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 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)