Somatic or body cells grow, repair, and in some cases, differentiate. Eventually, growing cells must divide or undergo mitosis, to maintain homeostasis. A cell grows and carries out all normal metabolic functions and processes in a period called G1 of the cell cycle, as seen here. G1 is followed by replication of the DNA, during the S phase. The S phase or synthesis phase, is period during which a cell replicates its DNA. Growth continues throughout G2 and then finally mitosis occurs. All of this requires energy. All BUT ONE is a step in supplying energy to maintain homeostasis and promote cell division. That is