BIOL-1507EL Lecture Notes - Lecture 1: Molality, Osmoregulation, Tonicity

• School: Laurentian
• Department: Biology / Biologie
• Course: BIOL-1507EL
• Professor: Nasserulla

Document Summary

Animals use different approaches to regulate osmosis. Animals excrete nitrogen compounds as metabolic wastes. Water molecules move across a selectively permeable membrane from a region of high concentration to a region of low concentration. Osmolality: osmotic concentration (osmotic pressure) of a solution: number of osmoles per kg of solute. A solution can be comparatively hyperosmotic, hypoosmotic, or isoosmotic to another solution. In osmoconformers, osmotic concentration of cellular and extracellular solution match that of environment. In osmoregulatros, osmolality of cellular and extracellular fluids kept constanct, but at levels that may be different from osmolality of surroundings. End products of metabolism of nitrogenous compounds must be eliminated. Water is solvent for waste products, thus their elimination closely tied to maintaining osmolality. Ammonia: soluble in water, highly toxic, aquatic invertebrates, teleosts. Urea: soluble, relatively nontoxic, mammals, some fish, terrestrial invertebrates. Uric acid: low solubility, nontoxic, reptiles, birds, some terrestrial invertebrates. The kidneys, ureters, bladder, and urethra constitute to urinary system.