Organic Acid Test

Lactic acid

Exercise and lactate

During power 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

oxidation to pyruvate by well-oxygenated muscle cells which is then directly used to fuel the Krebs cycle,

conversion to glucose via gluconeogenesis in the liver and release back into the circulation, see the Cori cycle.

Contrary to popular belief, this increased concentration of lactate does not directly cause acidosis, nor is it responsible for delayed onset muscle soreness. This is because lactate itself is not capable of releasing a proton, and secondly, the acidic form of lactate, lactic acid, cannot be formed under normal circumstances in human tissues.[citation needed] 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 is 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 cannot 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.[citation needed]

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 have 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). In using this stoichiometric process, Robergs et al. have ignored the causative factors (independent variables) of the concentration of hydrogen ions (denoted [H+]). These factors are strong ion difference [SID], PCO2, and weak acid buffers. Lactate is a strong anion, and causes a reduction in [SID] which causes an increase in [H+] to maintain electroneutrality. PCO2 also causes an increase in [H+]. During exercise, the intramuscular lactate concentration and PCO2 increase, causing an increase in [H+], and thus a decrease in pH. (See Le Chatelier’s principle)

Reference ranges for blood tests, comparing blood content of lactate (shown in violet at center-right) with other constituents.

Lactic acid as a polymer precursor

Main article: polylactic acid

Two molecules of lactic acid can be dehydrated to lactide, a cyclic lactone. A variety of catalysts can polymerise lactide to either heterotactic or syndiotactic polylactide, which as biodegradable polyesters with valuable (inter alia) medical properties are currently attracting much attention.

Nowadays, lactic acid is used as a monomer for producing polylactic acid (PLA) which later has application as biodegradable plastic. This kind of plastic is a good option for substituting conventional plastic produced from petroleum oil because of low emission of carbon dioxide. The commonly used process in producing lactic acid is via fermentation, and later to obtain the polylactic acid, the polymerization process follows.

Lactic acid in foods

Lactic acid is primarily found in sour milk products, such as: koumiss, leban, yogurt, kefir, and some cottage cheeses. The casein in fermented milk is coagulated (curdled) by lactic acid.

Lactic acid in detergents

Lactic acid has gained importance in the detergents industry the last decade. Being a good descaler, soap-scum remover and being a registered anti-bacterial agent – an economically beneficial as well as environmentally beneficial trend toward safer and natural ingredients has also contributed.

See also

Cori cycle

Alanine cycle

Dental caries

Biodegradable plastic

2-Hydroxybutyric acid

Acids in wine

References

^ a b R. Robergs, F. Ghiasvand, D. Parker (2004). “Biochemistry of exercise-induced metabolic acidosis”. Am J Physiol Regul Integr Comp Physiol 287 (3): R50216. doi:10.1152/ajpregu.00114.2004. PMID 15308499. 

^ Siggaard-Andersen, O.; Gthgen, I. H. (1995). “Oxygen and acid-base parameters of arterial and mixed venous blood, relevant versus redundant”. Acta Anaesthesiologica Scandinavica 39: 2144. doi:10.1111/j.1399-6576.1995.tb04325.x.  edit

^ Michael I. Lindinger, John M. Kowalchuk, and George J. F. Heigenhauser (2005). “Applying physicochemical principles to skeletal muscle acid-base status”. Am J Physiol Regul Integr Comp Physiol 289 (3): R891894. doi:10.1152/ajpregu.00225.2005. 

External links

Lactic acid and running: myths, legends and reality

Corn Plastic to the Rescue

Lactic acid: a safe and natural ingredient

Lactic Acid: Information and Resources

Lactic Acid Is Not Muscles’ Foe, It’s Fuel

Categories: Food acidity regulators | Hydroxy acids | Organic acids | Exercise physiology | Food additivesHidden categories: Articles needing additional references from July 2008 | All articles needing additional references | All articles with unsourced statements | Articles with unsourced statements from February 2010 | Articles with unsourced statements from February 2009 | Articles with unsourced statements from February 2007

I prepare test about Nucleic Acids and protin Synthesis.?

But I don’t know them because I didn’t have class because
of sick. please help me T_T fill in the blank to use below
voca.
thymine guanine uracil amino acid sugar DNA
messenger phosphate strand codon organic bases
hydrogen bond protein nucleic acid proteins Three-base transcription double helix replication

Here are some hints:

There are 4 nucleotides (also called bases) in RNA (adenine, guanine, cytosine and uracil). If you take a sequence of 3 of them, you have a codon. The number of possible combinations of the 4 nucleotides, when taken 3 at a time is 4^3 = 64. Each triplet codon codes for an amino acid. A string of amino acids is referred to as a polypeptide or protein.

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