BSC 2011 Lecture Notes - Lecture 14: Saltwater Fish, Extracellular Fluid, Cellular Respiration
21 Oct 2016
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Diffusion- movement of solutes along their concentration gradient. Osmosis- movement of water along its concentration gradient. If the osmolarity on both sides of the membrane are equal, the cell is isotonic (isosmotic: differences in osmotic pressure between cytoplasm and interstitial fluid can damage cells. Most marine vertebrates are osmoregulators: hypoosmotic to seawater, risk dehydration of body tissues. Most conserve fluids, excrete excess salt: saltwater fish tend to drink water. The gut of the fish is relatively impermeable to the salt: freshwater vertebrates are hyperosmotic relative to their environment. Terrestrial animals must deal with lack of water and salt: strategies. Animals must also eliminate nitrogenous waste from metabolizing protein and nucleic acids. Initially metabolized as ammonia can be converted to urea and uric acid. In vertebrates, renal artery brings blood to kidneys (about 25% of blood exiting heart: filtrate is drained through ureter to the bladder and excreted as urine, nephron- the main functional unit of the kidney.
