During the process of elongation, polypeptide synthesis takes place.
IRNA carries amino acids to mRNA.
Once a ribosome reaches a start codon, initiation occurs and the ribosomal subunits break away from the mRNA.
After transcription, mRNA leaves the nucleus and enters the cytoplasm of the cell.
Some ribosomes attach to the rough ER where polypeptides enter to be modified.
During the process of initiation, anticodon-codon complementary base pairing begins as the ribosomal subunits join together at a start codon.
Once there, it becomes associated with ribosomes, constructed out of and protein.
nucleus
IRNA
initiation
stop
termination
start
IRNA
cytoplasm
rough ER
elongation
Feb
The Correct Answer and Explanation is :
Corrected Statements:
- During the process of elongation, polypeptide synthesis takes place. ✅ (Correct)
- tRNA (not IRNA) carries amino acids to mRNA. ❌ (Correction: tRNA)
- Once a ribosome reaches a stop codon, termination occurs and the ribosomal subunits break away from the mRNA. ❌ (Correction: stop codon, not start codon)
- After transcription, mRNA leaves the nucleus and enters the cytoplasm of the cell. ✅ (Correct)
- Some ribosomes attach to the rough ER, where polypeptides enter to be modified. ✅ (Correct)
- During the process of initiation, anticodon-codon complementary base pairing begins as the ribosomal subunits join together at a start codon. ✅ (Correct)
- Once there, it becomes associated with ribosomes, constructed out of rRNA and protein. ❌ (Correction: rRNA, not IRNA)
Explanation:
Protein synthesis occurs in three main stages: initiation, elongation, and termination.
- Initiation: The process begins when the small ribosomal subunit binds to mRNA at the start codon (AUG). A tRNA carrying the amino acid methionine (Met) binds to this codon via its anticodon. The large ribosomal subunit then joins, forming a functional ribosome.
- Elongation: In this stage, amino acids are brought to the ribosome by tRNA molecules. Each tRNA has an anticodon that matches the codon on mRNA, ensuring correct amino acid placement. Peptide bonds form between amino acids, creating a growing polypeptide chain.
- Termination: When the ribosome reaches a stop codon (UAA, UAG, or UGA), no tRNA matches it. Instead, release factors cause the ribosome to detach from mRNA, releasing the completed polypeptide.
After transcription in the nucleus, mRNA moves to the cytoplasm, where ribosomes synthesize proteins. Some ribosomes are free-floating, while others attach to the rough ER, modifying proteins for secretion or specific functions.
Understanding this process is essential for biology and medicine, as protein synthesis is a fundamental mechanism in all living organisms.