Question

The protein factories of cells are ________________.
a. Ribosome
b. Nucleus
c. Chloroplast
d. Mitochondria
e. Endoplasmic Reticulum

Answer 1

Hint: It is found in both prokaryotic and eukaryotic organisms.

Complete answer:

Cell organelles are the characteristic feature of the eukaryotic cell but there is one organelle which is found in both types of organisms. The organelle is known as ribosomes and is used for protein synthesis. In eukaryotes, these are attached to either Endoplasmic Reticulum or nuclear membrane with the help of ribophorins protein. In the bacterial cell, these are attached to the plasma membrane of the cell. Mitochondria and chloroplast have their own ribosomes.

Structure: These are composed of two subunits, a large dome-shaped subunit and a small cap-shaped subunit. These two subunits are bound together at a critical ion concentration of $Mg^{2+}$. Any change in its concentration leads to their disassembly.
The size of ribosomes is measured with a specific unit known as Svedberg unit or ‘S’. The prokaryotic ribosome type is 70 S and in eukaryotic it is the 80S. Mitochondria and plastid have a different type which is 55S.
Ribosomes are found singly known as monosomes while when they form a complex group with mRNA it is known as polysomes.

So, the correct answer is ‘Ribosome’.

Note: Organelles like mitochondria and chloroplast have their own DNA hence they need separate ribosomes for the protein synthesis.
Endoplasmic reticulum attached with ribosomes are known as rough Endoplasmic reticulum.