Proteins are synthesized through a process called protein synthesis, which involves two main stages: transcription and translation.
Transcription
Initiation: In the cell nucleus, the enzyme RNA polymerase binds to a specific region of DNA called the promoter, signaling the start of a gene.
Elongation: RNA polymerase unwinds the DNA and synthesizes a single-stranded messenger RNA (mRNA) molecule by matching RNA nucleotides with complementary DNA bases.
Termination: When RNA polymerase reaches a terminator sequence, transcription ends, and the mRNA strand is released.
mRNA Transport: The mRNA leaves the nucleus and travels to the ribosome in the cytoplasm.
Initiation: The ribosome binds to the mRNA at the start codon (AUG), and a transfer RNA (tRNA) carrying the amino acid methionine binds to this codon.
Elongation: tRNAs bring specific amino acids to the ribosome, matching their anticodons with codons on the mRNA. The ribosome links the amino acids together in the sequence specified by the mRNA.
Termination: When a stop codon on the mRNA is reached, the ribosome releases the completed polypeptide chain.
The polypeptide chain folds into a specific three-dimensional shape to become a functional protein. This precise process ensures that proteins are accurately built to perform their various roles in the cell.
