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Standard B 2.7: Cell Regulation ● Intro: (do not have to copy) scientists observed healthy cells in petri dish w/ nutrients ● cells divide rapidly ● stop dividing when come in contact w/ one another ● ex: cut or broken bone-- cells grow 7 divide more rapidly to heal body; when 'fixed,' (cells touching each other) they stop dividing Cell Division is highly controlled ● ● ● Internal signals: chemicals (enzymes) External signals: sense presence of chemical (growth factor) produced in other cells Cells respond to physical signals from envt. turn off: too closely packed/ touching surface turn on: not in contact w/ surface Cell Cycle Check Points ● def: critical control point where stop & go signals can regulate cell cycle ● G1: healthy & large enough ? ● G2: check & correct mistakes in copied DNA ● large enough to divide ? Mitosis checkpoint: metaphase chromosomes properly attached to spindle fibers ? Uncontrolled Cell Division ● ● LEADS TO CANCER! : *( Cancer cells... do NOT heed normal signals divide when densely packed and/or when no growth factor present CANCER ● Cancer begins w/ one faulty cell: body normally destroys damaged cell if not, when it divides, produces cancer cells no regulation --> uncontrolled growth TUMORS ● benign: mass of abnormal cells that remains @ original site (does not move through body) ● ● can often be removed by surgery malignant: mass of cells that invades & impairs functions of one or more organs Cancer cells can separate from tumor & enter circulatory & lymphatic systems transplanted to invade other body parts Standard B 2.4: Cell Differentiation ● ● Nearly all cells in multicell. org have same chromosomes and DNA differentiation = specific parts of DNA are activated create ● ● different function & structure all cells initially have potential to become any type of cell differentiation CANNOT be REVERSED Stem Cells ● ● Unspecialized cells, continually reproduce Ability to differentiate into 1 or more type of specialized cells embryonic stem cells adult stem cells (bone marrow) ● Stem cell research: Scientists have demonstrated that stem cells diff. into specialized cells (w/ right lab culture conditions) Cell Hierarchy Websites ● NOVA: ● Video: How Cancer Spreads ● http://www.mayoclinic.com/health/cancer/MM00638 ● HowStuffWorks Video-The Cell: Cell Differentiation ● http://www.pbs.org/wgbh/nova/cancer/grow_flash.html http://videos.howstuffworks.com/hsw/10313-the-cell-cell-differentiationvideo.htm ● A Hard Sell on Stem Cells: Learning About Different Types of Stem Cells- ● http://learning.blogs.nytimes.com/2005/10/18/a-hard-sell-on-stem-cells/