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Homeostasis

Homeostasis is vital for all cells, particularly animal cells, which need to maintain an internal balance. They manage the intake of essential substances like glucose, oxygen, and water while exporting waste and carbon dioxide through a selectively permeable membrane. This membrane acts as a filter, constructed from a phospholipid bilayer containing embedded protein molecules that facilitate transport. Key processes include diffusion, osmosis, and active transport, each essential for maintaining cellular equilibrium and function. Understanding these mechanisms is crucial for grasping cell biology.

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Homeostasis

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  1. Homeostasis • All cells must maintain an internal balance For animal cells: • Allow glucose, oxygen and water in • Export wastes and carbon dioxide out

  2. Selectively Permeable • The ability of a membrane to allow some substances to pass through while keeping others out • Strainer • Filter • Screen door • ???

  3. Structure of the Plasma Membrane • Phospholipid Phosphate Lipids http://telstar.ote.cmu.edu/biology/downloads/membranes/

  4. Phospholipid Bilayer Meaning that there is two layers of the phospholipid molecule http://www.wiley.com/college/pratt/0471393878/student/animations/membrane_transport/index.html

  5. Protein Molecules • Are embedded throughout the bilayer, serve as channels for materials to pass through the membrane • http://home.earthlink.net/~shalpine/anim/Life/memb.htm • http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101

  6. Fluid Mosaic Model • The phospholipids are not bonded to each other and can freely move sideways throughout the bilayer • http://www.stolaf.edu/people/giannini/flashanimat/lipids/membrane%20fluidity.swf • http://telstar.ote.cmu.edu/Hughes/tutorial/cellmembranes/bil.swf

  7. Diffusion • The movement of particles from areas of high concentration to areas of low concentration • http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf • http://www.wisc-online.com/objects/index_tj.asp?objid=AP1903 • Movement occurs until dynamic equilibrium is reached – continuous movement with no overall change • Smells, dyes, ??

  8. Osmosis • The diffusion of water molecules through a membrane from a high to low concentration • http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

  9. Active Transport • Movement of materials against the concentration gradient • Requires energy!!! • http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html • http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitosis.swf • http://www.wisc-online.com/objects/index_tj.asp?objid=AP11203

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