Chp 5 Nutrition, Feeding, and Digestion

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1 Chp 5 Nutrition, 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 Nutrients: Carbohydrates 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

8 Needed in small amount, essential for life Nutrients: Vitamins 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)

9 Nutrients: Minerals 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

10 Feeding 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 for a partial description of some special feeding structures Symbiosis is a special arrangement between an animal and various microbes/algae

to synthesize organic molecules from inorganic molecules: Photosynthetic autotrophs use sun

11 Symbiosis: nutritional relationships with other types of life 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: sulfuroxidizing bacteria (in hydrothermal vents)

12 Hydrothermal vent worms with chemoautotrophic bacteria

13 Symbiosis in Invertebrates Termites host heterotroph microbes These microbes digest the wood cellulose ingested by the termites rmite/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)

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 Vertebrates foregut fermenters

17 Symbiosis in Vertebrates Midgut and hindgut fermenters 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

18 Hingut fermenters

19 Digestion and Absorption 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

Absorptive plans in Vertebrates 4 sequential tubular segments: Headgut (mouth, pharynx) capture food chewing Foregut (esophagus, stomach, crop in bird) begins digestion, acid production midgut (small

20 Absorptive plans in Vertebrates 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.

21 Absorptive plans in Arthropods 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

22 Absorptive plans in Molluscs 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

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

25 Nutrients Enzyme 1 S1 S2 Enzyme 2S2 S3 Carbohydrates polysaccharide disacch aride monoglyceride Protein protein dipeptide a.a. Cellulase, chitinase, amylase Proenzymes= zymogen: Endopeptidase (trypsin, elastase, collagenase, chymotrypsin, exopeptidase (carboxypeptidase A and B disaccharidases: Sucrase, lactase, trehalase Various peptidases Lipids triglyceride diglyceride monoglyceride (bile salts for emulsification) + lipases lipases

26 Absorption 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

28 Lipid absorption 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

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 Cases Python Concentration camp inmates

All organisms must obtain and process essential nutrients (food) *** Exception: Venus Fly Traps undergo photosynthesis but needs source of nitrogen

All organisms must obtain and process essential nutrients (food) AUTOTROPHS self feeder makes their own food eg. Plants do not require a digestive tract *** Exception: Venus Fly Traps undergo photosynthesis