Question

The eukaryotic 80S ribosome consist of

• A. 60S subunit and 20S subunit
• B. 50S subunit and 30S subunit
• C. 60S subunit and 40S subunit
• D. 50S subunit and 40S subunit

Hint:

Prokaryotes use odd tens: 30S + 50S = 70S.
Eukaryotes use even tens: 40S + 60S = 80S.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ribosomes are macromolecular ribonucleoprotein complexes that translate mRNA into protein.
Their sedimentation coefficients, measured in Svedberg units (S), reflect their sedimentation rate during ultracentrifugation and are determined by their mass, density, and shape.

Step 2: Detailed Explanation:
The fully assembled eukaryotic ribosome has a sedimentation coefficient of 80S.
It is composed of two primary functional subunits:
A large subunit, designated as 60S.
A small subunit, designated as 40S.
Because sedimentation rates depend on shape and surface area rather than just mass, the Svedberg values of the individual subunits are not directly additive (i.e., $60\text{S} + 40\text{S} = 80\text{S}$).
In prokaryotes, the 70S ribosome is composed of 50S and 30S subunits.

Step 3: Final Answer:
The eukaryotic 80S ribosome is assembled from a 60S large subunit and a 40S small subunit.