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Osmosis
Osmosis is the net movement of water molecules through a partially permeable membrane from an area of high water potential to an area of low water potentialhigh water potential - dilute - lots of waterlow water potential - concentrated - little waterpermeable to water but not solutein lipid bilayer or through aquaporins TERM 2
Osmotic Pressure
DEFINITION 2 Osmotic pressure is the pressure required to prevent the inward flow of water across a semipermeable membrane. Osmosis controls cell volumeHypotonic - More H2O enters cell rather than leaves. Swells and bursts.Hypertonic - More H20 leaves rather than enters. Shrivels and dies.Isotonic - No net movement of H20. TERM 3
Diffusion
DEFINITION 3 Movement of small, non polar particles from an area of high conc to low conc. Down conc gradient.No ATP required for simple diffusion due to kinetic energy possessed by particles.Random movement. TERM 4
Factors that Control
Diffusion
DEFINITION 4 Conc gradient - Larger gradient - faster diffusionTemp - Higher temp - faster diffusion (more kinetic energy)Surface Area - Higher SA - FasterDistance - Smaller distance - Faster TERM 5
Factors that Control
Diffusion
DEFINITION 5 Size of Solute - Smaller - FasterCharge - No charge - Able, Charge - Not ablePolarity/Hydrophobicity - Less polar - FasterO2, CO2, vitamins drugs etc - diffuse through membrane
Hydrophobicity
Dislike of a molecule for H2OMeasured using K = Cm / CaqCm = solubility in membraneCaq = solubility in H2OHigher K = more hydrophobic TERM 7
Facilitated Diffusion (no ATP needed) - passive
DEFINITION 7 Solute binds to protein in membraneMoves down conc gradientSpecific protein for specific soluteSpeed depends on amount of proteins availableSteepness of gradient TERM 8
Kinetics of Passive Transport
DEFINITION 8 Similar to enzyme kineticsVmax = maximum rate of transport1/2 Vmax = half max rateKtr = substrate conc at which 1/2 Vmax is TERM 9
Carrier Proteins used in Facilitated
Diffusion
DEFINITION 9 Undergo conformational changeChannel proteins - hydrophilic pores or ion channelsWhen conc of [S] inside = conc of [S] outsideNo net movementRate inward = rate outward TERM 10
Carrier Proteins
DEFINITION 10 Two conformational states - AllostericTransport one type of molecule - SpecificLimited no available for transport - SaturableUniport or cotransport exists (two molecules)Co transport - passive - conc gradient down used to move other molecule against their conc gradient
ABC transporters
Protein superfamilyUse energy from ATP hydrolysis to transport variety of substrates across membraneDrug is quickly pumped out cells using this method before it has an effect TERM 17
Secondary Active Transport
DEFINITION 17 Uses energy stored in ionic concentration gradientCouples transport of substrate against conc gradient with transport of substrate down conc gradientLactose permease symporter (H+ moves down) (Lactose moves up) TERM 18
Digitalis
DEFINITION 18 Slows action of Na+/K+ pump.Na+ accumulates in heart muscle cells.Smaller Na+ gradient in cellsCa2+ remains in cardiac cellsStrengthens force of cardiac contractionCauses disturbance to heart rhythm etc TERM 19
Vesicular Transport
DEFINITION 19 Vesicle - liquid within another liquid in bubblemembrane enclosed sac used to store, digest or transport materialOne lipid bilayerUseful for transport of proteinendocytosis - moves something into cellexocytosis - moves something out of cell TERM 20
Endocytosis
DEFINITION 20 Phagocytosis - bacteria and virus' engulfed and digested.
Exocytosis
Release of material from cellSecretions from cellVesicle fuses with membrane and releases products (synapses releasing neurotransmitters)Secretion is triggered by extracellular signal TERM 22
Pinocytosis and Phagocytosis
DEFINITION 22 Pinocytosis - lysosome fuses with pinocytic vesicle, digestion with lysosomal enzymes, residual body, exocytosis.No pseudopods form.Phagocytosis - lysosome fuses with phagosome, digestion with lysosomal enzymes, residual body, exocytosis.Pseudopods extend to form phagosome. TERM 23
Receptor Mediated Endocytosis
DEFINITION 23 Required substance binds to receptor protein inclathrincoated pit in cell membrane. Lattice structure of clathrin causes pit.Membrane folds inwards.Vesicle combines with endosome.Ligands digested by lysosomal enzymes or are transported across the cell in the vesicle
