Chp 5 Nutrition, Feeding, and Digestion

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Chp 5Nutrition, Feeding, and Digestion
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Nutrition

• 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.

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Nutrients proteins

• 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

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Nutrients Lipids

• 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 18.2?6 18number of carbons in the chain,
  2number of double bonds, 6position 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 ?3 and ?6 f.a.
• Saturated f.a. are solid (fat) at normal
  temperature (20-30oC) while double f.a. are
  liquid (oil)

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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

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Nutrients Vitamins

• 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)

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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

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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 120-123 for a partial description of
  some special feeding structures
• Symbiosis is a special arrangement between an
  animal and various microbes/algae

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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 sulfur-oxidizing bacteria (in
  hydrothermal vents)

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Hydrothermal vent worms with chemoautotrophic
bacteria
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Symbiosis in Invertebrates

• 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)

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Symbiosis in Vertebratesforegut fermenters

• Best examples Ruminant mammals? foregut
  fermenters (cattle, sheep, antelope..) and other
  non ruminants (kangaroo, hippopotamus)
• Their stomach has several pouches first
  pouchrumen 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

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Symbiosis in VertebratesMidgut 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

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Hingut fermenters
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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

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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.

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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
  

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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

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Clam anatomy
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Digestion

• 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

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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

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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

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Responses to eating
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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

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Cases

• Human lactase

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Cases

• Python

• Concentration camp inmates