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.
There are 20 amino acids present in living organisms. Within the DNA there is a code which determines which amino acids will come together to form that protein. So genes act by dictating the order of amino acids put together to make that protein. We have many different types of cells in our body, ranging from liver cells, to those of muscle and the brain. These cells differ quite markedly in their appearance and function.