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7b. Passive and Active Transport. Passive Transport. Diffusion across a membrane, no ___________. Diffusion: tendency to spread out, move from ____ concentration to ____ concentration. Any substance will diffuse down its __________ ____________. Osmosis.
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7b Passive and Active Transport
Passive Transport • Diffusion across a membrane, no ___________. • Diffusion: tendency to spread out, move from ____ concentration to ____ concentration. • Any substance will diffuse down its __________ ____________.
Osmosis • Diffusion of ____________ across a selectively permeable membrane • ____________: higher solute concentration outside the cell • ____________: lower solute concentration outside the cell • ____________: equal solute concentrations • Animal cells shrink in ____________, burst in _______________, stable in ______________. • Plant cells plasmolyzed in hypertonic, flaccid in isotonic, stable (turgid) in hypotonic
Facilitated Diffusion • Diffusion aided by a transport ___________. • Proteins are specific, can be saturated and inhibited. Some change shape to let the molecule go through. Some provide a channel: • Gated channels: opened or closed by a stimulus • Chemical: • Voltage: • Ex. Cystinuria: disease characterized by absence of protein that transports cystine and other amino acids across a membrane of kidney cells, aa’s not being reabsorbed into blood, instead clump and crystallize. AKA ____________________________.
Active Transport • Pumping against a concentration gradient, requires _______________! • Ex. Go through Na/K pump 3 Na pumped out, 2 K pumped in, net transfer of 1 + charge to ECM • Voltage: electrical PE, separation of opposite charges • Cytoplasm is negatively charged compared to ECM • Membrane potential: voltage across membrane -50 to -200 mV • Favors _________ into cell and ________ out of the cell. • Electrochemical gradient: 2 forces • Chemical: ions concentration gradient • Electrical: membrane potential Electrogenic pump: transport protein that generates voltage across a membrane.
Proton Pump • Actively transports H+ out of the cell, + charge to ECM, stores energy
Cotransport • ATP powered pump indirectly drives the active transport of other solutes
Endo and Exocytosis • ___________: secrete macromolecules by fusion of the membranes • ___________: takes in macromolecules by forming new vesicles. • ____________: cell eating, cell engulfs particle and forms vacuole where digestion takes place • ____________: cell drinks droplet of extracellular fluid. • Receptor mediated: specific ligand binds receptor and is then engulfed. • Ex. Cholesterol enters by LDL receptors. HYPERCHOLESTEROLEMIA: LDL receptor is defective, buildup of cholesterol in blood atherosclerosis