Since there are so many atoms in a protein, there exist a very large number of possible conformations into which a protein can fold. The native state is the conformation in which the protein exists in its natural biological environment. This is most often the lowest energy conformation the protein can adopt. A protein in its native state is able to carry out its biological function, while a protein that is unable to reach its native state often will be unable to do so. If a protein is taken out of a cell, for example, the pH or other factors related to its environment may cause it to adopt a conformation other than its native state.