on acidosis has been the topic of many recent conferences in the field of exercise physiology. Robergs et al. have accurately chased the proton movement that occurs during glycolysis. However, in doing so, they've suggested that [H
+] is an independent variable that determines its own concentration. A recent review by Lindinger et al. has been written to rebut the stoichiometric approach used by Robergs et al (2004).
Lactic acid is also present in
wheat beers, especially
lambic, due to the activity of
Pediococcus damnosus.
Lactic acid is widely used for inhibiting pathogenic bacteria like E.coli, Salmonella, Campylobacter and Listeria on animal carcasses like beef, pork and poultry during the slaughtering process.
Potassium lactate, sodium lactate and calcium lactate are the neutralized salts of lactic acid. Potassium lactate is used in many fresh and cooked meat products for shelf life control, color preservation and reduction of sodium content. Sodium lactate has a mild saline taste and is therefore suitable for flavour enhancement in meat products as well. Sodium lactate is being produced as liquids as well as powders. Calcium lactate is popular for fortification and improved texture in emulsified meat products like frankfurters.
Further Information
Get more info on 'Lactic Acid'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://lactic_acid.totallyexplained.com">Lactic acid Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
