BIOL 1411 1st Edition Lecture 7Outline of Last Lecture I. CellsII. MembranesOutline of Current Lecture I. Membrane Transporta. Active Transporti. Osmosis b. Passive TransportCurrent LectureI. Membrane Transport- The endomembrane system in dynamic and fluid- Passive transport- movement by diffusion, no outside energy required, concentration gradient is driving force (high concentration to low concentration)o Simple diffusion- directly across the phospholipid bilayero Facilitated diffusion- across a membrane via channel or carrier proteins- Active transport- requires energy, movement against concentration gradient, via a protein pump that requires energy to operateDiffusion Rate- The diffusion rate of each solute is independent- Factors that influence the rate:o Diameter of the molecule of iono Electrical chargeo Temperature of the solutiono Concentration gradient- Permeable for that solute (steroids)- Impermeable for that solute (ions)Facilitated Diffusion- Polar and charged solutes cant diffuse across a phospholipid bilayer so needs the aid of proteinsThese 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.- Carrier proteins- membrane proteins that function as channels that must bind the transported solutes to speed their diffusion through the bilayer ex. Sugar transporters- Allows much faster diffusion of glucose than would be possible by simple diffusion through the bilayer- Rate depends of concentration gradientChannel Proteins- integral membrane proteins that form a central pore lined with polar amino acids. Solute “streams” down the gradient. Ex. Gated ion channels, aquaporin- Gated Ion Channels: o Open to allow ion passageo Gate opens when protein is stimulate to change shape  Ligand-gated channel- Voltage-Gated Ion Channel:o Different ion channels Exist for different ions- specificityo Several different human diseases result from mutations in K channel genes (KCNQ) ex. Cardiac arrhythmias- Membrane Potential- electrical gradient across a membrane, inside is typically more negative relative to outsideo All cells maintains an imbalance of ion concentrations across a plasma membraneo Resting membrane potentialOsmosis- diffusion of water across a membrane that the solutes cannot pass through- Depends on the number of solute particles present, not the type of particles- Water molecules will diffuse from the region of higher water concentration (lower soluteconcentration) to the region of lower water concentration (higher solute concentration)- Hypertonic solution- more solutes on the outside of the cell- Hypotonic solution- more solutes inside of the cell ex. Turgor pressure- Isotonic- equivalent concentration inside and outside the cell, in constant equilibriumFacilitated Diffusion by water channels- Can cross a membrane directly or by hitchhiking with hydrated ions- Cross through special water channels call aquaporins (100 million H2O per second) - Aquaporin increases membrane water permeability Active Transport- opposite of diffusion, low concentration of water to high concentration, requires energyExample: cystic fibrosis is a mutation with a defective chloride “pump”- Uniporters: transports one substance in one direction- Symporters: - Antiporters: Na+ K+ pump- Sodium Potassium Pump: present in all cellso Important for membrane potentialo Higher Na outside of cell; higher K inside of cello Pumps Sodium out of cell against gradiento Pumps Potassium into the cell against gradiento 3 Na out, 2 K in, Net 1+ outo ATP is broken down into ADP and Phosphate- Active transport requires ATP (adenine triphosphate) - Primary active transport- direct hydrolysis of ATP provides energy- Secondary active transport- energy comes from an ion concentration gradient that is established by primary active transporto The glucose-Na symporter- found in intestinal and kidney cellso Glucose is transported across the membrane against its concentration gradiento Simultaneous diffusion of Na+ provides the energy to move glucose moleculeso Works in parallel to Sodium Potassium