Protein synthesis

Protein Synthesis Overview

  • Protein synthesis refers to the creation of proteins by cells. It involves two main stages: transcription and translation.
  • This is the process in which the genetic information from DNA is effectively used to produce functional proteins.
  • The nucleus, messenger RNA (mRNA), transfer RNA (tRNA), and ribosomes all play a critical role in protein synthesis.

Transcription

  • Transcription is the initial stage of protein synthesis. It occurs in the nucleus of the cell.
  • The process begins when an enzyme called RNA polymerase attaches to a specific region on the DNA molecule and starts reading the DNA sequence one base at a time.
  • As this happens, RNA polymerase constructs a strand of mRNA with bases complementary to the DNA. In this pairing, Adenine (A) pairs with Uracil (U) and Cytosine (C) pairs with Guanine (G).
  • Once transcription is complete, the produced mRNA strand detaches from the DNA and leaves the nucleus to enter the cytoplasm.

Translation

  • Translation is the second part of protein synthesis which occurs in the cytoplasm, specifically on the ribosomes.
  • Ribosomes read the sequence of codons (groupings of three bases) on the mRNA.
  • Each codon on the mRNA corresponds to a particular amino acid.
  • Amino acids are transported to the ribosomes by molecules of tRNA. Each tRNA has a specific anticodon at one end and an amino acid at the other end.
  • The tRNA’s anticodon binds with its complementary codon on the mRNA strand.
  • The amino acid carried by the tRNA is then added to the growing protein chain.
  • This process continues until a stop codon is reached on the mRNA, signalling the end of protein synthesis.
  • The completed chain of amino acids, known as a polypeptide, then folds into a specific shape to form a functional protein.

Post-Translational Modifications

  • Some proteins require additional changes after translation, known as post-translational modifications, to become fully functional.
  • Modifications may include the addition of other chemical groups like phosphate, methyl, or acetyl groups.
  • In some proteins, multiple polypeptide chains may also join together to form a quaternary structure.

Protein Synthesis and Genetics

  • Eventually, the sequence of nucleotides in the DNA, interpreted through the process of protein synthesis, determines the kind of protein produced.
  • Therefore, cells can manufacture a huge variety of proteins with different functions, depending on which genes are expressed.
  • Hence, protein synthesis is the essential process through which our genetic code is translated into the proteins that perform all of our body’s functions.