BIOL 200B 1st Edition Lecture 11Ch. 42 Animal Form and Function (cont) Ch. 43 Osmoregulation I. Volume RegulationII. Ion RegulationIII. Controlling osmosisIV. Osmoregulationa. Filtrationb. Reabsorptionc. Secretiond. Excretion at Collecting DuctOsmoregulationWater and Electrolyte balance- animals are 70-80% water and must manage the amount of water, electrolyes, and nitrogen waste- imbalances lead to enzymatic and cellular disruption- Osmoregulation (homeostasis) is the regulation of the balance of waterand solutes and is determined by 3 interrelated factors:1. Volume Regulationa. More concentrated solution-net flow of water out of vesicle; vesicle shrink b. More dilute solution-net flow of water into vesicle; vesicle swells or even burstsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. Solutes in equilibrium-no change2. Ion regulation •concentrations of individual inorganic ions are independently preserved•through active transporta. Controlling osmosis to balance water and salt- animal cells use ATP powered pumps for active transport- to set up a strong electrochemical gradient for one ion(Na+)- Cotransporter: as Na+ then moves along its concentration gradient thisaction can be used to transport another molecule against its concentration gradientb. Controlling osmosis to balance water and salt in sharks- Active Na+ pumping uses ATP (cellular energy currency) to set up “master gradient” that drives the movement of other ions- Cl- and K+ can then be moved against their gradients through cotransporters - driven by electrical gradient across membrane- Ion channels then allow diffusion of salts (NaCl) along gradients to environment=salt excretionNitrogenous waste: •Ammonia - highly toxic; requires lots of water but little energy to produce•Urea - moderately toxic; requires moderate water and a lot of energy•Uric acid - low toxicity; requires very little water and a lot of energy Osmoregulation in Terrestrial Vertebrates:- The Kidney - cortex, medulla- nephron - functional unit of the kidney - water only moves by diffusion- kidneys setup osmotic gradientsStep 1: Filtration •Pressure higher inside glomerulus than in surrounding Bowman’s capsule•water and solutes forced out of blood through pores in glomerus•formation of filtrate: pre-urine of ions, nutrients, wastes, and water •25% of water and solutes in blood is removedStep 2: Reabsorption•Selectively retrieves valuable substances•water leaves proximal tubule through membrane proteins called aquaporins•pumps and cotransporters recover water, nutrients, and electrolytes but leave wastes Step 3: Secretion•via loop of Henle•descending limb is highly permeable to water but impermeable to solutes•ascending limb is nearly impermeable to water but highly permeable to Na+ and Cl-•Vasa Recta - water and salt removed from loop of Henle diffuse into vasarecta and return to the body; associated network of countercurrent bloodvessels; if water from descending limb was not absorbed, the osmotic gradient would be destroyedStep 4:Excretion at Collecting Duct•membrane is impermeable to salt•urea gets so concentrated in filtrate=flows out of collecting duct•contributes to high osmolarity of inner