Chp 5 Nutrition, Feeding, and Digestion

1. Chp 5Nutrition, Feeding, and Digestion

3. See Chp 2 on Chemistry to review the various components of the body (proteins, carbohydrates, lipids) Animals needs to grow and to renew their components  food needed Animals composed of water, protein, mineral, carbohydrates, nucleic acids. vitamins Animals can synthesize most of their main components because they have enzymes that enable the reaction Essential amino acids, fatty acids, some vitamins, minerals cannot be synthesized, thus must be ingested. Nutrition

4. Proteins are the most abundant compound, after water. They have important structural and enzymatic roles. Despite abundant nitrogen gas, organic nitrogen (NH3)is a limiting factor in the amount of plant and animal lifes. Organic nitrogen is synthesized by plants an algae from nitrate (NO3-) or ammonia (NH4+) About 10 amino acids are essential in many animal groups. Proteins and amino acids cannot be stored like fat  need to consume proteins on a regular basis If one eats extra proteins, the excess amino acids are deaminated and the left-over carbon chain used for energy Proteins produce NH3 wastes which are costly to eliminate Nutrients: proteins

6. Almost as abundant as proteins Around 50 different types of fatty-acids Fatty-acids can have a full set of single bonds  saturated f.a. or one or several double bonds  unsaturated f.a. Defined by 3 integers: -ex: 18.2ω6: 18=number of carbons in the chain, 2=number of double bonds, 6=position of the first double bond from the end Functional role  in the cell membrane, as hormone Important energy storage In many animal, a layer of lipid on the integument surface reduces water evaporation  minimize water loss. Triacylglycerols are used as components for echolocation by dolphins Some fatty-acids are essential: mammals lack the enzymes to synthesize ω3 and ω6 f.a. Saturated f.a. are solid (fat) at normal temperature (20-30oC) while double f.a. are liquid (oil) Nutrients: Lipids

7. Large polysaccharides (ex: chitin) provide structural support and shape to cells. Cellulose, found in plants, provides dietary fibers to animals (who cannot digest them). Provide energy storage (glycogen). Serve as glucose store. However, it plays a role in cell osmotic pressure Some mono and disaccharides are carrier molecules Nutrients: Carbohydrates

8. Needed in small amount, essential for life Adapted from orignal molecules used by plants Vit B is essential for all animals as it is a component of a coenzyme Some vitamins are water soluble, others are lipid soluble (ADEK) Nutrients: Vitamins

9. Most are needed in small amount, others in greater amount (P, Na, Cl, Ca, K). Important for enzymatic function (Fe, Mg, Md, Zn, Cu, Mn, I..) Humans needed iodine for T3-T4 synthesis Some animals will go on migration to get some minerals Nutrients: Minerals

10. Animals need to gather the nutrients they need. Feeding mechanisms are very diverse: suspension feeders, filter feeders, grazers, hunters, use of venom, digestive enzymes, noxious compounds Aquatic animals can use suspension feeding Read book p 120-123 for a partial description of some special feeding structures Symbiosis is a special arrangement between an animal and various microbes/algae Feeding

11. Heterotroph microbes need organic compounds from external origin, include fermenting microbes Autotrophs microbes: Able to synthesize organic molecules from inorganic molecules: Photosynthetic autotrophs use sun light to synthesize organic compounds Chemoautotrophs: sulfur-oxidizing bacteria (in hydrothermal vents) Symbiosis: nutritional relationships with other types of life

12. Hydrothermal vent worms with chemoautotrophic bacteria

13. Termites host heterotroph microbes These microbes digest the wood cellulose ingested by the termites http://www.utoronto.ca/forest/termite/WebPage.html Scarabid beetles, such as dung beetles, digest wood fibers left over into cattle or animals dung Other examples: Shipworms (with wood products), leeches (with blood) Symbiosis in Invertebrates

16. Best examples: Ruminant mammals foregut fermenters (cattle, sheep, antelope..) and other non ruminants (kangaroo, hippopotamus…) Their stomach has several pouches: first pouch=rumen where the microbes reside cellulase breakdowns cellulose + fermentation: formation of short fatty chain acids, CO2, methane. Microbes synthesize B vitamins, essential amino acids Recycled nitrogen wastes into proteins Later pouches are more acid and/or have enzymes for digestion Symbiosis in Vertebratesforegut fermenters

17. The colon/cecum is a chamber holding fermenting microbes. Ex: Many mammals (rabbits, horses, rhinos, apes, elephant), birds (geese, ostriches, chickens), some lizards and turtles Because the microbes are posterior to the stomach, small intestine, they are not digested and they do not provide essential nutrients as in foregut digestion Symbiosis in VertebratesMidgut and hindgut fermenters

18. Hingut fermenters

19. Digestion: breakdown of food molecules by enzymatic action into smaller components Extracellular digestion: digestion in lumen, stomach, intestines  vertebrates, arthropods, many others Intracellular digestion: digestion within specialized cells  sponges, coelenterates, flatworms and molluscs Absorption: transfer of the products of digestion from the lumen to the blood --. Mammals, most groups In intracellular digestion: absorption is food particles entering the cells for digestion Absorption or assimilation is the entry of molecules into living tissues, from outside The functional roles of some organs in invertebrate can be very different from the invertebtates Digestion and Absorption

20. 4 sequential tubular segments: Headgut (mouth, pharynx) capture food  chewing Foregut (esophagus, stomach, crop in bird) begins digestion, acid production midgut (small intestines)  digestion of proteins and lipids + site of absorption hindgut (colon)  store wastes, reabsorbs water, minerals. 2 additional organs: pancreas and biliary system Food advancing through the tube through peristalsis, segmentation. Absorptive plans in Vertebrates

21. Insects: Foregut and hindgut are lined by chitinous exoskeleton =cuticle  no tissue exchange. The crop storage chamber, the proventriculus (or gizzard), in some species includes a grinding organ. Midgut: Lining allows for digestion and absorption. Has anterior ceca. The Malpighian tubules (excretory organs) empty at the junction of midgut-hindgut  part of excretory system also. Hindgut: important for controlling urine composition In crustaceans: Foregut is a tubular esophagus – stomach (with a gastric mill, sometimes) Midgut can have connections to the hepatopancreas, a set of digestive glands (food enters the hepatopancreas and nutrients are stored there) Hindgut: tube lined by chitin  little exchange Absorptive plans in Arthropods

22. Digestive system very different from other groups. Rely on ciliary action (rather than peristalsis) to move food Digestion is intracellular Foregut: Esophagus directs the food particles toward the stomach. Migut: The stomach has a gelatinous rod, the style: Reels in food caught into mucus strand Breaks down particles Has digestive enzymes  extracellular digestion The stomach wall has opening into digestive diverticula  food particulates directed into them, taken up into the cells by phagocytosis  intracellular digestion + absorption + nutrient storage Hindgut: passes throught eh heart ventricle and end at the anus Absorptive plans in Molluscs

23. Clam anatomy

24. Characteristics: Enzymatic hydrolysic reactions Specific for each compounds Different species might have different enzymatic forms Acts in 3 spatial contexts: Intraluminal enzymes Membrane-associated Intracellular enzymes Digestion

26. Extracellular digestion: absorption brings the nutrients across the digestive epithelium, from the lumen into the blood For efficient transfer, need of a large surface area membrane folds: villi 3 mechanisms of transfer: simple diffusion, facilitated diffusion and active transport Hydrophilic compounds (a.a., monosaccharies, H2O-soluble vitamins) require transport proteins to cross the digestive membrane Glucose: carrier-mediated with sodium-glucose transporter 1 (SGLT1) in secondary active transport and GLUT2 A.a. Transporters for each a.a. also driven by Na+ pump Absorption

28. Lipid: hydrophobic  can cross the cell membrane but can mix into the blood diffusion Once inside the cell, enzymes synthesize triglycerides These TG are combined with proteins chylomicron  carried into the lymph and blood Lipid absorption

29. Responses to eating

30. Adaptations to nutritional changes • When an animal changes diet, enzymes are up or down regulated in order to take advantage of the new nutrients • Takes a few days to a few weeks for full efficiency • Ex: SGLT1, GLUT2 and 5, a.a. transporters

31. Human lactase Cases

32. Python Concentration camp inmates Cases