Download Chapter 50: Animal Nutrition

Chapter 50: Animal Nutrition
Chapter 50
Animal Nutrition
Chapter 50: Animal Nutrition
Chapter 50: Animal Nutrition
Nutrient Requirements
Adaptations for Feeding
Digestion
Structure and Function of the Vertebrate Gut
Chapter 50: Animal Nutrition
Chapter 50: Animal Nutrition
Control and Regulation of Digestion
Control and Regulation of Fuel Metabolism
The Regulation of Food Intake
Toxic Compounds in Food
Chapter 50: Animal Nutrition
Nutrient Requirements
• Animals are heterotrophs that derive their
energy and structural building blocks from
food, therefore ultimately from autotrophs.
4
Chapter 50: Animal Nutrition
Nutrient Requirements
• Carbohydrates, fats, and proteins supply
animals with metabolic energy.
• A measure of the energy content of food is
the calorie.
• Excess caloric intake is stored as glycogen
and fat.
Review Figure 50.2
5
figure 50-02.jpg
Chapter 50: Animal Nutrition
50.2
Figure 50.2
Chapter 50: Animal Nutrition
Nutrient Requirements
• An animal with insufficient caloric intake is
undernourished and must metabolize its
stored glycogen, fat, and finally its own
protein.
• Overnutrition in humans can be a serious
health hazard.
Review Figure 50.3
7
figure 50-03.jpg
Chapter 50: Animal Nutrition
50.3
Figure 50.3
Chapter 50: Animal Nutrition
Nutrient Requirements
• For many animals, food provides essential
carbon skeletons they cannot synthesize
themselves.
Review Figure 50.4
9
figure 50-04.jpg
Chapter 50: Animal Nutrition
50.4
Figure 50.4
Chapter 50: Animal Nutrition
Nutrient Requirements
• Humans require eight essential amino acids.
• All are available in milk, eggs, or meat, but
not in all vegetables.
• Thus, vegetarians must eat a mix of foods.
Review Figure 50.5
11
figure 50-05.jpg
Chapter 50: Animal Nutrition
50.5
Figure 50.5
Chapter 50: Animal Nutrition
Nutrient Requirements
• Different animals need mineral elements in
different amounts.
• Macronutrients are needed in large
amounts.
• Micronutrients are needed in small amounts.
Review Table 50.1
13
table 50-01a.jpg
Chapter 50: Animal Nutrition
50.1
Table 50.1 – Part 1
table 50-01b.jpg
Chapter 50: Animal Nutrition
50.1
Table 50.1 – Part 2
Chapter 50: Animal Nutrition
Nutrient Requirements
• Vitamins are organic molecules that must be
obtained in food.
Review Table 50.2
16
table 50-02a.jpg
Chapter 50: Animal Nutrition
50.2
Table 50.2 – Part 1
table 50-02b.jpg
Chapter 50: Animal Nutrition
50.2
Table 50.2 – Part 2
Chapter 50: Animal Nutrition
Nutrient Requirements
• Malnutrition results when any essential
nutrient is lacking from the diet.
• Lack of any essential nutrient causes a
deficiency disease.
Review Table 50.2
19
table 50-02a.jpg
Chapter 50: Animal Nutrition
50.2
Table 50.2 – Part 1
table 50-02b.jpg
Chapter 50: Animal Nutrition
50.2
Table 50.2 – Part 2
Chapter 50: Animal Nutrition
Adaptations for Feeding
• Animals can be characterized by how they
acquire nutrition
• Saprotrophs and detritivores depend on
dead organic matter
• Filter feeders strain the environment for
food
• Herbivores eat plants
• Carnivores eat animals.
22
Chapter 50: Animal Nutrition
Adaptations for Feeding
• Behavioral and anatomical adaptations
reflect feeding types.
• In vertebrates, teeth have evolved to match
diet.
Review Figure 50.9
23
figure 50-09a.jpg
Chapter 50: Animal Nutrition
50.9
Figure 50.9 – Part 1
figure 50-09b.jpg
Chapter 50: Animal Nutrition
50.9
Figure 50.9 – Part 2
Chapter 50: Animal Nutrition
Digestion
• Digestion involves the breakdown of
complex food molecules into monomers that
can be absorbed and utilized by cells.
• In most animals, digestion is extracellular,
external to the body, occurring in a tubular
gut with regions specialized for different
digestive functions.
Review Figure 50.10
figure 50-10.jpg
Chapter 50: Animal Nutrition
50.10
Figure 50.10
Chapter 50: Animal Nutrition
Digestion
• Absorptive areas of the gut are
characterized by a large surface area.
Review Figure 50.11
28
figure 50-11a.jpg
Chapter 50: Animal Nutrition
50.11
Figure 50.11 – Part 1
figure 50-11b.jpg
Chapter 50: Animal Nutrition
50.11
Figure 50.11 – Part 2
Chapter 50: Animal Nutrition
Digestion
• Hydrolytic enzymes break down proteins,
carbohydrates, and fats into their
monomeric units.
• To prevent the organism itself from being
digested, these are released as inactive
zymogens, only activated when secreted
into the gut.
31
Chapter 50: Animal Nutrition
Structure and Function of the Vertebrate Gut
• Cells and tissues of the vertebrate gut are
organized in the same way throughout its
length.
• The innermost tissue layer, the mucosa, is the
secretory and digestive surface.
• The submucosa contains secretory cells and
glands, blood and lymph vessels, and nerves.
• External to the submucosa are two smooth
muscle layers that move food through the gut.
• Between these is a nerve network that controls
gut movements. Review Figure 50.13
32
figure 50-13.jpg
Chapter 50: Animal Nutrition
50.13
Figure 50.13
Chapter 50: Animal Nutrition
Structure and Function of the
Vertebrate Gut
• The swallowing reflex pushes food into the
esophagus.
• Waves of smooth muscle contraction and
relaxation (peristalsis) move food from the
beginning of the esophagus through the
length of the gut.
• Sphincters block the gut at certain locations,
but relax as a wave of peristalsis
approaches.
Review Figure 50.14
figure 50-14a.jpg
Chapter 50: Animal Nutrition
50.14
Figure 50.14 – Part 1
figure 50-14b.jpg
Chapter 50: Animal Nutrition
50.14
Figure 50.14 – Part 2
Chapter 50: Animal Nutrition
Structure and Function of the
Vertebrate Gut
• Enzymatic digestion begins in the mouth,
where amylase is secreted with saliva.
• Protein digestion begins in the stomach with
pepsin and HCl secreted by the stomach
mucosa.
• The mucosa also secretes mucus, to protect
gut tissues.
Review Figure 50.15
37
figure 50-15.jpg
Chapter 50: Animal Nutrition
50.15
Figure 50.15 – Part 1
figure 50-15b.jpg
Chapter 50: Animal Nutrition
50.15
Figure 50.15 – Part 2
Chapter 50: Animal Nutrition
Structure and Function of the Vertebrate Gut
• In the the duodenum, pancreatic enzymes
carry out most of digestion.
• Bile from liver and gallbladder assists in
digestion of fats, breaking them into
micelles.
• Bicarbonate ions from the pancreas
neutralize the pH of the chyme entering
from the stomach to produce an
environment conducive to pancreatic
enzyme action.
Review Figure 50.16, Table 50.3
40
figure 50-16.jpg
Chapter 50: Animal Nutrition
50.16
Figure 50.16
table 50-3.jpg
Chapter 50: Animal Nutrition
50.3
Table 50.3
Chapter 50: Animal Nutrition
Structure and Function of the Vertebrate Gut
• Final enzymatic cleavage of peptides and
disaccharides occurs on the cell surfaces of
the intestinal mucosa.
• Amino acids, monosaccharides, and many
inorganic ions are absorbed by the microvilli
of the mucosal cells.
• Often specific carrier proteins in the
membranes of these cells transport
nutrients into the cells.
• Sodium cotransport is a common
mechanism for actively absorbing nutrient
molecules and ions.
43
Chapter 50: Animal Nutrition
Structure and Function of the
Vertebrate Gut
• Fats are absorbed mostly as monoglycerides and
fatty acids, the product of lipase action on
triglycerides in food.
• These products pass through mucosal cell
membranes and are resynthesized into triglycerides
within the cells.
• The triglycerides are combined with cholesterol and
coated with protein to form chylomicrons, which
pass out of mucosal cells into lymphatic vessels in
the submucosa.
Review Figure 50.17
44
figure 50-17.jpg
Chapter 50: Animal Nutrition
50.17
Figure 50.17
Chapter 50: Animal Nutrition
Structure and Function of the
Vertebrate Gut
• Water and ions are absorbed in the large
intestine so that waste matter is
consolidated into feces.
46
Chapter 50: Animal Nutrition
Structure and Function of the
Vertebrate Gut
• In herbivores such as rabbits and
ruminants, some compartments of the gut
have populations of microorganisms that aid
in digesting molecules otherwise
indigestible.
Review Figure 50.18
47
figure 50-18.jpg
Chapter 50: Animal Nutrition
50.18
Figure 50.18
Chapter 50: Animal Nutrition
Control and Regulation of
Digestion
• Digestion processes are coordinated and
controlled by neural and hormonal
mechanisms.
• Salivation and swallowing are autonomic
reflexes.
• Stomach and small intestine actions are
largely controlled by the hormones gastrin,
secretin, and cholecystokinin.
Review Figure 50.19
figure 50-19.jpg
Chapter 50: Animal Nutrition
50.19
Figure 50.19
Chapter 50: Animal Nutrition
Control and Regulation of
Fuel Metabolism
• The liver interconverts fuel molecules and
plays a central role in directing their traffic.
• When food is being absorbed from the gut,
the liver takes up and stores fats and
carbohydrates, converting monosaccharides
to glycogen or fat.
• The liver also takes up amino acids and uses
them to produce blood plasma proteins.
51
Chapter 50: Animal Nutrition
Control and Regulation of
Fuel Metabolism
• Fat and cholesterol are shipped out of the
liver as low-density lipoproteins.
• High-density lipoproteins act as acceptors of
cholesterol and are believed to bring fat and
cholesterol back to the liver.
52
Chapter 50: Animal Nutrition
Control and Regulation of
Fuel Metabolism
• Fuel metabolism during the absorptive period is
controlled largely by insulin, which promotes glucose
uptake and utilization by most cells of the body, as
well as fat synthesis in adipose tissue.
• During the postabsorptive period, lack of insulin
blocks the uptake and utilization of glucose by most
body cells except neurons.
• If blood glucose levels fall, glucagon is secreted,
stimulating the liver to break down glycogen to
release glucose.
• Review Figures 50.20, 50.21
53
figure 50-20.jpg
Chapter 50: Animal Nutrition
50.20
Figure 50.20
figure 50-21a.jpg
Chapter 50: Animal Nutrition
50.21
Figure 50.21 – Part 1
figure 50-21b.jpg
Chapter 50: Animal Nutrition
50.21
Figure 50.21 – Part 2
Chapter 50: Animal Nutrition
The Regulation of Food
Intake
• Food intake is governed by sensations of
hunger and satiety determined by brain
mechanisms.
• When one hypothalamic region is damaged,
rats eat more; when another region is
damaged, they eat less.
• A number of molecules provide feedback
information to these brain areas.
57
Chapter 50: Animal Nutrition
The Regulation of Food
Intake
• Leptin is a hormone produced by fat cells
that inhibits food intake.
58
Chapter 50: Animal Nutrition
Toxic Compounds in Food
• Even natural plant and animal foods can
contain toxic compounds.
• Human activities such as pesticide use and
pollution of environment have made the
problem of toxins in food worse.
59
Chapter 50: Animal Nutrition
Toxic Compounds in Food
• An organism can accumulate toxic
compounds in its body, especially if those
compounds are lipid-soluble or take the
structural place of a natural molecule.
60
Chapter 50: Animal Nutrition
Toxic Compounds in Food
• Toxins such as PCBs and DDT that
accumulate in the bodies of prey are
transferred to and further concentrated in
the bodies of their predators.
• This bioaccumulation produces high
concentrations of toxins in animals high up
the food chain.
61