Protein synthesis in an animal cell occurs -
- On ribosomes present in the nucleolus as well as in cytoplasm
- On ribosomes present in cytoplasm as well as in mitochondria
- Only on the ribosomes present in cytosol
- Only on ribosomes attached to the nuclear envelope and endoplasmic reticulum
Answer
(2) On ribosomes present in cytoplasm as well as in mitochondria
Solution
Translation takes place on ribosomes. Cytoplasmic 80S ribosomes (free in the cytosol and attached to the RER) synthesise most proteins.
As per NCERT, the mitochondrial matrix contains its own circular DNA, RNA molecules and 70S ribosomes, and makes some of its own proteins.
The nucleolus, however, only assembles ribosomal subunits; it does not carry out translation.
∴ In an animal cell, proteins are made on ribosomes in the cytoplasm as well as in mitochondria.
Answer: (2)