Chapter 10

 Roots grow deep into the dirt and some surface cells are“scratched” away  So… Root Tip Cells must divide rapidly = MITOSIS!

 Cell division allows organisms to grow and reproduce.  Also, cells cannot function effectively if they are too large.  Compare the surface area to volume ratio.

 Cell differentiation: when cells take on specific structures and functions  Different organisms may have different types of cells (e.g. bacterium)  There may be many different types of cells in the SAME organism (e.g. human)

 Neurons (top)  Conduct impulses throughout our body so that we can move, think, feel, etc  Some NEVER divide  Muscle cells (bottom)  Used for movement  Works like a spring

 Cheek cells (top)  Divide approximately every three days because food scrapes off surface layers  Intestinal cells (bottom)  Divides quickly because food and bile scrape off surface layers  Frequently have cilia (hair-like projections) to help “move” food down the digestive tract

 Proteins called cyclins control parts of the cell cycle.  Internal regulators are cyclins that control events INSIDE the cell.  For example, some cyclins pause mitosis until chromosomes are copied. Once this occurs, then it resumes mitosis.  External regulators are cyclins that control events OUTSIDE of the cell.  For example, cells grow until they reach other cells (e.g. healing a wound). Some cyclins tell the cells to stop dividing so that it won’t interfere with other tissues.

 Cancer is uncontrolled cell division.  Since cancerous cells belong to the organism itself, the organism’s body has difficulty detecting and fighting the cancerous cells.  Glycoproteins on cell membrane are “self markers”

 Cancerous cells tend to form a clump called a tumor, but sometimes in later stages of cancer, the cancerous cells metastasize.  Metastasize means that they move to other parts of the body. For example, a cancerous lung cell might migrate to the brain and spread the cancer.

 Inherited  Genetic Mutation  Carcinogens (e.g. certain chemicals in cigarettes)  Overexposure to radiation (e.g. sunlight)  Diet / Exercise  Other

 Surgery  Radiation  Chemotherapy  Magnets???  Alternative Options