9 17 12 Chapter 6 The Cell Membrane Functions Regular passage of materials in and out of the cell Receptor proteins receive info from outside the cell Maintains structural and chemical relationships with neighboring cells Cell recognition Self vs Non self Example Organ transplant rejection Protects the cell Allows movement Involved in secretion Structure Fluid Mosaic Model of the cell membrane Amphipathic molecule with a hydrophobic and a hydrophilic region Example proteins Cell Fusion Experiment Membrane protein diversity Channel protein trans membrane protein Allows particular molecules or ions to pass into and out of the cell Carrier protein Active transport Selectively interacts with specific molecules or ions Pumps materials across the membrane by using energy ATP Signal transduction Molecule such as a hormone will bind to the receptor site Catalyze a reaction Substrate binds to an enzyme causes some reaction in the cell Cell recognition protein Identifies the cell Glycoproteins Receptor proteins Enzymatic protein Anchor protein Anchors the cell Inter cellular junctions Attach membranes of adjacent cells Freeze Fracture Technique Method for studying membranes Take liquid nitrogen frozen membranes Breaks open leaving portions of membrane exposed Displays proteins embedded in phospholipid bilayer 9 17 12 Cell Walls Found in plants algae bacteria fungi Contain lignin rigid fibers Made up of cellulose Made up of pectin Involved in wound healing Passage of Materials through Membranes Membrane structure Polar won t pass through very easily Size of molecule Charge of molecule Permeable substances will pass through Impermeable substances will not pass through Semi permeable some substances will pass through and some substances will not All biological membranes are semi permeable Movement of material solute from high concentration to low concentration in order to Diffusion establish an equilibrium Rate of diffusion Increase temperature increase rate of diffusion Size of molecule Shape of molecule Charge of molecule Brownian movement Dialysis Random movement of particles molecules due to their kinetic energy Diffusion of a solute through a selectively permeable membrane Facilitated Diffusion Moves glucose Uses carrier proteins Cell membrane is impermeable to polar molecules Must have concentration gradient for any type of diffusion to occur Carrier molecules proteins are passive conveyor belts No ATP required GLUCOSE glucose Big concentrations little concentrations Osmosis Diffusion of water through a semi permeable membrane Aquaporins water holes Channel proteins Isotonic 9 17 12 Equilibrium between solutions Hypertonic Movement of water out of the cell Higher concentration of water inside the cell Cell shrinks Hypotonic Hippo Movement of water into the cell Higher concentration of water outside of the cell Cell expands swells Active Transport Sodium Potassium Pump Aka Sodium Potassium ATPase Enzyme Moves 3 Na out while moving 2 K in Creates charge separation results in inside of cell being more negative Membrane Potential Co Transport Cell is negative 3 out for every 2 in Cell Signaling Receptor proteins Signal transduction The concentration gradient of K is used to move other substances x against its concentration gradient x is moving from low concentrations to high concentrations Requires energy Convert and amplify an extracellular signal into an intracellular signal Hormone first messenger Hormone Receptor protein G protein Adenylyl cyclase ATP Cyclic AMP protein kinases metabolic and structural changes in the cell Cyclic AMP second messenger cAMP activates a bunch of enzymes called protein kinases Endocytosis and Exocytosis Exocytosis Cell ejects waste products Endocytosis Phagocytosis Cell eating Pinocytosis Cell drinking Receptor mediated endocytosis Lymphocytes specific kind of cell eating Cell Junctions and Communication Desmosomes Join two cells together 9 17 12 Button like Allow movement of substances in the intracellular space Tight Junctions Impermeable connections between cells Membrane fused together Gap Junctions Channel between 2 cells Energy and Metabolism Energy Flow Metabolism the sum of all chemical reactions that take place within an organism Energy the ability to produce a change in the state or motion of matter 3 Major Processes Step by step process of creating glucose and oxygen through the chemical reactions of the Step by step break down of glucose starch which results in the production of energy rich Photosynthesis intake of carbon dioxide and water Cellular Respiration phosphate bonds ATP Cellular Work synthesize new molecules Chemical energy of ATP is utilized by the cell to do work muscle contraction active transport Certain Principles that Govern all Energy Transformations No such thing as a 100 effective machine Thermodynamics Study of energy Joules Calories Exothermic process Energy released to the environment Endothermic process Reaction energy is absorbed from the environment 1st law of thermodynamics 2nd law of thermodynamics Energy cannot be created or destroyed it just changes form All energy transformations result in the loss of some energy and it is unrecoverable ATP ADP P energy work Entropy energy lost heat 9 17 12 The measure of the disorder of a system Perpetual Motron Machine Violates the 2nd law of thermodynamics Gibbs Free Energy Energy available to do work G Exergonic Reaction G Reactants ATP activation energy products ADP P High Rise Low Can occur spontaneously Release free energy Perform work Endergonic Reactions G Reactants amino acids activation energy products proteins Low Rise High Absorbs energy from the environment Biosynthetic reactions G H T S Gibbs Free Energy Total Energy Stored Temperature Entropy Biological Systems are able to trap energy and compensate for the continual loss of energy Large energy releases are very inefficient ATP ADP P energy Small differences in energy between reactants and products reversibility Small energy input will reverse reaction Coupled reactions couple an exergonic reaction with an endergonic reaction Factors Affecting Chemical Reactions For a reaction to take place Existing bonds must be broken before new ones form Get reactants close enough Must have proper orientation Activation Energy overcome energy hill for the reaction to proceed Temperature kinetic energy collisions collisions that have proper orientation Concentration reactions collision Enzymes biological catalysts lower activation