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Chapter 21
Nutrition and Digestion
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
Introduction
 All animals must eat to provide
– energy and
– the building blocks used to assemble new molecules.
 Animals also need essential
– vitamins and
– minerals.
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Introduction
 The modern human diet in developed countries
allows access to relatively cheap and available
calorie-dense foods.
 This diet, combined with sedentary jobs and inactive
lifestyles, has led to an obesity crisis in the United
States leading to
– 68% of people categorized as overweight and
– 100 million people categorized as obese.
 Thus, the modern diet appears to be contributing to
shorter, less healthy lives.
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Figure 21.0_1
Chapter 21: Big Ideas
Obtaining and
Processing Food
Nutrition
The Human
Digestive System
OBTAINING
AND PROCESSING
FOOD
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21.1 Animals obtain and ingest their food in a
variety of ways
 Most animals have one of three kinds of diets.
– Herbivores eat plants and include cattle, snails, and sea
urchins.
– Carnivores eat meat and include lions, hawks, and
spiders.
– Omnivores eat plants and other animals and include
humans, roaches, raccoons, and crows.
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21.1 Animals obtain and ingest their food in a
variety of ways
 Animals obtain and ingest their food in different ways.
– Suspension feeders sift small organisms or food particles
from water.
– Substrate feeders live in or on their food source and eat
their way through it.
– Fluid feeders suck nutrient-rich fluids from a living host.
– Bulk feeders ingest large pieces of food.
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Figure 21.1C
Figure 21.1D
21.2 Overview: Food processing occurs in four
stages
 Food is processed in four stages.
1. Ingestion is the act of eating.
2. Digestion is the breaking down of food into molecules
small enough for the body to absorb.
3. Absorption is the take-up of the products of digestion,
usually by the cells lining the digestive tract.
4. Elimination is the removal of undigested materials out of
the digestive tract.
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Figure 21.2A
Pieces
of food
Small
molecules
Mechanical
digestion
1
Ingestion
2
Digestion
Undigested
material
Nutrient
molecules
enter body
cells
Chemical
digestion
(hydrolysis)
3
Absorption
4
Elimination
Figure 21.2B
Components
Food Molecules
Proteindigesting
enzymes
Amino acids
Protein
Polysaccharide
Carbohydratedigesting
enzymes
Disaccharide
Monosaccharides
Nucleic-aciddigesting
enzymes
Nucleotides
Nucleic acid
Fat-digesting
enzymes
Fat
Glycerol Fatty acids
Figure 21.2B_1
Food Molecules
Components
Proteindigesting
enzymes
Amino acids
Protein
Polysaccharide
Disaccharide
Carbohydratedigesting
enzymes
Monosaccharides
Figure 21.2B_2
Components
Food Molecules
Nucleic-aciddigesting
enzymes
Nucleotides
Nucleic acid
Fat-digesting
enzymes
Fat
Glycerol Fatty acids
21.3 Digestion occurs in specialized compartments
 Sponges digest food in vacuoles.
 Most animals digest food in compartments.
 Cnidarians and flatworms have a gastrovascular
cavity with a single opening, the mouth.
– Food enters the mouth.
– Enzymes break down the food.
– Food particles move into cells lining the compartment.
– Undigested materials are expelled back out the mouth.
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21.3 Digestion occurs in specialized compartments
 Most animals have an alimentary canal with
– a mouth,
– an anus, and
– specialized regions associated with one-way flow
of food.
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21.3 Digestion occurs in specialized compartments
 The normal one-way flow moves food
– into the pharynx or throat,
– down the esophagus to a
– crop where food is softened and stored,
– gizzard, where food is ground and stored, and/or
– stomach where food is ground and stored,
– to the intestines, where chemical digestion and nutrient
absorption occur, and finally
– undigested materials are expelled through the anus.
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Figure 21.3A
Tentacles
1
Digestive enzymes
being released from
a gland cell
2
Food digested to
small particles
3
A food particle
being engulfed
A food particle
digested in a
food vacuole
Mouth
Food
(a water flea)
Gastrovascular
cavity
4
Figure 21.3B
Earthworm
Mouth
Pharynx
Intestine
Esophagus
Anus
Crop
Gizzard
Grasshopper
Midgut
Esophagus
Anus
Mouth
Crop
Hindgut
Gastric
pouches
Bird
Stomach
Gizzard
Mouth
Intestine
Esophagus
Crop
Anus
Figure 21.3B_1
Earthworm
Mouth
Pharynx
Intestine
Esophagus
Anus
Crop
Gizzard
Figure 21.3B_2
Grasshopper
Midgut
Esophagus
Anus
Mouth
Crop
Hindgut
Gastric
pouches
Figure 21.3B_3
Bird
Stomach
Gizzard
Mouth
Intestine
Esophagus
Crop
Anus
THE HUMAN DIGESTIVE
SYSTEM
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21.4 The human digestive system consists of an
alimentary canal and accessory glands
 In humans, food is
– ingested and chewed in the mouth or oral cavity,
– pushed by the tongue into the pharynx,
– moved along by alternating waves of contraction and
relaxation by smooth muscle in the walls of the canal in a
process called peristalsis, and
– moved in and out of the stomach by sphincters.
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21.4 The human digestive system consists of an
alimentary canal and accessory glands
 The final steps of digestion and nutrient absorption
in humans occur in the small intestine.
 Undigested materials move through the large
intestine, feces are stored in the rectum, and then
expelled out the anus.
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Figure 21.4
Nasal cavity
A schematic diagram of the
human digestive system
Oral cavity
(mouth)
Tongue
Oral
cavity
Salivary
glands
Salivary
glands
Pharynx
Esophagus
Esophagus
Liver
Gallbladder
Liver
Pancreas
Esophagus
Stomach
Small
intestine
Sphincters
Gallbladder
Large
intestine
Pancreas
Rectum
Anus
Small
intestine
Large
intestine
Key
Alimentary canal
Accessory digestive
glands
Rectum
Anus
Stomach
Small intestine
Figure 21.4_1
A schematic diagram of the
human digestive system
Oral
cavity
Salivary
glands
Esophagus
Key
Alimentary canal
Accessory digestive
glands
Gallbladder
Liver
Pancreas
Stomach
Small
intestine
Large
intestine
Rectum
Anus
21.5 Digestion begins in the oral cavity
 Mechanical digestion and chemical digestion
begin in the mouth.
 Chewing cuts, smashes, and grinds food, making
it easier to swallow.
 The tongue
– tastes,
– shapes the food into a ball called a bolus, and
– moves it toward the pharynx.
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21.5 Digestion begins in the oral cavity
 Salivary glands release
– a slippery glycoprotein that moistens and lubricates
food for easier swallowing,
– buffers that neutralize acids,
– salivary enzyme amylase that begins the hydrolysis of
starch, and
– antibacterial agents that kill some bacteria ingested with
food.
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Figure 21.5
Incisors
Canine
Premolars
Molars
“Wisdom”
tooth
Tongue
Salivary
glands
Opening of
a salivary
gland duct
21.6 After swallowing, peristalsis moves food
through the esophagus to the stomach
 Air moves from the pharynx,
– into the larynx,
– past the vocal cords in the voice box,
– into the trachea, and
– into the lungs.
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21.6 After swallowing, peristalsis moves food
through the esophagus to the stomach
 Swallowed food and drink move from the pharynx,
– into the esophagus, and
– into the stomach.
 During swallowing,
– the tip of the larynx moves upward,
– preventing the food from entering the trachea.
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Figure 21.6A_s1
Tongue
Bolus of food
Pharynx
Epiglottis up
Larynx down
Trachea (windpipe)
Esophageal
sphincter
Esophagus
Starting to swallow
(sphincter contracted)
Figure 21.6A_s2
Tongue
Bolus of food
Pharynx
Epiglottis up
Larynx down
Trachea (windpipe)
Esophageal
sphincter
Esophagus
Starting to swallow
(sphincter contracted)
Epiglottis
down
Larynx up
Swallowing reflex
(sphincter relaxed)
Figure 21.6A_s3
Tongue
Bolus of food
Pharynx
Epiglottis up
Larynx down
Trachea (windpipe)
Esophageal
sphincter
Esophagus
Starting to swallow
(sphincter contracted)
Epiglottis
down
Larynx up
Swallowing reflex
(sphincter relaxed)
Epiglottis up
Larynx down
Swallowing completed
(sphincter contracted)
Figure 21.6A_4
Bolus of food
Tongue
Pharynx
Epiglottis up
Larynx down
Trachea (windpipe)
Esophageal
sphincter
Starting to swallow
(sphincter contracted)
Esophagus
Figure 21.6A_5
Epiglottis
down
Larynx up
Swallowing reflex
(sphincter relaxed)
Figure 21.6A_6
Epiglottis up
Larynx down
Swallowing completed
(sphincter contracted)
Figure 21.6B
Esophageal sphincter
(contracted)
Bolus of
food
Bolus of
food
Muscles contract,
squeezing the bolus
through the esophagus.
Muscles relax,
allowing the
passageway
to open.
Stomach
21.7 CONNECTION: The Heimlich maneuver can
save lives
 The Heimlich maneuver
– involves a forceful elevation of the diaphragm,
– pushes air into the trachea, and
– can dislodge food from the pharynx or trachea during
choking.
 Brain damage will occur within minutes if no airway
is open.
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Figure 21.7
21.8 The stomach stores food and breaks it down
with acid and enzymes
 The stomach can stretch and store up to 2 liters of
food and drink.
 Some chemical digestion occurs in the stomach.
 The stomach secretes gastric juice, made up of
– mucus,
– a protein-digesting enzyme, and
– strong acid with a pH of about 2 that
– kills ingested bacteria,
– breaks apart cells in food, and
– denatures proteins.
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21.8 The stomach stores food and breaks it down
with acid and enzymes
 Pepsinogen and HCl produce active pepsin.
– Pepsinogen, H+, and Cl– are secreted into the lumen of
the stomach.
– HCl converts some pepsinogen to pepsin.
– Pepsin helps activate more pepsinogen, starting a chain
reaction.
– Pepsin begins the chemical digestion of proteins.
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21.8 The stomach stores food and breaks it down
with acid and enzymes
 What prevents the gastric juices from digesting the
walls of the stomach?
– The secretion of pepsin in the inactive form of pepsinogen
helps protect the cells of the gastric glands.
– Mucus helps protect the stomach lining against HCl and
pepsin.
– New cells lining the stomach are produced about every
three days to those that have been damaged.
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Figure 21.8
Esophagus
Sphincter
Lumen (cavity)
of stomach
Stomach
Gastrin
Release of gastric juice
(mucus, HCl, and pepsinogen)
Pits
Sphincter
Epithelium
Small
intestine
Interior
surface
of the
stomach
3
Pepsinogen
2
Mucous
cells
HCl
1
H
Gastric
gland
Cl
Chief cells
Parietal cells
Pepsin
(active
enzyme)
Figure 21.8_1
Esophagus
Sphincter
Lumen (cavity)
of stomach
Stomach
Sphincter
Small
intestine
Interior
surface
of the
stomach
Gastrin
Figure 21.8_2
Release of gastric juice
(mucus, HCl, and pepsinogen)
Pits
Epithelium
Interior
surface
of the
stomach
3
Pepsinogen
2
Mucous
cells
HCl
1
H
Gastric
gland
Cl
Chief cells
Parietal cells
Pepsin
(active
enzyme)
21.9 CONNECTION: Digestive ailments include
acid reflux and gastric ulcers
 Acid reflux of chyme in the stomach back into the
esophagus causes the feeling of heartburn.
 Gastroesophageal reflux disease (GERD) results
from frequent and severe acid reflux that harms the
lining of the esophagus.
 Open sores in the lining of the stomach, called
ulcers, may form.
 Bacterial infections (Helicobacter pylori) in the
stomach and duodenum can produce ulcers.
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Figure 21.9
Bacteria
Mucous
layer of
stomach
21.10 The small intestine is the major organ of
chemical digestion and nutrient absorption
 The small intestine is
– named for its smaller diameter,
– about 6 meters long,
– the site of much chemical digestion, and
– where most nutrients are absorbed.
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21.10 The small intestine is the major organ of
chemical digestion and nutrient absorption
 The first 25 cm of the small intestine is the
duodenum, where chyme squirted from the stomach
mixes with digestive juices from the pancreas, liver,
gallbladder, and gland cells in the intestinal wall.
– The pancreas produces pancreatic juice containing a
mixture of digestive enzymes and an alkaline solution rich
in bicarbonate.
– The liver produces bile, which is stored in the gallbladder
until it is needed. Bile breaks up fats into small droplets
that are more susceptible to attack by digestive enzymes.
– The intestinal wall produces digestive enzymes.
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Figure 21.10A
Liver
Bile
Stomach
Gallbladder
Chyme
Intestinal
enzymes
Duodenum of
small intestine
Pancreatic juice
Pancreas
Table 21.10
21.10 The small intestine is the major organ of
chemical digestion and nutrient absorption
 The surface area for absorption in the small intestine
is greatly increased by
– folds of the intestinal lining,
– fingerlike projections called villi, and
– tiny projections of the surface of intestinal cells called
microvilli.
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Figure 21.10B
Lumen of intestine
Nutrient absorption
Vein carrying
blood to the liver
Microvilli
Amino
acids
and
sugars
Epithelial
cells
Muscle
layers
Lumen
Fats
Blood
capillaries
Large
circular folds
Blood
Lymph
vessel
Villi
Lymph
Nutrient
absorption
Villi
Intestinal wall
Fatty
acids
and
glycerol
Epithelial cells of
a villus
Figure 21.10B_1
Vein carrying
blood to the liver
Muscle
layers
Lumen
Large
circular folds
Villi
Nutrient
absorption
Intestinal
wall
21.10 The small intestine is the major organ of
chemical digestion and nutrient absorption
 Nutrients pass into epithelial cells by
– diffusion and
– against concentration gradients.
 Fatty acids and glycerol are
– recombined into fats,
– coated with proteins, and
– transported into lymph vessels.
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21.10 The small intestine is the major organ of
chemical digestion and nutrient absorption
 Other absorbed nutrients such as amino acids and
sugars pass
– out of the intestinal epithelium,
– across the thin walls of the capillaries into blood, and
finally
– to the liver.
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Figure 21.10B_2
Nutrient absorption
Lumen of intestine
Microvilli
Amino
Fatty
acids
acids
and
and
sugars glycerol
Epithelial
cells
Fats
Blood
capillaries
Blood
Lymph
vessel
Lymph
Villi
Epithelial cells of
a villus
21.11 One of the liver’s many functions is
processing nutrient-laden blood from the
intestines
 Blood from the digestive tract drains
– into the hepatic portal vein
– to the liver.
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21.11 One of the liver’s many functions is
processing nutrient-laden blood from the
intestines
 The liver performs many functions. The liver
– converts glucose in blood to glycogen,
– stores glycogen and releases sugars back into the
blood as needed,
– synthesizes many proteins including blood-clotting
proteins and lipoproteins that transport fats and
cholesterol to body cells,
– modifies substances absorbed in the digestive tract into
less toxic forms, and
– produces bile.
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Figure 21.11
Heart
Liver
Hepatic
portal
vein
Intestines
21.12 The large intestine reclaims water and
compacts the feces
 The large intestine, or colon,
– is about 1.5 m long and 5 cm in diameter,
– has a pouch called the cecum near its junction with the
small intestine, which bears a small fingerlike extension,
the appendix,
– contains large populations of E. coli, which produce
important vitamins,
– absorbs these vitamins and water into the bloodstream,
and
– helps form firm feces, which are stored in the rectum until
elimination.
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21.12 The large intestine reclaims water and
compacts the feces
 Diarrhea occurs when too little water is reclaimed
from the contents of the large intestine.
 Constipation occurs when too much water is
reclaimed.
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Figure 21.12
Large
intestine
(colon)
End of
small
intestine
Unabsorbed
food material
Appendix
Cecum
Small
intestine
Rectum
Anus
21.13 EVOLUTION CONNECTION:
Evolutionary adaptations of vertebrate
digestive systems relate to diet
 The length of the digestive tract often correlates
with diet. In general, the alimentary canals relative
to their body size are
– longer in herbivores and omnivores and
– shorter in carnivores.
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Figure 21.13
Stomach
Small intestine
Cecum
Colon
(large
intestine)
Carnivore
Herbivore
Figure 21.13_1
Stomach
Small intestine
Cecum
Colon
(large
intestine)
Carnivore
Herbivore
21.13 EVOLUTION CONNECTION:
Evolutionary adaptations of vertebrate
digestive systems relate to diet
 Many herbivores have specializations of the gut
that promote the growth of cellulose-digesting
bacteria and protists because these animals lack
the enzymes needed to digest cellulose in plants.
 These mutualistic organisms may be housed in
– the cecum, in a coyote or koala,
– the large intestine and the cecum in rabbits and some
rodents, or
– the stomach of ruminants such as cattle, sheep, and
deer.
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NUTRITION
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21.14 Overview: An animal’s diet must satisfy
three needs
 All animals have the same basic nutritional needs.
Animals must obtain
1. fuel to power all body activities,
2. organic molecules to build the animal’s own molecules,
and
3. essential nutrients, or substances the animal cannot
make for itself.
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21.15 Chemical energy powers the body
 Cellular respiration produces the body’s energy
currency, ATP,
– by oxidizing organic molecules digested from food and
– usually using carbohydrates or fats as fuel.
 A gram of fat has more than twice as many calories
as a gram of carbohydrate or protein.
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21.15 Chemical energy powers the body
 The energy content of food is measured in
kilocalories (1 kcal = 1,000 calories).
 Dietary calories are actually kilocalories and are
written as Calories.
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21.15 Chemical energy powers the body
 The rate of energy consumption by an animal is
called its metabolic rate, the sum of all the energyrequiring biochemical reactions over a given interval
of time.
 The basal metabolic rate (BMR) is the energy a
resting animal requires each day.
 The metabolic rate is the BMR plus the energy
needed for physical activity.
 Excess energy is stored as glycogen or fat.
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Table 21.15
21.16 An animal’s diet must supply essential
nutrients
 Essential nutrients cannot be made from any raw
material.
 There are four classes of essential nutrients.
1. Essential fatty acids, such as linoleic acid, are
– used to make phospholipids of cell membranes and
– found in seeds, grains, and vegetables.
2. Essential amino acids are
– used to make proteins and
– found in meats, eggs, and milk.
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21.16 An animal’s diet must supply essential
nutrients
3. Vitamins are organic nutrients discussed in Module
21.17.
4. Minerals are simple inorganic nutrients discussed in
Module 21.17.
 Malnutrition is a chronic deficiency in calories or
one or more essential nutrients. The most common
type of human malnutrition is protein deficiency.
 Undernutrition occurs when
– diets do not supply sufficient chemical energy or
– a person suffers from anorexia nervosa or bulemia.
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Figure 21.16
Essential amino acids
Methionine
Valine
(Histidine)
Threonine
Phenylalanine
Leucine
Corn
Isoleucine
Tryptophan
Lysine
Beans
and other legumes
21.17 A healthy human diet includes 13 vitamins
and many essential minerals
 Essential vitamins and minerals are
– required in minute amounts and
– absolutely essential to good health.
 Vitamins are organic nutrients that may be
– water soluble, such as vitamins B and C, or
– fat soluble, such as vitamins A, D, E, and K.
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Table 21.17A
Table 21.17A_1
Table 21.17A_2
21.17 A healthy human diet includes 13 vitamins
and many essential minerals
 Minerals are simple inorganic nutrients.
– Calcium and phosphorus are required in larger amounts.
– Iron is needed to make hemoglobin.
– Iodine is required to make thyroid hormones.
– Most people ingest more salt than they need.
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Table 21.17B
21.17 A healthy human diet includes 13 vitamins
and many essential minerals
 The Recommended Dietary Allowances (RDAs)
are
– the minimum amounts of nutrients that are needed each
day and
– determined by a national scientific panel.
 Overdoses of vitamins can be harmful.
– In general, excess water-soluble vitamins will be
eliminated in urine.
– However, excess fat-soluble vitamins can accumulate to
toxic levels in body fat.
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21.18 SCIENTIFIC DISCOVERY: Scientists use
observations and experiments to determine
nutritional needs
 Many insights into human nutrition have come from
epidemiology, the study of human health and
diseases within populations.
– The essential need for vitamin C was revealed by the
high incidence of scurvy in sailors on long sea voyages.
– The need for folic acid to prevent neural tube defects in
newborns was revealed by studies of pregnant women of
low socioeconomic status. Since 1998, folic acid has
been added to foods such as bread and cereals sold in
the United States.
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Table 21.18
21.19 CONNECTION: Food labels provide
nutritional information
 Food labels indicate
– serving size,
– calories per serving,
– amounts of selected nutrients per serving and as a
percentage of daily value, and
– recommendations for daily limits of selected nutrients.
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Figure 21.19
Ingredients: whole wheat
flour, water, high fructose corn
syrup, wheat gluten, soybean
or canola oil, molasses, yeast,
salt, cultured whey, vinegar,
soy flour, calcium sulfate
(source of calcium).
21.20 EVOLUTION CONNECTION: The human
health problem of obesity may reflect our
evolutionary past
 Overnourishment is the consumption of more food
energy than is needed for normal metabolism.
 Obesity is the excessive accumulation of fat.
 The World Health Organization recognizes obesity
as a major global health problem.
 In the United States, the percentage of obese
people has doubled to more than 30% in the past
two decades, and another 35% are overweight.
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21.20 EVOLUTION CONNECTION: The human
health problem of obesity may reflect our
evolutionary past
 Weight problems often begin at a young age.
– 15% of children and adolescents in the United States are
obese.
– Another 17% are overweight.
 Obesity leads to
– type 2 diabetes,
– cancer of the colon and breasts, and
– cardiovascular disease.
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21.20 EVOLUTION CONNECTION: The human
health problem of obesity may reflect our
evolutionary past
 Obesity is estimated to be a factor in 300,000
deaths per year in the United States.
 A 15-year study published in 2010 indicates that
obesity now surpasses smoking in its contribution
to disease and the shortening of healthy life spans.
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Figure 21.20A
21.20 EVOLUTION CONNECTION: The human
health problem of obesity may reflect our
evolutionary past
 The complexity of weight control in humans is
evident from studies of the hormone leptin.
 Leptin
– is produced by adipose (fat) cells and
– suppresses appetite.
– Obese children who have an inherited mutant form of
the leptin gene lose weight after leptin treatments.
– However, high levels in otherwise healthy people do not
suppress appetite.
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Figure 21.20B
21.21 CONNECTION: What are the health risks
and benefits of weight loss plans?
 Why are so many people overweight? Is it
– lack of exercise,
– the amount of food,
– the quality of food, or
– a combination of the above?
 The U.S. market for weight loss products and
services has gone from about $60 million a year in
1999 to more than $48 billion a year today.
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21.21 CONNECTION: What are the health risks
and benefits of weight loss plans?
 Weight loss diets may
– help individuals lose weight but
– have health risks leading to malnourishment.
 Some severely obese individuals may be candidates
for weight loss surgery.
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21.21 CONNECTION: What are the health risks
and benefits of weight loss plans?
 Scientific studies of weight loss diets indicate that
the best way to lose weight and keep it off is to
– increase exercise and
– eat a balanced diet with adequate amounts of all
essential nutrients.
© 2012 Pearson Education, Inc.
Figure 21.21
64
62
60
Height
510
58
56
54
52
50
410
100
120
140
160 180 200
Weight (pounds)
220
240 260
21.22 CONNECTION: Diet can influence risk of
cardiovascular disease and cancer
 A healthy diet may reduce the risk of
– cardiovascular disease and
– cancer.
© 2012 Pearson Education, Inc.
21.22 CONNECTION: Diet can influence risk of
cardiovascular disease and cancer
 Two main types of cholesterol occur in the blood.
1. Low-density lipoproteins (LDL) contribute to
– blocked blood vessels and
– higher blood pressure.
2. High-density lipoproteins (HDL) help to reduce blocked
blood vessels.
– Exercise increases HDL levels.
– Smoking decreases HDL levels.
– Trans fats in the diet tend to increase LDL levels.
– Eating mainly unsaturated fats tends to lower LDL levels.
© 2012 Pearson Education, Inc.
21.22 CONNECTION: Diet can influence risk of
cardiovascular disease and cancer
 The relationship between food and health is
complex.
 The American Cancer Society recommends
– regular exercise and
– a diverse diet of healthy foods with an emphasis on plant
sources.
© 2012 Pearson Education, Inc.
Table 21.22
Figure 21.22
You should now be able to
1. Define and distinguish between carnivores,
herbivores, omnivores, suspension feeders,
substrate feeders, fluid feeders, and bulk feeders.
2. Describe the four stages of food processing.
3. Compare the structures and functions of a
gastrovascular cavity and an alimentary canal.
4. Describe the specialized digestive systems of an
earthworm, a grasshopper, and a bird.
© 2012 Pearson Education, Inc.
You should now be able to
5. Describe the main components of the human
alimentary canal and the associated digestive
glands.
6. Describe the functional components of saliva and
the types and functions of the teeth in humans.
7. Explain how swallowing occurs and how food is
directed away from the trachea.
8. Explain how the Heimlich maneuver is performed.
9. Relate the structure of the stomach to its functions.
© 2012 Pearson Education, Inc.
You should now be able to
10. Describe the causes and treatments of heartburn,
GERD, and gastric ulcers.
11. Describe the different types of chemical digestion
that occur in the small intestine.
12. Explain how the liver helps to regulate the
chemical composition of blood.
13. Describe the structures and functions of the colon
and rectum.
14. Compare the digestive tracts of carnivores and
herbivores.
© 2012 Pearson Education, Inc.
You should now be able to
15. Describe the process of ruminant digestion.
16. List the three nutritional needs common to all
animals.
17. Define the basal metabolic rate and explain how
energy is obtained and stored in the body.
18. Describe the four classes of essential nutrients.
19. Define and distinguish between vitamins and
minerals.
20. Describe the types of information found on food
labels.
© 2012 Pearson Education, Inc.
You should now be able to
21. Describe the obesity epidemic in the
United States.
22. Describe the best approach to weight
control.
23. Explain how diet can influence the risks of
cardiovascular disease and cancer.
© 2012 Pearson Education, Inc.
Figure 21.UN02
a.
g.
b.
h.
c.
d.
e.
i.
j.
f.
k.
l.
Figure 21.UN03
A healthy
diet
satisfies three needs
(b)
(a)
(c)
which include
too much
leads to
needed to build
lack
results in
molecules
of cells
(e)
(d)
not enough
leads to
essential
fatty acids
(f)
undernutrition
type of
lack
produces
(g)
most common is
protein
deficiency
have many
functions,
such as
coenzymes,
ion balances,
nerve functions,
bone structure