Biology 102 Chapter 50
Animal Nutrition
1. Explain why animals need a nutritionally adequate diet and
how the energy requirements may be quantitatively measured.
---fuel (chemical energy) for cellular respiration
---raw organic materials for biosynthesis
---essential nutrients which must be obtained in
prefabricated form
---metabolic rate of animal is measure of the overall energy
needs that must be met by ingestion/digestion of food
--BMR (rate resulting from all essential physiological
functions of RESTING PERSON) is about 1300-1500 kcal/day
for adult female and 1600-1800 kcal/day for adult male
--physical activity adds to this requirement
---calorie (c)/kcalorie (C) used to measure the amount of
energy in foods
--fats = 9.5 kcal/g; carbs = 4.2 kcal/g; proteins = 4.1
kcal/g
---switching to ISU unit of joule where 1 calorie =4.184 joules
2. Distinguish between malnourished and undernourished.
---undernourished person or animal is one whose diet is
deficient in calories
---malnourished person or animal is one whose diet is missing
one or more essential nutrients
3. List the essential nutrients and describe what happens if
they are deficient in the diet.
---essential amino acids are those that must be obtained
in the diet in prefabricated form
--in humans, 8 amino acids are essential
--humans can manufacture the other 12 given precursors
--protein deficiency results when diet lacks 1 or more
essential amino acids
--human body CANNOT store essential amino acids
-deficiency retards protein synthesis
---essential fatty acids are those unsaturated fatty
acids that cannot be produced by the body
--linoleic acid is example in humans
-required to produce some of phospholipids for
membranes
--fatty acids deficiencies are rare
---vitamins are organic molecules required in the diet in
much smaller quantities than essential amino acids/fatty
acids
--many serve a catalytic function
--vitamin deficiencies can cause very severe effects
--water-soluble vs. fat-soluble vitamins
--if body of animal can synthesize certain compound, it
is NOT a vitamin
---minerals are inorganic nutrients required in the diet in
small quantities ranging from 1 mg to 2500 mg/daily
--some serve structural and maintenance roles
-calcium and phosphorous
--others serve as parts of enzymes (copper) or
other molecules (iron)
4. List and distinguish between water-soluble and fat-soluble
vitamins, and explain how the body uses them.
---water-soluble vitamins are not stockpiled in body
tissues so excesses are excreted in urine, and moderate
overdoses of these vitamins probably harmless
--include the B complex vitamins that generally function
as coenzymes in key metabolic processes
--includes vitamin C which is required for synthesis of
connective tissue/antioxidant
---fat-soluble vitamins are stockpiled in body tissues;
excesses are NOT secreted by the body but are deposited
in body fat; overdoses may result in accumulation of
these compounds to toxic levels
--fat soluble vitamins are A, D, E, and K
-A is incorporated into visual pigments of the eye
-D aids in calcium absorption/bone formation
-E seems to be antioxidant for phospholipids
-K is required for blood clotting
5. Describe the dietary sources and major body functions for
the following required minerals in the human diet: Calcium,
phosphorus, sulfur, potassium, chlorine, sodium, magnesium, and
iron.
---calcium is found in dairy products, dark green
vegetables, and legumes
--bone/tooth formation; blood clotting; nerve/muscle
functioning
---phosphorus is found in dairy products, meats, & grains
--bone/tooth formation; acid-base balance, nucleotide
synthesis
---sulfur is found in proteins from many sources
--component of certain amino acids
---potassium found in meats, dairy products, many fruits
and vegetables, and grains
--acid-base balance, water balance, nerve function
---chlorine found in table salt
--acid-base balance, formation of gastric juice,
nerve function, and osmotic balance
---sodium found in table salt
--acid-base balance, water balance, and nerve function
---magnesium found in whole grains, green leafy vegetables
--cofactor, ATP bioenergetics
---iron found in meats, eggs, legumes, whole grains,
and green leafy vegetables
--component of hemoglobin and of electron-carriers
in energy metabolism, and enzyme cofactor
6. Describe the adaptations to feeding used by animals to
acquire food.
---animals must eat to say alive so they eat other organisms
--heterotrophic (chemoheterotroph)
--eat plants and other animals
---herbivores eat autotrophic organisms (plants, algae, &
autotrophic bacteria)
---carnivores eat other animals
---omnivores eat other animals and autotrophs
---animals have evolved enormous diversity of adaptations to
exploit, directly/indirectly, resources made available by
autotrophs
---filter-feeding: (suspension-feeding) sift small food
particles from the water
--clams/oysters; baleen whales
---substrate-feeding: live on or in their food source and
eat their way through the food
--leaf miners tunnel through interior of leaves
---deposit-feeding: type of substrate-feeder that ingests
partially decayed organic materials along with their
substrate
--earthworm ingest soil and their digestive systems
extract the organic materials
---fluid-feeders: suck nutrient-rich fluids from a living
host
--aphids ingest phloem sap from plants; leeches and
mosquitoes suck blood from animals; hummingbirds &
bees ingest nectar from flowers
---bulk-feeders: eat relatively large pieces of food
7. Define digestion and describe why it is a necessary process.
---digestion is the process of breaking down food into
small molecules the body can absorb
---organic food composed of macromolecules (proteins, fats,
carbs) are too LARGE to cross membranes and enter
an animal’s cells
---digestion enzymatically cleaves these macromolecules into
component monomers that can be used by the animal
--poly/disaccharides to simple sugars
--proteins to amino acids
--fats to glycerol and fatty acids
8. Define gastrovascular cavity and explain why extracellular
digestive cavities are advantageous. Provide examples of animal
phyla exhibit a gastrovascular cavity.
---gastrovascular cavity is a digestive sac with single
opening; functions in both digestion and nutrient
distribution
---most animals with simple body plan have gastrovascular
cavity
---extracellular digestive cavities are advantageous
because they allow for ingestion of larger food items
than could be phagocytosed and digested intracellularly
---Phylum Cnidaria (Hydra)
---Phylum Platyhelminthes (planarians)
9. Describe some distinct advantages that complete digestive
tracts (tubular guts) have over gastrovascular cavities, and
list the major animal phyla with alimentary canals.
---complete digestive tract (alimentary canal) is digestive
tube running between two openings, the mouth (where food
is initially ingested) and the anus (where undigested
wastes are eliminated)
--food moves in one direction along the tube
--tube can be organized into specialized regions that
carry out digestion and absorption of nutrients in
stepwise fashion
--unidirectional passage of food and specialization of
function for different regions makes alimentary canal
more efficient
---Phyla Nematoda, Annelida, Mollusca, Arthropoda,
Echinodermata, and Chordata
10. Define peristalsis and describe its role in the digestive
tract.
---peristalsis is rhythmic smooth muscle contractions
---pushes food along the alimentary tract
---OMG, tummy growling?
11. Describe the role of each of the following structures of a
vertebrate digestive tract: Teeth, esophagus, stomach, small
intestine, large intestine, and rectum.
---teeth are adapted for acquisition and initial processing
of specific types of food
--used to tear, shred, grind, and pulverize food
--food in mouth is chewed and mixed with secretions of
salivary glands
---esophagus is the food tube that connects mouth to stomach
--peristalsis moves food down esophagus
--esophageal sphincter normally prevents food from exiting
stomach back into esophagus
---stomach stores food consumed during meal
--secretions of stomach kill most microorganisms and begin
digestion of proteins
--when properly processed into chyme, pyloric sphincter
allows passage from stomach to small intestine
---small intestine is major site of digestion
--digestion of carbs and proteins continues
--digestion of fats begins
--absorption of nutrients begins
--duodenum (site of most digestion)
--jejunum and ileum carry out ~ 90% absorption of nutrients
---large intestine (colon) absorbs water and ions
--immense populations of bacteria live in colon
--Vitamin K, biotin, methane, and hydrogen sulfide
--feces stored in last segment of colon and periodically
excreted
--too much water removed = constipation
--too little water removed = diarrhea
--fingerlike pouch (appendix) source of difficulty if
infected
---rectum is the terminal portion of large intestine, ending at
the anus
--site of fecal storage until elimination
12. Describe the general function of digestive enzymes and the
specific role(s) of the following enzymes in the vertebrate
digestive tract: Salivary amylase, pepsin, and pancreatic
enzymes.
---macromolecules (protein, carbohydrate, and fat) must be
broken down in monomeric units by hydrolytic enzymes
--hydrolysis occurs by addition of water molecules
---digestive enzymes classified according to substances they
hydrolyze
---carbohydrases-->carbs; proteases-->proteins; peptidases—->
peptides; lipases-->fats; nucleases-->nucleic acids
--exo and endo indicate where enzyme cleaves the molecule
--endoprotease hydrolyzes a protein at an internal site along
the polypeptide chain
SALIVARY AMYLASE
---secreted with saliva and mixed with food as it is chewed
---hydrolyzes bonds between glucose monomers that make up
starch molecules
--will make bread and crackers taste sweet if held in mouth
long enough
---starch digestion begins in mouth
---will begin again in duodenum where pancreatic amylases
hydrolyze starch and glycogen into disaccharides
PEPSIN
---major enzyme produced by stomach is endopeptidase called
pepsin
---secreted as a zymogen called pepsinogen by gastric glands
(deep folds in stomach lining)[sometimes called chief cells]
---along with HCl of stomach, begins protein digestion
---splits peptide bonds next to some amino acids (proteins)
---begins process of “unwinding” proteins; creating more
surface area for other enzymes to act upon
--endopeptidase that splits peptide bonds located within
the polypeptide chain
PANCREATIC ENZYMES
---pancreas is large gland that lies just beneath stomach
---functions as both endocrine and exocrine gland
---exocrine products delivered to gut via pancreatic duct
---produces a host of digestive enzymes including pancreatic
amylase, lipase, nuclease, trypsin, chymotrypsin, and
carboxypeptidase
13. Recall the normal pH of the stomach, and explain the
function of stomach acid.
---has pH of about 2
--acidic enough to dissolve iron nails
---function is to disrupt the extracellular matrix
that binds cells together in meat and plant material
---also kills most bacteria that are swallowed with food
14. Describe the sequence of events which occur in response to
acid chyme entering the duodenum and include the roles of:
Secretin, bicarbonate, cholecystokinin (CCK), gall bladder,
bile, pancreatic enzymes, enterogastrone.
---duodenum is the first 25 cm of the small intestine
---exocrine part of pancreas produces hydrolytic enzymes
that break down all major classes of macromolecules
and bicarbonate buffer that helps
neutralize acid chyme coming from the stomach
---increased delivery of acid chyme to duodenum stimulates
production of secretin by duodenum wall (an
enterogastrone)
--secretin stimulates bicarbonate release from pancreas
---gallbladder stores bile produced by liver
--bile does not contain digestive enzymes
--contains bile salts which emulsify fat
--contains pigments; byproducts of destroyed RBCs
---cholecystokinin (CCK) produced by duodenum wall
--stimulates pancreas to release pancreatic enzymes
to small intestine, stimulates gall bladder to contract
and release bile into the small intestine
---other enterogastrones (secreted by wall of duodenum)
inhibit peristalsis in stomach (slows food entry into
small intestine)
15. Describe enzymatic digestion of carbohydrates, proteins,
lipids, and nucleic acids, including the reactants and products
for each enzymatic reaction and whether they occur in the: Oral
cavity, stomach, lumen of small intestine, or brush border of
small intestine.
CARBOHYDRATES
---begins in mouth with action of salivary amylase
---begins again in duodenum where pancreatic amylases
hydrolyze starch and glycogen into disaccharides
--occurs in lumen of small intestine
---disaccharidases attached to surface of duodenal
epithelium hydrolyze disaccharides into monosaccharides
---each disaccharide has its own disaccharidase
--maltose/maltase; sucrose/sucrase; lactose/lactase
--occurs in epithelium of small intestine (brush border)
---since disaccharidases are on surface of epithelium,
final breakdown of carbohydrates occurs where sugars
will be absorbed
PROTEINS
---protein digestion involves teams of enzymes
---pepsin, (endopeptidase) begins protein digestion
in the stomach
---pancreas secretes proteases in form of zymogens that
will be activated only in lumen of duodenum by
intestinal enzyme enteropeptidase
--converts trypsinogen to trypsin
--chymotrypsin also produced
--both specific for peptide bonds adjacent to certain
amino acids; break large polypeptides into smaller
chains
---carboxypeptidase (exopeptidase) splits amino acids,
one at a time, off PP that has free carboxyl group
---lining of small intestine secretes protein-digesting
enzymes
--aminopeptidase splits one amino acid at time from
PP end that has free amino group
--dipeptidases attached to intestinal lining split
small polypeptides
---trypsin, chymotrypsin, & carboxypeptidase are secreted
in inactive form by the pancreas
---aminopeptidase, dipeptidase, and enteropeptidase are
secreted by the lumen of small intestine
---STOMACH = pepsin
---LUMEN OF SMALL INTESTINE = trypsin, chymotrypsin
aminopeptidase, carboxypeptidase
---EPITHELIUM OF SMALL INTESTINE (BRUSH BORDER) =
dipeptidases
NUCLEIC ACIDS
---also involves teams of enzymes
---nucleases hydrolyze DNA and RNA into nucleotides
---occurs in lumen of small intestine
---other hydrolytic enzymes (nucleotidases and
nucleosidases) break nucleotides into nucleosides
and nitrogenous bases, sugars and phosphates
---occurs in epithelium of small intestine (brush border)
FATS
---occurs only in lumen of small intestine
---emulsification produces many small fat droplets that
collectively have large surface area exposed for
digestion
---pancreatic lipase, secreted by duodenum, hydrolyzes
fats into glycerol and fatty acids
---macromolecules completely hydrolyzed as peristalsis
moves digestive juice-chyme mixture through duodenum
16. Explain the function of bile, describing where it is
produced and stored.
---bile is produced by the liver and stored in the gall
bladder
---acts as detergents and aids in digestion and absorption
of fats
---also contains pigments that are by-products of red blood
cell destruction in the liver
17. Explain where most nutrient absorption occurs.
---in the remaining areas of the small intestine
--the jejunum and ileum
18. Explain why the many folds, villi, and microvilli are
important in the small intestine.
---large folds increase the surface available for
absorption
---incorporation of villi (projections from surface)
increase surface area of small intestine
---villi are covered with microscopic microvilli which
also contribute to increasing surface area available
for contact with contents and > absorption
--this results in surface area of about 300 sq. meter
19. Explain where in the digestive tract that most reabsorption
of water occurs.
---review: in the large intestine (colon)
20. Describe the composition of feces, and explain what the main
source of vitamin K is for humans.
---feces = wastes of the digestive tract
---moved through colon by peristalsis
---intestinal bacteria live on organic material in feces
--produce some vitamin K which is absorbed by host
---feces may contain an abundance of salts
---stored in rectum, and pass through two sphincters
(one voluntary and one involuntary) to anus for
elimination