Two people are exercising at a gym. Person X notices a burning sensation in several muscles, while person Y does not feel any discomfort at all. Why are these two people feeling different sensations?

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Explanation:

Person X is feeling a burning sensation in several muscles because of the accumulation of lactic acid due to inadequate oxygen in their system. When oxygen becomes inadequate during exercises, anaerobic respiration takes place to augment the oxygen shortage and this leads to the production of lactic acid which accumulates up in the muscles and gives a burning sensation.

Person Y does not feel any burning sensation in their muscles because oxygen is adequate in their system and they do not need to respire anaerobically. Person X exercise regime must have been more rigorous than that of person Y.

answer; both surfaces of the membrane are nonpermeable