Proteins

There are many types of protein but four basic groups that often crop up in exams are structural proteins (examples keratin and collagen); enzymes (examples amylase and protease); hormones (examples insulin and growth hormone) and carrier molecules (example hemoglobin). Proteins are also found on the surface of microbes entering the body where they are called antigens. When these antigens are detected, they automatically trigger your immune system to produce other proteins, antibodies, which help to keep you free of infections.

There are approximately 20 different types of amino acid that make up proteins. Each protein molecule has hundreds (or even thousands) of these units joined together in a unique combination. The individual sequence of amino acids give the protein a specific shape which is created from the folding of the amino acid chain. This shape is very important as it allows the protein to join to other molecules in order to do its job.

Proteins work best at a particular temperature and pH. Outside if these values, their efficiency becomes less and less until at some point they do not work any more. If they are heated to temperatures higher than their optimum temperature (or cooled to lower temperatures), the molecules start to change shape. This makes them a lot less efficient at their job. We say that proteins that have been damaged permanently in this way have been denatured

One of the functions of many genes is to instruct cells to synthesize proteins. This is a complex biochemical process called transcription. In short, the DNA inside genes 'unzips' and is copied. The copies break free of the genes and travel into the rhibozomes of the cells, where the proteins are made by adding one amino acid at a time to the chains.

Proteins are vital to all living organisms. See how much you know about them by playing this quiz.