​What is the percentage of oxygen in air normally inhaled and exhaled by human beings?​

Correct option is C

The correct answer is (c) Around 21% in inhaled air and 16% in exhaled air

​Explanation:

• Air contains about 21% oxygen when we inhale it.
• During the process of respiration, our body absorbs the oxygen and releases carbon dioxide.
• After the oxygen is absorbed by the lungs and transported via the bloodstream to the cells, the exhaled air has a lower percentage of oxygen (around 16%) because some oxygen is consumed by the body for energy production.

Key Details about Respiration:

1. Composition of Inhaled Air:

   • Oxygen: About 21% of the air we breathe is oxygen.
   • Nitrogen: Around 78% is nitrogen, which is inert and does not play a direct role in metabolism.
   • Other Gases: Small amounts of carbon dioxide, argon, and water vapor are also present.

2. Exhaled Air:

   • After oxygen is absorbed into the bloodstream through the lungs, it is used in cellular respiration to produce energy (ATP). In the process, carbon dioxide (CO2) is produced as a waste product and transported back to the lungs to be exhaled.
   • The percentage of oxygen in exhaled air is about 16% (a decrease from the 21% inhaled), while the carbon dioxide content increases from about 0.04% in inhaled air to around 4% in exhaled air.

3. Breathing Process (Respiration):

   • When you inhale, the oxygen enters the lungs and is diffused into the blood through the alveoli (tiny air sacs in the lungs).
   • The oxygen-rich blood is then circulated throughout the body, and the oxygen is used by the cells in metabolic processes, particularly cellular respiration.
   • Carbon dioxide, a byproduct of this metabolism, is transported back to the lungs, where it is expelled when you exhale.

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