Protein Synthesis

Protein Synthesis Overview

• Definition of Protein Synthesis

  • The process in which a cell synthesizes proteins based on the genetic instructions encoded within its DNA.

• Structure of the Process

  • Protein synthesis is a two-step process consisting of:

  • Transcription

  • Translation

Transcription

• Definition

  • The process of converting a specific segment of DNA into a strand of messenger RNA (mRNA).

• Steps Involved in Transcription

  1. A portion of the DNA unwinds, facilitated by an enzyme called Helicase, similar to the process of DNA replication.

  2. RNA polymerase, an enzyme, binds to the unwound single-stranded DNA molecule and catalyzes the synthesis of RNA by assembling RNA nucleotides complementary to the DNA template.

  3. The newly formed RNA strand is released from the DNA, and subsequently, the DNA re-zips to return to its original double-helix structure.

• Products of Transcription

  • mRNA (Messenger RNA)

    • Function: Carries the genetic information of a gene from the DNA to a ribosome for protein synthesis.

  • rRNA (Ribosomal RNA)

    • Function: Combines with proteins to form the structural and functional components of ribosomes.

  • tRNA (Transfer RNA)

    • Function: Transports specific amino acids to the ribosome during protein synthesis to build a protein.

Translation

• Definition

  • The process by which the information contained in mRNA is used, along with the help of tRNA and rRNA, to synthesize a protein.

• Location of Translation

  • Translation occurs at the ribosome, a cellular structure composed of rRNA and proteins.

• Initiation of Translation

  • The ribosome attaches to the mRNA at a specific sequence known as the start codon, which is universally recognized as the locus where translation begins.

• Amino Acids and Codons

  • The genetic code comprises 20 different amino acids that can be specified by arrangements of three nucleotides known as codons.

  • Notably, multiple codons can encode the same amino acid due to the redundancy in the genetic code.

  • Certain codons serve essential functions in the translation process:

  • Some codons signal the ribosome to initiate protein synthesis.

  • Others indicate the termination of the protein synthesis process.

  • All proteins initiate translation with an AUG codon, which corresponds to the amino acid Methionine (Met).

Summary of Key Points

• Protein synthesis is a vital cellular function derived from the genetic code present in DNA, through the intermediary steps of transcription and translation.