BIOL-1507EL Lecture Notes - Lecture 2: Electrochemical Gradient, Passive Transport, Water Potential
Document Summary
Principles of water and solute movements in plants. Both passive and active mechanisms move substances into and out of plants. Material transport: short distances between cells, long distances between roots and shoot parts (xylem and phloem) Primary cell walls do not stop solutes. Passive transport requires no metabolic energy: substance moves down concentration or electrochemical gradient. Active transport requires metabolic energy (atp: substance moves against gradient. Simple diffusion is simplest form of passive transport. All other types of membrane transport assisted by transport proteins. In electrochemical gradients, membrane potential measure charge difference. Bulk flow of water due to pressure differences. Xylem sap: dilute water movement from roots to shoot parts. Osmosis: passive movement of water across cell membrane. Central vacuole: tonoplast membrane, maintains turgor pressure. Aquaporin proteins allow rapid movement of water through hydrophobic membrane core. Wilting occurs when plants lose more water than they gain (plasmolysis: low water potential of dry soil.