Transcript 41 Animalnutri

Chapter 41
Animal Nutrition
PowerPoint TextEdit Art Slides for
Biology, Seventh Edition
Neil Campbell and Jane Reece
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Figure 41.1 Modern humans foraging at a farmer’s market
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Figure 41.2 Four Main Feeding Mechanisms of Animals
SUSPENSION FEEDERS
SUBSTRATE FEEDERS
Feces
Baleen
Caterpillar
FLUID FEEDERS
BULK FEEDERS
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Baleen from an Atlantic Right Whale is an adaptation for Filter
Feeding or Suspension Feeding
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Food brush used for filter
feeding in mosquito larvae
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• Fluid-feeders make their living sucking nutrient-rich
fluids from a living host and are considered parasites.
– Mosquitoes and leaches suck blood from animals.
– Aphids tap the phloem sap of plants.
– In contrast, hummingbirds and bees are fluid-feeders that
aid their host plants, transferring pollen as they move from
flower to flower to obtain nectar.
Fig. 41.8
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41.2 Whale Eats Seal
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Figure 41.3 Homeostatic regulation of cellular fuel
1 When blood glucose
level rises, a gland called
the pancreas secretes insulin,
a hormone, into the blood.
2 Insulin enhances the
transport of glucose into body
cells and stimulates the liver
and muscle cells to store
glucose as glycogen. As a
result, blood glucose level
drops.
STIMULUS:
Blood glucose
level rises
after eating.
Homeostasis:
90 mg glucose/
100 mL blood
4 Glucagon promotes
the breakdown
of glycogen in
the liver and
there lease of
Glucose into the
blood,increasing
blood glucose level.
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STIMULUS:
Blood glucose
level drops
below set point.
3 When blood glucose
level drops, the pancreas
secretes the hormone
glucagon, which opposes
the effect of insulin.
Sinuses
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Figure 41.4 Fat cells from the abdomen of a human
100 µm
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Figure 41.5 A few of the appetite-regulating hormones
Secreted by the stomach
wall, ghrelin is one of the
signals that triggers feelings
of hunger as mealtimes
approach. In dieters who lose
weight, ghrelin levels increase,
which may be one reason
it’s so hard to stay on a diet.
Produced by adipose (fat)
tissue, leptin suppresses
appetite as its level increases.
When body fat decreases,
leptin levels fall, and appetite
increases.
Ghrelin
Insulin
The hormone PYY,
secreted by the small
intestine after meals,
acts as an appetite
suppressant that
counters the appetite
stimulant ghrelin.
Leptin
PYY
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A rise in blood sugar level
after a meal stimulates
the pancreas to secrete
insulin (see Figure 41.3).
In addition to its other
functions, insulin suppresses
appetite by acting on the brain.
Figure 41.6 A ravenous rodent
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Figure 41.8 Obtaining essential nutrients
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Figure 41.9 Kwashiorkor (a protein deficiency) in a Haitian boy
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Because the body cannot easily store amino acids, a
diet with all essential amino acids must be eaten each
day, otherwise protein synthesis is retarded.
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Figure 41.11 Storing protein for growth
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Vitamins are required in tiny amounts - from
about 0.01 mg to 100 mg per day - depending
on the vitamin, vitamin deficiency (or overdose
in some cases) can cause serious problems.
Vitamins are coenzymes or cofactors
• So far 13 vitamins essential to humans have
been identified.
– These can be grouped into water-soluble
vitamins and fat-soluble vitamins, with
extremely diverse physiological functions.
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Figure 41.12 The four stages of food processing
Small
molecules
Pieces
of food
Mechanical
digestion
Nutrient
molecules
enter body
cells
Chemical digestion
(enzymatic hydrolysis)
Undigested
material
Food
1 INGESTION
2 DIGESTION
3 ABSORPTION
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4 ELIMINATION
Intracellular
Digestion
food cannot be
bigger than cell
endocytosis
Absorption
Ingestion
Elimination
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• In most animals, at least some hydrolysis
occurs by extracellular digestion, the
breakdown of food outside cells.
– Extracellular digestion occurs within
compartments that are continuous with the
outside of the animal’s body.
– This enables organisms to devour much larger
prey than can be ingested by phagocytosis and
digested intracellularly.
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Gastrovascular
cavity allows
for extracellular
digestion
food can be
bigger than cell
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After food has
been broken up,
intracellular
digestion can
occur
Figure 41.13 Digestion in a hydra
Tentacles
Mouth
Food
Gastrovascular
cavity
Epidermis
Mesenchyme
Gastrodermis
Nutritive
muscular
cells
Flagella
Gland cells
Food vacuoles
Mesenchyme
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Complete digestive systems
have a mouth and an anus
one way gut
specialization of parts
Increases surface area for absorption
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Teeth starts
Mechanical
digestion
Starts Chemical
digestion
Compartmentalizes
alimentary canal
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Figure 41.15 The human digestive system
Salivary
glands
Oral cavity
Parotid gland
Sublingual gland
Esophagus
Pyloric
sphincte
r
Liver
Ascending
portion of
large intestine
Mouth
Pharynx
Esophagus
Submandibular gland
Salivary
glands
Cardiac
orifice
Tongue
Stomach
Gallbladder
Gallbladder
Liver
Pancreas
Small
intestines
Pancreas
IIeum
of small
intestine
Small intestine
Large intestine
Rectum
Appendix
Stomach
Anus
Cecum
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Duodenum of
small intestine
Large
intestines
Rectum
Anus
A schematic diagram of
the human digestive system
Figure 41.16 From mouth to stomach: the swallowing
reflex and esophageal peristalsis (layer 1)
Bolus of food
Tongue
Epiglottis
up
Pharynx
Glottis
Larynx
Trachea
To lungs
Esophageal
sphincter
contracted
Esophagus
To stomach
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Figure 41.16 From mouth to stomach: the swallowing
reflex and esophageal peristalsis (layer 2)
Bolus of food
Tongue
Epiglottis
up
Pharynx
Glottis
Larynx
Trachea
To lungs
Esophageal
Epiglottis
sphincter
down
contracted
Esophagus
To stomach
Glottis up
and closed
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Esophageal
sphincter
relaxed
Figure 41.16 From mouth to stomach: the swallowing
reflex and esophageal peristalsis (layer 3)
Epiglottis
up
Bolus of food
Tongue
Glottis
down
and open
Epiglottis
up
Pharynx
Glottis
Larynx
Trachea
To lungs
Esophageal
Epiglottis
sphincter
down
contracted
Esophageal
sphincter
relaxed
Esophageal
sphincter
contracted
Esophagus
To stomach
Glottis up
and closed
Relaxed
muscles
Contracted
muscles
Relaxed
muscles
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Figure 41.17 The stomach and its secretions
Esophagus
Cardiac orifice
Stomach
5 µm
Pyloric
sphincter
Small
intestine
Interior surface of stomach.
The interior surface of the
stomach wall is highly folded
and dotted with pits leading
into tubular gastric glands.
Folds of
epithelial
tissue
Epithelium
3
Pepsinogen
Gastric gland. The gastric
2
HCl
glands have three types of cells
that secrete different components
of the gastric juice: mucus cells,
chief cells, and parietal cells.
Pepsin (active enzyme)
1
2 HCl converts
pepsinogen to pepsin.
Mucus cells secrete mucus,
which lubricates and protects
the cells lining the stomach.
Chief cells secrete pepsinogen, an inactive form of the
digestive enzyme pepsin.
Parietal cell
Parietal cells secrete
hydrochloric acid (HCl).
1 Pepsinogen and HCI
are secreted into the
lumen of the stomach.
Chief cell
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3 Pepsin then activates
more pepsinogen,
starting a chain
reaction. Pepsin
begins the chemical
digestion of proteins.
Figure 41.18 Ulcer-causing bacteria
Helicobacter pylori
Bacteria
1 µm
Mucus
layer of
stomach
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polysaccharide
disaccharide
monosaccharide
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Pepsinogen activated by acid turns into Pepsin-> cuts at amino end of Tyr and Phe in the stomach
polypeptide
endopeptidase
Smaller polypeptide fragments
Aminopepsidase cuts at the amino end and carboxypepsidase cuts at the carboxyl end - they are both exopeptidases
dipeptides
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Pepsin is secreted in an inactive form
(zymogen), called pepsinogen by specialized
chief cells in gastric pits.
• Parietal cells, also in the
pits, secrete hydrochloric
acid which converts
pepsinogen to the active
pepsin only when both
reach the lumen of the
stomach, minimizing
self-digestion.
– Also, in a positivefeedback system,
activated pepsin can
activate more
pepsinogen molecules.
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Fig. 41.15
Figure 41.20 Protease activation
Pancreas
Membrane-bound
enteropeptidase
Inactive
trypsinogen
Other inactive
proteases
Lumen of duodenum
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Trypsin
Active
proteases
The pancreas secretes enzymes in inactive forms called Zymogens
Enteropeptidase
will activate the
zymogens
zymogens
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Figure 41.22 Hormonal control of digestion
Enterogastrone secreted by the
duodenum inhibits peristalsis and
acid secretion by the stomach,
thereby slowing digestion when
acid chyme rich in fats enters the
duodenum.
Liver
Enterogastrone
Gallbladder
CCK
Amino acids or fatty acids in the
duodenum trigger the release of
cholecystokinin (CCK), which
stimulates the release of digestive
enzymes from the pancreas and bile
from the gallbladder.
Gastrin
Stomach
Pancreas
Gastrin from the stomach
recirculates via the bloodstream
back to the stomach, where it
stimulates the production
of gastric juices.
Secretin
Duodenum
CCK
Key
Stimulation
Inhibition
GESC
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Secreted by the duodenum,
secretin stimulates the pancreas
to release sodium bicarbonate,
which neutralizes acid chyme
from the stomach.
In sharks the sprial valve
pushes food to the side of the
intestine to increase absorption.
What is the earthworm
equivalent?
Most chemical digestion
and absorption occur in
the small intestine
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• Penetrating the core of each villus is a net of
microscopic blood vessels (capillaries) and a
single vessel of the lymphatic system called a
lacteal.
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• In contrast, glycerol and fatty acids absorbed by
epithelial cells are recombined into fats.
• The fats are mixed with cholesterol and coated
with special proteins to form small globules
called chylomicrons.
– The capillaries and veins that drain nutrients
away from the villi converge into the hepatic
portal vessel, which leads directly to the liver.
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Figure 41.24 Digestion and absorption of fats
Fat globule
Large fat globules are
emulsified by bile salts
in the duodenum.
1
Bile salts
Fat droplets
coated with
bile salts
Micelles made
up of fatty acids,
monoglycerides,
and bile salts
Epithelial
cells of
small
intestine
Digestion of fat by the pancreatic
enzyme lipase yields free fatty
acids and monoglycerides, which
then form micelles.
Fatty acids and mono3
glycerides leave micelles
and enter epithelial cells
by diffusion.
2
Lacteal
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Chylomicrons containing fatty
4
substances
are transported out
of the epithelial cells and into
lacteals, where they are carried
away from the intestine by lymph.
Figure 41.19 The duodenum
Liver
Bile
Gallbladder
CCK
Stomach
Acid chyme
Intestinal
juice
Pancreatic juice
Pancreas
Duodenum of
small intestine
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Figure 41.25 Digital image of a human colon
Large intestine absorbs
water and minerals
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Canines for tearing food
and shorter intestine
Large Molars for grinding
and
a longer intestine for
absorption
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• The length of the vertebrate digestive system
is also correlated with diet.
• In general, herbivores and omnivores have longer
alimentary canals relative
to their body sizes than to
carnivores, providing
more time for digestion
and more surface areas
for absorption of nutrients.
• Vegetation is more
difficult to digest
than meat because it
contains cells walls.
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Fig. 41.21
Figure 41.27 The digestive tracts of a carnivore
(coyote) and herbivore (koala) compared
Small intestine
Small
intestine
Stomach
Cecum
Colon
(large
intestine)
Carnivore
Herbivore
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(1) When the cow first chews and swallows a mouthful of grass,
boluses enter the rumen and (2) the reticulum.
–
Symbiotic bacteria and protists digest this celluloserich meal, secreting fatty acids.
–
Periodically, the cow regurgitates and rechews the
cud, which further breaks down the cellulose fibers.
(3) The cow then reswallows the cud, which moves to the omasum,
where
water is removed.
(4) The cud, with many
microorganisms,
passes to the
abomasum for
digestion by the
cow’s enzymes.
Richie Rich makes ono abalone.
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Fig. 41.22
Ruminants vs False Ruminants
• Ruminants such as cows have rumen and
reticulums which are out cropping of the
esophagus. Since the protists digest the
cellulose before the intestine, the nutrients can
be absorbed by the intestine.
• False ruminants such as rabbits and horses
have their outcroppings derived from the large
intestine – which is after the intestine where
absorption can occur. Therefore they must
reswallow their feces to absorb the nutrients.
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