NRSC 2100 1st Edition Lecture 4 The Phospholipid Membrane Bilayer Hydrophylic and hydrophobic Polar hydrophylic heads on outside non polar hydrophobic tails on inside Proteins The variety of Life Structure Amino acids Alpha carbon and R groups Proteins Structure Peptide bonds amide bond covalent high energy Amino end N terminus Carboxyl end C terminus Proteins Levels of Structure Four levels of protein structure Primary a Secondary b Tertiary c Quaternary d Membrane Proteins the Workhorse of Neurons Spanning across the lipid bilayer Channel Proteins Polar R groups and nonpolar R groups Ion selectivity and gating Ion pumps Movement across the Lipid Bilayer Concentration 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 Diffusion Dissolved ions distribute evenly Ions flow down concentration gradient when Channels permeable to specific ions are present Concentration gradient across the membrane Movement across the Lipid Bilayer Electrically charged particles Electrical forces Electrical force influences electrically charged ion movement Electrical conductance g and resistance R R 1 g Electrical potential Voltage V Flow of electrically charged particles ions Current I Omh s law I gV or I V R Equilibrium Potentials Equilibrium Potential Eion No net movement of ions when separated by a phospholipid membrane Equilibrium reached when channels inserted into the phospholipid bilayer Point at which voltage electrical potential difference exactly balances ionic concentration gradient Ionic Equilibrium Potentials Equilibrium Potentials for each ions The Nernst Equation Used to calculates the exact value of the equilibrium potential for each ion in mV millivolts Takes into consideration Charge of the ion Temperature in absolute degrees Ratio of the external and internal ion concentrations The Ionic Basis of The Resting Membrane Potential The Nernst Equation Eion 2 303 RT log ion o zF ion i The Ionic Basis of The Resting Membrane Potential The Distribution of Ions Across the Membrane K more concentrated on inside Na Cl and Ca2 more concentrated outside many negative proteins inside
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