Animal Nutrition

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Animal Nutrition

• AP Biology

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Nutritionally Adequate Diet

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

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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

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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

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Essential Nutrients

• Chemicals an animal must have but cant
  synthesize
• Essential amino acids
• Most animals can make about ½ of the 20 amino
  acids needed to make proteins
• Human can produce 12

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Essential Nutrients

• Chemicals an animal must have but cant
  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 carnivoresrequire amino acid
  taurine from a meat source
• Essential fatty acids
• Humans cant make linoleic acid important in
  making membranes

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Essential Nutrients

• Vitaminsorganic 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
• Mineralsinorganic molecules needed in small
  quantities
• Serve structural and maintenance roles (Ca2 and
  Phosphorus)
• Serve as parts of enzymes (Cu) or other molecules
  (Fe)

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Feeding Adaptations

• Suspension-feederssift 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)

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Feeding Adaptations

• Substrate-feederslive 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

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Feeding Adaptations

• Deposit-feedersingests partially decayed organic
  materials along with their substrate
• Earthworms ingest soil and their digestive
  systems extract the organic materials

• Fluid-feederssuck nutrient-rich fluids from a
  living host

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Feeding Adaptations

• Bulk-feederseat relatively large pieces of food
• Have various adaptations to kill prey or tear off
  pieces of meat or vegetation

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Intracellular Digestion

• Protozoause endocytosis to form food vacuoles
  around food
• Hydrolytic enzymes are secreted into the food
  vacuole and digestion occurs

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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

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• 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
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Platyheminths
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Mammalian Digestive System

• Includes the alimentary canal and accessory
  glands that secrete digestive enzymes into the
  canal through ducts

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Four Main Stages of Food Processing

• Ingestionact of eating
• Digestionbreaking down food into small molecules
  the body can absorb
• Enzymatic hydrolysis breaks bonds of
  macromolecules
• Absorptionuptake of small molecules
• Eliminationundigested material passes out of the
  digestive compartment

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Ingestion

• Oral cavitylined with stratified
  squamous epithelium
• 32 teeth crush and tear food into smaller pieces
  and increases surface area for enzyme action

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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

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Ingestion

• Oral cavitylined 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

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Ingestion

• Pharynxintersection 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

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Ingestion

• Esophagusmuscular 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

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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

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Digestion

• Stomach
• Gastric Secretioncontrolled by nerve impulses
  and the hormone gastrin
• Mucous cells secrete
• Mucinthin mucus that protects stomach lining
• Gastrinhormone produced by stomach and released
  into bloodstream to stimulate secretion of HCl
  and pepsin
• Chief cells secrete
• Pepsinogeninactive protease that is the
  precursor to pepsin
• Zymogeninactive form of a protein-digesting
  enzyme
• Parietal cellssecrete HCl

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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

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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

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Simple Columnar Epithelium
Goblet cell
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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

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Digestion

• Small intestine
• Carbohydrate digestion
• Began in mouth with salivary amylase
• Begins again in duodenum
• Pancreatic amylasesstarch 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

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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

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?splits a.a. off
?digests large polypeptides into shorter chains
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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

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Absorption

• Small Intestinejejunum (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

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Absorption

• Small Intestinejejunum (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

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Elimination

• Large Intestine (Colon) (1.5m)
• Major function is to reclaim water not absorbed
  during the absorption of nutrients in the small
  intestine
• Feceswastes 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

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Evolutionary Adaptations

• Structural adaptations often associated with diet
• Dentition

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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

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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

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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