Ribosome Composition—Ribonucleoprotein Nature Ribosomes are the macromolecular machines that synthesize proteins. What are ribosomes composed of?

Introduction / Context:
Ribosomes are ribonucleoprotein particles—assemblies of ribosomal RNA (rRNA) and ribosomal proteins. The rRNA forms the structural and catalytic core, while proteins stabilize the architecture and contribute to assembly and regulation. This question tests recognition of that dual composition.

Given Data / Assumptions:

• Prokaryotic ribosomes: 70S (50S + 30S subunits); eukaryotic: 80S (60S + 40S).
• Peptidyl transferase activity is attributable to rRNA (a ribozyme).
• No essential lipid or carbohydrate components form the core particle.

Concept / Approach:
Select the option acknowledging both macromolecule classes. rRNA is the catalytic component, and proteins aid in folding, stability, and interactions. Together they create a functional translation apparatus that can be reconstituted in vitro from RNA and protein components.

Step-by-Step Solution:

Verification / Alternative check:
High-resolution structures show a protein shell decorating a largely rRNA core, with the peptidyl transferase center formed by rRNA alone.

Why Other Options Are Wrong:

• Proteins only or RNA only ignores the composite structure.
• Lipids/carbohydrates are not structural components of ribosomes.

Common Pitfalls:
Assuming proteins provide catalysis; in modern ribosomes, rRNA is the primary catalyst.

Final Answer:
Both (a) and (b)