Lec5 - Diffusion and Osmosis Move Substances across Membranes Concentration gradient Difference in the number of molecules or ions of a substance

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Diffusion and Osmosis Move Substances across Membranes Concentration gradient Difference in the number of molecules or ions of a substance between neighboring regions iffusion is the n t ovement f ubstances down a concentration radient Diffusion is the n et movement of substances down a concentration gradient Diffusion is a p assive transport – does not need energy Each solute moves down its own gradient Individual molecules move around whether or not there is a gradient – Brownian movement
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Water Crosses Membranes by Osmosis (diffusion of water across a plasma membrane)
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The Plasma Membrane Is “Selective” Selective permeability Small, nonpolar substances slip across Oxygen Carbon dioxide Water (polar) slowly slips through gaps Use of transport proteins for: Ions Large polar molecules, e.g., glucose
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3.11 Other Ways Substances Cross Cell Membranes Substances also cross cell membranes by mechanisms called 1) facilitated diffusion (passive transport, no ATP, transport proteins), ) acti e transport (ATP membrane p mps) 2) active transport (ATP, membrane pumps), 3) exocytosis, and 4) endocytosis.
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Cells need energy for their activities. Cell mitochondria convert the raw energy in organic compounds om food to TP hemical form the cell can use from food to ATP — a chemical form the cell can use. Metabolism = most of chemical reactions in cell, maintaining homeostasis
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This note was uploaded on 03/12/2012 for the course NPB 10 taught by Professor Moglinger during the Spring '12 term at UC Davis.

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Lec5 - Diffusion and Osmosis Move Substances across Membranes Concentration gradient Difference in the number of molecules or ions of a substance

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