Question

The cellular respiration is carried out by which of the following:
a) Ribosome
b) Mitochondria
c) Chloroplast
d) Golgi bodies

Answer 1

Cellular respiration is oxidative, exergonic and mainly a catabolic process. The mechanism of breakdown of food materials within the cell to release energy, and the trapping of this energy for synthesis of ATP. In prokaryotes and unicellular organisms this occurs in cytoplasm. But in eukaryotes it occurs in mitochondria along with cytoplasm. In aerobic respiration, glycolysis occurs in cytoplasm and further processes occur in mitochondria.

Complete answer:
a) Ribosome: Ribosomes are the granular structures, which are composed of RNA and proteins and not surrounded by any membrane. They are mainly responsible for protein synthesis.
Option (a) is incorrect.
b) Mitochondria: It is also known as the ‘powerhouse of the cell’, because it produces energy through Krebs cycle that occurs in the matrix of mitochondria and through ETS, which occurs on the inner-mitochondrial membrane. These steps are part of cellular respiration.
Option (b) is correct.
c) Chloroplasts: They contain chlorophyll and carotenoid pigments which are responsible for trapping the light energy essential for photosynthesis. These are found only on plant cells.
Option (c) is incorrect.
d) Golgi bodies: It is the densely stained reticular structure near the nucleus, which mainly performs the function of packaging of materials. It is also an important site for formation of glycolipids and glycoproteins.
Option (d) is incorrect.

Hence the correct answer is option (b).

Note:
The compounds that are oxidized during respiration are called respiratory substrates. Usually, carbohydrates are respiratory substrates but proteins, fats and even organic acids can act as respiratory substrates. These substrates enter the respiratory pathway in different steps.
Also, the respiratory process is mainly considered as a catabolic process (breakdown of complex molecules into simpler forms) but it is important to note that compounds can be withdrawn from the respiratory pathway as and when needed for the synthesis of a particular substrate. This makes the respiratory pathway anabolic also. Hence, it would be better to use an ‘amphibolic pathway’ i.e., both catabolic and anabolic.