Question

8.Paheli participated in a 400 m race competition held at her school and won the
race. When she came home she had mixed feelings of joy and pain as she had
cramps in her leg muscles. After a massage, she was relieved of the pain.
Answer the following questions related to the situation.
(a) What can be the possible reasons for the pain in her legs?
(b) Why did she fell comfortable after a massage? [NCERT Exemplar; HOTS]
Answer:
(a) Paheli had cramps in her leg muscles after running. She felt pain in her legs
because of accumulation of lactic acid in the leg muscles. Lactic acid is formed
due to anaerobic respiration in the muscle cells after heavy exercise or running.
After heavy exercise, we require large amount of energy.
To produce more energy to meet the oxygen requirement of muscles, muscle
cells perform anaerobic respiration for a short duration.
Lactic acid is formed due to partial breakup of glucose. It gets accumulated in the
muscle cells and causes pain and muscle cramps.

Answer 1

Answer:

b) Massage leads to conversion of lactic acid to pyruvic acid.

Explanation:

lactic acid contains alcoholic group, while pyruvic acid contains ketonic group. High temp upto 573K and Cu converts alcohol to ketone, results into conversion of lactic acid to pyruvic acid.