Assertion (A): The site of translation (protein synthesis) is ribosomes.
Reason (R): Ribosomes bind to mRNA and provide a platform for joining of amino acids.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both A and R are true and R is the correct explanation of A.
Assertion (A): The site of translation (protein synthesis) is ribosomes. — True. A is about where translation happens. Translation is the joining of amino acids into a polypeptide, in the order set by the bases of the mRNA. The ribosome is the cell’s factory for making proteins.
Reason (R): Ribosomes bind to mRNA and provide a platform for joining of amino acids. — True. R is about what the ribosome does. Its small subunit binds the mRNA, and translation begins. Its large subunit has two sites where amino acids (brought by tRNAs) sit close enough to form a peptide bond. The ribosome also acts as the catalyst for this bond.
Why R explains A? Making a protein needs two things: the mRNA has to be read, and the amino acids have to be brought side by side and joined. R shows that the ribosome does both, since it holds the mRNA and gives the amino acids a place to join. This is the very reason translation takes place on the ribosome, so R is the correct explanation of A.
NCERT Extract:
Translation – “… The cellular factory responsible for synthesising proteins is the ribosome. The ribosome consists of structural RNAs and about 80 different proteins. In its inactive state, it exists as two subunits; a large subunit and a small subunit. When the small subunit encounters an mRNA, the process of translation of the mRNA to protein begins. There are two sites in the large subunit, for subsequent amino acids to bind to and thus, be close enough to each other for the formation of a peptide bond.”