Sinh học - Chương 41: Warm up

WARM-UP(Ch. 40) What is the principle of countercurrent exchange?(Review) What are the 4 classes of macromolecules?(Ch. 41) You eat a piece of candy. List the structures it passes through as it travels through your alimentary canal.Where does most of the digestion of the candy in #3 happen?Chapter 41: Animal NutritionWhat you need to know:Major compartments of alimentary canal (organs) – and their contributions to animal nutrition.Digestive glands: salivary, pancreas, liver, gall bladder – and their contributions to animal nutrition.Digestion of carbs, proteins, fats, nucleic acids.Essential Nutrients: required by cells, obtained through foodFour classes of essential nutrients:Essential amino acids (8)Essential fatty acidsVitamins (13) - fat-soluble, water-solubleMineralsDietary DeficienciesUndernourished: diet is deficient in calories, not enough energyMalnourishment: missing 1+ essential nutrients Herbivore licks exposed salts and minerals lacking in plants.The main stages of food processing:Ingestion: eatingDigestion: breakdown of food into small moleculesMechanical (chewing, grinding)Chemical (enzymes)Absorption: cells take up nutrientsElimination: pass undigested materials from digestive systemDigestive CompartmentsMost animals process food in specialized compartmentsIntracellular: digestion of food inside cells by food vacuolesEx. phagocytosis, pinocytosis, spongesExtracellular: food broken down outside of cellsGastrovascular cavity (simple) or alimentary canal (complex)Intracellular Digestion: SpongesExtracellular DigestionCompartments are outside of the animal’s bodyGastrovascular cavity: simple animals; single-opening, two-way digestion (food in, waste out)Digestion in a hydraAlimentary canal: more complex, one-way tubes with mouth and anusSpecialized organs for digestion in HumansDigestive system = alimentary canal + glandsGlands = salivary glands, pancreas, liver, and gallbladderQ: Can you name the organs of the human alimentary canal in order?Peristalsis: push food through rhythmic contractions of muscles in the wall of the canalSphincters: valves regulate the movement of material between compartmentsDigestion of Macromolecules:Mouth = carbsStomach = proteinsSmall Intestine = carbs, proteins, fats, nucleic acidsOral cavity: mechanical, chemical digestionSalivary glands: saliva lubricates foodTeeth chew food into smaller particlesSalivary amylase: breakdown glucose polymersSaliva contains mucus, a viscous mixture of water, salts, cells, and glycoproteinsPharynx: back of throatEpiglottis: flap of cartilage, covers trachea when swallowingEsophagus: food tube (pharynx  stomach)Digestion in the MouthDigestion in the StomachThe stomach stores food and secretes gastric juice, which converts a meal to acid chymeHCl: pH 2, kills bacteria & denatures proteinsPepsin: enzyme (protease) that hydrolyze proteins into smaller peptidesPepsinogen (inactive)  pepsin (active) by HClMucus: protects lining of stomachGastric ulcers: lesions in the lining, caused mainly by bacterium Heliobacter pyloriSI = major organ of digestion and absorptionDuodenum: first section, digestive juices, major chemical digestionDigestive juices:Pancreas: bicarbonate (basic), trypsin & chymotrypsin (proteases); lipase (fats); amylase (carbs); nuclease (DNA, RNA)Bile: made in liver, stored in gall bladderEmulsify fats (make smaller droplets) Digestion in the Small IntestineHormones that coordinate digestion:Gastrin: produced by stomach, production of gastric juicesEntrogastrin: produced by SI (duodenum), peristalsis to allow time for fat digestionSecretin & CCK (cholesystokinin): secreted by SI (duodenum), flow of digestive juices from pancreas & gall bladderAbsorption in the Small IntestineVilli and microvilli increase surface areaVilli  capillaries  hepatic portal vein  liver  heartLiver: distribute nutrients, detox, glucose storage (glycogen)Absorption in the Large IntestineLI = colonFunction = compact waste, reabsorb waterCecum: pouch where SI & LI meet, ferment plant materialAppendix = extension of cecum, role in immunityRectum: end of LI, feces stored until eliminationEvolutionary adaptations of vertebrate digestive systems correlate with dietDentition: teeth correlate with dietHerbivores: longer alimentary canal, longer cecumMutualistic AdaptationsMany herbivores have fermentation chambers, where mutualistic microorganisms digest cellulose (ruminants)Homeostatic MechanismsVertebrates store excess calories as glycogen in the liver and muscle cells, and as fat in adipose tissueOvernourishment can lead to obesityLeptin: hormone, suppresses appetite Glucose Homeostasis