Week 4 of notes
Week 4 of notes Life 102
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This 3 page Class Notes was uploaded by Kerrigan Reading on Monday September 28, 2015. The Class Notes belongs to Life 102 at Colorado State University taught by Jennifer L Neuwald in Fall 2015. Since its upload, it has received 54 views. For similar materials see Attributes of Living Systems in Biology at Colorado State University.
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Date Created: 09/28/15
Wednesday September 23 2015 Life 102 Membrane Structure and Function Membrane Cellular boundary selectively permeable Made of phospholipid bilayers 1 Temperature affects fluidity A higher temperature increases fluidity a cooler temperature causes it to be more viscous 2 Hydrocarbons affect fluidity Unsaturated hydrocarbon tails are more fluid saturated hydrocarbons are more visous 3 Cholesterol affects fluidity Helps to maintain fluidity equilibrium Makes the membrane less fluid when hot and more fluid when cold The amount of cholesterol varies with each membrane Membrane Proteins 1 lntegral transmembrane meaning they span the entire membrane 2 Peripheral sit on the outside of the membrane Most peripheral proteins are attached to transmembrane proteins Location and orientation are important for cell function Functions transport enzymatic activity signal transduction cellcell recognition intercellular joining attachment to membrane Plant cells are normally turgid They go limp in isotonic solutions or flaccid and are plasmolyzed in hypertonic solutions Animal cells lyse in hypotonic solutions are normal in isotonic and shrivel in hypertonic Facilitated Diffusion does not require energy 1 Channel Proteins have a hydrophilic core that allows molecules to move down the concentration gradient 2 Carrier Proteins molecules bind to binding sites changes shape of molecule allows molecules to enter cell Active Transport requires energy ATP 1 Carrier Proteins function in the same way but requires ATP 2 Sodium Potassium Pump Na is high outside K is low outside Na is low inside and K is high inside Na binds to the pump s binding sites ATP donates phosphate group the pump folds and outputs Na out of the cell the binding sites change shape K binds to pump s binding site and the pump drops the phosphate group the pump folds back in towards the call and outputs K into the cell Sodium Potassium pumps require 20 of the food energy that we take in for every 3 Na ions that leave the cell 2 K come into the cell This creates an energy potential across the membrane Positive on the outside and negative on the inside Ions experience electrical force Cations are positive attracted to inside of cell Anions are negative attracted to outside of cell Na is naturally attracted to the inside of the cell and K as well Electrochemical Gradient 1 Concentration Gradient if stronger than membrane potential ions will move down the concentration gradient and against the membrane potential 2 Membrane Potential if stronger than the concentration gradient ions will move with the membrane potential and against the concentration gradient Wednesday September 23 2015 Proton Pump H pumps against the concentration gradient Makes the outside of the membrane positive and inside negative Creates membrane potential that can be used to synthesize ATP Makes the process continuous This is true for the sodium potassium pump as well Passive Transport does not require energy Cotransport H and Sucrose allowed into the cell only if they are paired Do not require direct input of energy Sucrose is moving against its concentration gradient but does not require energy because H is moving with the gradient because it is attracted to the negative interior of the cell There are many different cotransporters and not all of them use passive transport Vesiclemediated Transport vesicle collect molecules fuse with membrane and dump these collected molecules exocytosis also works in endocytosis Phagocytosis Pinocytosis and Receptormediated endocytosis Glycoproteins and Glycolipids Cellular lD s Cellular Metabolism Metabolism all chemical reactions within a cell Catabolic when a reaction produces energy Breaking larger molecules into smaller molecules Anabolic when a reaction requires energy Building larger molecules from smaller molecules Energy the capacity to do work The ability to rearrange a collection of matter Kinetic Energy energy associated with movement Other forms are heat light Potential Energy energy associated with an object when it s not moving Potential to do work Can be based on location or structure Chemical bonds are also a form of potential energy Laws of Thermodynamics 1 The energy of the universe is constant 2 The entropy of the universe is constantly increasing entropy the disorder of the universe When entropy increases the reaction is spontaneous When entropy decreases the reaction is nonspontaneous Gibbs Free Energy usable energy Free energy the total energy minus the temperature multiplied by the entropy When delta G the entropy is less than 0 the reaction is spontaneous and exergonic When delta G is greater than 0 the reaction is nonspontaneous and endergonic Endergonic reactions are fueled by exergonic reactions 3 types of work 1 Chemical work breaking and creating bonds 2 Transport work transport proteins 3 Mechanical work moving down cytoskeleton ATP adenosine triphosphate stores energy composed of adenine ribose and a triphosphate group Hydrolysis of ATP adding water to a reaction ATP drops a phosphate group which yields energy This is an exergonic reaction and yields 73 kcalmol Activation energy the energy required to begin a reaction Enzymes act to lower the activation energy increase the rate of reaction and act as catalysts but are not consumed by the reaction The free energy of a reaction is not affected by enzymes or activation energy Induced fit occurs when a substrate binds to an enzyme The active site of an enzyme can Act as a template Wednesday September 23 2015 Stress substrate bonds Provide microenvironment Bond to substrate briefly Enzymes do not Add energy to a reaction Change the free energy of a reaction Get changed in the net reaction Temperature affects enzyme activity Optimal temperature for a human enzyme is 37 C Optimal temperature for thermophilic bacteria is 77 C pH affects enzyme activity Optimal pH varies within the human body Ex optimal pH in stomach is 2 while in the intestines it is 8 Some enzymes need cofactors Organic molecule cofactors are coenzymes Coenzymes create a type of secondary active site so the substrate can bind to the enzyme Enzyme Inhibitors Competitive inhibitor binds to active site and prevents substrate from binding to the active site Noncompetitive inhibitor binds somewhere on enzyme that is not the active site and prevents the activation of the enzyme Can be reversible or nonreversible Activators and inhibitors act to regulate enzyme activity Activators change the shape of the active site so a substrate can bind to the active site Allosteric Regulation changing an enzyme s shape and function by binding somewhere other than the active site Enzymes can have multiple subunits with their own active sites
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