Membrane Notes BIOL 1406 02
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This 2 page Class Notes was uploaded by locnaschek on Monday September 19, 2016. The Class Notes belongs to BIOL 1406 02 at Lamar University taught by Dr. Randall Terry in Fall 2016. Since its upload, it has received 9 views. For similar materials see General Biology I (Majors) in Biology at Lamar University.
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Date Created: 09/19/16
Membrane Structure and Function Plasma Membranes: o Surround the cell Selectively Permeable General membrane structure o Made up of a phospholipid bilayer Amphipathic partially water loving (head) and partially water hating (tail) The tails are hydrophobic and the heads are hydrophilic o Fluid structures which allows materials to pass through This is essential for normal membrane function Higher temperature correlates to greater movement, so when temperature is higher, the membrane is more fluid Cells can control fluidity through the saturation of their phospholipids Unsaturated have double bonds and thus bend, causing looser packing and more fluidity Saturated have single bonds and are thus straight, causing tighter packing and less fluidity A plant can change the chemical composition of its tissues if they start to die in order to maintain homeostasis and live longer Animals input cholesterol to increase fluidity Membrane functions: o Controlled by proteins o Transport (channels from one side of membrane to another) o Enzymatic Activity o Receiving Signals (stretch across membranes to receive and transmit data) o CellCell Recognition (glycoprotein= protein with attached carbohydrate) o Intercellular joining Synthesis of membranes o Occurs through the secretory pathway of protein targeting o Membranes “turn over” as a consequence of time This means that membranes are exchanged piece by piece as time goes on Composition changes completely; cells die with completely different membranes than they started with Movement across membranes o Terms to know: Solution results from dissolving solute in solvent Solvent dissolves things (ex. water, the universal solvent) Solute gets dissolved (ex. salt) Hypotonic comparison, below or less saturated with respect to another Hypertonic comparison, above or more saturated with respect to another Isotonic comparison, same saturation as another Passive Transport (does NOT require energy) Diffusion Solute particles always move from hypertonic to hypotonic solutions Particles move across membranes to achieve equilibrium (isotonic) Solute moving from high to low concentration= simple diffusion Particles are small to fit through the spaces of the membrane and hydrophobic to get across the tails of the phospholipid bilayer When channel proteins help larger or hydrophilic particles to get across the membrane= facilitated diffusion Both of these types of diffusions go from hyper to hypo solutions This does not require the use of energy and occurs spontaneously Active Transport (requires energy) Requires the use of a protein Happens against the natural gradient Solute goes from hypotonic to hypertonic solutions Osmosis Diffusion of water Water moves in the opposite direction of solute particles If solute is going to the left of the membrane, water would move to the right to achieve equilibrium o Intake of materials outside the cell Moves large quantities of materials all at once A valley is formed in the membrane which pinches off as a vacuole or vesicle for transport, sometimes called “engulfment” Two kinds: Phagocytosis uptake of solids Pinocytosis uptake of solute particles Can be mediated by proteins as well
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