Week 7: Bacteria, Membranes, and Cell Signaling
Week 7: Bacteria, Membranes, and Cell Signaling Bio 107
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This 10 page Class Notes was uploaded by Rachel Johnson on Monday October 12, 2015. The Class Notes belongs to Bio 107 at Washington State University taught by William Davis in Summer 2015. Since its upload, it has received 23 views. For similar materials see Biology in Biology at Washington State University.
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Date Created: 10/12/15
Bacteria III Other Mechanisms of Genetic Transfer 339 Transduction Transfer of DNA from one cell to another by viruses Results in new genes being transferred to a recipient cell after viral infection 339 Transformation Uptake of DNA from the environment Demonstrated by the Griffith Experiment Antibiotic Resistance 339 R plasmids resistance plasmids Small plasmids transferred by conjugation Contain antibiotic resistance genes Presence in cell is similar to F factor Contribute to widespread resistance 339 How antibiotics work Kill bacteria by inhibiting disrupting Cell wall formation peptidoglycan synthesis Gene expression ribosomes and DNA polymerase Other targets Only affect bacteria not viruses or eukaryotic cells 339 Where antibiotics come from Fungi Fleming s discovery of penicillin Plaques demonstrated the antimicrobial nature Bacteria Chemically synthesized 339 Resistance mechanisms Mutations in genes can allow bacteria to Reduce drug uptake Remove drug from cell Protein binds to drug and pumps it out Alter amplify target Inactivate degrade drug Example penicillinase 339 Why Incorrect use of antibiotics Wrongful prescription of antibiotics Overuse of antibiotic cleaners Example hand sanitizer Misuse of antibiotics in animals Using them to enhance growth Membranes I Lipids 0 v Includes C H and O typically 0 v Found in many different types of biological structures Triacylglycerides Phospholipids Cholesterols and sterols Hydrocarbons 339 Made of only H and C 0 v Serve as energy storage molecules Allows energy storage in a very small space high energy density Isomers v Structural Differ in covalent arrangement bonds between the carbons are different 339 Cis trans Differ in spatial arrangement Cis the same molecules are on the same side of the carbon backbone Trans the same molecules are opposite sides of the carbon backbone Fats 339 Functions Storage Structure v Synthesized by dehydration reaction Between glycerol and fatty acids Forms triacylglycerol Triacylglycerol 339 Three fatty acids linked to glycerol via ester linkages Bond between a hydroxyl and carboxyl Saturated and Unsaturated Fats 339 Saturated with H No double bonds Solid at room temperature Highest energy density possible Found in animal products 339 Unsaturated with H One or more double bonds Causes bend in the chain Liquid at room temperature Found in plant products Trans Fats 339 Made in the process of hydrogenation Invented by the food industry to increase the shelf life of food 0 v Less reactive than naturally occurring fats 339 Increases level of bad cholesterol and decreases level of good cholesterol Membranes II Phospholipids 339 Contain Glycerol The backbone of the molecule Two fatty acids Phosphate group 339 Two different types of chemical regions Hydrophilic head Hydrophobic tail Lipid Bilayers 0 v Cell membrane structure is made of phospholipid bilayers 0 v Phospholipids line up with each other forms the bilayer Minimizes tail interaction with water and maximizes head interaction 0 v Fluid mosaic model Phospholipids can move within membrane as can the embedded proteins Lateral movement side to side movement very frequent 107 times per second Flip op moving from one face of the membrane to the other about once a month Flipase aids in the movement 0 v Factors affecting uidity Temperature Increase temperature increase uidity Decrease temperature decrease uidity Amount of unsaturated hydrocarbons Higher amounts increased uidity Lower amounts decreased uidity Achieved by changing membrane composition 0 v Cholesterol Reduces uidity at moderate temperatures Prevents solidification at low temperatures Membrane Permeability 339 Water Polar molecule 0 is more electronegativity than H Electronegativity affinity for electrons H has a partial positive charge and O has a partial negative charge Causes of solubility A high dielectric constant Ability of a solvent to keep opposite charges apart Forms a hydration shell around ions 0 v Easily cross membrane Hydrophobic molecules Small uncharged and nonpolar molecules 0 v Don t cross membrane easily need channels Hydrophilic molecules Large charged and polar molecules Membrane Transport 339 Passive transport Diffusion Random movement towards equilibrium Molecules will spread out Results from a net inbalance in concentration Substances move from high to low areas of concentration down their concentration gradient Only moves in one direction Facilitated diffusion Requires proteins but not energy 339 Active transport Solute moves up its gradient Used when an inbalance is needed ie neurons Requires proteins and energy input 339 Channel proteins Forms a corridor for solutes to pass through has some regulation Examples Aquaporins For facilitated diffusion of water Ion channels For facilitated diffusion of ions Na K Ca2 and Cl Can open or close in response to stimuli 0 v Carrier proteins Similar to a revolving door Alternate between shapes to move solutes Examples Glucose transporter For facilitated diffusion of sugar Sodium potassium pump For active transport Used for action potential in neurons Cell Signaling I Types of Differentiated Cells 0 v Muscle cells Used to generate force for movement pumping uids etc 0 v Neural cells Originate from a gt Used for commun1cation and Signaling Sing1e genome 339 Skin cells Used to separate the organism from the environment and to provide a selective barrier Mesenchynal Stem Cells MSCs O 39 Progenitor cells for many tissues Extracellular signals are needed 0 90 Decides What type of cell the MSCs turn into to Activates division to make identical copies or self renewal Stem Cells vs Differentiated Cells 0 9 Stem cells and differentiated cells Have the same genes Can send and receive signals 0 9 Stem cells Has potential to become anything can divide and differentiate O Differentiated cells 9 Can t divide further once differentiated Carries out a specific function until apoptosis Cell Signaling Overview 0 v Stage 1 signal receiving cell receives an external signal in the form of a molecule Signaling molecule binds to a receptor on the target cell surface 339 Stage 2 signal transduction A series of chemical changes Within the cell triggered by receptor binding 0 v Stage 3 cellular response Signal Transduction 339 Often a series of protein chemical transformations Kinase enzyme that adds a phosphate group to a protein Phosphatase enzyme that removes a phosphate group from a protein
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