What are proteins and what do they do?

Proteins are molecules found inside cells and even within their membranes. 

Many proteins work as enzymes, which act as catalysts, speeding up biochemical reactions so that life can happen at the relatively low temperatures on this planet.

Other proteins in the cell membrane control which particles enter or leave the cell.

The protein haemoglobin, packed inside red blood cells, circulates in our blood to carry oxygen around the body.  Other proteins called antibodies can help to protect us from disease.

These are just a few of the important functions of proteins - without them, cells cannot live!

What are proteins made of?

The building blocks, or monomers, of proteins are called amino acids, and there are 20 naturally occurring amino acids which can be joined together by peptide bonds into a long chain.

This chain can fold up into interesting shapes due to attractions between amino acids.  For example, some amino acids can make hydrogen bonds between them and fold into the shapes called alpha-helix or beta sheet.

Many proteins are called globular because in 3-D they fold into a 'ball' shape.  Each protein in our body folds into its unique shape due to the attractions between the amino acids that it is made of.  Only if it has the correct shape (conformation) will it be able to do its job correctly.

Where are proteins made in the cell?

Ribosomes are the organelles in the cytoplasm that make proteins during translation.

How do ribosomes know which protein to make?

The instructions to make the correct protein comes from the DNA in the nucleus.  Genes are sequences of DNA that are copied into messenger RNA in the nucleus of the cell by transcription.  The messenger RNA then leaves the nucleus and goes to the ribosomes in the cytoplasm for translation.

Why should we eat protein every day?

Our body cannot store protein, so we need to eat a little every day to provide the amino acids our own cells need for renewing their own proteins and growing new cells.