BMB 251 1st Edition Lecture 33 Outline of Last Lecture I. Channel proteinsII. Na+/K+ portsa. Antiportb. Symportc. UniportIII. Membrane PotentialIV. AquaporinsV. NeuronVI. Action potentialOutline of Current Lecture VII. AxonsVIII. Patch-clamp recordingIX. SynapsesX. Pre/Postsynaptic cellXI. Synaptic clefXII. –Gated ion channelsXIII. Parts of the cella. Organelleb. ER’sc. GolgiCurrent Lecture- Clicker Question 1: How does the K+ channel exclude Na+?o Na+ is too small to be stabilized by the selectivity filter- Axons of many vertebrate are insulated by a myelin sheath: greatly increases rate at which an axon can conduct an action potential- Patch-clamp recording: studies the transport of a molecule through a single ion channel o Individual voltage-gated Na+ channels open in an all-or-nothing fashion always has the same large conductness even though it opens and closes at random- Synapses: transmit neural signals are transmitted from cell to cell through these- Presynaptic cell is separated form postsynaptic cell by a synaptic clefo Change in electrical potential in presynaptic cell triggers release of small signals called neurotransmitters (stored in membrane-bound synaptic vesicles)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.o Neurotransmitters diffuses across clef and causes electrical change in postsynaptic cell by binding to transmitter-gated ion channels and opening them- Transmitter-gated ion channels are specialized for rapidly converting extracellular chemical signals into electrical signals at chemical synapses- Excitatory neurotransmitters open cation channels influx of Na+ depolarization- Inhibitory neurotransmitter: open either Cl- or K+ channels makes it harder to fire signal because postsynaptic cell does not depolarize- Organelle: individual compartment in cell with its own enzymes and specialized molecules- Lumen: interior of organelles- Lipid bilayer of organelle membranes is impermeable to most hydrophilic molecules, each membrane must contain membrane transport proteins to import/export specific metabolites- Nucleus: contains genome; principle site for DNA/RNA synthesis- Cytoplasm: consists of cytosol and cytoplasmic organelles suspended in it- Cytosol: site of protein synthesis and degradation, degrade small molecules and synthesizes other that become building blocks of macromolecules- Rough ER: has many ribosomes bound to surface synthesizes soluble and integral membrane proteinso Also produces lipids and is a store for Ca2+ cationso Extends from nucleus through the entire cytosol- Smooth ER: lacks ribosomes- Golgi: ER sends proteins and lipids here; stacks of disc-like compartments called Golgi cisternae; receives lipoids and proteins, and dispatches them to various locations- Lysosomes: digestive enzymes degrade defunct intracellular organelles and macromolecules o Must first pass through endosomes- Peroxisomes: small vesicle compartments that contain enzymes used in various oxidation
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