Cells are made of a substance called protoplasm. This substance is jelly like, opaque, and colorless. The plasma membrane of a cell holds the contents of a cell together and is flexible to allow the cell to conform to many shapes. Substances move across cell membranes in four ways: passive diffusion, facilitated diffusion, osmosis, and active transport. The seven stages of mitosis are, 1. centrosome divides, 2. nuclear material becomes visible, 3. nuclear membrane dissapears and chromosomes arrange themselves around the centre of the cell, 4. chromosomes divide longitudinally, 5. chromosomes arrange themselves around chromosomes, 6. the cell becomes narrower around the centre, 7. cell divides. Mitosis produces somatic cells. Reproductive cells such as sperm and ovum are called gametes. these cells receive half the number of chromosomes through meiosis. The resulting multicelled organism is called a zygote. the male contains the Y chromosome. The cells, of which the human body and all other organisms are comprised of are called eukaryotic cells. The cells of bacteria are different in some respects and these are called prokaryotic cells, which are characterised by having a nucleus and a plasma membrane.
--Nurse207 17:15, 17 August 2009 (BST)
