Bio 103
Lake Tahoe Community College
Winter Quarter
Instructor: Sue Kloss
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Chapter 41 - Digestion
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A Humpback whale is a medium sized member of the whale group. Humpbacks can be 53 feet long and weigh up to 72
tons, about as much as 70 medium sized cars. It takes an enormous amount of food to feed an animal that big. Their
stomachs can hold about .5 tons of food at once, and over the course of a day, they take in about 2 tons of small fish and a
crustacean called krill.
Beginning about 20 m. below the surface, the humpbacks will swim in a slow spiral, releasing what becomes a circular net of
bubbles that rises to the surface of the ocean. The small fish and krill swim to the center of the cylinder instinctively; the
whale will then surge up the center of the cylinder harvesting the catch. Instead of teeth, humpbacks have baleen, as do a
number of other types of whales. Baleen is an array of brushlike plates that the whale uses to sift the catch through, trapping
it in its mouth as it expels the water after filtering it through the baleen. The food is then swallowed whole, passing into the
stomach where digestion begins.
The humpbacks harvest much more food than they burn up in the summer in the Pacific Northwest. After summer, the
humpbacks head south to breeding and calving grounds about 3500 miles away. They live off their body fat until they return
to the N. Pacific 8 months later. In about 4 months, a humpback eats, digests and stores enough food for its entire 72 ton
body to live off for a year.
I. Obtaining and Processing Food
A. Animals ingest food in a variety of ways. (Fig. 41.2)
1. Animals and methods of feeding vary enormously
a. parasites such as tapeworms absorb food
b. they lack mouth and digestive system, absorb food thru body surface
c. most animals eat via ingestion (take in living or dead organisms thru mouth)
2. Animals that ingest both plants and animals are called omnivores
a. humans, crows, cockroaches and raccoons are all omnivores
3. Plant eaters are called herbivores
a. cows, deer, gorillas
4. carnivores eat other animals
a. lions, sharks, spiders, snakes
5. ingestive feeders take in food in a variety of ways
a. suspension feeders extract food particles from surrounding water - whales, clams oysters
b. mucus on gills traps morsels, cilia sweep food from gills to mouth
6. substrate feeders live in or on food source and eat their way through food
a. caterpillar, bark beetle, parasitoids, earthworms
7. fluid feeders suck nutrient rich fluids from a living host, either plant or animal
a. aphids are plant fluid feeders
b. mosquitoes and ticks suck blood from their hosts
8. bulk feeders - ingest relatively large pieces of food.
a. equipment such as tentacles, beak, claws, pincers, fangs, jaws kill and take in prey
B. Food processing occurs in 4 stages (Fig 41.12)
1. ingestion - act of eating
2. digestion - breaking down of food into molecules small enough for body to absorb
3. most of the organic matter in food consists of proteins, fats and carbos - all large polymers
4. polymers are macromolecules too large to pass thru plasma and enter the cells
5. the animal has to make up the polymers it needs using monomers, so it has to break the polymers
down anyway.
6. All animals basically use the same monomers,
a. amino acids to make the proteins they need.
b. fatty acids and lipids make up fats
c. simple sugars make up the di and monosaccharides
d. nucleotides make up the nucleic acids
7. digestion occurs in 2 phases
a. food is mechanically broken down to smaller pieces
b. in animals w/ teeth, this is accomplished with chewing
c. then comes the chemical breakdown of food called hydrolysis
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d. polymers are all broken into monomers by adding water to them which breaks the
chemical bonds in the food polymers
e. monomers are small enough for your body to use
8. The last two stages are called absorption a. cells lining the digestive tract absorb small nutrient molecules
b. molecules travel in blood to body cells where they are incorporated into the cells or
broken down further to provide energy
9. animals that consume more food than they can use convert the excess to fat
10. Elimination is the final stage in food processing - undigested material is passed from digestive
tract.
C. Digestion occurs in specialized compartments
1. To process food an animals body must provide an environment that favors the action of digestive
enzymes.
2. That environment must be contained in some type of compartment where the enzymes will not
attack or damage the organisms own macromolecules.
3. Single celled organisms have digestive compartments
a. amoebas have vacuoles where hydrolytic enzymes don’t mix w/cell’s own cytoplasm
b. sponges also carry out all digestion within their cells
c. most other animals have specialized compartments in the body but outside the cells
d. hydras have gastrovascular cavity - digestive cavity w/mouth as single opening
e. gastrovascular cavity functions in both digestion and the distribution of nutrients thru
body - can digest prey much larger than any of its cells
f. hydra stings its prey, then uses tentacles to stuff food into its mouth
g. cells lining the gastrovascular cavity secrete digestive enzymes (Fig. 41.13)
h. Flagella on cells keep food mixed with enzymes; hydrolysis breaks down soft tissues into
tiny particles
I. when pieces are small enough, cells lining cavity engulf particles into food vacuoles;
additional enzymes complete the process - simple nutrient molecules remain
k. undigested materials eliminated through the mouth
4. some animals have alimentary canals - tube btn 2 openings, mouth and anus (fig. 41.14)
a. food moves in one direction, so different regions can be specialized for digestion and
absorption
b. typical sequence = mouth - pharynx - esophagus - (crop, gizzard, stomach; and many
animals have all three)
c. crop = pouchlike organ where food is softened and temporarily stored
d. stomachs and gizzards = may store food temporarily but are more muscular and actively
churn and grind food.
e. gizzards often contain teeth or grit to assist grinding.
f. Chemical digestion and absorption occur mainly in the intestine (btn stomach/gizzard and anus)
g. anus - opening for expulsion of undigested material
5. Regions of alimentary canal differ depending on diet of animal
6. earthworm is an omnivorous substrate feeder
a. burrows thru ground sucking up soil into mouth w/ muscular pharynx
b. food passes thru esophagus and is stored and moistened in crop
c. muscular gizzard retains sand and gravel, which pulverize the food
d. Organic matter in food is chemically digested and nutrients absorbed in intestine
e. intestine is not a simple cylinder; contains inward fold to increase surface area
f. greater numbers of cells are exposed to food passing thru
g. indigestible material eliminated thru anus
h. mostly sand, fine gravel and inorganic material
7. grasshoppers are herbivorous
a. jawlike mouthparts cut and chew plant leaves into small pieces
b. crop - stores and moistens food
c. gizzard w/ hard teeth to pulverize food
d. from gizzard, food passes to stomach where most chemical digestion occurs
e. nutrients absorbed in stomach and in gastric pouches which extend from stomach
f. intestine absorbs water and compacts waste to expel thru anus
8. Alimentary canal system of birds has same major organs as earthworms and grasshoppers
a. birds eat variety of foods
b. hawks and owls are carnivores, catching and eating mice, birds, snakes, insects
c. other birds are omnivores
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d. most birds have a crop to eat large amts of food quickly
e. w/ no teeth, birds swallow food whole into crop, which stores and softens food
f. mechanical and chemical digestion begin in crop and continue in gizzard
g. many birds eat gravel which collects and pulverizes food in gizzard
h. chemical digestion is completed in bird’s intestine
I. n nutrients and water absorbed thru intestinal wall; undigested material passes out thru anus
j. humans are also omnivores
II. Human Digestive System
A. Human digestive system consists of an alimentary canal and accessory glands
1. Parts of the alimentary canal (fig. 41.15)
a. mouth oral cavity, tongue, pharynx, esophagus, stomach, small intestine, large intestine,
rectum, anus (
2. glands of the digestive system
a. salivary glands, pancreas, liver (labeled in blue in figure) secrete digestive juices that enter
alimentary canal thru ducts.
b. secretions from the liver are stored in the gall bladder
3. peristalsis - rhythmic waves of contraction of smooth muscle in walls of digestive tract
4. food passes from pharynx to esophagus to stomach in 5 - 10 seconds
5. constriction at base of esophagus keeps food in the gut
6. pyloric sphincter works like drawstring, regulating passage of food from stomach to small intestine
7. It will close off s.i. and keep food in stomach long enough for stomach acids and enzymes to begin
digestion
8. final steps of digestion and nutrient absorption take place in the s.i. over 5 - 6 hours
9. Undigested material passes through the large intestine, where water is taken into the body from food
and digestive juices, and feces are formed
B. Digestion begins in oral cavity
1. you walk into a pizza shop and the smell or thought of pizza and coke may cause your salivary glands
to start delivering saliva to your mouth.
2. on regular days, you salivary glands produce about a liter of saliva
3. saliva a. glycoprotein, slippery for protecting mouth’s soft lining and lubes solid food for easy swallowing
b. buffers neutralize acids in say, coke or pizza sauce, preventing tooth decay
c. antibacterial agents kill many microbes that may enter the mouth with the food
d. digestive enzyme - salivary amylase - starts digesting starch in pizza crust
4. mechanical and chemical digestion begins
a. chewing cuts, smashes and grinds food
b. makes food easier to swallow and exposes more of food surface to enzyme action
5. Teeth – mechanical breakdown
6. tongue - muscular organ covered with taste buds
a. tongue manipulates food and shapes it into a ball called bolus
7. In swallowing, tongue pushes bolus to back of oral cavity, into pharynx
C. Food and breathing passages both open into the pharynx
1. Openings in both our esophagus and trachea are in pharynx
2. Most of time, esophagus is closed off by a sphincter and trachea is open for breathing
3. When you swallow and the pizza goes down your throat, the bolus enters the pharynx triggering
the swallowing reflex (Fig. 41.16)
4. the esophageal sphincter relaxes and the bolus enters the esophagus
5. Simultaneously, the larynx moves upward and tips the epiglottis (a flap of cartilage and connective
tissue) over the tracheal opening
6. this prevents food from passing into the windpipe (trachea). You can also see this in the bobbing of
your adams apple when you swallow
7. After the bolus has entered the esophagus, the larynx moves downward and the breathing passage
reopens.
8. Esophageal sphincter closes above the bolus
D. Esophagus squeezes food along to stomach
1. muscular tube that conveys food boluses from pharynx to stomach
2. esophageal muscles are arranged in 2 layers
3. circular muscle layer runs around the esophagus and a longitudinal layer runs the length of the
esophagus
4. contraction of the circular layer constricts the esophagus,
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5. contraction of the long layer shortens it
6. both layers are smooth muscle, which contracts involuntarily
7. whenever one contracts, the other is relaxed
8. wavelike contractions of circular then long muscles push bolus downward (peristalsis)
9. simultaneously, long muscles contract ahead of the bolus, shortening the esophagus
10. these contractions continue in waves till bolus of pizza and coke reaches stomach
E. Stomach stores food and breaks it down with acids and enzymes
1. Our stomach is highly elastic and can stretch to accommodate about 2 liters of food and drink
2. some chemical digestion occurs in the stomach
a. stomach secretes gastric juices - mucus, enzymes and strong acids
b. interior stomach is highly folded (Fig. 41.17)
c. folds are dotted with pits to gastric glands - three types of cells to secrete different
components of gastric juice
1) mucous cells secrete mucus - lube and protect cells lining the stomach
2) parietal cells secrete hydrochloric acid (HCl)
3) chief cells - secrete pepsinogen - inactive form of enzyme pepsin
3. Pepsinogen, HCl and pepsin interact in stomach during digestion
a. pepsinogen and HCl are secreted into the interior of the gastric gland
b. HCl converts the pepsinogen to pepsin
c. pepsin itself then activates more pepsinogen, starting a chain reaction
d. Pepsin begins chemical digestion of proteins - cheese on pizza - splitting protein chains
into smaller polypeptides
e. further digestion of these proteins will occur in the small intestine
4. secreting pepsin in the inactive form of pepsinogen helps keep your stomach from digesting itself, and
helps protect the glands and stomach lining. Still, your stomach undergoes mitosis almost constantly,
generating enough cells to replace the lining of the stomach every three days.
5. Cells in stomach only secrete gastric juices when stimulated to do so, by a combo of nerve signals and
hormones.
a. smelling, seeing or tasting food stimulates your brain to cause your gastric glands to secrete
gastric juices
b. food in stomach stimulates cells in stomach wall to release the hormone gastrin in the
circulatory system
c. gastrin circulates thru body, returning to stomach wall, where it stimulates release of more
gastric juices
d. Thus the initial release of gastrin lasts for some time.
e. negative feedback loop inhibits secretion of gastrin when stomach contents becomes too acidic
f. acid inhibits the release of gastrin and with less gastrin in blood, gastric glands secrete less
gastric juice
6. Contraction of stomach wall aids in digestion, churning the food with gastric juices, forming a mixture
called acid chyme.
7. most time, the stomach is closed off at both ends
8. opening between esophagus and stomach is closed except when a bolus arrives there
9. Acid chyme is prevented from flowing back into the esophagus.
10. occasionally, it gets into the lower end, a feeling we call heartburn
11. When you throw up, peristalsis changes directions and drives the stomach contents upward into the
oral cavity.
12 Between the stomach and small intestine, the pyloric sphincter helps regulate the passage of
acid chyme from stomach into s.i.
13. acid chyme leaves the stomach only a squirt at a time, sot it takes about 2 - 6 hours to empty
F. Ulcers can be caused by bacterial infections
1. stomach acid can dissolve steel; mucous normally protects our stomach lining
2. Helicobacter pylori is the bacteria that can thrive in conditions of really low pH (fig. 41.18)
a. attaches itself to lining and surrounds itself w/ chemicals to neutralize acid
b. growth of this bacteria causes a localized loss of mucus, which allows damage to stomach
lining
c. Mild inflammation of stomach occurs (gastritis) and if the gastritis worsens, gastric ulcers
develop.
d. stomach wall may erode to the point where it has a hole in it, and can become life threatening
e. generally ulcers respond to antibiotics and bismuth, (active ingred. in Pepto Bismal)
So getting back to our pizza and coke, which are now thru the pyloric sphincter and into the small intestine. The food has
been mechanically reduced by chewing and the churning of the stomach. It was mixed with liquids and lubricants both in the
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saliva and in the stomach. The mixture now resembles a thick, chunky soup. Digestion of the starches began in the mouth
with amylase and in the stomach, protein digestion was initiated with pepsin. Aside from this, virtually all chemical digestion
of the original macromolecules of the pizza and coke will occur in the small intestine. Nutrients are also absorbed into the
blood.
G. The small intestine is the major organ of chemical digestion and nutrient absorption
1. Small intestine is over 6 meters in length (18 - 20 feet).
a. its the longest organ of the alimentary canal.
b. Its name is not based on its width but on its length, it is only about an inch wide.
c. 2 large glandular organs contribute to chemical digestion in the s.i. (Fig. 41.19)
2. Pancreas produces digestive enzymes and an alkaline solution rich in bicarbonate.
a. the alkaline solution neutralizes acid chyme as it enters the small intestine
3. liver performs a wide variety of functions, including the production of bile.
a. bile contains no enzymes, but the bile salts dissolved in bile make fats more susceptible
to enzyme attack.
b. the gall bladder stores bile until it is necessary
4. the duodenum is the first 25 cm 10 inches of the s.i. This is where acid chyme squirted from the
stomach mixes with the bile and digestive enzymes and with substances secreted from the wall of the
s.i. itself.
5. Lots of other digestive enzymes are secreted in the duodenum. (Fig. 41.21)
a. all 4 types of macromolecules are digested - carbs, proteins, fats and nucleic acids
b. proteases activated by enteropeptidase, bound to epithelium in duodenum
6. the digestion of starch, which began in the mouth, continues in the duodenum.
a. pancreatic amylase, an enzyme, hydrolyzes starch (a polysaccharide) into maltose, a
dissaccharide.
b. The enzyme maltase then splits maltose into the monosaccharide glucose
c. Maltose is one enzyme in a family that splits disaccharides into monosaccharides
d. sucrase breaks down (hydrolyzes) table sugar
e. lactase digests milk sugar- lactose
f. kids generally have more lactase than adults; some adults lack lactase altogether, which is
what we call lactose intolerant. cramps and diarrhea ensue bc they can’t digest lactose
7. Protein digestion is also completed in the duodenum.
a. pancreas and duodenum secrete hydrolytic enzymes to split proteins to polypeptides to
amino acids
b. enzymes trypsin and chymotripsin split polypeptides into smaller chains after pepsin starts
the process
c. aminopeptidase and carboxypeptidase split off one amino acid at a time, working from the
ends of the polypeptides.
d. dipeptidase hydrolyzes fragments only 2 or 3 aminos long
e. they all work together faster than any single enzyme could
8. Group of enzymes called nucleases hydrolyze nucleic acids.
a. nucleases from the pancreas split DNA and RNA into component nucleotides
b. nucleotides are then broken down into nitrogenous bases, sugars and phosphates by the
other enzymes produced by the duodenal cells.
9. Fat digestion does not begin until duodenum.
a. hydrolysis of fat is a special problem because fat is insoluble in water.
b. first, bile salts from gall bladder coat each droplet and keep them separate - emulsification
c. when there are many small droplets, a large surface area of fat is exposed to lipase
d. lipase is an enzyme that breaks fat molecules down into fatty acids and glycerols
10. By the time peristalsis moves the chyme through the duodenum, chemical digestion is complete
a. remaining length of the duodenum is adapted for absorption of the nutrients
b. The lining of the s.i. has as much area as a tennis court - about 300 m. 2
c. extensive surface area results from several kinds of folds and projections (fig. 41.23)
d. around the walls of the s.i. are large circular folds with numerous small fingerlike projections
called villi. Each of the villi has many tiny surface projections called microvilli
e. microvilli extend into the interior of the intestine
f. small lymph vessel and capillary network penetrate each villus
g. nutrients pass through epithelial cells of the villi and into the capillaries or lymph vessels
1) some diffuse, some are actively pumped
11. capillaries drain to larger vessels that take the nutrient rich blood directly to the liver
a. the liver converts many nutrients into new substances that the body needs
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b. removes excess glucose and stores it as glycogen (a polysaccharided) which is stored in
the liver cells
c. blood travels from liver to heart which pumps nutrient rich blood all over your body
12. large intestine, or colon, is about 5-6 ft long and 2 inches in diameter Fig. 41.25)
a. It joins s.i. at T junction, where a sphincter controls the passage of unabsorbed food
out of the s.i.
b. one arm of the T is a dead end pouch called the cecum
c. appendix is a small fingerlike extension of the cecum - mass of wbcs that make a minor
contribution to immunity
d. it is prone to infection and can be removed with out damage to the immune system
e. colons main function is absoprtion of water
f. about 7 liters of water enter the alimentary canal each day as part of digestion
g. 90% is reabsorbed by the s.i. and colon
h. as water is absorbed and peristalsis moves the mass along, waste products become more
solid.
I. feces contain undigestible plant parts (cellulose, e.g.) and prokaryotes that normally live in
your colon
j. E. coli produce important vitamins inc. biotin, folic, several B vitamins and K. These are
absorbed by colon into blood
13. terminal portion of colon is called rectum- feces are stored here until they can be eliminated.
a. strong contractions of the colon give you the urge to defecate
b. 2 rectal sphincters, one voluntary and one involuntary, control the anus
c. if the lining of the colon is irritated, by say infection of a microbe, the colon is less effective
at reclaiming water and diarrhea may result
d. if peristalsis moves the feces along too slowly, constipation may result
e. constipation may result from a diet too low in plant fibers, or from lack of exercise
III. Diets and Digestive Adaptations
A. Adaptations of vertebrate digestive systems reflect diet
1. we have just finished reviewing the basic vertebrate digestive system
a. there are many variations
b. In every case, the structure and function of the digestive system reflect the kind of food
eaten
2. length of digestive tract tells us something about animals diet (
a. in general, herbivore and omnivores have longer alimentary canals, relative to body size
b. extra time for digesting vegetation, more difficult to digest than meat - cellulose
c. more surface area for absorbing nutrients, which are less concentrated
3. frogs are herbivorous as tadpoles, carnivores as adults- in tadpoles, the intestine is long, but it
doesn’t grow as much as rest of body as it turns into an adult so it ends up short
4. herbivorous mammals have very long alimentary canals;
a. also have special pouches for microbes to digest cellulose
b. mammals then absorb either products of microbe digestion (sugars) or microbes themselves
c. microbes often in colon or in cecum - pouch where small and large intestine meet e.g. horses
and elephants
1. many nutrients are excreted in feces, which is why other animals will eat their feces
a. second time around, not enough nutrients left for reingestion
2. many desert rodents conserve water by eating first round of feces
d. Fig. fig. 41.27 - coyotes same size as koala, but koala’s intestine is much longer w/ long cecum
5. Ruminants, such as cattle, sheep and deer have more elaborate system to digest cellulose
a. stomach of ruminant has 4 chambers, which are in pink fig. 41.28
1. rumen and reticulum - big chambers w/ cellulose digesting microbes
2. cow helps by regurgitating and rechewing food
3. rumination helps break down plant fibers to microbes can get to them
4. cow swallows cud into omasum, where water is absorbed
5. cud passes to abomasum where cows own enzymes complete digestion
6. cow obtains many nutrients by digesting microbes and their nutrients
7. microbes reproduce so rapidly, their numbers stay constant
b. ruminants can obtain way more nutrients from poor quality plant material than nonruminants
IV. Nutrition
A. Overview - healthful diet satisfies 3 needs (fig. 41.8 and 9)
1. fuel to power all bodies activities
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B.
C.
D.
E.
F.
G.
H.
2. organic raw materials for building all the body’s own molecules
3. essential nutrients the animal can’t make for itself
Chemical energy powers the body
1. all activities require energy, in form of ATP
a. usually cells break down fats and sugars, but will use protein if these are in short supply
2. food energy is measured in kilocalories (= calories on food labels)
a. need energy for heart beat, breathing, body temp maintenance, etc. = BMR
b. for adults, BMR = 1300 - 1800 kilocalories/day
c. approximately equal to 100 w light bulb energy requirements if it burned all day
d. any activity increases calorie usage
e. liver and muscles store about a day’s worth of glycogen for BMR
d. liver converts excess protein and carbo to fat
Body fat and fad diets
1. body fat is important to health
a. healthy women - 20 - 25% fat
b. healthy men - 15 - 18 % fat
2. obesity can increase chance of disease
3. human bodies tend to store fat
a. fat we eat goes right into storage
b. amt of fat in diet may be more important than amt of carbos
c. some people have more or less constant weight no matter how much or little they eat
4. fad diets can be unhealthy
a. high protein low carbs can cause increase in cholesterol - risk factors for hearth disease
b. often you crash when you go off the diet
5. best method is over time, use as many calories as you take in, or more
a. at least 1200 kcal and all RDA of essential nutrients
b. regular aerobic exercise
Vegetarians must get all 8 essential amino acids
1. adult humans can not make 8 of the 20 amino acids required for protein production
a. these 8 are essential amino acids and must be obtained from diet
b. body cant store excess amino acids
c. protein and foods with adequate energy deficiency is relatively common in developing
countries
d. eating meat and animal products (eggs, dairy) helps us get all essential amino acids (fig 41.10)
e. or, eat complementary proteins to obtain all correct nutrients - e.g. eat beans and corn
together - Mexico tradition - tortillas and beans
Vitamins (13 of them) required in much smaller quantities then essential amino acids (Table 41.1)
1. most vitamins serve as coenzymes or parts of coenzymes
2. used over and over in metabolic reactions
3. water soluble vitamins (B complex vitamins - the first 8 in table) - cell metabolism
4 . Vitamin C is also water soluble - excess of these excreted in urine or feces
5. fat soluble vitamins collects in fats and excesses can cause toxic effects.
Essential minerals are required for many body functions (table 41.2)
1. minerals are other than CHON
2. minerals are inorganic, unlike aminos and vitamins
3. high sodium is an issue
Food labels
1. low fat or lite does not mean “low fat” - just less than regular
2. labels list serving size and calories/serving
a. nutrients are listed in amt per serving and % of daily value
3. food labels emphasize nutrients believed to be associated w/ disease risks (fat, cholesterol and
sodium,) and w/ healthy diet - eg fiber, protein, vitamins and minerals
4. reducing saturated fat may lower risk of developing certain diseases, including cancer
Diet can influence C V disease and cancer
1. hydrogenation produces “transfats” which are linked to cardio vascular disease
2. LDL’s are bad for vessels, HDLs are good for vessels
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Ch 41 OBJECTIVES
1. Name the three nutrition needs that must be met by a nutritionally adequate diet.
2. Distinguish among undernourishment, overnourishment, and malnourishment.
3. Explain why fat hoarding may have provided a fitness advantage to our hunter-gatherer ancestors.
4. Define essential nutrients and describe the four classes of essential nutrients.
5. Distinguish between water-soluble and fat-soluble vitamins.
6. Define and compare the four main stages of food processing.
7. Compare intracellular and extracellular digestion.
8. Describe the common processes and structural components of the mammalian digestive system.
9. Name three functions of saliva.
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Compare where and how the major types of macromolecules are digested and absorbed within the mammalian digestive
system.
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Explain why pepsin does not digest the stomach lining. .Explain how the small intestine is specialized for digestion and
absorption.
12. Explain how the small intestine is specialized for digestion and absorption.
13. Describe the major functions of the large intestine.
14. Relate variations in dentition and length of the digestive system to the feeding strategies and diets of herbivores, carnivores,
and omnivores.
15. Describe the roles of symbiotic microorganisms in vertebrate digestion.
16.
Draw in correct sequence and label and describe each of the major organs in a human digestive
system
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