Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Membrane Transport Suzanne D'Anna 1 Membrane Transport method by which substances move through the cell membrane cells bathed by interstitial fluid cells must take nutrients from this fluid to remain healthy reject unnecessary substances Suzanne D'Anna 2 Selective Permeability the ability of the plasma membrane to regulate entry and exit of materials Movement of materials through plasma membrane can be: - passive - active Suzanne D'Anna 3 Passive Processes simple diffusion osmosis filtration facilitated diffusion Suzanne D'Anna 4 Passive Processes Simple Diffusion random movement of particles (ions and molecules) particles move along a concentration gradient - a region of higher concentration to a region of lower concentration. Suzanne D'Anna 5 Passive Processes Osmosis diffusion of solvent - water diffuses from a region of higher solvent concentration toward a region of lower solvent concentration through a selectively permeable membrane Example: - the small intestines absorb water from digested food by osmosis Suzanne D'Anna 6 Osmotic Pressure the pressure required to prevent the net movement of water from one solution to another when the solutions are separated by a membrane permeable only to water the pressure needed to stop the flow of water across the membrane Suzanne D'Anna 7 Tonicity normal firmness or functional readiness in body tissues or organs maintain the shape of red blood cells; they must be bathed in an isotonic solution. - normal saline solution is isotonic for red blood cells Suzanne D'Anna 8 Isotonic Solution (iso = same) same concentration of water and particles (solute and solutes) as in the cells when RBC’s are in 0.9% NaCl solution water molecules enter and exit the cells at equal rates (5% glucose) RBC’s maintain their normal shape and volume Suzanne D'Anna 9 Hypotonic Solution (hypo = less than) lower concentration of solutes than in cells higher concentration of water when RBC’s are placed in distilled H2O, water molecules enter the cell faster than they leave RBC’s will swell and burst (hemolysis) Suzanne D'Anna 10 Hypertonic Solution (hyper = greater than) higher concentration of solutes lower concentration of water than in the cells if RBC’s are placed in hypertonic solution more water leaves the cells than enters - cells will shrivel and die (crenation) Suzanne D'Anna 11 Passive Processes Filtration solvent and solute move across a membrane due to gravity or water pressure (hydrostatic) Example: - in kidneys blood pressure forces water and small creatinine (a waste product) molecules through a plasma membrane Suzanne D'Anna 12 Filtration (cont.) filtered liquid enters kidneys large molecules such as proteins remain in blood smaller harmful molecules can then be eliminated in the urine Suzanne D'Anna 13 Passive Processes Facilitated Diffusion lipid-insoluble molecules and molecules too large to diffuse through membrane or ion channels are carried through membrane by transporter (carrier) proteins Example: - glucose Suzanne D'Anna 14 Facilitated Diffusion (cont.) after glucose bonds to transporter on the outside of the membrane, the transporter changes shape glucose passes through membrane and is released inside the cell Suzanne D'Anna 15 Active Transport requires the use of energy from ATP to move substances across the membrane substances move from areas of lesser concentration to areas of greater concentration opposite direction of diffusion movement occurs against a concentration gradient Suzanne D'Anna 16 Actively Transported Substances: Na+ K+ H+ Ca + 2 I Cl Suzanne D'Anna (Sodium) (Potassium) (Hydrogen) (Calcium) (Iodine) (Chlorine) amino acids monosaccharides 17 Active Transport (cont.) Two Types: - primary active transport - secondary active transport Suzanne D'Anna 18 Primary Active Transport: The Sodium Pump ATP energy directly moves substances across membrane sodium pump - most prevalent - maintains a low concentration of (Na+) ions in the cytosol - also moves (K+) ions into cells in nerve and muscle cells Suzanne D'Anna 19 The Sodium Pump Na+ ions are more abundant outside the cell they are constantly diffusing into the cell, (their area of lesser concentration) not needed in such abundance sodium pumps must return Na+ ions to outside (their presence will bring about unwanted nerve impulses or muscle contractions) Suzanne D'Anna 20 Secondary Active Transport energy stored in ion gradients moves substances across the membrane indirectly uses energy from splitting ATP Suzanne D'Anna 21 Endocytosis Suzanne D'Anna Processes that bring large substances into cells: - phagocytosis - pinocytosis - receptor-mediated endocytosis 22 Phagocytosis projections on outside of plasma membrane, called pseudopods, flow around large particles (bacteria, debris) engulfing and bringing them into cell once surrounded, membrane sac is formed (phagocytic vesicle) vesicle enters cytoplasm material in vesicle is digested by enzyme produced by lysosome Suzanne D'Anna 23 Pinocytosis membrane folds or sinks beneath liquid to be digested forming pinocytic vesicle pinocytic vesicle allows liquid to flow inward trapping the liquid vesicle pinches off or detaches from membrane into cell interior Suzanne D'Anna 24 Receptor-Mediated Endocytosis similar process to pinocytosis substances bind to receptors on the plasma membrane causing a folding of the membrane and the formation of an endocytic vesicle highly selective cells take up specific molecules or particles Suzanne D'Anna 25 Exocytosis membrane enclosed sacs (secretory vesicles) form inside cell - fuse with plasma membrane - release contents into extracellular fluid - important in nerve cells - secrete digestive enzymes or protein hormones such as insulin requires ATP Suzanne D'Anna 26