Protein synthesis - Higher

Protein synthesis consists of two stages – transcription and translation. In transcription the DNA code is read, and in translation the code is used to build up protein molecules.

DNA is a triplet code. Each triplet, a group of three bases, codes for a specific amino acid.

Transcription

The DNA code for a protein remains in the nucleus, during transcription but a copy, called mRNA, moves from the nucleus to the ribosomes where proteins are synthesized during translation in the cytoplasm. To make the mRNA the double stranded DNA unzips.

Translation

The mRNA leaves the nucleus and goes to the ribosomes.

Carrier molecules bring specific amino acids to add to the growing protein in the correct order. There are only about 20 different naturally-occurring amino acids. The protein produced depends on the template used, and if this sequence changes a different protein will be made.

Diagram showing how protein is synthesised in a DNA structureDiagram illustrating the process of transcription - when a gene is converted to protein

Each protein molecule has hundreds, or even thousands, of amino acids joined together in a unique sequence. It is then folded into a unique shape. This is very important, as it allows the protein to do their jobs, such as enzymes or hormones, and it can form structures within the body, such as collagen.

A straight amino acid sequence folds into a precise 3D shape, the protein functions as an enzyme.
A molecular model of haemoglobin which is a protein found in red blood cells
A molecular model of haemoglobin which is a protein found in red blood cells