Lecture 19 Water PDF

1. Water molecules are polar Partial positive charges on the hydrogens, a partial negative charge on the oxygen, and a bent overall structure. This is because oxygen is more electronegative, meaning that it is better than hydrogen at attracting electrons. 2. Water is an excellent solvent...

1. Water molecules are polar Partial positive charges on the hydrogens, a partial negative charge on the oxygen, and a bent overall structure. This is because oxygen is more electronegative, meaning that it is better than hydrogen at attracting electrons. 2. Water is an excellent solvent Unique ability to dissolve polar and ionic substances making it possible for transporting nutrients. 4. Water has high heat of vaporization 3. Water has high specific heat Animals exploit this feature to cool off. Water is converted from its It takes a lot of energy to raise the liquid form to gas when the heat of temperature of a certain amount of water vaporization is reached. Since by a degree, so water helps with regulating sweat is made mostly of water, the temperature in the environment. evaporating water absorbs excess body heat, which is released into Remember: Heat is end product of cellular the atmosphere - known as evaporative cooling. metabolism – critical to keep it low. 5. Water has cohesive and adhesive properties. Cohesive forces due to hydrogen bonds - responsible for surface tension i.e. the tendency of a liquid’s surface to resist rupture when placed under tension or stress. Adhesive properties allow it to stick to substances other than itself. § Essential to life. § Dissolves salts and hydrophilic organic molecules (sugars, AAs etc). § Solvent in all biochemical reactions. § Adequate volume necessary to maintain intra- and extra-cellular concentrations of all nutrients (AAs, Glucose, FA etc) within physiological ranges. § Maintains osmo-equilibrium in all animals i.e. salt and water balance. § Maintains acid-base balance.  Major fluid compartments in the body Extracellular § Water Interstitial Plasma content Intracellular ~15% ~5% in the ~50% fat-free body is laru 72- asc 75% in rav various int Cell animal species Intracellular fluid Extracellular fluid compartment compartment ~50% of BW ~20% of BW Dietary water absorbed primarily by the SI and LI aquaporins Average Daily Requirements of Animals for Water (temperate climate)  Other Sources of Water Feed Water Metabolic Water Can be highly Carbs ~ 55 g variable Protein ~ 42 g Grains = 9-30% Fat ~ 110 g Forages: Hay 90% § Hibernating animals and desert rodents versus marine animals  Urine – salts, urea (mammals), ~75 to 85 % of total other waste loss products. Feces – variable (cows vs sheep) High in Horses Evaporation from Water Loss skin (sweat) Chickens and Dogs have poorly developed sweat glands Respiration Milk  Water Loss Affected by nutritional, physiological, and environmental factors. An increase in Higher ambient Fecal loss increases glucose, ketones, and temperature greater with undigested feed. urea increases water water loss. loss via urination. Cow ~450kg BW consuming 10 kg DM/d 28 L 41 L 61 L 40 C 210C 320C Water Turnover In ruminants, body water turnover is about 7 days Nonruminants have a more rapid turnover due to less water in the GIT  Camels 6-7 months w/o water….How? Temp range 93o to 105oF Can tolerate 30% of body water loss Elliptical RBC 30 gal in 13 min Heterotherms: constant body temperature, Low urine output (0.5 – 1 l/d) except periods “Adaptive when Heterothermy” temperature Low fecal water content can vary (hibernation , torpor) Low evaporative water loss  A Desert Lizard That Drinks From Sand The thorny devil stays hydrated thanks to its skin, which pulls water away from moist grains, against gravity and into its mouth. ….the water from the skin ends up in the gut…. Some people might say that these reptile drainpipes are living the Australian male’s dream – they have two penises, they lie around in the Sun all day, and, best of all, when they want a drink, they don’t even have to stand up. A thorny devil glares for a picture. IMAGE CREDIT: Jules Farquhar