Question

Protein synthesis in the animal cell occurs
(a) On cytosolic ribosomes only.
(b) On ribosomes attached to ER and Nuclear envelope
(c) On ribosomes present in the nucleolus as well as cytoplasm
(d) On ribosomes present both in the cytoplasm as well as mitochondria.

Answer 1

Hint: Ribosomes present inside the plant and animal cell, cytoplasm, endoplasmic reticulum, mitochondria, nucleus helps in the synthesis of proteins. Nuclear envelopes and nucleolus are devoid of ribosomes.

Complete answer:
Ribosomes are non-membrane bound granular structures present in both plant and animal cells i.e, eukaryotic cells. They are composed of RNA and proteins. Main cell organelles such as mitochondria, endoplasmic reticulum, and nucleus contain ribosomes. Ribosomes are also present inside the cytoplasm. synthesis of proteins is the main function of ribosomes. They are present inside the nucleus but the nuclear envelope and nucleolus are devoid of ribosomes.

Additional Information: - Synthesis of protein is done by the polymerization of amino acids to form a peptide and this order and sequence of amino acids are defined by the sequence of bases in the mRNA. This process is called translation.
- The process of translation occurs by ribonucleic acid(RNA). As ribosomes contain RNA and proteins it is involved in the synthesis of proteins.
- If the surface of the endoplasmic reticulum is covered with ribosomes it is called the rough endoplasmic reticulum.
- All the ribosomes present inside the plant and animal cell, cytoplasm, endoplasmic reticulum, mitochondria, nucleus helps in the synthesis of proteins.
So, the correct answer is ‘On ribosomes present both in the cytoplasm as well as mitochondria’.

Note: -There are two types of ribosomes namely 80s ribosomes and 70s ribosomes. The 80s ribosomes are present in the eukaryotic cell whereas 70s ribosomes present in the prokaryotic cell.
-They were first observed by George Palade in 1953 under the electron microscope.