Chapter7Biology.pdf BIOLOGY 108 - 0001
Popular in General Biology I
Popular in Biology
This 4 page Class Notes was uploaded by Koral Shah on Friday September 11, 2015. The Class Notes belongs to BIOLOGY 108 - 0001 at University of Missouri - Kansas City taught by Marilyn Yoder in Fall 2015. Since its upload, it has received 54 views. For similar materials see General Biology I in Biology at University of Missouri - Kansas City.
Reviews for Chapter7Biology.pdf
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/11/15
Chapter 7 Membrane Structure and Function 71 Cellular Membranes Selective Permeability controls what can be transported in and out of the cell cell bouncer Basic Structure Phospholipids hydrophobic tails and hydrophilic heads make a bilayer Proteins hydrophobic and hydrophilic Rgroups Amphiapathic both polar and nonpolar regions water dictates positioning Fluid Mosaic Model uid nonrigid structure with various proteins embedded in or attached to the bilayer Fluidity phospholipids can move laterally more common or ip op sides of the bilayer less common held together by hydrophobic interactions much weaker than covalent bonds membrane remains uid until temperature is so low it solidifies plants can change from unsaturated fatty acid tails to saturated fatty acid tails depending on environment Unsaturated better for cold weather will still be liquid and allow for transport through organism cg It I Saturated better for warm weather unsaturated would be too uid and could not support protein function Cholesterol uidity buffer regulates uidity of membrane through environment changes Practice Question Would a cell need to increase or decrease its cholesterol level when temperature rises Answer Increase What about when temperature falls Answer Still Increase cholesterol is a regulator Protein Component Transport proteins allow very polar substances too polar to venture through the bilayer in and out of the cell Integral Proteins within the hydrophobic inner region of the phospholipid bilayer Peripheral Proteins sit outside membrane to communicate with other proteins Transmembrane Protein integral and spans the entire double bilayer some integral membranes are transmembrane but not all Protein Types Transport Proteins provides a hydrophilic channel across the membrane or shuttles a substance from one side to the other by changing shape Enzymatic Activity enzyme with an active site exposed to substances in adjacent solution Signal Transduction binding site that fits a chemical messenger example hormones CellCell Recognition quotidentification tagsquot recognized by membrane proteins of other cells shortlived bond cells recognize other cells by binding to carbohydrate molecules Glycolipids short carbohydrate chains bonded to lipids in the membrane Glycoproteins short carbohydrate chains bonded to proteins in the membrane Example Blood Types vary due to variation in carbohydrates in red blood cell membrane Intercellular Joining membrane proteins of adjacent cells hook together longlasting bond Attachments to the Cytoskeleton and Extracellular Matrix anchors membrane proteins and maintains cell shape Membrane Synthesis 1 Membrane proteins and lipids are synthesized in ER 2 Carbohydrates are added making them glycoproteins 3 Transported to the Golgi Apparatus 4 Glycoproteins undergo carb modification and carbs are added to lipids making glycolipids 5 Vesicles take them to the plasma membrane 6 Vesicles fuse with plasma membrane vesicle becoming part of the membrane 7 Exocytosis occurs secreting proteins from the cell and positions carbs on membrane 72 Membrane Selective Permeability GateKeeping System hydrophobic inner region of phospholipid bilayer makes polar molecules extremely slow to enter and exit the cell ex glucose or water Transport Proteins allow transport of hydrophilic substances inout of the cell Channel Proteins hydrophilic channel allowing certain molecules inout Aquaporins channels that allow passage of water Carrier Proteins shuttle passengers and change shape to bring them across the membrane vastly speeds up passage of molecules such as glucose Transport proteins are specific to the substance it transfers a glucose transporter will ONLY transport glucose 73 Passive Transport Diffusion movement of molecules so they spread evenly into all available space Concentration Gradient any substance will diffuse from where it is more concentrated to where it is less concentrated reaching an equilibrium Diffusion is spontaneous requiring no work Cell membrane traffic is caused by diffusion higher concentration on one side of the cell it39ll diffuse to the other side Passive Transport transport that does not requiring expending any energy concentration gradient represents potential energy driving diffusion Osmosis diffusion of free water molecules across selectively permeable membrane if there39s a higher concentration of something in water on one side than the other water will diffuse to the side of higher concentration until the concentrations of the substance are equal Tonicity ability of a surrounding solution to cause a cell to gainlose water Isotonic no net movement of water across plasma membrane Hypertonic higher concentration of nonpenetrating solutes in a solution a cell in a hypertonic environment will lose water shrivel and die in an effort to equal out concentrations of the solute Hypotonic lower concentration of nonpenetrating solutes in a solution a cell in a hypotonic environment will swell with water and burst Osmoregulation control of solute concentrations and water balance cells with cell walls such as plantscan tolerate being immersed in hypotonic environment plant cells still cannot tolerate hypertonic environment Turgid very firm state of a plant cell when it is saturated to capacity with rainwater Flaccid if plants are not immersed in isotonic uid plant cells go limp Plasmolysis a plant in a hypertonic environment will shrivel and membrane will pull away from the cell wallleads to plant death Facilitated Diffusion passage of polar molecules with the help of transport proteins Ion Channels transport proteins that transport ions gated channels can open or close in response to stimulus Animal Cell States In A Hypo Environment Lysed Bursts In An Iso Environment Normal In A Hyper Environment Shrivels Plant Cell States In A Hypo Environment Turgid Pressure ideal In An Iso Environment Flaccid In A Hyper Environment Plasmolysis 74 Active Transport Active Transport membrane traffic requiring work fueled by ATP pumping a solute across the membrane against its concentration gradient low to high concentration All carrier proteins not channel proteins Energy supplied by ATP transports terminal phosphate group directly to transport protein Cell Voltage Cytoplasmic side is negatively charged cations are favored to enter the cell Extracellular side is positively charged anions are favored to exit the cell Membrane Potential voltage across a membrane acts like a battery Electrochemical Gradient two driving forces of diffusion of ions chemical and electrical Electrogenic Pump transport protein that generates voltage across a membrane can store that voltage and be used for cellular work SodiumPotassium Pump exchanges Na for K the major electrogenic pump in animal cells Proton Pump actively transports protons out of plant cells major electrogenic pump in plants Cotransport a single ATP powered pump transports a specific solute this pumping across the membrane does work which drives cotransport Analogy water pumped uphill performs work as it ows downhill 75 Bulk Transport Exocytosis secretion of molecules by fusion of vesicles with plasma membrane vesicle binds to membrane dumps its contents out of the cell and becomes part of the membrane used in the export of products Exocytosis causes cell to increase in size example pancreas secretes insulin to extracellular uid Endocytosis cell takes in substances by forming new vesicles from plasma membrane basically the reverse of exocytosis gt Endocytosis causes cell to decrease in size Phagocytosis cell engulfs a particle in order to consume it packaged in a food vacuole Pinocytosis cell quotgulpsquot drops of extracellular uid into vesicles molecules dissolved in uid are needed by the cell ReceptorMediated Endocytosis enables cell to acquire substances in bulk receptor proteins are brought into coated pits of cell contents of those proteins are ingested then protein leaves the cell example taking in cholesterol for membrane synthesis Ligands any molecule that binds specifically to a receptor site on another molecule Water Potential Likelihood water will undergo osmosis Water Potential Solute Potential Pressure Potential Solute Potential icRT i ion constant ex NaCl 2 c molarity R 0831 T Temperature degrees celcius 273 Water always moves from high water potential to low water potential