Question

Which of the following cellular structure found in all prokaryotes?
(A). Ribosome
(B). Capsules
(C). Flagellum

Choose the correct answer from the options given below:

• A. (A), (B) and (C).
• B. (A) only.
• C. (B) only.
• D. (C) only.

Hint:

Ribosomes are universal to all cellular life forms, including both prokaryotes and eukaryotes.
Appendages like flagella and outer coatings like capsules are specialized and are only found in certain species.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
All prokaryotic organisms (Bacteria and Archaea) lack a membrane-bound nucleus and specialized membrane-enclosed organelles.
However, they share a core set of cellular components that are required to sustain life, carry out genetic translation, and maintain cellular integrity.

Step 2: Detailed Explanation:
Let us analyze the cellular distribution of each structure across prokaryotes:
- Ribosome (A): Ribosomes are the cellular machinery responsible for translation (protein synthesis).
Because all cells must synthesize proteins to survive, ribosomes (specifically 70S ribosomes in prokaryotes) are universally present in all prokaryotic cells. Thus, (A) is correct.
- Capsules (B): A capsule is an outer, gelatinous layer composed of polysaccharides or polypeptides that surrounds the cell wall of some bacteria.
It helps prevent dehydration and acts as a virulence factor.
However, many prokaryotes (especially non-pathogenic, soil, or laboratory strains) do not produce a capsule. Thus, (B) is incorrect.
- Flagellum (C): Flagella are long, whip-like appendages used for locomotion.
While many bacteria and archaea are motile and have flagella, a large number of prokaryotes are non-motile (sessile) and lack flagellar genes entirely. Thus, (C) is incorrect.
Therefore, only ribosomes are universally found in all prokaryotic cells.

Step 3: Final Answer:
The correct option is (B) (A) only.