BIOL 125 Chapter Notes - Chapter 42, page 904-923: Electrochemical Gradient, Extracellular Fluid, Electrolyte
2 Feb 2017
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Their tissues are hypotonic relative to salt water = lose h2o, gain salt. This is important in the gills which are responsible for gas exchange. They replace the lost water by drinking large amounts of water; this brings in excess electrolytes where the fish must actively pump ions out of their bodies and back into the seawater. If the water lost is not replace, the fish"s cells shrivel and die: freshwater fish are also osmoregulators. Their tissues are hypertonic relative to sea water = gain h2o, lose salt. They replace the h2o from their urine/ sweating/panting by drinking, ingesting water in food or gaining metabolic h2o produced during cellular respiration (42. 2) The mechanism of salt excretion is sharks is found in many species. Animal cells possess amino acids and nucleotides to produce proteins, rna and. In freshwater fish, nh3 is diluted (lower conc"n) and released as watery urine.
