Lactic Acid

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Pyruvate

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Skeletal Muscles

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NADH

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Lactic Acid


lactic-acidLactic acid is a result of anaerobic respiration. Anaerobic respiration occurs in the cells when no oxygen is present. It does produce energy, like aerobic respiration, but is much less efficient. Lactic acid typically forms in muscle cells and red blood cells. It can build up in the body if there is not enough oxygen for all of the cells in the body. The formula for lactic acid is CH3CH(OH)CO2H, and it is white and water soluble in its solid state and clear in its liquid state

What Happens during Respiration

During respiration, glucose is turned into energy in the cells. The glucose is broken down and the result is the formation of adenosine triphosphate (ATP) molecules. Respiration typically occurs in three stages when oxygen is present. The first stage is glycolysis. During this stage, no oxygen is needed. Glucose is broken down into pyruvates. If there is oxygen present in the cells, respiration will go through the Krebs cycle and through Oxidative Phosphorylation. When there is no oxygen, after glycolysis, the cells will go through fermentation, which is how lactic acid is be formed.

Lactic Acid Fermentation

In addition to the formation of 2 molecules of ATP during the glycolysis, 2 molecules of Nicotinamide Adenine Dinucleotide Hydrate (NADH) are formed. During fermentation, the NADH transfers its electrons to the pyruvate. The byproduct of this reaction is lactate. The lactate then ferments with the help of the red blood cells to create lactic acid. Lactic acid can build up in the body. The body is able to get rid of the lactic acid by breaking it down to carbon dioxide and water vapor. Those products can then be exhaled from the body.

The Myths of Lactic Acid

Lactic acid has long been misunderstood, and has been blamed for many things in the body. Here are some commonly believed myths about lactic acid.

  • Lactic acid causes muscle fatigue – Many people believe that lactic acid builds up in the body when the muscles are exercised, and that the resulting buildup causes fatigue and soreness in the body. It is true that there will be more lactic acid formed during exercise, but this actually helps the muscles prevent fatigue. Lactic acid can help depolarization in the muscles, a process that is like draining the battery in a cell phone. The more the muscles are depolarized, the more tired the muscles feel, but lactic acid slows this process down.
  • Lactic acid causes muscle soreness – Like the fatigue belief, the idea here is that the buildup of lactic acid during exercise promotes soreness. In reality, the amount of lactate that is produced during exercise is not enough to cause soreness. The soreness is the result of damage to the cells caused by the exercise.
  • Lactate is not responsible for increasing muscle – The lactate that is formed in muscle cells actually can help make the muscles stronger and can help increase the endurance of the muscles. Lactate is able to increase the concentration of the mitochondria in the muscle cells.
  • Lactic acid has a role in aerobic respiration – While lactic acid can be formed as a result of anaerobic respiration, when it is metabolized aerobically in the mitochondria, it becomes a fuel source for the cells.
  • The stronger you are, the less lactic acid you produce – It is thought that athletes have more endurance because they produce less lactic acid. The actual truth is that athletes are probably producing the same amount of lactic acid as anyone else, if not more. They have lower levels of lactic acid because they use more of it up.

Most people can adequately remove the lactic acid that builds up in their body and cells through normal processes. However, there are times when outside influences prevent the body from removing the excess lactic acid that forms in the body. This can result in a painful condition known as gout.

Resources

Image taken from Khanacademy.org Anaerobic Respiration 

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