B6A10Osmoreg - Osmoregulation & Excretion...

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Heyer 1 Water is needed to maintain the macromolecules. Anhydrobiosis : Life without water? (85% water) (2% water) How to acquire body water? Moisture in food Metabolic water Organic food molecules + O 2 CO 2 + H 2 O + energy Fat yields 2.5x as much energy and 2.5x as much water per gram than do carbs or proteins! Passive Transport ( Diffusion) • Net movement of molecules from a region of high concentration to a region of low concentration ¸ Caused by random (Brownian) movements of molecules ¸ (Increase entropy) ¸ Each type of molecule follows its own concentration gradient ¸ At equilibrium, movement is equal in both directions REVIEW: Water and Solutes - Uptake by Cells Osmosis: simple diffusion of the solvent (water) • Water diffuses according to its concentration gradient Osm [water] Osm [water] • Osmosis can generate force (osmotic pressure) Semi permeable membrane Osmotic pressure REVIEW: Water and Solutes - Uptake by Cells REVIEW: Water and Solutes - Uptake by Cells v Water moves across lipid bilayer and through aquaporins (membrane gate proteins) v Move the water by moving the solutes ! ß Hypertonic solution: higher concentration of solutes ß Hypotonic solution: lower concentration of solutes ß Isotonic solution: equal solute concentrations
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Heyer 2 REVIEW: Water and Solutes - Uptake by Cells Hypotonic solution Isotonic solution Hypertonic solution Animal cell Plant cell Water Potential ( Y ) • Osmotic pressure pulls water to the right. • Osmotic potential (= solute potential [ Y S ] ): solution on left has potential energy to push water to the right Osm Y S • Physical pressure (= pressure potential [ Y P ] ): solution on right has potential energy to push water to the left If Y S & Y P are equal but opposite no net flow Y = Y S + Y P = 0 REVIEW: Water and Solutes - Uptake by Cells REVIEW: Water and Solutes - Uptake by Cells v Water moves across lipid bilayer and through aquaporins v Move the water by moving the solutes ! v Ions and small molecules use protein channels and pumps Selective permeability • Except for water and small nonpolar solutes, permeability of cell membranes is selective and regulated . • Permeability determined by transporter proteins . – Channels and carriers are solute specific – If no transporter, than that solute cannot cross membrane (Artificial membranes are only semipermeable —i.e., only discriminate based upon molecular size .) REVIEW: Water and Solutes - Uptake by Cells Types of cellular transport Passive transport : driven by Brownian motion – Facilitated diffusion (carrier mediated passive transport) Active transport : requires chemical energy (ATP) – Carrier mediated – Can transport against concentration gradient REVIEW: Water and Solutes - Uptake by Cells REVIEW: Homeostasis : maintaining a constant, optimal internal environment
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Heyer 3 REVIEW:
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B6A10Osmoreg - Osmoregulation & Excretion...

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