F10_L03_RMP - Psy 111/211 Basic concepts in Biopsychology...

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Psy 111/211 Basic concepts in Biopsychology Lecture 3: The Membrane At ±Rest²
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Summary of Protein Synthesis 1. Transcription 2. Translation 3. Post-translational processing
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Objectives ± Describe the electrical properties of (excitable) membranes. ± Describe the bases of charged molecules and their interactions with water and non-polar molecules. ± Identify the two forces which act on ions to control their movement: diffusion and electricity. ± Discuss the principles of ion movement across a semi-permeable membrane and the electro-chemical “equilibrium potential”. ± Explain the Nernst equation and how alterations in ion concentration relate to equilibrium potential. ± Discuss the relation between equilibrium potential for an ion and the membrane potential. ± Discuss interactions between multiple ions within a cell/system, “relative permeability” and the Goldman equation. ± Discuss the proteins which control permeability: channels and pumps.
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Membrane potential -relative net ionic differences between inside and outside of cell with outside defined as 0. Phospholipid bilayer. Hydophillic -interacts with water/environment Hydophobic -barrier to water and charged particles.
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Membrane Potentials in ±Excitable² and ±Non-excitable² Cells. 0 -50 50 V m 0 -50 50 V m Hepatocyte (non-excitable) Neuron (excitable) Recordings from 2 mSec Today we focus on what is happening when the membrane is at rest; non- excited state.
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Outline Ions, charges, & water •F o r c e s a c t i n g o n i o n s •P r i n c i p l e s o f M o v e m e n t o f I o n s A c r o s s a S e l e c t i v e Membrane •M u l t i p l e I o n s , R e l a t i v e p e r m e a b i l i t y , a n d t h e membrane potential. •C o n t r o l o f I o n M o v e m e n t
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The Basis of Biological Electricity: Ions, charges, & water Atomic Chloride (Cl) Chloride Ion (Cl - ) 1 electron (e - ) Atomic Sodium (Na) Sodium Ion (Na + ) Outer shells are full; stable configuration
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Ions, charges, & water Ions Valency = net electrical properties Anions ± net negative charge due to extra electron(s); eg Cl- Cations ± net positive charge due to less electron(s); eg Na+ Monovalent (e.g. Na + ) Divalent (e.g. Ca ++ ) -> Two parts: valency (more or less e-) magnitude (diff in e- verus p+)
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Ions, charges, & Water Water is a POLAR molecule with a separation of charge such that oxygen is more negative and hydrogens are more positive (this is why water does not mix with oil which is non-polar).
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Ions, charges, & water Many biological building blocks carry charge. ¾ This gives the macromolecule electrical properties. ¾ Charge is often distributed unevenly.
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Ions, charges, & water (containing components with distinctly different properties) e.g. phospholipid components of cell membrane; many proteins; etc.
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