UNI101Y1 Study Guide - Trimethylamine N-Oxide, Nitrogen Cycle, Osmosis
16 Feb 2013
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Hhyyppoo--oossmmoottiicc orgnms are surrounded by water w/ a salt conc. higher than their bodies. Tend to lost water, must drink seawater to replace. Salts in water and food and by diffusion through body surfaces must be excreted by gills and kidneys. Retain urea (nitrogenous by-product of protein metabolism in vertebrates) in blood (instead of excreting it) Urea conc. of up to 2. 5% (compared to <0. 03% in other vertebrates) raise osmotic pot. of blood to the level of seawater w/o any increase in conc. of na+ and cl- ions. Thus, the mvmt of water across a shark"s body is balanced (neither gain nor loss) They don"t have to drink extra salt water to replace water loss by osmosis. They accumulate high conc. of trimethylamine oxide to protect proteins from ve effects. Animals must excrete excess nitrogen without losing too much water.
