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Transcript
Cell Membrane and Membrane Transport Cells Cell Membrane & Membrane transport A Composite Cell · 3 basic parts cell membrane - encloses the cells nucleus - houses genetic materials and controls cellular activities cytoplasm - fills out cell and houses organelles · cells are the basic unit of life · 75 trillion in an adult human · vary greatly in size, shape, contents, and function The Cell Membrane · a.k.a. plasma membrane · functions a. maintains cell integrity (distinct inside and distinct outside) b. controls passage of materials into and out of cell (selectively permeable - only certain substances can enter or leave) · structure a. phospholipid bilayer b. cholesterol - helps stabilize membrane c. proteins - channels, transporters, receptor for hormones d. carbohydrates - cell markers Membrane Transport · interstitial fluid - extracellular fluid rich in nutrients · to maintain homeostasis cells must extract the exact amount of substances it needs at specific times · 2 ways passive - does not require cellular energy active - ATP needed to move substances across membrane A. phospholipid A1 - hydrophilic head A2 - Hydrophobic tails C, F, G. Proteins D. Carbohydrates E. Cholesterol Cell Membrane and Membrane Transport · passive process · characteristics Diffusion a. diffusion - molecules or ions move down their conc. gradient (high conc. to low conc.) b. 3 requirements 1. molecule/ion must be lipid soluble 2. small enough to pass through membrane channels (simple diffusion) 3. or, assisted by a carrier molecule (facilitated diffusion) · source of energy - kinetic energy of molecules · example - exchange of CO2 and O2 in the lungs · drawing - · passive process · characteristics Facilitated Diffusion · passive process · characteristics facilitated diffusion - carrier proteins move molecules through a membrane from high to low conc. limitations - # of carrier proteins in cell membranes · energy - kinetic energy of molecules · example - movement of glucose through cell membrane · drawing - Osmosis Active Transport osmosis - H2O moves from high to low conc. through a selectively permeable mem. · energy - kinetic energy of molecules · examples - a. isotonic - conc. of H2O equal inside and out b. hypertonic - conc. of H2O high inside cell c. hypotonic - conc. of H2O high outside cell · active transport (requires ATP) · characteristics carrier molecules move molecules or ions from regions of low conc. to regions of higher conc. (move up concentration gradient) · energy - cellular energy (ATP) · example - movement of ions, sugars, and amino acids through mem. · drawing - · drawing - endocytosis · active process (requires ATP) · characteristics bringing materials into the cell · energy - cellular energy (ATP) · examples pinocytosis (cell drinking) - mem. engulfs droplets of liquid from surroundings phagocytosis (cell eating) - mem. engulfs solid particles from surroundings · drawing - exocytosis · active process (requires ATP) · characteristics vesicles fuse with mem. to expel substances from the cell · energy - cellular energy (ATP) · example - release of neurotransmitter from neurons · drawing -