Question

Peptide synthesis in a cell occurs in
1. Mitochondria
2. Chloroplast
3. Ribosome
4. Nucleus

Answer 1

Correct Answer - Option 3 : Ribosome

Concept:

• Translation refers to the process of polymerization of amino acids to form polypeptides.
  • Activation of Amino acids
  • Charging of tRNA
  • Activation of Ribosomes
  • Assembly of Amino acids (Polypeptide Formation)
  • Modification of the released polypeptide

Explanation-

• The amino acids are joined by a bond which is known as a peptide bond. 
  •            The formation of a peptide bond requires energy.
  • Therefore, in the first phase itself, amino acids are activated in the presence of ATP  and form the Amino acyl AMP enzyme complex that is also known as activation of amino acid.
  • Activated amino acid linked to their cognate tRNA – a process commonly called as charging of tRNA or aminoacylation of tRNA to be more specific. 
  • If two such charged tRNAs are brought close enough, the formation of a peptide bond between them would be favoured energetically.
  • The presence of a catalyst would enhance the rate of peptide bond formation.

           Since Protein synthesis takes place in ribosomes so peptide formation also occurs in ribosomes.

• Polypeptide chain synthesis is signaled by two initiation codon AUG or GUG.
• Out of 64 codons, 3- codons are nonsense codons.
• Ribosomes are also called “Organelle within an organelle” and “Protein factory of the cell”
• Ribosomes are the smallest cell organelles.