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Week 5 Notes

by: Rebecca Sharp
Rebecca Sharp

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These notes cover what we went over in class this week
Principles Of Biology I
Stevan Marcus
Class Notes
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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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