BIO 181 Lecture Notes - Passive Transport, Electrochemical Gradient, Active Transport
Document Summary
Molecules move across the membranes because they possess an inherent kinetic energy that causes them to be in a state of constant motion. In living organisms, small molecules and ions constitute solutes that usually are dissolved in water (the solvent: these dissolved solutes form the biological solutions that support life. A difference in solute concentrations across a selectively permeable membrane creates a concentration gradient. Random movement of solutes due to kinetic energy. The mechanism that drives the spontaneous movement of small, nonpolar solutes across a membrane. Occurs when solutions of different concentrations are separated by a membrane that"s permeable to water but not the solutes. Water moves spontaneously across the membrane toward the solution with the higher solute (lower water) concentration. If solution outside is higher concentration, water moves out: cells shrinks/shrivels; hypertonic; crenation (plasmolysis in plants) If solution outside is lower concentration, water moves in: cells swell; hypotonic; turgor pressure increases; can burst (lyse) if its an animal cell.
