Chapter 3 Cells The Living Units

Membrane diffusion through the plasma membrane

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Unformatted text preview: n through the plasma membrane Membranes often porous to solvent (water, via aquaporins) but not solutes Plasma Membranes Membrane are selectively permeable to solutes K+, Na+, Cl, proteins, etc. How are these concentrations maintained against the diffusion gradient? Filtration Active transport (primary and secondary) Vesicular Ex. The Na+/K+ pump Operation of the sodiumpotassium pump K+ high inside Na+ high outside Secondary active transport Stored energy from the active transport of molecules can be used to power further systems Taking in, and getting rid of, particles Exocytosis Removal of products Endocytosis Absorption of products phagocytosis: pseudopods engulf particles bulk phase: nonselective absorption of extracellular fluids and molecules receptor mediated: absorption of specific molecules Exocytosis Types of endocytosis Types of endocytosis Types of endocytosis Membrane potentials and cell polarity Caused by the selective permeability of ions Inside of cells more negative than outside creates a resting membrane potential (20 to 200mV) Ions move in relation to the electrochemical gradient rather than just the concentration Summary of forces that generate and maintain membrane potentials How do cells communicate? Contact signaling Electrical signaling Chemical signaling Ligands: chemicals that bind to specific receptors Model of the...
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This note was uploaded on 03/10/2012 for the course BIOL 2403 taught by Professor Campbell during the Spring '12 term at Texas Pan American.

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