Week 5 Notes
Week 5 Notes BSC 114
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This 2 page Class Notes was uploaded by Rebecca Sharp on Sunday February 28, 2016. The Class Notes belongs to BSC 114 at University of Alabama - Tuscaloosa taught by Stevan Marcus in Winter 2016. Since its upload, it has received 30 views. For similar materials see Principles Of Biology I in Biological Sciences at University of Alabama - Tuscaloosa.
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Date Created: 02/28/16
The Phospholipid Bi Layer Made out of a hydrophilic head and a hydrophobic carbon/fatty acid tail, linked by a phosphate group. Called “amphipathic molecules” They line up with the tails facing each other, making a hydrophobic layer sandwiched by a hydrophilic layer. This is a membrane. When mixed vigorously with water, phospholipids naturally assemble into bilayers, which was helpful in the origination of life on earth Hydrophilic heads flip laterally about 10^7 times a second Head/Tail pairs rotate about the fatty acid tail joint about once a month Proteins involved with the Phospholipid Bi Layer Transmembrane Proteins go all the way through the phospholipid bi layer. They have an N terminus and a C terminus. (C faces the cytoplasm, N faces the outside) They contain an alpha helix. Peripheral Proteins are connected to the phospholipid bilayer or the transmembrane proteins. Aquaporin channel proteins that facilitate the passage of H2O into a cell Major Functions of Membrane Proteins Transport Membrane Proteins work like a pump moving materials into and out of the cell Signal Transduction proteins read signals in the cell to coordinate complex cellular activities Cell-Cell Recognition proteins allow cells to connect to the correct cells by shape recognition, the proteins embedded in the bi layer change the shape of the cell. Intercellular Joining works the same way as cell-cell recognition Attachment to Extra Cellular Matrix and the Cytoskeleton Enzymic Activity is facilitated by proteins Movement Across Membranes Diffusion is defined as the tendency of molecules to spread out evenly into the available space. Diffusion with the concentration gradient is called passive transport o Facilitated diffusion is when transport proteins speed passive diffusion o Active diffusion is when molecules are moved against the concentration gradient with an expenditure of energy Osmosis is defined as the diffusion of a solvent (like water) across a selectively permeable membrane Osmoregulation is the control of solute concentration/water balance. o Hypertonic is a high water balance o Hydrotonic is a low water balance o Isotonic is a balanced water balance Nonpolar molecules (hydrophobic) can easily cross, or diffuse, across cell membranes. EX; O2, N2, CO2 Small polar molecules can cross cell membranes with some difficulty, like H2O, Glycerol Urea, and Ethanol Large polar molecules cannot cross cell membranes, like Glucose, or Sucrose Ions cannot cross cell membranes, like H, Na, K, Ca, Cl Electricity as it Relates to Cells Membrane Potential; voltage difference across a membrane. Maintaining voltage potential is very important to cellular respiration. Is generated primarily by o The Sodium Potassium Pump in animal cells o The Proton Pump in all the other cells Electrochemical Gradient; chemical force (ion concentration gradient) combined with electrical force (effect of membrane potential on ion movement) Transport Cotransport; when the active transport of one solute indirectly causes the transport of another solute Bulk Transport is used for bigger molecules and requires energy, it uses vesicles o Vesicle Use in Bulk Transport; Endocytosis; a cell takes in a macro molecule by forming a bubble around it called a vesicle. Phagocytosis; the cell eats a large molecule or possibly another cell by forming a food vacuole. That food bubble meets up with a lysosome, and then they digest the contents of the food bubble. Pinocytosis; stuff that dissolves outside the cell is pulled in to the cell by a vesicle. Receptor-Mediated Endocytosis; ligands and receptors bind together and trigger vesicle formation. Ligands are any molecule that binds specifically with another molecule’s receptor site. o Vesicle Use in Bulk Transport; Exocytosis; how stuff is exported from the cell. Transport/Secretory vesicles merge with the cell membrane and proceed to empty their contents in to the outsides of the cell
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