4. The main purpose of a cell is to organize. Cells hold a variety of pieces and each cell has a different set of functions. Some cells move throughout the body, like blood cells. Others are attached to one another like muscle cells, and they stay in one place. Some cells, like skin cells, divide and reproduce quickly. Nerve cells, do not divide or reproduce except under usual circumstances.
5. The longest cells in the human body are the motor neurons. They can be up to 4.5 feet (1.37 meters) long and run from the lower spinal cord to the big toe.
6. Red blood cells carry oxygen around the body. They are created inside the bone marrow of your bones.
7. The largest cell, a fertilized egg, is too small to be seen with the naked eye.
8. Human cells have a membrane that holds the contents together. However, this membrane is not just a sac. It has receptors that identify the cell to other cells.
9. Within the cell membrane are two major compartments, the cytoplasm and the nucleus. The cytoplasm contains structures that consume and transform energy and perform the cell's functions. The nucleus contains the cell's genetic material and the structures that control cell division and reproduction.
10. Although there are different types of cells, most cells have the same components. A cell consists of a nucleus and cytoplasm which is contained within the cell membrane. The cell membrane regulates what passes in and out of the cell. Inside every cell are mitochondria. Mitochondria are tiny structures that provide the cell with energy.