Video Transcript
Why is it important that lactic acid be removed from the body after exercise? (A) Lactic acid is toxic at high concentrations and can cause muscle pain. (B) Lactic acid is toxic at high concentrations and can break down cell walls. (C) In high concentrations, lactic acid can build up in arteries and clog them. (D) In high concentrations, lactic acid can interact with stomach acid and lower the
pH of the body. Or (E) lactic acid is poisonous and can cause blood poisoning.
This question asks us about lactic acid removal, which occurs in the liver. Cellular respiration is a process that cells can use to produce high-energy compounds
like ATP by breaking down sugars, such as glucose. ATP can then be quickly broken down in cells to release energy whenever it is
needed.
There are two main types of cellular respiration: aerobic respiration and anaerobic
respiration. Aerobic respiration reacts glucose with oxygen to produce carbon dioxide, water, and
several molecules of ATP. Sometimes, for example, when we carry out intense exercise, our cells require so much
energy in the form of ATP that the amount of oxygen inhaled for aerobic respiration
is not sufficient to meet the body’s energy demand. In these scenarios, anaerobic respiration can take place in the absence of
oxygen. In fact, the word “anaerobic” derives from the Greek words that mean life without
air.
In humans, anaerobic respiration is sometimes called lactic acid fermentation. This is because it breaks down glucose to produce a substance called lactic acid. Too much lactic acid can be toxic to human cells. With this information we can narrow our answer choices down to either (A) or (B) as
they both mention that high concentrations of lactic acid are toxic.
It is commonly believed that a buildup of lactic acid is linked to the immediate
muscle pain you may feel during intense exercise, suggesting that the correct answer
is option (A). To avoid these potentially harmful effects, lactic acid is usually transported to the
liver where it can be broken down into a less toxic form through a process called
detoxification.
As the cells of animals like humans do not have cell walls, a buildup of lactic acid
could not break down a cell wall that does not exist. So, we can eliminate answer choice (B). This means we can confirm that the reason it is important for lactic acid to be
removed from the body after exercise is (A). Lactic acid is toxic at high concentrations and can cause muscle pain.
