Animal Nutrition

1. Animal Nutrition AP Biology

2. Nutritionally Adequate Diet • Fuel (chemical energy) for cellular respiration • Raw organic materials for biosynthesis • Essential nutrients which must be obtained in pre-made form

3. Homeostatic Mechanisms • Chemical energy is obtained from the oxidation of complex organic molecules • Too many calories taken in, liver and muscle store excess as glycogen; further excess stored in adipose tissue as fat • Too little calories taken in, glycogen is utilized first; then fat • Fat stores twice as much energy as carbohydrates or proteins

4. Biosynthesis • Proteins can be broken down into amino acids that can supply the nitrogen necessary to build other amino acids • Fats can be synthesized from carbohydrates • Liver is responsible for the conversions of nutrients from one type of organic molecule into another

5. Essential Nutrients • Chemicals an animal must have but can’t synthesize • Essential amino acids • Most animals can make about ½ of the 20 amino acids needed to make proteins • Human can produce 12

7. Essential Nutrients • Chemicals an animal must have but can’t synthesize • Essential amino acids • Most animals can make about ½ of the 20 amino acids needed to make proteins • Human can produce 12 • Cats are obligate carnivores—require amino acid taurine from a meat source • Essential fatty acids • Humans can’t make linoleic acid; important in making membranes

8. Essential Nutrients • Vitamins—organic molecules needed in smaller quantities than essential a.a. or f.a. • Can serve as catalysts (coenzymes) • Excess water soluble vitamins get excreted in urine • Excess fat soluble vitamins (A, D, E, and K) are stored in body fat; can reach toxic levels • Minerals—inorganic molecules needed in small quantities • Serve structural and maintenance roles (Ca2+ and Phosphorus) • Serve as parts of enzymes (Cu) or other molecules (Fe)

9. Feeding Adaptations • Suspension-feeders—sift small particles from the water • Trap food on gills (clams and oysters) • Strain food from water forced through screen-like plates on their jaws (baleen whale)

10. Feeding Adaptations • Substrate-feeders—live on or in their food source and eat their way through their food • Leaf miners (larvae of various insects) tunnel through the interior of leaves

11. Deposit-feeders—ingests partially decayed organic materials along with their substrate Earthworms ingest soil and their digestive systems extract the organic materials Fluid-feeders—suck nutrient-rich fluids from a living host Feeding Adaptations

12. Feeding Adaptations • Bulk-feeders—eat relatively large pieces of food • Have various adaptations to kill prey or tear off pieces of meat or vegetation

13. Intracellular Digestion • Protozoa—use endocytosis to form food vacuoles around food • Hydrolytic enzymes are secreted into the food vacuole and digestion occurs

14. Extracellular Digestion • Occurs within compartments that are continuous, via passages, with the outside of the body • Animals with a simple body plan have a gastrovascular cavity (digestive sac with single opening) • Cnidarians and platyhelminths

15. Stings prey with nematocysts on tentacles • Pulls food into its mouth and into gastrovascular cavity • Gastrodermal cells secrete digestive enzymes • Some gastrodermal cells have flagella • Endocytosis of food particles by gastrodermal cells and food vacuoles • Hydrolysis completed by intracellular digestion • Undigested materials expelled back out the mouth Cnideria: Hydra

16. Platyheminths

17. Mammalian Digestive System • Includes the alimentary canal and accessory glands that secrete digestive enzymes into the canal through ducts

18. Four Main Stages of Food Processing • Ingestion—act of eating • Digestion—breaking down food into small molecules the body can absorb • Enzymatic hydrolysis breaks bonds of macromolecules • Absorption—uptake of small molecules • Elimination—undigested material passes out of the digestive compartment

19. Ingestion • Oral cavity—lined with stratified squamous epithelium • 32 teeth crush and tear food into smaller pieces and increases surface area for enzyme action

20. Ingestion • Salivary glands produce saliva to moisten food and initiate carbohydrate digestion • Mucin-protects from abrasion, lubricates food • Buffers-neutralize acids • Antibacterial agents-limit bacterial flora in mouth • Salivary amylase-hydrolyzes starch and glycogen to maltose or small polysaccharides • Tongue (muscle)-tastes and forms food into a bolus; pushes it into the pharynx

21. Ingestion • Oral cavity—lined with stratified squamous epithelium • 32 teeth crush and tear food into smaller pieces and increases surface area for enzyme action • Salivary glands produce saliva to moisten food and initiate carbohydrate digestion • Mucin-protects from abrasion, lubricates food • Buffers-neutralize acids • Antibacterial agents-limit bacterial flora in mouth • Salivary amylase-hydrolyzes starch and glycogen to maltose or small polysaccharides • Tongue (muscle)-tastes and forms food into a bolus; pushes it into the pharynx

22. Ingestion • Pharynx—intersection for both the digestive and respiratory systems • Thick prominent layer of elastic fibers and several overlapping layers of skeletal muscle • Swallowing moves the epiglottis to block the windpipe and direct food into esophagus

23. Ingestion • Esophagus—muscular tube that conducts food from pharynx to stomach • Distensible because of longitudinal folds along interior of the tube (mucosa) • Peristalsis (rhythmic smooth muscle contractions) pushes food along the tract • Initial entrance of bolus into esophagus is voluntary • The distension stimulates muscular contraction (involuntary) to propel food toward the stomach

25. Digestion • Stomach • Food storage • Elastic walls with rugae, folds that can expand to accommodate up to 2 L of food • Churning • Longitudinal, vertical, and diagonal muscles contract to mix food every 20 seconds • Converts food into a nutrient broth, acid chyme • Passage into small intestine regulated by pyloric sphincter

26. Digestion • Stomach • Gastric Secretion—controlled by nerve impulses and the hormone gastrin • Mucous cells secrete: • Mucin—thin mucus that protects stomach lining • Gastrin—hormone produced by stomach and released into bloodstream to stimulate secretion of HCl and pepsin • Chief cells secrete: • Pepsinogen—inactive protease that is the precursor to pepsin • Zymogen—inactive form of a protein-digesting enzyme • Parietal cells—secrete HCl

27. Digestion • Stomach • Protein digestion • HCl provides acidity (pH 1-4) which: • Kills bacteria • Denatures proteins • Starts the conversion of pepsinogen to pepsin; newly formed pepsin also aids in conversion of more pepsin • Pepsin splits peptide bonds next to some amino acids • Does not hydrolyze protein completely • Endopeptidase that splits peptide bonds located within the polypeptide chain

28. Digestion • Small Intestine: duodenum (.25m) • Site of most hydrolysis of food and absorption • Luminal surface has numerous mucosal folds, villi, that increase absorptive surface area

30. Simple Columnar Epithelium Goblet cell

31. Digestion • Small Intestine • Accessory organs contribute to digestion in this section of the tract • Pancreas produces: • Hydrolytic enzymes that break down all major macromolecules • Bicarbonate buffer that neutralizes acid chyme from the stomach • Liver produces bile that is stored in gallbladder • No digestive enzymes • Bile salts emulsify fats • Contains pigments that are byproducts of destroyed erythrocytes

32. Digestion • Small intestine • Carbohydrate digestion • Began in mouth with salivary amylase • Begins again in duodenum • Pancreatic amylases—starch & glycogen  maltose and other disaccharides • Disaccharides attach to surface of duodenal epithelium and are hydrolyzed into monosaccharides • Maltose hydrolyzed by maltase; sucrose by sucrase; lactose by lactase • Monosaccharides absorbed at the surface

33. Digestion • Small intestine • Protein digestion • Began in stomach with pepsin • Pancreas secretes proteases in form of zymogens that get activated only in lumen of duodenum by enteropeptidase

34. splits a.a. off digests large polypeptides into shorter chains

35. Digestion • Small intestine • Nucleic acid digestion • Nucleases hydrolyze DNA and RNA into nucleotides • Nucleotidases and nucleosidases break nucleotides into nucleosides and nitrogenous bases, sugars, and phosphates • Fat digestion • Occurs only in duodenum • Emulsification produces many small fat droplets • Pancreatic lipase secreted in duodenum hydrolyzes fats into glycerol and fatty acids

36. Absorption • Small Intestine—jejunum (2.4m), ileum (3.6m) • Brush border (microvillar surface) is exposed to lumen of the intestine • Nutrients are absorbed by diffusion or active transport across the two cell-thick epithelium and into the capillaries or lacteals

37. Absorption • Small Intestine—jejunum (2.4m), ileum (3.6m) • Amino acids and sugars inter capillaries and are transported by blood • Absorbed glycerol and fatty acids are recombined in epithelial cells and coated with proteins (chylomicrons) which enter lacteals • Capillaries and veins draining nutrients away from villi dump into hepatic portal vessel which leads to liver • Organic molecules used, stored, or converted to different forms

40. Elimination • Large Intestine (Colon) (1.5m) • Major function is to reclaim water not absorbed during the absorption of nutrients in the small intestine • Feces—wastes of digestive tract are moved by peristalsis • Intestinal bacteria live on organic material in the feces; some producing vitamin K which is absorbed by the host • May contain an abundance of salts • Stored in rectum and pass through 2 sphincters (one involuntary, one voluntary) to the anus for elimination • Strong contractions of the colon signal need to defecate • Too much water absorbed = constipation • Viral or bacteria infection may lead to too little water being absorbed = diarrhea

41. Evolutionary Adaptations • Structural adaptations often associated with diet • Dentition

42. Evolutionary Adaptations • Structural adaptations often associated with diet • Poisonous snakes • Teeth modified to inject venom into prey • Hollow or grooved • Loosely hinged lower jaw-skull articulation

43. Evolutionary Adaptations • Structural adaptations often associated with diet • Length of Digestive Tract • Herbivores and Omnivores have longer alimentary canals than carnivores • Cell walls in vegetation more difficult to digest than meat, and nutrients less concentrated • Longer tract allows for more time for digestion and provides a greater surface area for absorption • Functional length may be longer than its superficial appearance • Spiral valve in sharks

44. Evolutionary Adaptations • Symbiotic Microorganisms • Special fermentation chambers present in many herbivores • Symbiotic bacteria and protozoa produce cellulase which digests cellulose • Microbes digest cellulose into simple sugars and convert them into essential nutrients • Microbes housed in cecum (horses); cecum and colon (rabbits); or specialized chamber (reticulum) found in ruminants