The clear protein of an egg become opaque and firm when cooked because the heat CHANGES THE PROTEIN STRUCTURE BY DENATURING THE PROTEIN. Each enzymes has its own range of temperature at which it remains active, when this temperature is exceeded the protein becomes denatured and loses its three dimensional structure which determines its functions.
An organism that cannot make its own food is called a heterotroph. All animals and species of fungi, along with some types of bacteria, are heterotrophs.
