Astudent runs 5 kilometers (km) each afternoon at a slow, leisurely pace. one day, she runs 2 km as fast as she can. afterward, she is winded. the next morning, she wakes up very sore. she thought she was in great shape - why was she winded? what has accumulated in her muscles? identify the name of this type of cellular respiration.

The correct answer is lactic acid.

Explanation:

Lactic acid comes from the breakdown of glucose when there is no oxygen present (glycolytic metabolism), that is, in an anaerobic exercise such as lifting weights or running at high speed, like our student in the question, where there is a lot of intensity and short duration. Under normal conditions that lactic acid and when we are trained it is reused and there is no problem.  

But when we continue with intensity an exercise, lactic acid will begin to accumulate by not giving the body time to remove it. This causes high concentration of lactic acid in the muscle fibers, which has two important consequences:

1. The enzymes responsible for breaking the glucose molecule to obtain energy are inhibited, so the energy grind of this path is cut off and as we know, if there is no energy, there is no movement.

2. It prevents calcium from joining the muscle fibers and consequently from contraction.  Therefore, when there is a lot of lactic acid in the body, we have neither energy nor capacity to contract the muscles, this is nothing but fatigue and the best we can do is stop the exercise or activity. That's our recommendation to our student after running 2 km as fast as she could.

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i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.