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The lungs are vital organs in the human respiratory system responsible for gas exchange between the blood and the external environment. When we breathe in, oxygen enters the lungs and diffuses into the bloodstream, while carbon dioxide (COâ‚‚), a waste product of cellular metabolism, is carried back to the lungs and expelled during exhalation.
Inside the body, cells perform cellular respiration to produce energy in the form of ATP. During this process, glucose and oxygen are metabolized, releasing energy along with water and carbon dioxide. Since COâ‚‚ is toxic at high levels, it must be efficiently removed from the body.
Oxygen intake (Inhalation): Air rich in oxygen enters the alveoli (tiny air sacs in the lungs). Oxygen diffuses into capillaries and binds to hemoglobin in red blood cells.
Carbon Dioxide removal (Exhalation): Blood arriving at the lungs contains a higher concentration of COâ‚‚. This gas diffuses from the blood into the alveoli and is expelled during breathing out.
This exchange happens due to the concentration gradient: oxygen moves from high concentration (lungs) to low concentration (blood), while carbon dioxide moves from high concentration (blood) to low concentration (lungs).
Maintains acid-base balance (pH) of the blood
Prevents respiratory acidosis, which can occur if COâ‚‚ accumulates
Ensures smooth functioning of enzymes and body processes
Nitrogen (Nâ‚‚): The most abundant gas in the air, but not metabolically exchanged in normal breathing.
Hydrogen (Hâ‚‚): Not a normal respiratory waste gas.
Argon (Ar): An inert gas present in the air but does not participate in gas exchange.
Lungs remove carbon dioxide from the blood.
COâ‚‚ is a by-product of cellular respiration.
Removal maintains blood pH and prevents toxicity.
Other gases like nitrogen and argon are inhaled but not metabolized.
👉 Correct Answer: Option 3 – Carbon Dioxide
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