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Eukaryotic Cell Membrane. Cell Membrane. Cell membrane : the flexible boundary of a cell (also called a plasma membrane ) It separates a cell from its surroundings . It allows nutrients to enter and waste to be removed. Cell Membrane. Homeostasis : maintaining a healthy balance
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Cell Membrane • Cell membrane: the flexible boundary of a cell (also called a plasma membrane) • It separates a cell from its surroundings. • It allows nutrients to enter and waste to be removed.
Cell Membrane • Homeostasis: maintaining a healthy balance • The cell membrane allows some molecules into the cell and keeps others out.
Cell Membrane • Selective permeability: allowing only certain molecules to enter and leave the cell • Selective permeability is like a screen on a window
Cell Membrane • What gets in? • H2O freely enters cell • O2 in ,CO2 out • Na and Ca at certain times in certain amounts • Waste leaves but can’t reenter
Membrane Structure • Phospholipid: lipid with a glycerol backbone and two fatty acid chains, and a phosphate group
Membrane Structure • The polar head is hydrophilic: it likes water • Fatty acid tail is hydrophobic: it does not like water. • They form a bilayer
Membrane Structure • The cell membrane also contains proteins to help support the cell structure. • Cholesterol to keep the fatty acid tails from sticking together
Membrane Structure • Fluid Mosaic Model: the organization of the cell membrane. • Fluid because it is not fixed in a particular spot • Mosaic because of the patterns the proteins make
Membrane Structure • Proteins in the membrane function as: • Transport proteins: moving molecules across the membrane • Identify chemicalsignals