Proteins are important components of all cells.
They determine a cell's colour, shape and function. Proteins can have a structural role, such as keratin that makes up your hair, or myosin and actin that are found in muscle cells. Proteins may also have a functional role, allowing and regulating the myriad of reactions that occur in each of our cells. An example here could be the enzymes you use to digest your food. Every protein is made up of a chain of building blocks called amino acids.