Week 3 Notes
Week 3 Notes BISC 207025
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This 10 page Class Notes was uploaded by Lauren Buch on Sunday September 20, 2015. The Class Notes belongs to BISC 207025 at University of Delaware taught by Dr. Oyenike Olabisi in Spring 2015. Since its upload, it has received 26 views. For similar materials see Introductory Biology I in Nursing and Health Sciences at University of Delaware.
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Date Created: 09/20/15
Introduction to Biology Dr Olabisi Week 3 914918 Quiz on Canvas Sunday afternoonevening Hour Exam 1 Next Friday Normal class time 1 hour 45 minutes closed notes 15 minutes open notes non electronic nonprinted STUDY SHEET Lecture and lab material Can write on exam save for open notes About 50 questions give or take 51 Structure of Cell Membranes A Membrane function a Physically separate cells from their external environment boundary b De ne spaces within many cells that allow them to carry out their diverse functions c De nes the outline of a cell d Allowsprevents things going in and out e Export of waste import of nutrients B Lipids are the main component phospholipids a Proteins can be found embedded in or associated with the membrane i Transport cell recognition b Carbohydrates can be found attached to lipids or proteins glycolipids and glycoproteins C Composed of two layers of lipids a Phospholipids i Hydrophilic head 1 Polar able to form hydrogen bonds with water ii Hydrophobic tail fatty acid iii Amphipathic hydrophilic and hydrophobic regions iv Only attraction are weak vanderWahl s forces v Saturated and unsaturated fatty acids determine rigidity b Spontaneously arrange themselves into various structures that have the polar head groups on the outside c Micelles spherical structures that form when lipids with bulky heads and a single tail are wedgeshaped like soap cleaning surrounds dirt inside micelle and pulls it away d Liposome in neutral pH balance i Bilayer forms hollow sphere ii We care because they are often arti cially synthesized for drug delivery targeted therapies by protecting drugs from pH in liposomes e Bilayer twolayered structure organized so that the hydrophilic portion of the lipid faces toward the aqueous environment i lipids with less bulky heads and two tails ii cholesterol is interspersed contains hydroxyl group little polar region similar to hydrophilic head and hydrophobic tail 1 keeps the membrane uid yet rigid balances the switch iii form closed structures with an inner space free edges would expose the tails to the aqueous environment iv 1 membranes are selfhealing tears seal rapidly to prevent exposure to water 2 able to serve as a barrier difficult for things that are polar or charged to pass through the membrane selectivity bilayer forms spontaneously as long as the concentration of free phospholipids is high enough and the pH is similar to that of a cell pH ensures that the head groups are ionized and therefore hydrophilic f uid mosaic model transmission electron microscopy TEM biological sample that is thin sectioned and stained with heavy metal dyes dye binds tightly to polar head group but not fatty acid chain looks like two dark rings with a light ring in between little bumps and craters when membrane was sliced open D Cell membranes are dynamic a Semi uid Lipids can rotate freely around their long axes and move laterally within the membrane lea et b Semipermeable Allows molecules to cross dependent upon their chemical characteristics Barrier to hydrophilic molecules and ions due to hydrophobic interior Gases and a few small uncharged molecules can passively diffuse across iv Ions and large polar molecules have a difficult time v Need a solution for molecules that cannot cross but the cell needs to transport vi High permeability oxygen nitrogen carbon dioxide ethanol vii Moderate permeability water urea viii Low permeability sugars metals E Protein association with cell membranes a an Specialized membrane proteins function in moving certain molecules large or charged that cannot pass through the phospholipid bilayer Channel transporter that allows movement of molecules through Carrier transporter that facilitates movement Receptor allows the cell to receive signals from the environment Enzyme catalyzes chemical reactions Anchors attach to other proteins that help maintain cell structure and shape Integral membrane proteins permanently associated with cell membranes and cannot be separated from the membrane without destroying it i Most are transmembrane span the entire bilayer 1 Two hydrophilic regions with a hydrophobic in between to interact with other proteins in the cytoplasm and signaling molecules Peripheral membrane proteins temporarily associated with the bilayer or integral proteins through weak noncovalent interactions easily separated via simple experimental procedures that leave the membrane intact i Associated with either inside or outside of membrane May limit the ability of transmembrane proteins to move within the membrane and assist proteins to cluster in lipid rafts proteins can move freely in the membrane indicated in uid mosaic model proteins were labeled with dye and their movement in the membrane was tracked 1 membranes are uid to allow lipids and proteins to move laterally and contains a mosaic of lipids and proteins F Membrane transport a Structure ensures essential molecules enter metabolic intermediates remain waste products exit b Passive transport Moving along concentration gradient high to low move to balance the concentrations out Cells maintain gradients across membranes Simple diffusion movement with concentration gradient 1 Most rapid for small molecules that are soluble in lipids Facilitated diffusion 1 Passive transport at rates higher than predicted from their lipid solubility 2 Depends on membrane proteins allows for channelpath a Swimming across Hudson vs Lincoln tunnel b Channels and carriers are transport proteins i Provide a passageway for the movement of ions and hydrophilic molecules ii Aquaporin for water polar iii Some proteins have gated channeb iv Others are receptors enzymes and anchors 3 Follows concentration gradient 4 Speci c for certain substances 5 Becomes saturated at high concentrations of the transported substance c Active transport movement against the gradient low to high i Energetically unfavorable and requires the input of energy ii Primary active transport uses a pump 1 Directly uses energy to pass substance 2 ATP hydrolysis G USE TRANSPORT MECHANISMS SLIDE FROM CANVAS ON OPEN NOTES TEST H Cystic brosis caused by faulty membranes channel protein cannot regulate mucus 52 The Plasma Membrane and Cell Wall A Fundamental de ning feature of all cells B Boundary that de nes the space of the cell separating internal contents form the environment i Maintains homeostasis internal conditionsstability ii Selective barrier due to the combination of lipids and embedded proteins 1 Lipid bilayer prevents ions as well as chargedpolar molecules from diffusing freely 2 Gases lipids and small polar molecules move freely 3 Proteins and polysaccharides are too large to cross on their own Some cells have a cell wall external to the plasma membrane Passive transport random movement of molecules down the concentration gradient diffusion Facilitated diffusion molecule moves by diffusion through a membrane protein to bypass the lipid bilayer Osmosis diffusion of water across a selectively permeable membrane i Only the solvent not the solute ii Concentration ends up the same more water on one side to balance it out iii Water molecules are small enough to move passively through the membrane to a limited extent by simple diffusion iv Many cells have aquaporins protein channels that allow water to ow more freely facilitated diffusion v Tonicity a property of a solution that depends on the osmotic force exerted across the membrane 1 In uenced by the differing concentrations of solutes in and out of the cell 2 lsotonic equal water and solute concentrations on either side of the membrane 3 Hypertonic solute concentration is higher and water concentration is lower on one side of the membrane 4 Hypotonic solute concentration is lower and water concentration is higher on one side of the membrane 5 Pay attention to which environment is discussed outside or inside tonicity is relative 6 Hypertonic solution cell shrunk isotonic normal hypotonic swollen very hypotonic lysed burst G Primary active transport taken against the concentration gradient i Requires energy 1 From chemical energy stored in ATP ii Cells move substances through transport proteins embedded in the membrane eg sodium potassium pump moves sodium out of cell and potassium into a cell H Secondary active transport driven by electrochemical gradient i Charge and chemical gradients result from movement of protons l Transport of larger molecules such as proteins and polysaccharides and even very large particles i Exocytosis material inside the cell packaged into vesicles and excreted into the extracellular medium ii Endocytosis plasma membrane folds inward to form a vesicle that brings substances into the cell 53 The Internal Organization of Cells A Discovery of the cell was made possible through the invention of the microscope a 1665 Robert Hooke build a microscope that he used to observe thin sections of dried cork from plants b 17005 Anton van Leeuwenhoek improved the magnifying power of microscope lenses and scientists were able to see unicellular organisms bacteria protozoa and algae c Cell theory was formally articulated in 1839 by Schleiden and Schwann i All organisms are made up of cells ii The cell is the fundamental unit of life iii Cells come from preexisting cells d Modern cell theory only adds to original i All living cells arise from preexisting cells by division ii The cell is the fundamental unit of structure and function in all living organisms iii The activity of an organism depends on the total activity of independent cells iv Energy ow metabolism and biochemistry occurs within cells v Cells contain DNA in the chromosome and RNA in the cell nucleus and cytoplasm B Eukaryote Organization a with b contains nucleus DNA in membranebound structure c plasma membrane d compartmentalization membranebound organelles e plant and animal C Prokaryote Organization a before b does not contain nucleus no membrane bound structures just DNA c plasma membrane with cytoplasm contained inside cell wall d nucleoid where genetic material is found e plasmids circular DNA f ribosomes involved in protein synthesis 54 The Endomembrane System inside the membrane eukaryotic cells A Compartmentalizes the cell B Nucleus a Nuclear envelope i Pouch doublelayer membrane ii Perforated by membrane protein openings nuclear pores iii Small molecules and ions can passively diffuse through the pores but large proteins and RNA require active transport C Endoplasmic Reticulum a Smooth i Lacks ribosomes ii Primary site of lipid synthesis b Rough i Contains ribosomes proteins designed for secretions ii Proteins synthesized by ribosomes on the surface and are released in the lumen space between in the membrane D Golgi Apparatus E Lysosomes F Protein Sorting GET SLIDE FROM LECTURE WITH DIAGRAMS draw cell with organelles to study annotate Be able to compare and contrast plant cells 55 Mitochondria and Chloroplasts A Mitochondria proves the eukaryotic cell with most of its usable energy B Chloroplasts capture energy from sunlight 101 Tissues and Organs A Tissues and organs communities of cells B Structure and function of skin 10
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