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Unit 9 End of Year Review What do animals need to live? • Animals make energy using: – food – oxygen food • Animals build bodies using: – food for raw materials • amino acids, sugars, fats, nucleotides ATP O2 – ATP energy for synthesis Getting & Using Food • Ingest – taking in food • Digest – mechanical digestion • breaking up food into smaller pieces – chemical digestion intracellular digestion • breaking down food into molecules small enough to be absorbed into cells • enzymes (hydrolysis) • Absorb – absorb across cell membrane • diffusion • active transport • Eliminate – undigested extracellular material passes out of digestive system extracellular digestion mouth break up food moisten food digest starch kill germs liver produces bile - stored in gall bladder break up fats pancreas produces enzymes to digest proteins & carbs stomach kills germs break up food digest proteins store food small intestines breakdown food - proteins - starch - fats absorb nutrients large intestines absorb water Stomach • Functions – food storage • can stretch to fit ~2L food – disinfect food • HCl = pH 2 – kills bacteria – breaks apart cells – chemical digestion • pepsin – enzyme breaks down proteins – secreted as pepsinogen » activated by HCl But the stomach is made out of protein! What stops the stomach from digesting itself? mucus secreted by stomach cells protects stomach lining Ooooooh! Zymogen! Small intestine • Function – major organ of digestion & absorption – chemical digestion • digestive enzymes – absorption through lining • over 6 meters! • small intestine has huge surface area = 300m2 (~size of tennis court) • Structure – 3 sections • duodenum = most digestion • jejunum = absorption of nutrients & water • ileum = absorption of nutrients & water Pancreas • Digestive enzymes – peptidases • trypsin – trypsinogen • chymotrypsin small intestines – chimotrypsinogen • carboxypeptidase – procarboxypeptidase – pancreatic amylase • Buffers – reduces acidity • alkaline solution rich in bicarbonate (HCO3-) Explain how this is a • buffers acidity of material from molecular example of stomach structure-function theme. Liver • Digestive System Functions – produces bile • stored in gallbladder until needed • breaks up fats – act like detergents to breakup fats Circulatory System Connection bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown Absorption by Small Intestines • Absorption through villi & microvilli – finger-like projections • increase surface area for absorption Ooooh… Structure-Function theme! Absorption of Nutrients • Passive transport – fructose • Active (protein pumps) transport – pump amino acids, vitamins & glucose • against concentration gradients across intestinal cell membranes • allows intestine to absorb much higher proportion of nutrients in the intestine than would be possible with passive diffusion – worth the cost of ATP! Large intestines (colon) • Function – re-absorb water • use ~9 liters of water every day in digestive juices • > 90% of water reabsorbed – not enough water absorbed back to body » diarrhea – too much water absorbed back to body » constipation respiration for respiration Why do we need a respiratory system? • Need O2 in – for aerobic cellular respiration – make ATP • Need CO2 out food – waste product from Krebs cycle O2 ATP CO2 Optimizing gas exchange • Why high surface area? – maximizing rate of gas exchange – CO2 & O2 move across cell membrane by diffusion • rate of diffusion proportional to surface area • Why moist membranes? – moisture maintains cell membrane structure – gases diffuse only dissolved in water High surface area? High surface area! Where have we heard that before? Counter current exchange system • Water carrying gas flows in one direction, blood flows in opposite direction Why does it work counter current? Adaptation! just keep swimming…. Gas Exchange on Land • Advantages of terrestrial life – air has many advantages over water • higher concentration of O2 • O2 & CO2 diffuse much faster through air – respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills • air is much lighter than water & therefore much easier to pump – expend less energy moving air in & out • Disadvantages – keeping large respiratory surface moist causes high water loss • reduce water loss by keeping lungs internal Why don’t land animals use gills? Medulla monitors blood • Monitors CO2 level of blood – measures pH of blood & cerebrospinal fluid bathing brain • CO2 + H2O H2CO3 (carbonic acid) • if pH decreases then increase depth & rate of breathing & excess CO2 is eliminated in exhaled air Hemoglobin • Why use a carrier molecule? – O2 not soluble enough in H2O for animal needs • blood alone could not provide enough O2 to animal cells • hemocyanin in insects = copper (bluish/greenish) • hemoglobin in vertebrates = iron (reddish) • Reversibly binds O2 – loading O2 at lungs or gills & unloading at cells heme group cooperativity Circulatory systems • All animals have: – circulatory fluid = “blood” – tubes = blood vessels – muscular pump = heart open hemolymph closed blood Vertebrate circulatory system • Adaptations in closed system –2 number of heart3 chambers differs 4 low pressure to body low O2 to body high pressure & high O2 to body What’s the adaptive value of a 4 chamber heart? 4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure Evolution of 4-chambered heart • Selective forces – increase body size • protection from predation • bigger body = bigger stomach for herbivores – endothermy • can colonize more habitats – flight • decrease predation & increase prey capture • Effect of higher metabolic rate – greater need for energy, fuels, O2, waste removal • endothermic animals need 10x energy • need to deliver 10x fuel & O2 to cells convergent evolution systemic Mammalian circulation pulmonary systemic What do blue vs. red areas represent? Cardiac cycle • 1 complete sequence of pumping – heart contracts & pumps – heart relaxes & chambers fill – contraction phase • systole • ventricles pumps blood out – relaxation phase • diastole • atria refill with blood systolic ________ diastolic pump (peak pressure) _________________ fill (minimum pressure) 110 ____ 70 • Arteries: Built for high pressure Arteries pump – thicker walls • provide strength for high pressure pumping of blood – narrower diameter – elasticity • elastic recoil helps maintain blood pressure even when heart relaxes • Veins: Built for low pressure Blood flows flow toward heart Veins – thinner-walled – wider diameter Open valve • blood travels back to heart at low velocity & pressure • lower pressure – distant from heart – blood must flow by skeletal muscle contractions when we move Closed valve » squeeze blood through veins – valves • in larger veins one-way valves allow blood to flow only toward heart Capillaries: Built for exchange • Capillaries – very thin walls • lack 2 outer wall layers • only endothelium – enhances exchange across capillary – diffusion • exchange between blood & cells Exchange across capillary walls Fluid & solutes flows out of capillaries to tissues due to blood pressure • “bulk flow” Lymphatic capillary Interstitial fluid flows back into capillaries due to osmosis plasma proteins osmotic pressure in capillary BP > OP BP < OP Interstitial fluid What about edema? Blood flow 85% fluid returns to capillaries Capillary Arteriole 15% fluid returns via lymph Venule Animals poison themselves from the inside by digesting proteins! Intracellular Waste • What waste products? – what do we digest our food into… • • • • CO2 + H2O lots! carbohydrates = CHO CO2 + H2O lipids = CHO CO2 + H2O + N proteins = CHON CO2 + H2O + P + N nucleic acids = CHOPN cellular digestion… cellular waste NH2 = ammonia H| O || H N –C– C–OH | H R very little CO2 + H2O 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 least toxic Mammalian System blood filtrate • Filter solutes out of blood & 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 + solutes + toxins) from body concentrated urine How can Mammalian kidney different sections allow the diffusion of different molecules? • 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 • • • • 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 glucose salts / ions urea – 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 blood pH Descending limb Ascending limb Nephron: Re-absorption Loop of Henle structure fits function! descending limb high permeability to H2O many aquaporins in cell membranes low permeability to salt few Na+ or Cl– channels reabsorbed H2O Descending limb Ascending limb Nephron: Re-absorption Loop of Henle structure fits function! ascending limb low permeability to H2O Cl- pump Na+ follows by diffusion different membrane proteins reabsorbed salts maintains osmotic gradient Descending limb Ascending limb Nephron: Re-absorption Distal tubule reabsorbed salts H2O HCO3 bicarbonate Nephron: Reabsorption & Excretion Collecting duct reabsorbed H2O excretion concentrated urine passed to bladder impermeable lining Descending limb Ascending limb 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 why Summary selective reabsorption & not selective filtration? • Not filtered out – cells proteins – remain in blood (too big) • Reabsorbed: active transport – Na+ – Cl– amino acids glucose • Reabsorbed: diffusion – Na+ – H2O Cl– • Excreted – urea – excess H2O excess solutes (glucose, salts) – toxins, drugs, “unknowns” Blood Osmolarity ADH pituitary increased water reabsorption increase thirst nephron high blood osmolarity blood pressure low ADH = AntiDiuretic Hormone Blood Osmolarity Oooooh, zymogen! JGA = JuxtaGlomerular Apparatus high blood osmolarity blood pressure adrenal gland low increased water & salt reabsorption in kidney JGA nephron renin aldosterone angiotensinogen angiotensin Blood Osmolarity ADH increased water reabsorption pituitary increase thirst nephron high blood osmolarity blood pressure adrenal gland low increased water & salt reabsorption JuxtaGlomerular Apparatus nephron renin aldosterone angiotensinogen angiotensin