Question

A very important feature of respiration is the
a. Synthesis of complex compounds
b. Utilization of $CO_2$
c. Liberation of oxygen
d. Liberation of energy

Answer 1

Respiration comprises all the processes that accomplish ongoing passive movement of $O_2$ from the atmosphere to the tissues to support cell metabolism and the continuous passive movement of $CO_2$, produced metabolically, from tissues to the lungs.

Complete answer:
- The respiratory system contributes to homeostasis by exchanging $O_2$ and $CO_2$ between the atmosphere and the blood. $O_2$ and $CO_2$ are transported by blood between the respiratory system and the tissues.
- Cellular respiration comprise of the intracellular metabolic processes carried out within the mitochondria in which, $O_2$ is consumed to produce $CO_2$ while deriving energy from the nutrient molecules in the form of Adenosine triphosphate (the energy currency of the cell).
- Respiration as a whole is a catabolic process that involves the breakdown of a complex organic molecule to harness the energy within that complex macromolecule. It does not involve the synthesis of complex compounds and thus, option (A) is wrong.
- As mentioned above, it involves the liberation of $CO_2$ rather than utilization of it, and thus, option (B) is wrong as well.
- Respiration involves the utilization of $O_2$ rather than its liberation and thus option (C) is wrong too.

Hence, the correct answer is option (D).

Note: In aquatic animals, the rate of breathing is much faster than terrestrial animals.
- Moist cuticles in an earthworm are used as a respiratory organ.
- Anaerobic respiration doesn’t involve $O_2$ for the oxidation complex macromolecules.
- Hemoglobin in the blood is also referred to as the respiratory pigment and is responsible for binding to $O_2$ and $CO_2$ and their transport from the lungs to the tissues and vice versa.