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Kidney Structure & Function Removing Intracellular Waste Glucose Amino acids H2O Mg++ Ca++ H2O Na+ ClH2O H2O Na+ ClH2O H2O Loop of Henle AP Biology Collecting duct Animal systems evolved to support multicellular life single cell aa O2 CH CHO CO2 aa NH3 CHO O2 O2 CH aa CO2 CO2 aa NH3 CO2 NH3 CO2 O2 NH3 CO2 CO2 aa NH3 CH NH3 NH3 CO2 AP Biology CO2 NH3 CO2 intracellular waste O2 NH3 but what if the cells are clustered? CHO CO2 aa Diffusion too slow! extracellular waste for nutrients in & waste out Overcoming limitations of diffusion Evolution of exchange systems for distributing nutrients circulatory system removing wastes excretory system CO2 CO2 aa CO2 CO2 O2 NH3 CO2 systems to support multicellular organisms AP Biology NH3 CO2 CO2 NH3 NH3 CO2 CH NH3 NH3 CO2 aa O2 NH3 NH3 CHO CO2 aa Osmoregulation hypotonic Water balance vs. Habitat freshwater hypotonic to body fluids water flow into cells & salt loss saltwater hypertonic to body fluids water loss from cells hypertonic land dry environment need to conserve water may also need to conserve salt Why do all land animals have to conserve water? always lose water (breathing & waste) AP may lose life while searching for water Biology Intracellular Waste What waste products Animals poison themselves from the inside by digesting proteins! are made inside of cells? what do we digest our food into… carbohydrates = CHO CO2 + H2O lipids = CHO CO2 + H2O lots! proteins = CHON CO2 + H2O + N very little nucleic acids = CHOPN CO2 + H2O + P + N cellular digestion… cellular waste NH2 = AP Biology ammonia H| O || H N –C– C–OH | H R CO2 + H2O Nitrogenous waste disposal Ammonia (NH3) very toxic carcinogenic very soluble easily crosses membranes must dilute it & get rid of it… fast! How you get rid of nitrogenous wastes depends on who you are (evolutionary relationship) where you live (habitat) aquatic AP Biology terrestrial terrestrial egg layer Nitrogen waste Aquatic organisms can afford to lose water ammonia most toxic Terrestrial need to conserve water urea less toxic Terrestrial egg layers need to conserve water need to protect embryo in egg uric acid AP Biology least toxic Freshwater animals Hypotonic environment water diffuses into cells Manage water & waste together remove surplus water & waste use surplus water to dilute ammonia & excrete it also diffuse ammonia continuously through gills overcome loss of salts reabsorb in kidneys or active transport across gills AP Biology H Land animals Nitrogen waste disposal on land H H H need to conserve water must process ammonia so less toxic N C O N urea = larger molecule = less soluble = less toxic 2NH2 + CO2 = urea Urea produced in liver costs energy kidney to synthesize, but it’s worth it! filter solutes out of blood reabsorb H2O (+ any useful solutes) excrete waste urine = urea, salts, excess sugar & H2O AP Biology urine is very concentrated concentrated NH3 would be too toxic mammals Egg-laying land animals Nitrogen waste disposal in egg no place to get rid of waste in egg need even less soluble molecule uric acid = BIGGER = less soluble = less toxic birds, reptiles, insects itty bitty living space! AP Biology Uric acid Polymerized urea And that folks, is why most male birds don’t have a penis! large molecule precipitates out of solution doesn’t harm embryo in egg white dust in egg adults still excrete N waste as white paste no liquid waste uric acid = white bird “poop”! O H H N N O O N N AP Biology H H Mammalian System Filter solutes out of blood & blood filtrate reabsorb H2O + desirable solutes Key functions filtration fluids (water & solutes) filtered out of blood reabsorption selectively reabsorb (diffusion) needed water + solutes back to blood secretion pump out any other unwanted solutes to urine excretion expel concentrated urine (N waste + AP Biology solutes + toxins) from body concentrated urine Mammalian Kidney inferior vena cava aorta adrenal gland kidney ureter bladder urethra AP Biology nephro n renal vein & artery microvilli on epithelial cells Nephron Functional units of kidney 1 million nephrons per kidney Function filter out urea & other solutes (salt, sugar…) blood plasma filtered into nephron high pressure flow AP Biology selective reabsorption of valuable solutes & H2O back into bloodstream greater flexibility & control why selective reabsorption & not selective filtration? “counter current exchange system” How can different sections allow the diffusion of different molecules? Mammalian kidney Interaction of circulatory & excretory systems Circulatory system glomerulus = ball of capillaries Bowman’s capsule Proximal tubule Distal tubule Glomerulus Excretory system nephron Bowman’s capsule loop of Henle AP Biology proximal tubule descending limb ascending limb distal tubule collecting duct Glucose Amino acids H2O Mg++ Ca++ H2O Na+ ClH2O H2O Na+ Cl- H2O H2O Loop of Henle Collecting duct Nephron: Filtration At glomerulus filtered out of blood H2O H2O & solutes glucose salts / ions (Na+ / Cl–) urea cells & large molecules AP Biology not filtered out cells proteins high blood pressure in kidneys force to push (filter) H2O & solutes out of blood vessel BIG problems when you start out with high blood pressure in system hypertension = kidney damage Nephron: Re-absorption Proximal tubule reabsorbed back into blood NaCl active transport of Na+ Cl– follows by diffusion H2O glucose HCO3 bicarbonate buffer for AP Biology blood pH Nephron: Re-absorption Loop of Henle descending limb reabsorbed H2O structure many aquaporins in cell membranes high permeability to H2O no Na+ or Cl– channels impermeable AP Biology to salt structure fits function! Nephron: Re-absorption Loop of Henle ascending limb reabsorbed Na+ & Cl– structure many Na+ / Cl– channels in cell membranes high permeability to Na+ & Cl– no aquaporins impermeable to H2O AP Biology structure fits function! Nephron: Re-absorption Distal tubule reabsorbed salts H2O bicarbonate HCO3 regulate blood pH AP Biology Nephron: Reabsorption & Excretion Collecting duct reabsorbed H2O = through aquaporins excretion concentrated urine to bladder impermeable lining = no channels in cell membranes AP Biology Osmotic control in nephron How is all this re-absorption achieved? tight osmotic control to reduce the energy cost of excretion use diffusion instead of active transport wherever possible the value of a counter current exchange system AP Biology why selective reabsorption & not selective filtration? Summary Not filtered out of blood cells proteins remain in blood (too big) Reabsorbed back to blood: active transport Na+ glucose amino acids Reabsorbed back to blood: diffusion H2O Cl– Excreted out of body AP Biology urea excess H2O excess solutes (glucose, salts) toxins, drugs, “unknowns” Any Questions? AP Biology