Download Your Body`s Need for Food

Section 1
Section 1
Focus
Your Body’s Need
for Food
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces students to the role each nutrient plays
in maintaining a healthy body.
Students will also learn about health
disorders related to malnutrition.
Bellringer
Have students list the nutrients
they think they get from eating a
small bag of chips and a bottle of
soda pop. Then have them estimate
the number of calories this “snack”
provides. If possible, bring in samples of each—empty bags and
bottles are okay. Students may be
amazed at how many servings are
in even these “individual sizes” of
food and drink and how that multiplies the calories—and the relatively
poor nutrition. LS Logical Bio 11C
Objectives
Food
Your body uses energy to move, to grow, and even to lie still and
sleep. The amount of energy you need depends on many factors,
including your age, your sex, your rate of growth, and your level of
● Relate the role of
physical activity. Different activities use different amounts of
carbohydrates, proteins,
energy, as shown in Figure 1.
lipids, vitamins, minerals,
You obtain energy from the nutrients in the foods and beverages
and water in maintaining
a healthy body.
4B 11C TAKS 2 you consume. A nutrient is a substance required by the body for
energy, growth, repair, and maintenance. Nutrients in food and
● Describe each of the parts
beverages include carbohydrates, lipids, proteins, vitamins, and
of the USDA food guide
minerals. Each nutrient plays a different role in keeping your body
pyramid.
11C
healthy. Water is essential for life and for maintaining health.
● Name one health disorder
The large molecules in food must be broken down in order to be
associated with high levels
absorbed into the blood and carried to cells throughout the body.
of saturated fats in
The process of breaking down food into molecules the body can use
10A 11C TAKS 2
the diet.
is called digestion . Your cells then break the chemical bonds of the
Key Terms
digested food molecules and use the energy that is released to make
ATP during the process of cellular respiration.
nutrient
The energy available in food is measured by using a unit called a
digestion
calorie. A calorie is the amount of heat energy required to raise the
calorie
temperature of 1 g of water 1°C (1.8°F). The greater the number of
vitamin
mineral
calories in a quantity of food, the more energy the food contains.
Because a calorie represents a very small amount of energy, nutritionists use a unit called the Calorie (with a capital C), which is
equal to 1,000 calories. On food labels and throughout this book,
the word calories represents Calories (1,000 calories).
● Identify five nutrients
found in foods.
9A
Motivate
Identifying
Preconceptions
GENERAL
Have students list the nutrients
necessary for proper body
functioning and food sources
where each nutrient can be found.
(For example: Calcium is necessary
for healthy teeth and bones; calcium
can be found in milk.) Have students revisit the list after reading
Section 1. LS Verbal Bio 11C
Figure 1 Energy required
for common activities. Quiet
activities require just a little
more energy than what it takes
to keep you alive. Strenuous
activities require more energy.
900
Chapter Resource File
pp. 900–901
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 9D
TEKS Bio 4B, 9A, 9D, 10A, 11C
Teacher Edition
TAKS Obj 4 IPC 8A
TEKS Bio 3F, 9A, 11C
TEKS IPC 8A
900
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
Chapter 39 • Digestive and Excretory Systems
Transparencies
TT Bellringer
TT Nutrients in Food
Energy and Building Materials
Each nutrient plays a different role in maintaining a healthy body.
Carbohydrates, proteins, and lipids are involved in providing both
energy and building materials to the cells.
Organizing Information
Make a table to organize
information about food
nutrients and water. Across
the top, write the headings
Carbohydrates, Proteins,
Lipids, Vitamins, Minerals,
and Water. Along the left
side, write Functions, Food
sources, and Additional
comments. Add information
to the table as you read
Section 1.
Carbohydrates
Carbohydrates that exist as single sugar molecules are called monosaccharides or simple carbohydrates. Carbohydrates made of two
or many sugar molecules linked together by chemical bonds are
called complex carbohydrates. Complex carbohydrates must be
digested (broken down) into simple sugars before cells can use their
energy.
Many foods contain carbohydrates, as shown in Figure 2. Glucose,
fructose, and other simple sugars are found in fruits, honey, and
onions. Glucose, a simple sugar, is used by cells for energy, and it
can be directly absorbed into your bloodstream. Table sugar contains sucrose, two simple sugars linked together. Starches are long
chains of sugars found in cereal grains and in vegetables such as
potatoes, beans, and corn. Cellulose is a major component of plant
cell walls and is found in all foods that come from plants. Cellulose,
which is a major part of fiber, does not provide energy because we
do not have the enzymes to digest it. However, cellulose aids in
human digestion by stimulating the walls of the digestive tract to
secrete mucus, which helps pass food through the digestive tract.
If excess carbohydrates are consumed, they are stored as the
carbohydrate glycogen in the liver and in some muscle tissue.
Glycogen can later be broken back down into glucose when the
body needs energy. The remainder of the excess glucose is converted to fat and stored in fatty tissue.
SKILL
BUILDER
Interactive Reading Assign
Chapter 39 of the Holt Biology
Guided Audio CD Program to help
students achieve greater success in
reading the chapter. English Language
Learners
LS Auditory
GENERAL
Have students study Figure 2.
Ask students why it is important
for weight-conscious people to
get a balance of nutrients from
carbohydrate- and protein-rich
foods while limiting fat intake.
(Carbohydrates take less time to
digest, providing quick energy and
satisfying hunger quickly. Proteins
take longer to digest providing energy
and satisfying hunger over a longer
period of time. Both release only 4
Calories per gram. Although fats provide energy and satisfy hunger over a
longer period of time than carbohydrates or proteins do, they contain
more than twice the number of
Calories per gram.) Tell students
that insufficient protein in the diet
can cause a person to eat more
because hunger and energy requirements are not met for as long as
they need to be. However, as
Figure 2 shows, proteins contain
hidden fats and should be consumed in lesser quantities than
carbohydrates. LS Visual Bio 11C
Although most foods contain a mix of nutrients, some foods are richer
than others in a specific nutrient.
Carbohydrate-rich foods
Protein-rich foods
Fat-rich foods
(Carbohydrates contain
4 calories per gram.)
Breads, pasta, grains, cereals,
potatoes, fruits
(Proteins contain 4 calories per
gram.) Fish, eggs, poultry, beef
pork, nuts, legumes, milk,
cheese, tofu
(Fats contain 9 calories per gram.)
Milk, cheese, meats, butter,
olives, avocados, fried foods,
oils, chips
901
Have students identify some of the various chemical
bonds that are broken in the mouth, stomach, and
small intestine by digestive enzymes. For example, the
mouth’s saliva contains amylase which breaks the
chemical bonds of long starch molecules, while
pepsin, which is added in the stomach, begins the
chemical breakdown of protein molecules.
TAKS 4 IPC 8A
READING
Using the Figure
Figure 2 Nutrients in food
IPC Benchmark Fact
Teach
HISTORY
CONNECTION
ATP is the energy currency of all living cells.
Fritz Lipmann isolated ATP from muscle tissue in 1929. In research he began in 1941,
he discovered that ATP and similar compounds shuttle energy around the cell, once
the energy is captured from carbohydrates,
fats, and proteins during cellular respiration.
In 1953 Lipmann shared the Nobel Prize in
physiology or medicine for his discoveries.
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Problem Solving Using Food Labels
to Calculate Percentage of Nutrients
and Calories GENERAL
Bio 3F, 9A
Chapter 39 • Digestive and Excretory Systems
901
Proteins
Teach, continued
continued
Teaching Tip
GENERAL
The digestive products of proteins—amino acids—are normally
used by the body for making other protein molecules, such as
enzymes and antibodies. When more protein is eaten than is needed
by the cells, the amino acids are used for energy or converted to fat.
The body requires 20 different amino acids to function. A child’s or
teen’s body can make 10 of the amino acids from other amino acids.
The other 10, called essential amino acids, must be obtained
directly from food. Most animal products, such as eggs, milk, fish,
poultry, and beef, contain all of the essential amino acids. No single
plant food contains all of the essential amino acids. But eating
certain combinations of two or more plant products can supply all
the essential amino acids. Adults must get eight essential amino
acids from food.
The guidelines for healthy eating are summarized in the USDA
(U.S. Department of Agriculture) food guide pyramid, as shown in
Figure 3. The pyramid lists the daily number of servings needed
from each food group to obtain a variety of nutrients in your diet.
www.scilinks.org
Topic: Foods Grown in
Texas
Keyword: HXX4007
Analyzing Vegetarian Diets
Have students make a list of protein food sources and note whether
the food contains all of the essential amino acids or only some of
them. Then discuss the different
types of vegetarian diets such as
those that omit only red meat,
omit all meat but fish, omit all
meat but include animal products
such as milk and eggs, and omit all
animal products. Have students
create a meal for each of these diet
types and decide how it is difficult
to obtain a nutritionally complete
meal for each diet. LS Logical Bio 11C
Lipids
Lipids, organic compounds that are insoluble in water, are used to
make steroid hormones and cell membranes and to store energy.
Fats are lipids that store energy in plants and animals. Fats are
Figure 3 The USDA food guide pyramid
SKILL
BUILDER
Interpreting Visuals Have
students look at Figure 3 and
Figure 4. Ask students to write a
brief essay explaining how the
percentage of calories from each
dietary nutrient in Figure 4 relates
to the number of servings of each
food group in Figure 3.
(Carbohydrates are mainly found in
the lower tiers of the pyramid, which
corresponds to the high percentage
of calories from carbohydrates.
Proteins are mainly in the second
level and lipids are in the first and
second levels of the pyramid, which
corresponds to lower percentages.
The percentage of calories from proteins may seem small compared to
the percentage from fats since their
number of recommended servings are
similar, but fats carry twice the calories that proteins do.) LS Verbal
TAKS 1 Bio/IPC 2C; Bio 3E
Food groups at the bottom of the pyramid should be eaten in greater amounts than those at the top.
Fats, oils, and sweets
(Use sparingly.)
Milk, yogurt, cheese
(2–3 servings a day)
Vegetables
(3–5 servings
a day)
Fruits
(2–4 servings a day)
Grains
(6–11 servings a day)
Serving Sizes
Milk, yogurt, cheese
• 1 cup of milk
• 1 cup of yogurt
• 1.5 oz of cheese
• 2 oz of processed
cheese
Meat, beans, eggs, nuts
• 1 egg
• 2 tbsp of peanut butter
• 2–3 oz of meat, chicken,
or fish
1
cup of cooked beans
•—
2
Vegetables
• —12 cup of vegetables
• —34 cup of vegetable
juice
• 1 cup of raw, leafy
vegetables
Fruits
• 1 apple, banana,
or orange
• —12 cup of fruit
• —34 cup of fruit
juice
Grains
• 1 slice of bread
1
cup of rice or
•—
2
pasta
1
cup of hot cereal
•—
2
• 1 oz cold cereal
• 1 tortilla
902
Transparencies
TT The USDA Food Guide Pyramid
pp. 902–903
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10B
TEKS Bio 4B, 10B
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 10A
TEKS Bio 3E, 10A, 11A, 11C
TEKS Bio/IPC 2C, 2D
902
Meat, beans, eggs, nuts
(2–3 servings a day)
Chapter 39 • Digestive and Excretory Systems
Trends in Nutrition
Food Guides Around the World Countries
around the world use different graphics to
illustrate their dietary guidelines. Canada uses
a four-banded rainbow, with each color representing one of its food groups and the width
of each band representing the amount recommended. Israel uses a chalice with water at the
top, largest section and grains at the wide base
of the chalice. The Philippines uses a sixpointed star. The United Kingdom, Germany,
and Norway use a wheel or dinner plate
divided into sections that represent the food
groups. The size of each section indicates its
relative importance to the total diet. Bio 3E
stored around organs and act as padding and insulation.
Fats also act as solvents for fat-soluble vitamins.
Although lipids are essential nutrients, too much fat in
the diet is known to harm several body systems. For
example, a diet high in saturated fats is linked to high
blood-cholesterol levels, which in turn may be connected
to cardiovascular diseases. It is recommended that no
more than 30 percent of your day’s calories come from
fats and that most of these fats be unsaturated. Examples
of foods containing fats are shown in Figure 2.
Complex
carbohydrates
(48%)
Protein
(12%)
Unsaturated
fats
(20%)
Simple
carbohydrates
(10%)
Balancing Nutrients and Energy
Demonstration
Regardless of their source, the excess calories you eat will be stored
as either glycogen or body fat, and you will gain weight. If you use
more calories than you take in, additional energy will be obtained
from your body’s energy stores, and you will lose weight. Your diet
and overall activity level determine in part whether you store excess
calories as glycogen or as fat. Figure 4 summarizes what percentage
of the day’s total calories should come from each nutrient.
Obesity is described as being more than 20 percent heavier than
your ideal body weight. Obesity significantly increases an individual’s risk of diabetes, heart disease, osteoarthritis, and many other
disorders. Regular physical activity is important in maintaining
energy balance.
Saturated fats
(10%)
Figure 4 A balanced meal.
The percentages of the day’s
total calories that should come
from each nutrient are shown.
At least half of your day’s
calories should come from
foods high in complex
carbohydrates.
Bring some French fries and a plain
baked potato to class, or show students a picture of these foods. Have
students examine the baked potato
and the French fries carefully, and
ask them to brainstorm differences
between the two foods with regard
to cooking, taste, and nutritional
value. (Unlike the baked potato,
French fries are peeled, sliced, fried in
oil or fat, and salted.) Ask students
how the body is affected by a diet
high in oils, fats, and salt. (Oils and
fats increase caloric intake. Saturated
fats may increase cholesterol levels. A
diet high in salt can cause fluid to be
retained in the body. Over a long
period of time, high salt intake can
contribute to hypertension.) LS Visual
TAKS 1 Bio/IPC 2D; Bio 11C
Obesity and Health TAKS 2
Obesity and Health
TAKS 2 Bio 10A; Bio 11A, 11C
T
he National Center for Health
Statistics reported that by
the year 2000, 31 percent of
adults in the United States were
obese. Medically, obesity is
defined as having a body mass
index (BMI) of 30 or higher. To
calculate your BMI, first multiply
your weight in pounds by 703,
and then divide by your height in
inches squared.
BMI weight in pounds 703
(height in inches) 2
For example, someone who is
6'0" (72 inches) tall and who
weighs 189 pounds has a body
mass index of (189 703) (72
72) 25.6.
Unfortunately, being obese often
has a serious consequence—
diabetes. Late-onset diabetes
affected 14 million Americans in
2000, and 80 percent of those so
affected were obese. Like the rate
of obesity, the rate of late-onset
diabetes is soaring, up 40 percent
in the last 10 years.
Late-onset diabetes is a disorder in which the hormone insulin
is unable to induce the body’s
cells to take up glucose from the
blood. Glucose-starved tissues
consume their own protein, and
waste away. Diabetes is the
leading cause of kidney failure,
blindness, and amputation in
adults.
What is the link between obesity and late-onset diabetes?
Researchers have recently found
that fat cells produce a hormone
called resistin that prompts cells
to resist insulin. Mice given
resistin by researchers lose
much of the ability to respond to
insulin and fail to take up blood
sugar. Drugs that inhibit resistin
restore insulin’s effectiveness.
Researchers hypothesize that
resistin blocks the same glucosetransporting molecules in the
plasma membrane that insulin
activates.
903
Cultural
Awareness
Mediterranean Diets and Heart Disease
The French, Greeks, and other southern
Europeans suffer from less heart disease
than either their northern European neighbors or Americans. The Mediterranean diet
is thought to play a role. The Mediterranean
diet is rich in canola oil, fish, fruits, cereals,
and beans. Even when researchers account
for age, sex, alcohol intake, and lifestyle
differences, eating a Mediterranean diet
appears to reduce the probability of heart
problems.
MISCONCEPTION
ALERT
Athletes, Proteins, and Carbohydrates
A common misconception is that athletes
need to eat more protein to improve their
athletic performance and maintain greater
muscle mass. Actually, a diet rich in complex carbohydrates is much more effective
in sustaining intense muscle activity than a
diet high in protein. Bio 11C
Teacher’s Notes
Be sensitive to those students in
your class that may be overweight. The Centers for Disease
Control and Prevention publishes the Morbidity and
Mortality Weekly Report. If
possible, bring some of these to
class. Have students conduct
research about these topics and
present their research in oral
reports and/or fact sheets.
Discussion
Ask students: Is a person who
is 5’8” and 180 pounds obese?
(No, the person’s BMI is 27.4.)
What hormone does not work
appropriately in diabetes?
(insulin) What hormone causes
cells not to respond to insulin?
(resistin) What type of cell produces resistin? (fat cells) How
does that fact link obesity with
diabetes? (Obese people have
more fat cells, which produce
more resistin, which causes more
insulin to be blocked, which can
lead to diabetes.)
Chapter 39 • Digestive and Excretory Systems
903
Vitamins, Minerals, and Water
Vitamins, minerals, and water are required in our diets. They do
not provide energy, but they contribute to many different functions,
including regulating the reactions that release energy.
Teach, continued
continued
Activity
Analyzing Diet Have students list
the kinds and amounts of each
food they eat in a day. The next
day, have students compare their
number of servings for each food
group to the recommended
amounts given in the food pyramid
shown in Figure 3, as well as the
amount of vitamins and minerals
they are receiving. Ask students to
plan how they can reasonably
change their diet to make it more
balanced. LS Intrapersonal Bio 9A, 11C
Using the Figure
Diagnosing Deficiencies Tell
students to imagine that they are
physicians. Ask them to use information in Table 1 to answer the
following questions: If a child
suffers from frequent internal
infections and has difficulty seeing
in dim light, what problem would
you suspect? (The child likely is suffering from a vitamin A deficiency.)
What foods would you prescribe to
someone who has sore gums and
tends to bruise easily? (fruit, especially citrus fruits) LS Interpersonal
TAKS 1 Bio/IPC 2C; Bio 11C
Group Activity
Vitamin Nutrition Organize students into groups. Give each group
a few boxes of cereal. Ask the
groups to identify the vitamins that
are listed on the cereal labels. Have
students use Table 1 to list the role
of each vitamin and the effects of a
deficiency in that vitamin. LS Visual
Co-op Learning
pp. 904–905
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10A
TEKS Bio 4B, 9A, 10A, 11A, 11C
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 3B, 3C
TAKS Obj 2 Bio 10A
TEKS Bio 9A, 10A, 11A, 11C,
TEKS Bio/IPC 2C, 3B, 3C
904
Vitamins Many different vitamins , organic substances that occur in
many foods in small amounts, are necessary in trace amounts for
the normal metabolic functioning of the body.
Vitamins dissolve in either water or fat, as summarized in Table 1.
Fat-soluble vitamins—vitamins A, D, E, and K—can be stored in
body fat. Excessive amounts of vitamins A and D can be toxic.
Excess water-soluble vitamins—vitamin C and the B vitamins—are
excreted in urine and must be replenished by the diet.
GENERAL
Table 1 Vitamins
Vitamin
Food sources
Role
Effects of deficiency
Most vegetables, nuts, whole
grains, organ meats
Assists in carbohydrate
metabolism, helps nerves and
heart to function properly
Digestive disturbances,
impaired senses
Vitamin B2
(riboflavin)
Fish, poultry,
cheese, yeast,
green vegetables
Needed for healthy skin and
tissue repair, assists in
carbohydrate metabolism
Blurred vision, cataracts,
cracking of skin, lesions of
intestinal lining
Vitamin B3
(niacin)
Whole grains, fish, poultry,
tomatoes, legumes, potatoes
Keeps skin healthy, assists in
carbohydrate metabolism
Mental disorders, diarrhea,
inflamed skin
Vitamin B12
(cobalamin)
Meat, poultry, green
vegetables, milk, dairy products
Needed for formation of red
blood cells
Reduced number of red
blood cells
Citrus fruits, strawberries,
potatoes
Needed for wound healing,
healthy gums and teeth
Swollen and bleeding gums,
loose teeth, slow-healing
wounds
Vitamin A
(retinol)
Butter, eggs, liver, carrots,
green leafy vegetables,
sweet potatoes
Keeps eyes and skin healthy,
needed for strong bones
and teeth
Infections of urinary and
digestive systems, night
blindness
Vitamin D
(cholecalciferol)
Salmon, tuna, fish liver
oils, fortified milk,
cheese
Assists in calcium uptake by
the gut, needed for strong
bones and teeth
Bone deformities in children,
loss of muscle tone
Vitamin E
(tocopherol)
Many foods, especially
wheat and other vegetable
oils, olives, whole grains
Protects cell membranes from
damage by reactive oxygen
compounds (free radicals)
Reduced number of red
blood cells, nerve tissue
damage in infants
Vitamin K
(menadione)
Leafy green vegetables,
liver, cauliflower
Needed for normal blood
clotting
Bleeding caused by prolonged clotting time
Water-soluble
Vitamin B1
(thiamin)
Vitamin C
(ascorbic acid)
Fat-soluble
904
Vitamin Overdoses Some people have
the idea that if a little is good, then a lot must
be better. Unfortunately, this is not the case
with certain vitamins. For example, overdoses
of vitamin A can cause enlargement of the
liver and spleen. Overdoses of vitamin D can
cause kidney damage and calcification of soft
tissues. Although vitamins A and D are both
Chapter 39 • Digestive and Excretory Systems
fat-soluble, making them more difficult for
the body to eliminate, even the water-soluble
vitamins have some negative effects if overused. Massive doses of vitamin C can cause
kidney stones and enhance blood coagulation.
Megadoses of niacin, one of the B vitamins,
can cause liver damage and gout. Bio 11C
Minerals Different minerals are required to maintain a healthy
body. Minerals are naturally occurring inorganic substances that
are used to make certain body structures and substances, for normal nerve and muscle function, and to maintain osmotic balance.
Some minerals are essential for enzyme function. Minerals are not
produced by living organisms. Minerals must be replaced on a daily
basis because they are soluble in water. Teeth and bones require the
minerals calcium and phosphorus. Iron is required for transporting
oxygen. Magnesium, calcium, sodium, potassium, and zinc help
regulate function of the nerves and muscles.
Trace elements, such as those listed in Table 2, are minerals present in the body in small amounts. Humans usually obtain adequate
amounts of the required trace elements directly from the plants they
eat or indirectly from animals that have eaten plants.
Teaching Tip
Calcium and Vitamin D Ask students to identify the predominant
mineral in milk. (calcium) Ask students to identify what nutrient is
added to milk, (vitamin D) and
then ask students why. (Accept any
answers that tie vitamin D and calcium together.) Tell students that
vitamin D is needed for the absorption of calcium from the intestines.
Explain that rickets, a disease that
affects growing bones and is
caused by a vitamin D deficiency,
used to be common in the United
States. In the 1930s the federal
government mandated the enrichment of milk with vitamin D.
Today rickets is virtually unknown
in the United States. LS Verbal
Water You can survive only a few days without water, though you
can live several weeks without food. Water is used by the body as a
medium to transport gases, nutrients, and waste products. Water
also plays a role in regulating body temperature. Two-thirds of the
body’s weight is water.
Table 2 Trace Elements
Trace element
Food sources
Role
Bio/IPC 3C; Bio 11C
Iodine
Seafood, plants grown in
iodine-rich soil, iodized table salt
Synthesis of thyroid
hormones
Cobalt
Leafy vegetables, liver, kidney
Synthesis of vitamin B12
Zinc
Meat, shellfish, dairy products
Synthesis of digestive enzymes, proper
immune function
Molybdenum
Legumes, cereals, milk
Protein synthesis
Manganese
Whole grains, nuts, legumes
Hemoglobin synthesis, urea formation
Selenium
Meat, seafood, cereal grains
Preventing chromosome breakage
Close
Reteaching
Bring in a label from a cereal
box. List the nutrients in a table on
the board or overhead. Have students write the function of each
nutrient. Also, students can review
their lists of nutrients and sources
from the Motivate: Identifying
Preconceptions activity at the start
of this section. Bio 11C
Section 1 Review
Predict four nutrients that would be found in a
9A 11C
serving of green beans.
Compare the functions of carbohydrates and pro-
teins in maintaining a healthy body.
guide pyramid provides.
11C
Evaluate the roles vitamins, minerals, and water
play in maintaining a healthy body.
Critical Thinking Applying Information
Your friend wants to feed her elderly grandmother more food in order to keep her healthy.
Is this a good idea? Explain.
10A 11C
11A 11C
Describe the type of information the USDA food
4B 10A 11C
TAKS Test Prep One of the functions of
lipids in the body is to
9A
A enhance enzyme
C make steroid
activity.
hormones.
B make glycogen.
D make proteins.
905
Answers to Section Review
1. carbohydrates, vitamins, minerals, protein
Bio 9A, 11C
2. Both can be used as a source of energy, but the
body usually uses amino acids from proteins as
building blocks for other proteins. Bio 11A, 11C
3. The food guide recommends the number of
servings of each different type of food group a
person should eat daily to obtain a variety of
nutrients in the diet. Bio 11C
4. Vitamins enhance enzyme activity. Minerals are
necessary for making certain body structures
and substances, for normal nerve and muscle
functions, for maintaining osmotic balance,
and for enzyme function. Water transports
GENERAL
gases, nutrients, and waste and regulates body
temperature. TAKS 2 Bio 4B, 10A; Bio 11C
5. Answers will vary. Students who disagree
might argue that elderly people have a lower
metabolic rate, and thus need fewer calories.
Students who agree might point out that elderly
people tend to eat less and may get sick if they
become malnourished. TAKS 2 Bio 10A; Bio 11C
6.
A. Incorrect. Enzyme activity
is enhanced by vitamins and minerals.
B. Incorrect. Glycogen is made of carbohydrates. C. Correct. Lipids make steroid hormones. D. Incorrect. Proteins are made of
amino acids. Bio 9A
Quiz
GENERAL
1. Which nutrient type should
make up a majority of your
diet? (carbohydrates)
2. Name two nutrients that do not
provide energy but are needed
to proper enzyme function.
(vitamins and minerals)
3. What nutrient could you live
only a few days without? (water)
Alternative
Assessment
GENERAL
Have students describe any fad
diets they may have read about or
tried. Have them analyze these
diets in terms of how they may fail
to provide certain nutrients.
TAKS 1 IPC 3B
Transparencies
TT Trace Elements
Chapter 39 • Digestive and Excretory Systems
905
Section 2
Section 2
Digestion
Focus
Breaking Down Food
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces
students to the functions of the
digestive organs and how food is
broken down and absorbed.
Bellringer
Tell students to write down in correct sequence all the organs (at
least 5) through which their food
passes as it travels along the digestive tract. Then have them try to
list any glands or organs (3) that
are found along the digestive tract
that help digestion but through
which food does not pass.
TAKS 2 Bio 10A
Motivate
Imagine you just ate your favorite meal. What happens to that
● Relate the four major funcfood? Before your body can use the nutrients in the food you eat,
tions of the digestive system
to the processing of food.
10A the large food molecules must be broken down physically and
● Summarize the path of TAKS 2 chemically. The process of breaking down food into molecules the
body can use is called digestion. The digestive system is the body
food through the digestive
system that is involved in the taking in and processing of food for
system and the major
digestive processes that
use by your body cells. The digestive system takes in food, breaks it
occur in the mouth, stomdown into molecules small enough for the body to absorb, and gets
ach, small intestine, and
rid of undigested molecules and waste.
large intestine.
10A TAKS 2
As shown in Figure 5, the digestive system is made up of a long,
● Describe how nutrients are
winding tube, the digestive tract, that begins at the mouth and
absorbed from the digestive
winds through the body to the anus. Food travels more than 8 m
system into the bloodstream
(26 ft) through your digestive tract. The digestive tract includes the
or lymphatic system.
10A
TAKS 2 mouth, pharynx, esophagus, stomach, small intestine, large intes-
● Identify the role of the
pancreas and liver in
digestion.
10A TAKS 2
tine, and rectum. Although the liver and pancreas (PAN kree uhs)
are not part of the digestive tract, they deliver secretions into the
digestive tract through ducts (tubes).
Key Terms
amylase
esophagus
pepsin
lipase
villus
colon
Digestive System
Demonstration
Esophagus
Salivary glands
Hang an 8 m (26 ft) piece of
clothesline or rope at the front of
the room. Explain to students that
it represents the approximate
length of the digestive system. Use
clothespins and markers to label
the clothesline as follows:
PART
LENGTH
AVERAGE TIME
FOOD SPENDS HERE
Mouth
8 cm (3 in.)
5–30 s
Pharynx/
25 cm (10 in.) 5–10 s
esophagus
Stomach
Small
intestine
15 cm (6 in.)
4–6 m
(13–20 ft)
2–6 h
3–6 h
Large
intestine
1.2 m (4 ft)
up to 2 d
Pharynx
Mouth
Liver
Stomach
Duodenum
Gallbladder
Pancreas
Small intestine
Large intestine
Rectum
Figure 5 Processing food.
The digestive system breaks
down food into individual
nutrient molecules that can be
absorbed into the bloodstream.
Anus
906
LS Visual TAKS 1 Bio/IPC 2C
Chapter Resource File
pp. 906–907
Student Edition
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TEKS Bio 10A,10B
Teacher Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 10A
TEKS Bio 9C, 10A, 11D
TEKS Bio/IPC 2C
906
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Quick Lab
Chapter 39 • Digestive and Excretory Systems
Transparencies
TT Bellringer
TT Digestive System
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
Starting Digestion
The digestion of food begins as soon as the food is
ingested. The teeth rip and chew food into shreds, and the
tongue mixes the pieces with a watery solution called
saliva. Taste buds on the tongue are sensitive to certain
chemicals in the food. Saliva is secreted into the mouth by
three pairs of salivary glands, shown in Figure 5. Saliva
moistens and lubricates the food so that it can be swallowed more easily.
Saliva also contains amylases (AM uh lay sehs),
enzymes that begin the breakdown of carbohydrates
such as starch, into monosaccharides (single sugars).
The mechanical action of chewing and the chemical
action of amylase are both part of the digestion of carbohydrates in the mouth.
Notice in Figure 6 that the structure of our teeth helps
in the breakdown of food. The two front teeth, the incisors, cut
food. The cuspids, or canines, shred food. The back teeth, the
molars, crush and grind food.
After passing through the region in the back of the throat called
the pharynx (FAIR ihnks), the food triggers a swallowing response.
The action of swallowing moves the epiglottis (a flap of cartilage)
over the opening of the trachea—the tube that leads to the lungs.
This action prevents food from entering the trachea and eventually
the lungs. Instead, food enters the esophagus (ih SAHF uh guhs).
Incisors
Cuspid
(canine)
Bicuspids
(premolars)
Molars
SKILL
Uvula
Opening of duct
of salivary gland
Figure 6 Teeth and
digestion. Canine and incisor
teeth are used for cutting and
tearing food. The molars are
used to grind food.
The esophagus is a long tube that connects the mouth to the
stomach. No digestion takes place in the esophagus. Its role is to act
as a kind of descending elevator, moving food down to the stomach.
The esophagus is about 25 cm (10 in.) long. The lower two-thirds
of the esophagus is wrapped in sheets of smooth muscle. Food
does not simply fall into the stomach; it is pushed down, as shown
in Figure 7. Successive rhythmic waves of smooth muscle contraction in the esophagus, called peristaltic (pehr uh STAHL tihk)
contractions, or peristalsis, move the food toward the stomach.
Peristalsis can be thought of as waves moving through the muscle
with the area where the wave is passing causing the muscle to
narrow. It takes about 5 to 10 seconds for food to pass down the
esophagus and into the stomach.
Esophagus
Wave of
contraction
Food
Stomach
Figure 7 Peristalsis
moves food. Food is pushed
down the esophagus and
toward the stomach by waves
of smooth muscle contractions
in the wall of the esophagus.
907
INCLUSION
• Learning Disability
• Attention Deficit Disorder
Using Figure 5, have students write each body
part responsible for digestion on a note card.
Students will then write the function of each
body part in the digestive process. The cards
should be numbered on the back to indicate
the order the food is processed through the
body. The students may study the digestive
process by attempting to order the note cards
by body part and function. Students may also
use the note cards to present the digestive
process to the class, small groups, or pairs.
REAL WORLD
CONNECTION
Halitosis (bad breath) results when decomposing food particles accumulate in the mouth,
allowing bacteria to flourish. Saliva aids in
washing away the food particles. Therefore,
people who suffer from any disease that
inhibits saliva secretion usually have problems
with dental caries and bad breath, as well as
difficulty talking, swallowing, and eating.
Bio 11D
BUILDER
Reading Organizer Have students
create a reading organizer that lists
the organs of the digestive system,
their functions, and associated
enzymes. If students are confused
about any of these, encourage them
to use outside sources of information such as an encyclopedia.
LS Verbal TAKS 2 Bio 10A
Activity
GENERAL
Salivation Organize the class
into groups. Give each group two
test tubes with stoppers, four
saltine crackers, water, a straw or
stirring rod, and an iodine solution. In one test tube stir two
crushed crackers with water, then
add a few drops of iodine and
invert to mix. The solution in the
test tube will turn blue-black, indicating the presence of starch. Have
a volunteer chew up the other two
crackers without swallowing, and
spit them into the second test tube.
Add some water, stir, and then add
a few drops of iodine, and invert to
mix. The solution starts out blueblack, but as salivary amylase
enzymes start to break the starch
down into sugars, the color will
fade to purple and eventually disappear. LS Kinesthetic Co-op Learning
The Stomach
Strategies
READING
Tonsil
The Esophagus
Food exits the esophagus and enters the stomach through a muscular valve called a sphincter (SFIHNGK tuhr). The sphincter prevents
acid-soaked food in the stomach from making its way back into the
esophagus. The stomach is a saclike organ located just beneath the
diaphragm. Besides temporarily storing food, the stomach, shown
in Figure 8 on the next page, also mechanically breaks down food
and chemically unravels and breaks down proteins.
Teach
Bio 9C
Demonstration
Cut the legs off of an old pair of
pantyhose. Place a tennis ball in
the toe and tie off the other end.
You can show the process of peristalsis by rhythmically squeezing
the tennis ball from one end to the
other. Remind students that this
happens automatically after swallowing, and several “swallows”
(boli) can travel down the esophagus at one time.
English Language
Learners
LS Visual
TAKS 2 Bio 10A
Transparencies
TT Teeth and Digestion
Chapter 39 • Digestive and Excretory Systems
907
Teach, continued
continued
Figure 8 The stomach and
accessory digestive organs.
Many organs are involved in
the complete breakdown of
nutrients.
Liver
Eating Disorders
TAKS 2 Bio 10A, 10B, (grade 11 only); Bio 11B, 11C
Teacher’s Notes
Eating disorders are a sensitive
issue with teens.You may have a
student with an eating disorder
that has not yet been diagnosed.
Be sure to address these issues
openly and without judgment.
Be prepared to direct students
to a person or place where they
can seek help.
Discussion
Ask students: What is the difference between anorexia nervosa and bulimia nervosa?
(Anorexics do not eat sufficient
nutrients. Bulimics eat, but purge
their digestive system through
vomiting or the use of laxatives.)
Why does weight stay nearly
constant for bulimics? (Because
food is actually ingested, some
nutrients are absorbed. If laxatives are the method of purging,
the food has the chance to travel
throughout the whole digestive
system, just at a more rapid pace.)
Should advertisers seek models
with fuller figures to reduce the
incidence of eating disorders?
(Answers will vary. For example:
Yes, people might feel better
about themselves with less cultural emphasis on being thin.)
Transparencies
TT The Stomach and Accessory
Digestive Organs
Gallbladder
Duodenum
(small intestine)
Pancreas
When food enters the stomach, gastric juice is secreted by the cells
that line the inside of the stomach. Gastric juice is a combination of
hydrochloric (HIE droh klawr ihk) acid (HCl) and pepsin. The acid
breaks the bonds in proteins and unfolds large protein chains into
single protein strands. Pepsin , a digestive enzyme
secreted by the stomach, cuts the single protein strands
into smaller chains of amino acids. Pepsin is effective
only in an acidic environment.
The stomach mixes its contents by using peristaltic
waves. Swallowed food can spend from 2 to 6 hours in the
stomach. Your stomach secretes about 2 L (2.11 qt) of HCl
Stomach
every day, which creates a solution about 3 million times
more acidic than your bloodstream. The hormone gastrin
regulates the synthesis of HCl. Thus, HCl is made only
when the pH in the stomach is higher than about 1.5.
A coating of mucus protects the lining of the stomach
from gastric acid. Bicarbonate in the stomach helps neutralize digestive fluids. Blood circulation in the stomach
lining also helps protect stomach tissues.
Eating Disorders TAKS 2
M
illions of teens are on
weight-reducing diets. Although maintaining a healthy
body weight is important, obsessive dieting can lead to eating
disorders. Eating disorders can
disrupt lives and sometimes
even result in death.
Starving Oneself
Anorexia nervosa is an eating
disorder in which people starve
themselves. Anorexics have an
irrational fear of becoming fat
and see themselves as much
heavier than they really are. They
shun food and may exercise for
hours every day in an attempt to
lose weight.
Female anorexics may never
mature sexually or may stop
menstruating because they lose
too much body fat, causing normal levels of sex hormones to
fall. Their body temperature and
pulse rate become abnormally
low; their hair becomes thin and
dry; and their resistance to infection drops.
Bingeing and Purging
Patients with bulimia engage in
frequent episodes of bingeing
(eating a large amount of food in
a short time). After a binge,
bulimics may purge by selfinduced vomiting or by using
laxatives. Therefore, their weight
stays fairly constant. Unlike
anorexic patients, bulimics often
recognize that their behavior is
abnormal and often feel guilty,
depressed, and helpless.
The frequent purging removes
salts from the body, which can
eventually lead to muscle weakness, heart failure, and kidney
disease. The vomiting gradually
destroys tooth enamel
results in unhealthy gums.
and
Help for People with
Eating Disorders
Little is known about what
causes anorexia nervosa and
bulimia. Many people believe
that Western society’s emphasis
on thinness in women is largely
to blame. However, recent research suggests that genetic
factors might also be involved.
Both eating disorders can be
managed with a combination of
medical treatment, counseling,
and family support.
908
Career
pp. 908–909
Student Edition
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TEKS Bio 10A, 10B
Teacher Edition
TAKS Obj 1 Bio/IPC 2D
TAKS Obj 2 Bio 4B, 10A, 10B
TAKS Obj 4 IPC 9B
TEKS Bio 3D, 4B, 10A, 10B, 11B, 11C
TEKS Bio/IPC 2D
TEKS IPC 9B, 9E
908
Counselor Counselors give clients moral
support and an opportunity to discuss personal or work-related problems. Counselors
may be professional social workers, psychologists, or community workers interested in
helping people. Employers include treatment
centers, hospital-based programs, or
government agencies. Each state has its own
Chapter 39 • Digestive and Excretory Systems
requirements for counselors. In some states
counselors must earn a certificate. Have students interview a counselor that works with
persons with eating disorders such as
anorexia or bulimia. Ask each student to
compile a list of 10 questions and answers
from the interview. Bio 3D
The Small Intestine
Food passes from the stomach into the small intestine when a
sphincter between the two organs opens. The small intestine is a
coiled tubular organ about 6 m (19.8 ft) long that is continuous with
the stomach and that functions mainly in the digestion and absorption of nutrients. The word small refers to the small diameter of the
small intestine as compared with the diameter of the large intestine—not to its length. Peristalsis mixes the food, which remains in
the small intestine for about 3 to 6 hours.
The first part of the small intestine, the duodenum (doo oh DEE
nuhm), receives secretions from the pancreas, liver, and gallbladder,
as shown in Figure 8. Cells that line the small intestine and the pancreas secrete digestive enzymes involved in completing the digestion of carbohydrates into monosaccharides, proteins into amino
acids, and lipids into fatty acids and glycerol.
Before fats can be digested by pancreatic enzymes called
lipases (LIE pays uhs), the fats must first be treated with bile, a
greenish fluid produced by the liver. Bile breaks up fat globules
into tiny fat droplets, a process called emulsification (ee MUHL
suh fih kay shuhn). The gallbladder, a green muscular sac attached
to the liver, concentrates and stores bile until it is needed in the
small intestine.
Most absorption (passage of nutrients to the blood or lymph)
occurs in the small intestine. The lining of the small intestine is covered with fine fingerlike projections called villi (singular form, villus).
Villi, shown in Figure 9, are too small to see with the naked eye. In
turn, the cells covering each villus have projections on their outer surface called microvilli. The villi and microvilli greatly increase the area
available for absorption of nutrients. Sugars and amino acids enter
capillaries in the villi and are carried in the blood to the liver for further metabolism. Fatty acids and glycerol enter lymphatic vessels in
the villi and eventually enter the bloodstream.
Demonstration
You will need two beakers of tap
water, a sugar cube, a crushed
sugar cube, and two stirring rods.
At the same time, drop the sugar
cube and crushed sugar into two
separate beakers. Stir rapidly and
observe which sugar dissolves first.
Ask students for an explanation.
(The crushed sugar cube has more
surface area, so it dissolves faster.)
Relate this principle to the increase
of surface area in the intestine
brought about by the villi and
microvilli. LS Verbal
TAKS 1 Bio/IPC 2D; IPC 9E
Using the Figure
Have students look at the structure
of the small intestine in Figure 9.
Use two pieces of yarn to show
how surface area increases with the
number of villi. (This can be
demonstrated on the overhead.)
Make a circle with a short piece of
yarn. Use a much longer piece of
yarn to simulate villi inside of the
shorter piece. When you compare
the lengths of the yarn, it becomes
clear that villi (and microvilli) significantly increase surface area.
Figure 9 Villi in the small intestine
Inside each villus are capillaries and lymphatic vessels where
nutrients enter the bloodstream.
Microvilli
GENERAL
Capillaries
LS Visual TAKS 2 Bio 4B, 10A
Activity
Villus
Lymphatic
vessels
Small intestine
909
IPC Benchmark Fact
Explain to students that acids are substances that
react with water to form hydronium ions, H3O. Since
gastric juice contains hydrochloric acid, a strong
acid, its pH is significantly below 7, it would have a
sour taste, and it is corrosive.
TAKS 4 IPC 9B (grade 11 only)
MISCONCEPTION
ALERT
Digestion and Absorption Although
some digestion occurs in the mouth and
stomach, most chemical digestion occurs in
the small intestine. All nutrient absorption
into the bloodstream occurs in the small
intestine, not the stomach. However, both
alcohol and aspirin are absorbed from the
stomach directly into the bloodstream,
accounting for their fast-acting effects on
the body. TAKS 2 Bio 4B
Viewing Digestive Organs
Provide students with a compound
light microscope and prepared
slides of several different digestive
organs. You might want to include
cross sections of tissue from the
stomach, the small intestine, the
liver, and the pancreas. Have students observe the specimens,
compare the different cross sections, and make sketches of them.
Encourage students to link the
structures they observe with the
functions of each organ. For example, students may relate the
structure of villi to the function
of nutrient absorption of the small
intestine.
English Language
LS Visual
Learners
TAKS 2 Bio 4B, 10A, 10B, (grade 11 only)
Transparencies
TT Villi in the Small Intestine
Chapter 39 • Digestive and Excretory Systems
909
The Large Intestine
All components of food that are not for energy production (for
example, cellulose) are considered wastes. The wastes move into
the large intestine. The large intestine, or colon (KOH luhn), shown
in Figure 10, is much shorter than the small intestine. However, the
diameter of the large intestine is about three times larger than the
diameter of the small intestine. The colon is not coiled like the
small intestine. Instead, it is composed of three relatively straight
segments. No digestion takes place in the colon.
The volume of material that flows through the digestive system
each day is large—about 10 L of food, drink, and secretions enter
the small intestine. But the amount of material that leaves the body
as waste is small. This is because almost all of the fluids and solids
(about 90–95 percent) are absorbed during their passage through
the small intestine. Mostly mineral ions and water are absorbed
through the wall of the large intestine.
Most of the colon’s contents are dead cells, mucus, digestive secretions, bacteria, and yeast. A thriving colony of bacteria live in the
human colon. These microbes synthesize many compounds that
your body needs and cannot get easily from the food you eat, including vitamin K and several B vitamins. In addition, bacteria aid in
transforming and compacting the undigested materials into the
final waste product, feces.
The final segment of the large intestine is the rectum. Solids in
the colon pass into the rectum as a result of peristalsis in the large
intestine. From the rectum, the solid feces are eliminated from the
body through the anus. Undigested material passes through the
large intestine and is expelled through the anus in 12 to 24 hours.
Balancing water absorption in the intestine is important. Wastes
rushed through the large intestine before the remaining water is
absorbed result in diarrhea (watery feces). When food remains in
the colon for long periods of time, which causes much water to be
absorbed, constipation (hard feces) results. Hard feces are difficult
to pass.
Teach, continued
continued
Teaching Tip
GENERAL
Enzymes and Nutrients Help
students remember enzymes and
the nutrients they break down
straight by making a Graphic
Organizer similar to the one at the
bottom of this page. Remind students that the suffix –ase means
“to break apart.” LS Visual Bio 9C
SKILL
BUILDER
Graphing Provide students with the
following average lengths of the
digestive organs: esophagus—25 cm,
stomach—25 cm, small intestine—
6 m, large intestine—1.5 m. Then
have students prepare a bar graph
or another graphic to compare the
average lengths of each digestive
organ listed. You might also want
to have students measure and
label the lengths using addingmachine tape or a skein of yarn
and compare them to the illustration of the digestive system in
this chapter.
English Language
LS Logical
Figure 10 X ray of the
large intestine (colon).
Stretched out, the large
intestine, which appears
orange, is about 1 m
(3.3 ft) long.
Learners
The Liver’s Role in Digestion
The human liver, shown in Figure 8, is about the size of a football and
weighs more than 1.4 kg (3.1 lb). It presses upward against the
diaphragm and occupies the upper right side of the abdominal cavity.
The liver plays several roles in digestion. The liver secretes bile,
which aids in the emulsification of fats. Bile also promotes the
absorption of fatty acids and the fat-soluble vitamins A, D, E, and
K. Bile pigments (the products of hemoglobin breakdown) give bile
a yellowish green color. Jaundice, a condition in which the eyes,
skin, and urine become abnormally yellow, is a result of increased
amounts of bile pigments in the blood. Jaundice often occurs as a
result of hepatitis, an inflammation of the liver.
IPC Benchmark
Review
To prepare students for the TAKS and
accompany the discussion of digestion,
have students Chemical Changes,
TAKS 4 IPC 8A on p. 1052 of the IPC
Refresher in the Texas Assessment
Appendix of this book.
910
Graphic Organizer
pp. 910–911
Student Edition
TAKS Obj 1 Bio/IPC 2A
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TEKS Bio 9C, 10A, 10B, 11C
TEKS Bio/IPC 2A, 2C
Teacher Edition
TAKS Obj 1 Bio/IPC 2A, 2C
TAKS Obj 2 Bio 10A, 10B
TEKS Bio 3E, 9A, 9C, 10A, 10B, 11C
TEKS Bio/IPC 2A, 2C
910
Use this graphic organizer with
Teaching Tip on this page.
Chapter 39 • Digestive and Excretory Systems
Digestive enzymes
amylase
pepsin
lipases
starches
into sugars
large proteins into
smaller proteins
fats into fatty acids
and glycerol
mouth
stomach
intestine
The Liver’s Role in Metabolism
Digested food molecules in the bloodstream are transported to the
liver. The liver stabilizes blood sugar by converting extra sugar to
glycogen for storage. The liver then breaks down the glycogen when
it is needed for energy. The liver also modifies amino acids. Fatsoluble vitamins and iron are stored in the liver. The liver monitors
the production of cholesterol and detoxifies poisons. If the liver is
unable to change a substance’s harmful form, it stores it. In this
way, toxins, including heavy metals and pesticides, accumulate in
the liver.
The liver can also be damaged by viral infections, chronic drug
or alcohol use, and traumatic injury. As a result of any of these,
healthy liver cells are destroyed and replaced by scar tissue. The
scarring of the liver is called cirrhosis (suh ROH sihs).
www.scilinks.org
Topic: Poisons
Keyword: HX4142
The Function
of Bile
TAKS 1 Bio/IPC 2A, 2C; Bio 9A, 9C
Skills Acquired
Relating concepts,
inferring conclusions,
comparing
Teacher’s Notes
Detergents are made of molecules with hydrophobic and
hydrophilic ends. The hydrophobic ends surround the
grease and pull it toward the
water, breaking up the grease.
Modeling the Function of Bile
You can use a detergent and cooking oil to simulate the
effect bile has on breaking up (emulsifying) fats as part
2A 2C 9C TAKS 1
of digestion.
Answers to Analysis
1. The oil spreads away from the
water and the oil droplets
associate.
2. The oil was broken up.
3. Detergent breaks up oil like
bile breaks up fat.
4. They both increase surface
area. For the bile this speeds
up the breakdown of foods.
Materials
two 250 mL beakers, water, cooking oil, dish
detergent, stirring rod, graduated cylinder
Procedure
Analysis
1. Label one beaker A and one
beaker B. Fill each beaker
halfway with water.
1. Describe how oil reacts
with the water.
2. Add 10 mL of the cooking oil
to each beaker.
2. Describe what happened to
the oil when the dish detergent was added.
3. While stirring, slowly add
10 drops of dish detergent to
beaker B only.
3. Compare the effect of dish
detergent on oil with the
effect of bile on fats.
4. Critical Thinking
Inferring Conclusions
Do the detergents and bile
increase or decrease the
surface area of oil? In the
case of bile, how does this
help the digestive process?
Close
Reteaching
Section 2 Review
Summarize the path a piece of cheese pizza
would follow through the digestive system.
Critical Thinking Applying Information
10A
Relate the role of the mouth, stomach, small
intestine, and large intestine in the digestion of
10A
a piece of cheese pizza.
Locate the area of the digestive system where
nutrients are absorbed into the bloodstream.
10A 10B
State how the liver and pancreas are involved
10A 10B
in digestion.
A person has a small intestine that has villi but a
reduced number of microvilli. Would you expect
this person to be underweight or overweight?
10A 11C
Explain.
TAKS Test Prep The enzyme pepsin is
involved in the digestion of
9C
A starches.
C monosaccharides.
B fats.
D proteins.
1. mouth, pharynx, esophagus, stomach, small
intestine, large intestine, rectum TAKS 2 Bio 10A
2. mouth—mechanical and chemical digestion of
carbohydrates in the pizza; stomach—
mechanical digestion and chemical digestion
of the proteins in the pizza; small intestine—
chemical digestion of the carbohydrates,
proteins, and lipids in the pizza, and absorption; large intestine—reabsorption of water
and compaction of waste TAKS 2 Bio 10A
3. small intestine TAKS 2 Bio 10A, 10B (grade 11 only)
4. Both the pancreas and the liver provide digestive enzymes. The liver also provides bile to
TAKS 2 Bio 10A
Quiz
GENERAL
1. What muscular movements
911
Answers to Section Review
Have students make flashcards
with a digestive organ named on
one side and its function on the
other. Have students arrange them
in order from mouth to anus and
identify each as part of the digestive tract or as accessory organs.
cause food to be passed through
the digestive tract? (peristalsis)
2. What two organs are important
in digestion but are not a part of
the digestive tract? (liver and
pancreas) TAKS 2 Bio 10A
the small intestine, maintains blood sugar levels, modifies amino acids, stores vitamins and
minerals, regulates cholesterol production,
and detoxifies poisons. TAKS 2 Bio 10A, 10B (grade 11 only)
5. The person would be underweight—more
Alternative
food will pass out as waste. The person will
GENERAL
Assessment
probably also be malnourished.
Refer
to
the
clothesline
from
the
TAKS 2 Bio 10A; Bio 11C
Demonstration on the first page of
6.
A. Incorrect. Starches are
this section. Remove the labels,
digested by amylase enzymes. B. Incorrect.
and have students identify the parts
Fats are digested by lipases. C. Incorrect.
of the digestive system and what
Monosaccharides are already broken down
happens to food in each of those
into absorbable units. D. Correct. Proteins are
parts.
digested by the enzyme pepsin. Bio 9C
Chapter 39 • Digestive and Excretory Systems
911
Section 3
Section 3
Excretion
Teach, continued
continued
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces
students to how metabolic wastes
are removed from the blood and
excreted from the body. Students
will also learn about the causes and
consequences of kidney damage.
Bellringer
Tell students that the blood must
be cleaned regularly. Then ask students to speculate, without looking
in the textbook, how the body
cleans blood. Once students have
written a description of the cleaning process, allow them to check
their answers against their textbook. LS Verbal
Motivate
Activity
● Identify major wastes
produced by humans and
the organ or tissue where
they are eliminated from
the body.
10A TAKS 2
● Relate the role of nephrons
to the filtering of blood in the
kidneys.
10A TAKS 2
● Summarize how nephrons
form urine.
10A TAKS 2
● Describe the path of urine
through the human urinary
system.
10A TAKS 2
● Predict how kidney
damage might affect
homeostasis and
threaten life.
10A 10B 11A
Key Terms
excretion
urea
nephron
urine
ureter
urinary bladder
urethra
Water and Metabolic Wastes
Cleaning up, though not always a pleasant chore, must be done to
maintain a healthy living environment. In the same way, our bodies
must get rid of wastes to maintain health. Food residues are eliminated from the body in the form of feces. Other wastes produced as a
result of metabolic reactions that occur in the body must also be
eliminated. For example, water and carbon dioxide are produced during cellular respiration. During the metabolism of proteins and
nucleic acids, a toxic nitrogen-containing waste, ammonia, is formed.
The body must remove wastes. It must also maintain osmotic
balance and stable pH by either excreting or conserving salts and
water. Excretion is the process that rids the body of toxic chemicals,
excess water, salts, and carbon dioxide while maintaining osmotic
and pH balance.
The organs involved in excretion are shown in Figure 11. Carbon
dioxide (and some water vapor) is transported to your lungs by the
circulatory system and excreted every time you exhale. Excess
water is excreted through the skin in sweat and through the kidneys
in urine. In the liver, ammonia is converted to a much less toxic
nitrogen waste called urea (yoo REE uh), which is then carried by
the bloodstream to the kidneys, where it is removed from the blood.
Organs of Excretion
GENERAL
Observing Sweat Have a volunteer put his or her hand in a clear
plastic bag and tape it loosely to
the wrist. Study the bag after 10 or
15 minutes. What do students
observe? (tiny droplets of moisture
on the bag) Explain that sweat is
constantly evaporating from the
skin. If time permits, have the student rub some of their own sweat
onto individual slides and observe
salt crystals. Red dye will make the
crystals easier to see. LS Kinesthetic
TAKS 2 Bio 4B, 10A; Bio 11B
Lungs
Figure 11 Organs of
excretion. The lungs, the kidneys, and the skin all function
as excretory organs. The main
excretory products are carbon
dioxide, water, and nitrogen
wastes (urea).
1
The lungs excrete carbon
dioxide and water vapor
in exhaled air.
Kidneys
The kidneys excrete nitro2 gen
wastes, salts, water,
and other substances in urine.
Skin
The skin excretes water,
3 salts,
small amounts of
nitrogen wastes, and other
substances in sweat.
912
Chapter Resource File
pp. 912–913
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TEKS Bio 4B, 10A, 10B, 11A
Teacher Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 4B, 10A, 10B
TEKS Bio 4B, 10A, 10B, 11B, 11C
TEKS Bio/IPC 2C
912
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
Transparencies
TT Bellringer
TT Organs of Excretion
Chapter 39 • Digestive and Excretory Systems
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Supplemental Reading Guide
Microbe Hunters
The Kidneys
The kidneys are extremely important organs because of their role in
regulating the amount of water and salts contained in blood
plasma. The kidneys are a pair of bean-shaped, reddish brown
organs located in the lower back. Each kidney is the size of a small
fist. The body has to maintain a certain level of salts in the blood
plasma and in the fluid surrounding cells, or serious harm to the
body’s cells and organ systems can result.
Blood Filters
The word glomerulus is
from the French gloméruli,
meaning “a compact cluster.” Knowing this makes it
easier to remember that the
glomerulus is a compact
cluster of capillaries within
a nephron.
Each kidney is a complex organ composed of roughly 1 million
microscopic blood-filtering units called nephrons (NEHF rahns), as
shown in Figure 12. Nephrons are tiny tubes in the kidneys. One end
of a nephron is a cup-shaped capsule surrounded by a tight ball of
capillaries that filters wastes from the blood, retains useful molecules, and produces urine. Three different phases occur as the blood
flows through a nephron: filtration, reabsorption and secretion.
Kidneys Ask students to point to
the location of their kidneys. They
are located in the middle of the
back, near the spinal cord, just
under the last ribs. English Language
Review how passive transport
processes (blood pressure) account
for the filtration of blood in the
nephron. Have students locate
where filtration occurs in the
nephron shown in Figure 12. (in
Bowman’s capsule) Review how
active transport processes account
for the reabsorption of materials as
blood passes through the nephron
and both passive and active
processes are involved in secretion.
Have students locate where reabsorption and secretion occur in the
nephron shown in the figure. (the
renal tubules) Point out that
because of active transport, the
kidney has an extremely high
energy requirement, even higher
than that of the heart, when comparing their relative weights.
The kidneys filter out toxins, urea, water, and mineral salts from the blood as fluid
passes through the microscopic filtering units called nephrons.
Glomerulus
Renal
tubule
Bowman's
capsule
LS Visual
Blood
vessels
TAKS 2 Bio 4B, 10B (grade 11 only)
Collecting
duct
SKILL
To renal
vein
Filtration
Reabsorption
Ureter
Loop
To ureter
(urine)
Secretion
913
REAL WORLD
CONNECTION
Exercise and sweating deplete the body of
many necessary materials. Sports drinks are
beverages that consist of water with about a
6 percent concentration of carbohydrates and
electrolytes (salts, particularly sodium). Sports
drinks are thought to improve performance
in athletes who are exercising for more than
Learners
Using the Figure
Figure 12 Kidneys and nephrons
Renal vein
(filtered
blood)
Teaching Tip
LS Kinesthetic
Filtration Filtration begins at the cup-shaped capsule called
Bowman’s capsule. Within each Bowman’s capsule an arteriole
enters and splits into a fine network of capillaries called a glomerulus (gloh MEHR yoo luhs). The glomerulus acts as a filtration
device. The blood pressure inside the capillaries forces a fluid composed of water, salt, glucose, amino acids, and urea into the hollow
interior of the Bowman’s capsule. This fluid is called filtrate. Blood
cells, proteins, and other molecules too large to cross the membrane remain in the blood.
Renal artery
(blood with wastes)
Teach
90 minutes because the carbohydrates maintain
blood sugar (glucose) levels during exercise
when muscle glycogen (stored glucose) levels
start to run critically low. The electrolytes in
the sports drink are supposed to allow the
carbohydrates and water in the drink to be
absorbed into the body faster. Bio 11C
BUILDER
GENERAL
Math Skills Tell students that the
heart pumps about 5 L (2.6 gal) of
blood per minute. Keeping in mind
that one-fourth of this volume
travels to the kidneys, have students calculate the volume of blood
that is filtered each day. (5 L/min 60 min/hr 24 h 0.25 1,800 L
per day) Ask students to calculate
how much of the blood is actually
filtered if about 55–60 percent of
the 5 L of blood is plasma, and
only 18–20 percent of the plasma,
water, and small solutes are actually filtered out of the blood and
into the nephron capsule. (1,800 L
0.55 0.18 178.2 L are actually filtered per day.) LS Logical
TAKS 1 Bio/IPC 2C
Transparencies
TT Kidneys and Nephrons
Chapter 39 • Digestive and Excretory Systems
913
Real Life
Teach, continued
continued
Real Life
Answers TAKS 3
Bio 4D; Bio 11C
Answers will vary. Researchers
have found nanobacteria in kidney stones. It is thought that the
bacteria cause kidney stones in
genetically susceptible humans.
The mineral shells that cause calcium deposits in the body form
around the bacteria. Nanobacterial infections can be
treated with antibiotics.
Teaching Tip
GENERAL
Water Treatment Plant Ask the
manager from a water treatment
plant to come and discuss the
processes the plant uses to remove
substances from water. Have students write a short report that
relates this information to how the
kidney removes substances from
the blood. LS Auditory Bio 3D
Demonstration
Kidney stones are
painful.
Kidney stones
form from crystallized mineral
and urea salts.
The crystals
form “stones”
that block the passage of
urine and result in extreme
pain. Ultrasound waves
can be used to crush kidney stones until they are
small enough to pass with
the urine.
Finding Information
Research the role of
nanobacteria in the
formation of kidney
4D, 11C TAKS 3
stones.
TAKS 1 Bio/IPC 1A
Urine Formation The urine that is excreted from the body is formed
from the water, urea, and various salts that are left after the absorption and secretion processes. Collecting ducts receive fluid from
several nephron segments and empty the urine into areas of the kidneys that lead to the ureters. Ureters (yoo REET uhrs) are tubes
that carry the urine from the kidney to the urinary bladder. The collecting duct removes much of the water from the filtrate that passes
through it. As a result, human urine can be very concentrated. In
fact, it can be as much as four times more concentrated than blood
plasma is.
Elimination of Urine
Figure 13 The organs
of urinary excretion. Urine
exits the kidneys by way of
two ureters that empty into
a storage organ called the
urinary bladder. Urine exits
the body through the urethra.
GENERAL
Obtain a pig or sheep kidney from
a local butcher. Cut the kidney in
half lengthwise. Have students
identify the obvious structures.
Ask students if they can identify
the smell. (ammonia) Ask students
how kidneys are prepared before
cooking. (You must soak the kidney
in salt water to release the ammonia
before cooking it.) Students should
wear disposible gloves if they are
to handle the kidney. Ask students
to wash their hands after the
demonstration. LS Visual
Reabsorption and Secretion Reabsorption begins when the filtrate passes from the Bowman’s capsules into the renal tubules—
long, narrow tubes connected to Bowman’s capsules. Renal
tubules bend at their center, which forms a loop. As the filtrate
passes through the renal tubules, the tubules extract from the filtrate a variety of useful molecules, including glucose, ions, and
some water. These substances reenter the bloodstream through
capillaries that wrap around the tubule. This arrangement prevents these molecules from being eliminated from the body in the
urine. Some substances can pass from the blood into the filtrate
in a process called secretion.
Kidney
Ureter
Urinary
bladder
Urethra
The ureters, shown in Figure 13, have smooth muscle in their walls.
The slow, rhythmic contractions of this muscle move the urine
through the ureters. The ureters direct the urine into the
urinary bladder, a hollow, muscular sac that stores urine. The urinary
bladder gradually expands as it fills. The average urinary bladder can
hold up to about 0.6 L (0.63 qt) of urine. The urinary bladders of
males tend to be larger than those of females.
Muscular contractions of the bladder force urine out of the
body. Urine leaves the bladder and exits the body
through a tube called the urethra (yoo REE
thruh). A healthy adult eliminates from about
1.5 L (1.6 qt) to 2.3 L (2.4 qt) of urine a day, depending on the volume of fluid he or she consumes.
In females the urethra lies in front of the
vagina and is only about 2.5 cm (1 in.) long. Such
a short length makes it easy for bacteria and
other pathogens to invade the female urinary
system, which explains why females are more
prone to urinary infections than males are. There
is no connection between the urethra and the
genital (reproductive) system in females.
In males the urethra passes through the penis.
In males, both sperm and urine exit the body
through the urethra. The tube that carries sperm
from the testes eventually merges with the
urethra.
914
IPC Benchmark Mini-Lesson
pp. 914–915
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TAKS Obj 3 Bio 4D
TEKS Bio 4B, 4D, 10A, 10B, 11C
Teacher Edition
TAKS Obj 1 Bio/IPC 1A
TAKS Obj 3 Bio 4D
TAKS Obj 4 IPC 9B
TEKS Bio 3D, 3E, 4D, 11B, 11C
TEKS Bio/IPC 1A, 3C
TEKS IPC 9B
914
Biology/IPC Skills TAKS 4 IPC 9B (grade 11 only)
Daily Fluid Intake It is ironic that as food
Relate the concentrations of ions in a solution to
conscious as Americans are, they often pay little
chemical properties including pH.
attention to the other side of the coin—their
Activity Tell the students they can calculate the
fluid intake. In fact, people can survive without
hydronium ion concentration ([H3O]) of stomach acid
food much longer than they can survive without
(hydrochloric acid (HCl)) when they know the pH of
water. On average, an adult needs 1.5–3 L of
stomach acid is about 2.0. Write the following on the
board: [H3O] antilog(pH). Students can use their
water per day, some of it being supplied by
calculators to find the answer.
foods with high water content such as lettuce,
[H3O] 10–pH 10–2, therefore the concentration of
watermelon, and citrus fruits. Any combination
[H3O] is 0.01 molar solution.
of foods and beverages that provides the needed
amount of water is acceptable, but most nutritionists recommend 6–8 glasses of liquid a day
over and above the amount contained in food. Bio 11C
Chapter 39 • Digestive and Excretory Systems
The elimination of urine from the body through the urethra is
called urination. When the bladder fills with urine, stretch receptors in the bladder’s wall send nerve impulses to the spinal cord. In
response, the spinal cord returns impulses to the bladder and urethra
simultaneously. These impulses cause contraction of the bladder’s
muscular walls and relaxation of the rings of muscle closing off the
urethra. The bladder then empties its contents through the urethra.
In older children and adults, the brain overrides this urination
reflex, which delays the release of urine until a convenient time.
www.scilinks.org
Topic: Kidney Diseases
Keyword: HX4109
Activity
Interview Have students interview a person who has had kidney
stones or talk to a physician about
them. Students should ask about
the causes of kidney stones and the
treatment. If possible, allow students to bring in a kidney-stone
specimen for the class to observe.
Damage to the Kidneys
Because of the vital role played by the kidneys in maintaining homeostasis, diseases affecting these organs may eventually threaten life. If
one kidney is lost in an accident or by disease, the other may enlarge
and do the work of both. Nephrotic syndrome refers to a number of
signs and symptoms that result from damage to the glomeruli, which
leads over time to kidney failure. The most common causes of kidney
failure are infection, diabetes, high blood pressure, and damage to the
kidneys by the body’s own immune system.
Because of their function in excretion, kidneys often are exposed to
hazardous chemicals that have entered the body through the lungs,
skin, or gastrointestinal tract. Household substances that, in concentration, can damage kidneys include paint, varnishes, furniture oils,
glues, aerosol sprays, air fresheners, and lead. When kidneys fail,
toxic wastes, such as urea, accumulate in the plasma, and bloodplasma ion levels increase to dangerous levels. If both kidneys fail,
there are only two treatment options.
Kidney Dialysis Kidney dialysis, also called hemodialysis (HEE moh
die AL uh sihs), is a procedure for filtering the blood by using a
dialysis machine, as shown in Figure 14. A dialysis machine, just as
the nephrons in the kidney, sorts small molecules in the blood, keeping some and discarding others. Dialysis machines are sometimes
used for kidneys that are damaged but
either will eventually heal or be replaced
by a kidney transplant.
GENERAL
LS Auditory
Teaching Tip
Concept Map Have students
define the new terms in this section
and use the terms to construct a
concept map. Make sure the maps
contain appropriate words and
phrases linking the terms. LS Verbal
Bio 3E
Figure 14 Hemodialysis.
Hemodialysis has prolonged
the lives of many people with
damaged or diseased kidneys.
The dialysis machine functions
like a kidney in that it filters
urea and excess ions from
the blood.
Transparencies
TT Kidney Dialysis
Kidney Transplants A more permanent
solution to kidney failure is transplantation of a kidney from a healthy donor. A
major problem with kidney transplants
is common to all organ transplants—
rejection of the transplanted organ by the
recipient’s immune system. Recall that
the cells of your body have “self-markers,”
or antigens, on their surfaces that identify
the cells to your immune system so it will
not attack them. The combination of
these antigens displayed on your body’s
cells is as unique as your fingerprints.
915
did you know?
Urine Output High blood pressure, drinking
lots of fluids, and cold weather promote
increased urine output. High blood pressure
increases the filtration pressure in the kidneys.
Increased fluid consumption raises the blood
pressure and decreases the output of antidiuretic hormone (ADH). Cold weather increases
the metabolic rate and thus increases the rate
of filtration. Low blood pressure, reduced
intake of fluids, and hot weather decrease
urine output for the converse reasons. Bio 11B
Career
Dialysis Technician Dialysis technicians
operate dialysis machines and monitor and
record a patient’s weight and vital signs before,
during, and after dialysis. Have students
research the career of a dialysis technician and
prepare a short report. The report should
include a job description, training required,
employer, growth potential, starting salary,
and job satisfaction. Bio/IPC 3C, Bio 3D
Chapter 39 • Digestive and Excretory Systems
915
Only identical twins have the same set of antigens. The more closely
related two individuals are, the more likely they are to have common
antigens. This is why tissue transplants are more likely to succeed if
the donor and recipient are closely related. But even in close
matches, there is some chance of transplant rejection. To reduce
chances of rejection, the recipient is treated with drugs that suppress the activity of the immune system.
Kidney Dialysis
TAKS 2 Bio 4B, 10A, 10B
To demonstrate osmosis, bring
in some dialysis tubing and
show students how permeable it
is. Pour a starch solution into
the tubing, which is immersed
in an iodine and water solution.
The iodine will diffuse into the
tubing, turning the starch solution blue-black.
Discussion
Ask students why dialysis
machines are less effective than
kidneys. (Machines do not dialyze constantly as the body does.
Levels of salt, protein and water
cannot be closely regulated with
a machine.)
Close
Reteaching
Have students return to their statements in the Opening Activity for
this chapter. Ask students if their
opinions have been confirmed or
changed in any way. TAKS 2 Bio 4B
Quiz
GENERAL
1. What are the three organs of
excretion? (lungs, kidneys, skin)
2. What tubelike structures are the
main blood-filtering units of the
kidneys? (nephrons)
TAKS 2 Bio 10A
Alternative
Assessment
Dialysis machine
Exploring Further
Catheter
Kidney Dialysis
TAKS 2
People whose kidneys are damaged cannot filter
their blood. Kidney dialysis is one option for artificially filtering the blood. In kidney dialysis, tubes
called catheters are surgically inserted into an
artery and a vein, usually on a forearm. The
catheters are equipped with valves. Every few
days the catheters are connected to a dialysis
machine, as shown to the right.
Blood Is Filtered
Blood passes from the patient’s artery into the
dialysis machine. Inside the machine, the blood
travels through many hollow tubes, each of which
is surrounded by a thin, permeable membrane.
Waste materials and ions that have accumulated
in the person’s blood diffuse through the membrane into a fluid that has the same makeup
as normal blood plasma and is free of wastes.
The filtered blood is then returned to the
person’s vein.
Dialysis is not a permanent solution to kidney
failure. A single healthy kidney can meet all of the
homeostatic needs of the body, but no dialysis
machine can. Dialysis patients must carefully
manage their salt, protein, and water intake
Student Edition
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TEKS Bio 4B, 10A, 10B, 11A
Teacher Edition
TAKS Obj 1 IPC 3B
TAKS Obj 2 Bio 4B, 10A, 10B
TEKS Bio 3B, 3E, 4B, 10A, 10B
TEKS IPC 3B
916
Fresh dialysis
solution
Compressed
air
Used
dialysis
solution
because the dialysis machine cannot regulate
these blood components as well as the
kidney can.
www.scilinks.org
Topic: Kidney Dialysis
Keyword: HX4108
Critical Thinking Applying Information
is produced and excreted.
A doctor has just informed a patient that his urine
contains a high sugar concentration. Explain why
10A 11A
this may indicate damaged kidneys.
10A 10B
Relate the following terms to the formation of
10A
urine: filtration, reabsorption, and secretion.
Name the liquid stored inside the collecting duct
10A
from the body.
10A
TAKS Test Prep The substances that are
removed from the body by the excretory system
10A 10B
are carried to the kidneys by the
A nervous system.
C circulatory system.
B respiratory system.
D digestive system.
916
Answers to Section Review
1. Carbon dioxide is produced during cellular
respiration and excreted through the lungs.
TAKS 2 Bio 10A, 10B (grade 11 only)
pp. 916–917
Solution
Identify how the carbon dioxide in your body
Summarize how urine is stored and eliminated
Ask students to summarize the
function of the urinary system,
using as many science terms as
possible. TAKS 2 Bio 10A
Blood
Section 3 Review
of a nephron.
GENERAL
Semipermeable
membrane
2. filtration—kidneys filter blood, removing
water, salt, glucose, amino acids, and urea;
reabsorption—useful molecules and water are
reabsorbed by the bloodstream; secretion—
wastes and toxic materials pass from blood
into filtrate TAKS 2 Bio 10A
3. urine TAKS 2 Bio 10A
4. Urine is stored in the bladder. When stretch
receptors in the bladder send nerve impulses
to the spinal cord, the bladder muscles relax
and urination occurs. TAKS 2 Bio 10A
Chapter 39 • Digestive and Excretory Systems
5. Sugar should be reabsorbed by the bloodstream in the kidney. TAKS 2 Bio 10A; Bio 11A
6.
A. Incorrect. The nervous system does not carry waste products to the kidney. B. Incorrect. The respiratory system can
carry metabolic waste (carbon dioxide) but
carries it to the lungs. C. Correct. Wastes
to be removed from the body are carried
to the kidney by the circulatory system.
D. Incorrect. The digestive system does not
carry waste products to the kidney for
removal. TAKS 2 Bio 10A, 10B (grade 11 only)
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
Alternative
Assessment
Key Terms
Section 1
1 Your Body’s Need for Food
●
Food and beverages provide the nutrients and water required
by the body for growth, energy, repair, and maintenance.
●
Carbohydrates and lipids provide most of the body’s energy.
Proteins are normally used for making other proteins.
●
The USDA food guide pyramid graphically summarizes the
daily recommended servings from each food group.
●
Vitamins enhance the activity of enzymes and regulate the
release of energy. Minerals are used to make certain body
structures and substances, for normal nerve and muscle function, to maintain osmotic balance, and for enzyme function.
●
Water acts as a lubricant, solvent, and coolant, and as a
support medium for cells and tissues.
nutrient (900)
digestion (900)
calorie (900)
vitamin (904)
mineral (905)
Section 2
2 Digestion
●
Teeth break down food into smaller pieces. Amylase begins
the breakdown of starch to sugars. The stomach stores and
mechanically breaks down food. Stomach acid and pepsin
chemically break down proteins.
●
Most chemical digestion occurs in the small intestine with the
help of secretions from the pancreas, liver, and gallbladder.
●
Usable compounds are absorbed into capillaries or lymphatic
vessels in villi. Compounds not absorbed are eventually
excreted as feces.
●
The liver releases bile, helps to maintain blood sugar levels,
and detoxifies poisons.
GENERAL
Commercial diet programs are big
business. Have students research
commercial diet programs and
report how each claims to bring
about weight loss. Encourage students to look for information on
how these programs might affect
either the digestive or excretory
systems. For example, a highprotein diet places added stress on
the liver and kidneys, because the
body must produce and then rid
itself of more urea, secondary to
higher nitrogen intake. Have students present their research in a
multimedia format. LS Verbal
amylase (907)
esophagus (907)
pepsin (908)
lipase (909)
villus (909)
colon (910)
TAKS 1 IPC 3B; Bio 3B
Chapter Resource File
• Science Skills Worksheet
• Critical Thinking
Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
GENERAL
Section 3
3 Excretion
●
The skin, lungs, and kidneys are specialized to excrete wastes.
●
Nephrons in the kidneys filter wastes from the blood. Most
of the water, some of the salts, and all of the sugar and
amino acids in the filtrate are reabsorbed into the bloodstream. The water, urea, and salts that remain in the
nephron are eliminated as urine.
●
Kidney dialysis and organ transplants are treatment options
when both kidneys fail.
excretion (912)
urea (912)
nephron (913)
urine (914)
ureter (914)
urinary bladder (914)
urethra (914)
917
Answer to Concept Map
The following is one possible
answer to Performance Zone
item 15 on the next page.
Nutrients
most absorbed in
small intestine
some absorbed in
large intestine
include
Bio 3E
carbohydrates
proteins
digested by
digested by
enzymes
pepsin
hydrochloric acid
in
secreted by
secreted by
saliva
pancreas
stomach
lipids
vitamins
emulsified by
bile
secreted by
liver
secreted into
protected by
mouth
mucus
minerals
TAKS Test Prep
• The Science TAKS Prep Appendix
in this book provides integrated
biology and IPC TAKS practice.
• The Holt Science TAKS Practice
Workbook provides a review of
biology, chemistry, and physics
concepts tested on the grades 10
and 11 science TAKS.
Chapter 39 • Digestive and Excretory Systems
917
Performance
ZONE
CHAPTER 39
ANSWERS
Using Key Terms
1. c Bio 9A
2. d TAKS 2 Bio 10A
3. c TAKS 2 Bio 10A; Bio 9C
4. a TAKS 2 Bio 10A
5. a. absorption—the other terms
refer to processes involved in
the filtering of blood by
nephrons.
b. villi—the other terms refer to
structures in the kidney
Understanding Key Ideas
6. c TAKS 2 Bio 10A; Bio 9A
7. a Bio 11C
8. b Bio 9C
9. d TAKS 2 Bio 10A, 10B (grade 11 only)
10. d TAKS 2 Bio 10A
11. c TAKS 2 Bio 10A
12. A. grains, 6–11 servings a day;
B. fruits, 2–4 servings a day Bio 11C
13. In anorexia the levels of sex
hormones may fall, the body
temperature and pulse rate
become abnormally low, the hair
becomes thin and dry, and resistance to infections drops. In
bulimia the teeth, gums, and
esophagus often are damaged,
and muscle weakness, heart
failure, and kidney disease
can occur. Bio 11C
CHAPTER REVIEW
8. The body needs vitamins because they
a. supply energy.
b. activate enzymes.
c. function as enzymes.
d. act as hormones.
Using Key Terms
1. Proteins are made up of
a. fatty acids.
b. glycerol.
c. amino acids.
d. monosaccharides.
9A
9. Which substance is not a waste eliminated
from the body through the kidneys?
a. urea
c. salts
b. water
d. oxygen
2. During digestion, food passes through the
mouth, esophagus, stomach, _______, and
large intestine.
10A
a. pancreas
c. gallbladder
b. lungs
d. small intestine
3. Which of the following correctly pairs
10. The _______ are involved in excretion.
a. kidneys and stomach
b. liver and pancreas
c. pancreas and kidneys
d. kidneys and lungs
10A
10A
move from
a. the filtrate to the blood.
b. the urethra to the bladder.
c. the blood to the filtrate.
d. the bladder to the urethra.
4. Nutrients in the small intestine enter the
12. Identifying Information Identify the food
groups represented by A and B. Indicate
the number of servings that should be
11C
eaten daily for A and B.
bloodstream by passing through
10A
a. villi.
b. gastric pits.
c. glomeruli.
d. nephrons.
A
5. For each set of terms below, choose the
B
term that does not belong and explain why
it does not belong.
a. absorption, filtration, secretion,
reabsorption
b. nephron, villi, glomerulus, renal tubule
Understanding Key Ideas
6. The primary function of carbohydrates
is to
9A 10A
a. break down molecules.
b. aid in digestion.
c. supply the body with energy.
d. regulate the flow of acid.
7. Food from the _______ food group should
11C
13.
Describe the body changes
11C
caused by anorexia and bulimia.
14.
Summarize how a kidney
10A 10B 11C
dialysis machine filters blood.
15.
Concept Mapping Make a concept
map that shows how nutrients are digested.
Try to include the following words in your
map: carbohydrates, proteins, lipids, enzymes,
saliva, pancreas, stomach, bile, liver, small
2C 3E
intestine, and large intestine.
918
14. Blood moves through tubes composed of
semipermeable membranous material, which
are bathed in fluid with the same composition as clean plasma. Wastes diffuse out of
the tubes and into the “plasma.” The filtered
blood circulates into the patient’s body.
TAKS 2 Bio 10A, 10B; 11C
918
10A 10B
11. During secretion in the kidney, substances
the enzymes with the food molecules
they digest?
9C 10A
a. lipases, starches
b. amylases, fats
c. lipases, fats
d. pepsin, starches
be eaten in the greatest abundance.
a. grains
b. fats, oils, and sweets
c. vegetables
d. milk, yogurt, and cheese
pp. 918–919
Review and Assess
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 10A, 10B
TAKS Obj 3 Bio 4D, 12B
TEKS Bio 3E, 4D, 9A, 9C, 10A, 10B,
11A, 11C, 12B
TEKS Bio/IPC 2C
9C
15. One possible answer to the concept map is
found at the bottom of the Study Zone page.
TAKS 1 Bio/IPC 2C; Bio 3E
Chapter 39 • Digestive and Excretory Systems
Assignment Guide
Section
1
2
3
Questions
1, 6–8, 12–13, 15
2–4, 15
5a–b, 9–11, 14
Critical Thinking
Alternative Assessment
Critical Thinking
16. Evaluating Conclusions The length
20. Finding Information Compile a list of
16. Answers will vary. Students who
agree might argue that water is
more readily available so that
their need to conserve water is
not as critical as in humans.
of the looped tubule in a nephron varies
among mammal species. A friend believes
the looped tubules of mammals that live
in the water would be shorter than those
found in humans. Do you agree or
disagree? Explain.
10A 10B
agencies and programs in your community
that work with teens who have eating
disorders. Develop a fact sheet for each
eating disorder and include them with
your list.
11C
21. Communicating Write an article that
needs an acidic environment for optimal
absorption. What kinds of foods would
you recommend be combined with
calcium-rich foods in order to
maximize absorption?
11C
18. Determining the Validity of a Claim A
Bio 11C
22. Relating Concepts Look at books that
friend believes a vegetarian diet would
decrease his intake of saturated fat and
cholesterol. Do you agree or disagree?
10A 11C
Explain.
19. Relating Concepts Describe the symbiotic
role of bacteria in the human intestine.
17. acidic foods such as tomatoes,
oranges, and other citrus fruits
discusses diuretics (substances that
increase urine excretion) for your
school or local newspaper. Emphasize
diuretics that most people have heard
of, such as the caffeine in coffee and
soft drinks.
10A 11A
17. Recommending Information Calcium
4D 12B
TAKS 2 Bio 10A, 10B (grade 11 only)
describe the cultures and customs of other
nations. Find information relating to ideas
about body shape, ideal body weight, and
eating habits for at least five different
countries. Describe how these ideas differ
11C
from those in the United States.
18. Answers will vary. Students who
agree might point out that in
most nonvegetarian diets, most
fats and cholesterol come from
animal products.
TAKS 2 Bio 10A; Bio 11C
19. Bacteria live in the human colon
where they synthesize vitamin K
and several B vitamins, and aid in
the elimination of feces.
TAKS 3 Bio 4D, 12B
TAKS Test Prep
Alternative Assessment
Use the food label below and your knowledge
of science to answer questions 1–3.
Nutrition
Facts
Amount /serving
Total fat 1g
% DV*
1%
Serv. size 2 oz
Sat. fat 0 g
0%
(56 g / –18 box)
Servings per container 8 Cholesterol 0 mg 0%
Calories 210
Fat Cal. 10
*Percent Daily Values (DV) are
based on a 2,000 Calorie diet.
Sodium 0 mg
0%
Amount /serving
% DV*
Total carb. 43 g 14%
Dietary fiber 2 g
8%
Sugars 3 g
Protein 6 g
Vitamin A 0% • Vitamin C 0% • Calcium 2% • Iron 10%
Thiamin 30% • Riboflavin 10% • Niacin 15%
1. What is the main function of dietary
11C
fiber?
A to provide energy
B to provide materials for making
enzymes
C to help food pass through the digestive
tract
D to maintain osmotic balance
2. A healthful diet should provide no more
than 30 percent of a day’s calories from
fats. Approximately what percentage of the
11C
calories in pasta come from fats?
F 1 percent
H 10 percent
G 5 percent
J 14 percent
3. A food is considered to be a good source
of a vitamin or mineral if it provides at
least 10 percent of that vitamin or mineral.
Based on that criterion, pasta is a good
11C
source of
A vitamin A, vitamin C, calcium, and iron.
B vitamin A, vitamin C, riboflavin, and
niacin.
C iron, thiamin, riboflavin, and niacin.
D calcium, iron, thiamin, and riboflavin.
20. Answers will vary. Students may
start by contacting your local
public health authority or mental
health agency. Bio 11C
21. Answers will vary. Students’ lists
might include caffeine, parsley,
juniper, buchu leaves, uva ursi,
and other herbs, as well as prescription drugs.
TAKS 2 Bio 10A; 11A
23. Answers will vary. Bio 11C
Test
If time permits, take short mental breaks
during the test to improve your concentration.
919
1. A. Incorrect. Providing energy is a function of
carbohydrates. B. Incorrect. Providing materials for making enzymes is a function of proteins. C. Correct. The main function of dietary
fiber is to help food pass through the digestive
tract. D. Incorrect. Maintaining osmotic balance is a function of minerals. Bio 11C
2. F. Incorrect. The percentage of fat that a pasta
serving contributes to the Daily Values is 1%,
not the percentage of its total calories that are
from fats. G. Correct. To determine the percentage of calories from fat, the number of fat
calories (10) should be divided by the total
calories (210), which equals about 5%.
H. Incorrect. The fat calories per serving is 10,
which is not the percentage of its total calories
that are from fats. J. Incorrect. The percentage
of carbohydrates that a serving contributes to
the Daily Values is 14%, not the percentage of
its total calories that are from fats. Bio 11C
3. A. Incorrect. Iron is the only nutrient in this list
that meets the criterion; the others are less than
10%. B. Incorrect. Riboflavin and niacin meet
the criterion, but the other nutrients are at less
than 10%. C. Correct. All these nutrients meet
the criterion of at least 10% provided by the
pasta. D. Incorrect. These nutrients meet the criterion except for calcium, which is only 2%. Bio 11C
Chapter 39 • Digestive and Excretory Systems
919