BCMB 230 1st Edition Lecture 6 Outline of Last Lecture I Energy II Cellular Respiration III Anaerobic Respiration IV Protein and Amino Acid Metabolism V Fat Metabolism Outline of Current Lecture I Diffusion II Different Types of Diffusion III Exocytosis and Endocytosis IV Osmosis V Tonicity Current Lecture Molecular Movement I Diffusion Diffusion is the primary mechanism for moving things around the cells Solutes move down the gradient with the gradient If there is a great difference between both sides of the gradient it is called a steep gradient Eventually equilibrium will be reached particles can be equally distributed but this is not always the case Things that concern diffusion direction the movement of solutes from a greater concentration of solutes to a lesser concentration of solutes down the gradient rate to increase rate of diffusion increase temp increase concentration gradient decrease size of particles decrease viscosity increase surface area increase permeability rate also depends on the state the solution is in will be faster in gases slower in solids viscosity the thickness of a liquid permeability ability to go through something diffusion can occur across a membrane but cell membranes are selectively permeable and will allow some things to go through and some things are not look for proteins that are present These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II Different Types of Diffusion Passive transport moves down the gradient no energy ATP is used instead it is procured from the concentration gradient by random thermal movement for lipid soluble materials can go through the lipid bilayer other materials have to use channels which will allow specific ions and water through aquaporin membrane protein that only lets water through ion channel channels for a specific ion show selectivity for the type of ion or ions that can diffuse through them can only allow monoatomic not polyatomic ions through small size of the channel protein prevents larger molecules from entering or leaving can be gated three types of gated channels ligand gated membrane channel operated by the binding of specific molecules to channel proteins voltage gated cell membrane ion channel opened or closed by changes in membrane potential mechanical gated membrane ion channel that is opened or closed by deformation or stretch of the plasma membrane does not need to change shape only distort to open or close channel Facilitated diffusion uses a transporter protein to move a solute using a transporter Transporter integral membrane protein that mediates passage of molecules through the membrane transported solute must first bind to a specific site on a transporter a site exposed to the solute on one surface of the membrane a portion of the transporter then undergoes a change in shape exposing this same binding site to the solution on the opposite side of the membrane also shows chemical specificity use to move small organic molecules like glucose amino acids ions bicarbonate and phosphate bind molecule from outside potential energy in concentration gradient causes protein to change shape dump molecule on inside of cell when affinity is lost Active transport uses energy ATP directly or indirectly and allows for movement against the gradient requires transporters Primary active transport transporter actually an enzyme called ATPase will catalyze the breakdown of ATP also called pumps add phosphate group to change the shape of transporter protein can create a gradient in the process move Na K Ca 2 H controlled by primary active transport relatively few ions involved creates ion gradients Secondary active transport uses ion gradients from primary active transport for energy does not use ATP directly the movement of an ion down its gradient is coupled to the transport of another molecule glucose or an amino acid transporters that mediate secondary active transport have two binding sites one for an ion and another for the cotransported molecule ion goes down the gradient cotransported molecule goes against the gradient Coupled transport types of secondary active transport Cotransport Ion goes into the cell with its gradient but also transfers something else against the gradient both ion and other molecule are going into the cell Countertrasnport Move ion and transported material in opposite directions ion is going into cell other molecule is going out of cell requires specific arrangement of binding sites Amino acids and glucose can be moved by both facilitated diffusion and secondary active transport III Exocytosis and Endocytosis Exocytosis moving a protein out of the cell Endocytosis uses endocytotic vesicles to move a protein into the cell proteins can only be moved into the cell if it s enclosed in a vesicle different than getting it across the membrane and getting it into the cytosol IV Osmosis Osmosis is the diffusion of water have movement of water from a greater concentration of water to a lower concentration of water OR the movement of water from a lesser concentration of solute to a greater concentration of solutes Molarity tells us concentration of solutes Osmolarity tells us concentrations of solutes in terms of water the more solute particles you have the less water total solute concentration of a solution ex 1M glucose 1 Osm glucose ex 1M NaCl 1M Na 1M Cl 2M particles 2 Osm NaCl V Tonicity Tonicity measure of osmotic pressure Iso means same Hypo means less Hyper means more Isotonic solution water may move in and out of cell but there is no net movement of water Hypotonic solution water moves into the cell causes the cell to swell which depending on the elasticity of the cell could cause the cell to break lysis Hypertonic solution water moves out of the cell causes the cell to shrink Important Assumptions to make when measuring tonicity water can move solute particles didn t move If something is lipid soluble you can t control permeability membrane is permeable for lipid soluble but if something is water soluble we can control permeability Solutes penetrating and nonpenetrating penetrating go through the membrane lipids nonpenetrating does not go through the membrane used to determine tonicity For tonicity only look at nonpenetrating solutes For osmolality look at both penetrating and nonpenetrating solutes total solute particles Examples for tonicity and osmolality 300 mOsm is the