Chapter 7 Notes
Chapter 7 Notes BSC 2010
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This 7 page Class Notes was uploaded by Meghan Cooper Mendes de Oliveira on Saturday September 26, 2015. The Class Notes belongs to BSC 2010 at Florida State University taught by Dr. Steven Marks in Fall 2015. Since its upload, it has received 123 views. For similar materials see Biological Science in Biological Sciences at Florida State University.
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Date Created: 09/26/15
Exam 2 Notes Thursday September 17 2015 BSC 2010 0001 Chapter 7 Membrane Structure and Function Structure of membranes The plasma membrane is a uid boundary made up of a combination of lipids and proteins separates the living cell from its surrounding All membranes have two distinct sides with different functions how do molecules pass through membranes lVlembranes are Selectively permeable lVlembrane proteins aid in movement of certain molecules Concentration gradients dictate the direction of molecular movement and the energy requirement Some molecules cannot pass through Cellular membranes are made of lipids and proteins uid mosaic model Phospholipids are the most abundant amphipathic molecules hydrophobic and hydrophilic uid mosaic model membrane is a uid structure with a mosaic of various proteins embedded in it Membrane Proteins and their function membrane is a collage of different proteins embedded in the uid matriX of the lipid bilayer Exam 2 Notes Thursday September 17 2015 proteins determine most of the membrane s speci c functions Types of Proteins Peripheral proteins bound to the surface of the membrane Integral proteins penetrate the hydrophobic core Very Rare Transmembrane proteins proteins that span the membrane in order for the protein to be transmembrane it has to be amphipathic hydrophilic and hydrophobic passes through the membrane is always odd Six major functions of membrane proteins 0053320 Hill w lllllt 3333 cffffff ffff LLW LLW d Cellcell recognition e Intercellularjoining f Attachment to 2 the cytoskeleton and extracellular matrix ECM Exam 2 Notes Thursday September 17 2015 Role of membrane Glycoproteins in cellcell recognition cells recognize each other by binding to surface proteins Glycoproteins transmembrane proteins with carbohydrates attached on the external side of the plasma membrane Synthesis of sidedness of membranes membranes have distinct faces inside and outside asymmetrical distribution of proteins lipids and carbohydrates is determined by the ER and Golgi apparatus when the membrane is built Selective permeability lVlembrane separates the cell into separate chemical environments Selectivity allovvs molecules to enter or eXit the cell hydrophobic molecules can dissolve in the lipid bilayer pass easily through the membrane Nonpolar Polar molecules do not cross easily Passive Transport diffusion of a substance across a membrane with no energy required Diffusion molecules spread out evenly into available space diffusion of certain molecules can be directional dynamic equilibrium as many molecules cross the membrane in one direction as in the other direction Exam 2 Notes Thursday September 17 2015 materials diffuse down the concentration gradient region in which the density of a substance chemical increases or decreases no work is done to move a substance down the concentration gradient Passive transport diffusion of substances across a biological membrane that eXpends no energy Facilitated Diffusion Facilitated Diffusion transport proteins assist in moving molecules across the plasma membrane openings in the plasma membrane that allow only a speci c molecule or ion to cross are called Channel Proteins Channel Proteins Aquaporins diffuse water Ion Channels open or close with stimulus also called gated channels Carrier Proteins Osmosis effects on water balance Osmosis the diffusion of water across a selectively permeable membrane water diffuses across the membrane from an Lower Higher Same concentration concentration concentration of solute of solute sugar of solute area of lower solute concentration to an area of higher solute concentration until the Sugar quot5 T molecule solute concentration is equal permeable membrane Exam 2 Notes Thursday September 17 2015 Water Balance of Cells Tonicity ratio of solute concentration inside the cell vs outside the cell lsotonic solution Solute concentration is the same as What is inside the cell no net water movement Hypertonic solution Solute concentration is higher than that inside the cell cell Will lose water Hypotonic solution Solute concentration is less than that inside the cell cell Will gain water Hypotonic Isotonic Hypertonic solution solution solution a Animal cell H20 Lysed H20 Cell wall r 25 A w tquot l b Plant cell Turgid normal 2011 Pearson Education Inc Cell walls rnaintain water balance Turgid plant cells in a hypotonic solution Will swell and become rigid Exam 2 Notes Thursday September 17 2015 Flaccid no movement of water across the cell wall of a plant Plasmolysis in a hypertonic solution plant cell loses vvater Active transport transport proteins move solutes against their concentration gradient requires energy Active Transport moving substances against their concentration gradient requires energy usually in the form of ATP Performed by speci c proteins allovvs cells to maintain concentration gradients Ionic pump typical form of active transport Sodiumpotassium pump type of active transport system very common How lon pumps maintain membrane potential membrane potential voltage difference across a membrane Voltage is created by differences in distribution of positive and negative lODS across a membrane electrogenic pump transport protein that generates voltage across a membrane Cotransport Cotransport active transport of a solute directly drives transport of other solutes this is active transport Exam 2 Notes Thursday September 17 2015 Bulk Transport exocytosis transport vesicles migrate to the membrane fuse With it and release their contents endocytosis cell takes in macromolecules by forming vesicles from the plasma membrane requires energy phagocytosis cell engulfs a particle in a vacuole vacuole fuses With a lysosome to digest the particle receptormediated endocytosis binding of ligands to receptors that encourages vesicle formation ligand any molecule that binds to a receptor site of another molecule
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