<P> Cell division involves a single cell (called a mother cell) dividing into two daughter cells . This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms . Prokaryotic cells divide by binary fission, while eukaryotic cells usually undergo a process of nuclear division, called mitosis, followed by division of the cell, called cytokinesis . A diploid cell may also undergo meiosis to produce haploid cells, usually four . Haploid cells serve as gametes in multicellular organisms, fusing to form new diploid cells . </P> <P> DNA replication, or the process of duplicating a cell's genome, always happens when a cell divides through mitosis or binary fission . This occurs during the S phase of the cell cycle . </P> <P> In meiosis, the DNA is replicated only once, while the cell divides twice . DNA replication only occurs before meiosis I. DNA replication does not occur when the cells divide the second time, in meiosis II . Replication, like all cellular activities, requires specialized proteins for carrying out the job . </P> <P> Between successive cell divisions, cells grow through the functioning of cellular metabolism . Cell metabolism is the process by which individual cells process nutrient molecules . Metabolism has two distinct divisions: catabolism, in which the cell breaks down complex molecules to produce energy and reducing power, and anabolism, in which the cell uses energy and reducing power to construct complex molecules and perform other biological functions . Complex sugars consumed by the organism can be broken down into simpler sugar molecules called monosaccharides such as glucose . Once inside the cell, glucose is broken down to make adenosine triphosphate (ATP), a molecule that possesses readily available energy, through two different pathways . </P>

What are the different types of molecular movements found in living organisms