For example, we know that hemoglobin is a type of protein that transports oxygen from the lungs and to the tissues and cells of our body. And oxygen is necessary to basically produce ATP. Now, proteins can also be embedded inside cell membranes. And when proteins are embedded inside cell membranes, usually they act as transport proteins, and they allow the movement of different types of molecules and ions across the cell membrane of cells. Now, proteins are also involved in giving our cells structure. For example, the entire cytoskeleton structure consists of different types of proteins.