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CHAPTER 18
NUTRITION AND METABOLISM
LEARNING OBJECTIVE 1: Define nutrition, nutrients, and essential nutrients.
Lecture Suggestions and Guidelines
1. Discuss several factors, which influence what we choose to eat.
2. Define nutrition in terms of its interaction with physiological, psychological, social, cultural, economic, and
technological factors.
3. Describe macronutrients and micronutrients.
4. Define metabolism.
5. Discuss essential nutrients as those, which must be provided in the diet. Give examples of essential nutrients.
Application Question(s)
1. Ask students to provide specific examples of how nutrients help meet the body’s energy requirements, the need
to maintain structure, and the need to regulate body functions.
Answer: Examples might include carbohydrates in the form of blood glucose being used for cellular energy;
minerals in the form of calcium and phosphorus help maintain tooth structure; proteins in the form of
transferring help regulate the transport of iron.
Critical Thinking Issue(s)
1. Discuss the nutritional health of the nation. Students should consult various sources to accumulate their facts.
What is the students’ overall assessment of nutritional health in the U.S.?
Answer: Responses should include discussion of food availability, consumption, food composition and
labeling, attitudes, behavior, and knowledge about food-related issues.
LEARNING OBJECTIVE 2: List the major sources of carbohydrates, lipids, and proteins.
Lecture Suggestions and Guidelines
1. Describe the major sources of carbohydrates. Include a discussion of starch, glycogen, disaccharides,
monosaccharides, and cellulose.
2. Discuss the major sources of lipids, including fats, phospholipids, and cholesterol. The most common dietary
lipids are triglycerides obtained from plants and animal products.
3. Lecture on the major sources of proteins. Discuss essential amino acids. Distinguish between complete and
incomplete proteins.
Application Question(s)
1. Apply the information discussed in this learning objective to a discussion of the six major types of vegetarian
diets. Can a person be nutritionally healthy while staying on one of these diets?
Answer: Responses will vary. Benefits and pitfalls exist for vegetarian diets. On one hand, vegetarian diets
may reduce disease risks, are more economical, etc. Pitfalls may include a concern about certain vitamin and
mineral deficiencies.
Critical Thinking Issue(s)
1. Discuss the potential causes of obesity.
Answer: Obesity usually equates to 15 - 20% or more over a person’s “ideal weight”. It is due to an abnormal
accumulation of adipose tissue. The causes are many and varied; obesity could be caused by poorly matched
caloric intake and physical activity, a genetic component, a behavioral component, cultural and environmental
factors, or a combination of the above. Treatment may involve diets, exercise programs, medications, and/or
behavioral modification.
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LEARNING OBJECTIVE 3: Describe how cells utilize carbohydrates.
Lecture Suggestions and Guidelines
1.
2.
3.
4.
Discuss the absorption of carbohydrates as monosaccharides.
Describe the liver’s role in converting fructose and galactose to glucose.
Define oxidation.
Explain how excess glucose is stored as glycogen or converted to fat.
Application Question(s)
1. What recommendations would students give in terms of changes in carbohydrate intake in a typical North
American diet?
Answer: Responses will vary.
Critical Thinking Issue(s)
1. Trace the pathways which starch, sucrose, maltose, and lactose take upon being digested.
Answer: All are converted to monosaccharides. Starch is converted to glucose, sucrose to glucose and fructose,
maltose to glucose, and lactose to glucose and galactose. The monosaccharides are then utilized in a variety of
processes, including respiration, glycogenesis, and lipogenesis.
LEARNING OBJECTIVE 4: Describe how cells utilize lipids.
Lecture Suggestions and Guidelines
1.
2.
3.
4.
Describe the role of the liver and adipose tissue in controlling triglyceride metabolism.
Briefly introduce the structure of fatty acids and how the liver may alter their structures.
Describe linoleic acid.
Discuss the regulation of cholesterol levels by the liver.
Application Question(s)
1. Which lipids are synthesized from fatty acids processed in the liver?
Answer: Triglycerides, lipoproteins, cholesterol, phospholipids, and some fatty acids.
Critical Thinking Issue(s)
1. Compare/contrast the roles of chylomicrons, VLDLs, LDLs, and HDLs.
Answer: Chylomicrons transport lipids from the intestines and carry triglycerides to the body cells, very-lowdensity lipoproteins transport lipids from the liver and carry triglycerides to the body cells, low-density
lipoproteins transport cholesterol to body cells, and high-density lipoproteins transport cholesterol away from
body cells (and are thus called “good” lipoproteins).
LEARNING OBJECTIVE 5: Describe how cells utilize amino acids.
Lecture Suggestions and Guidelines
1. Distinguish between essential and nonessential amino acids.
2. Identify the eight essential amino acids.
3. Discuss several uses of polymers of amino acids (proteins), including enzymes, clotting factors, keratin, elastin,
collagen, plasma proteins that regulate water balance, actin, myosin, hormones, and antibodies. Give examples.
4. Distinguish between complete and incomplete proteins.
Application Question(s)
1. Ask the students to name twenty-one amino acids. Which eight are considered to be essential? Which two
additional amino acids are essential in growing children?
Answer: The eight essential amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, and valine. The two additional essential amino acids in growing children are arginine and histidine.
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Critical Thinking Issue(s)
1. Describe the process by which deaminated amino acids may be used to produce cellular energy.
Answer: Responses should include a discussion of glycolysis in the cell cytoplasm, the formation of acetylCoA in the mitochondria, the citric acid cycle in the mitochondria, and the electron transport chain mechanism
in the mitochondrial membrane.
LEARNING OBJECTIVE 6: Define nitrogen balance.
Lecture Suggestions and Guidelines
1. Lecture on the concept that the amount of nitrogen taken in is equal to the amount excreted.
2. Distinguish between a negative and positive nitrogen balance. Give examples of people who would fall into
each category.
Application Question(s)
1. Ask students to give specific examples of cases in which a positive nitrogen balance may occur; A negative
nitrogen balance.
Answer: The textbook provides the following examples of a positive nitrogen balance: a growing child, a
pregnant woman, or an athlete in training. A negative nitrogen balance may be the result of starvation. Ask
students for additional examples.
Critical Thinking Issue(s)
1. Given the information provided in the above application question, under what circumstances might an athlete in
training actually exhibit a negative nitrogen balance?
Answer: It is possible for an athlete in training to exhibit a negative nitrogen balance if he/she were
participating in a low protein diet while attempting to lose weight. A low energy, low protein diet may result in
a negative nitrogen balance because the athlete’s body is breaking down protein to meet energy needs, resulting
in excess excretion of nitrogen in the urine.
LEARNING OBJECTIVE 7: Explain how the energy values of foods are determined.
Lecture Suggestions and Guidelines
1. Define calories and kilocalories.
2. Describe a bomb calorimeter.
3. Discuss the caloric values derived from the oxidation of one gram of carbohydrate, one gram of protein, and
one gram of fat.
Application Question(s)
1. Ask students to prepare a list of twenty activities. Assign the number of calories used per hour to each activity.
Of all activities investigated, which used the greatest number of calories? Least?
Answer: Answers will vary.
Critical Thinking Issue(s)
1. Demonstrate the use of a bomb calorimeter to the class. Each student could submit one food source for
experimentation. Rank the foods based on amount of heat released during combustion.
Answer: Responses will vary.
LEARNING OBJECTIVE 8: Explain the factors that affect an individual’s energy requirements.
Lecture Suggestions and Guidelines
1. Discuss basal metabolic rate (BMR).
2. Emphasize the concept that the amount of energy required varies from one individual to another.
3. Discuss factors that influence energy requirements.
Application Question(s)
1. What factors determine basal metabolic rate?
Answer: Surface area of the individual, sex, thyroxine production, age, and emotions have all been shown to
have an effect on BMR.
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Critical Thinking Issue(s)
1. Compare and contrast the terms basal metabolic rate and total metabolic rate.
Answer: BMR is the amount of heat produced when the body is at rest. TMR is the total amount of calories the
body needs to support activity such as work by the skeletal muscles. Homeostasis is maintained when TMR is
equal to the total calories consumed.
LEARNING OBJECTIVE 9: Define energy balance.
Lecture Suggestions and Guidelines
1. Define the term energy balance.
2. Distinguish between positive and negative energy balance.
3. Describe the effects of energy balance upon body weight.
Application Question(s)
1. What is the difference between hunger and appetite?
Answer: Hunger is the physiological drive to consume food, stimulated by the body’s internal signals. Appetite
relates to a drive to eat, not related to hunger. For instance, the desire to eat dessert after a big meal, (as a form
of reward system) is based on appetite, not hunger.
Critical Thinking Issue(s)
1. Ask students to address the effects of emotions upon appetite.
Answer: Responses will vary. An emotion which causes one individual to eat, for example, stress, may cause
another individual to “lose” his appetite.
LEARNING OBJECTIVE 10: Explain what is meant by desirable weight.
Lecture Suggestions and Guidelines
1. Discuss what is meant by desirable weight.
2. Define overweight and obese. Compare the terms.
3. Discuss cases in which being slightly overweight or underweight may be desirable.
Application Question(s)
1. What is each student’s desirable weight? Obtain an obsolete chart of weight standards based on average
weights and heights. How many students are within the acceptable range of desirable weight?
Answer: The results may be surprising when compared to the numbers of students who fall into the desirable
weight range based on more recent charts. More recent charts are based on people who live the longest, and are
more lenient than prior standards.
Critical Thinking Issue(s)
1. Ask students to devise a list of instances in which weight gain may be desirable; undesirable. Compose another
list, which summarizes when weight loss may be desirable; undesirable. Do all students agree?
Answer: Responses will vary.
LEARNING OBJECTIVE 11: List the fat-soluble and water-soluble vitamins.
and
LEARNING OBJECTIVE 12: Describe the general functions of each vitamin.
Lecture Suggestions and Guidelines
1. Lecture on the general characteristics of fat-soluble vitamins and water-soluble vitamins. Compare and contrast
their characteristics.
2. Discuss the structures, functions, and locations of the fat-soluble vitamins, including vitamins A, D, E, and K.
3. Discuss the structures, functions, and locations of the water-soluble vitamins, including eight forms of the
vitamin B complex and vitamin C (ascorbic acid).
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Application Question(s)
1. Prepare a set of index cards, each of which features the name of a fat-soluble or water-soluble vitamin on one
side, and the characteristics, functions, sources, conditions associated with excesses, and conditions associated
with deficiencies on the other side.
Answer: The students will have a set of thirteen index cards when finished, which they can use for future
reference.
Critical Thinking Issue(s)
1. Ask students to prepare a short report on a disease of malnutrition based on deficiency of a major vitamin.
Topics may include beriberi, pellagra, scurvy, osteomalacia, etc.
Answer: The report should include a definition of the disease, cause, signs and symptoms, course, outcome,
and prognosis.
LEARNING OBJECTIVE 13: Distinguish between a vitamin and a mineral.
Lecture Suggestions and Guidelines
1. Reiterate the concept that vitamins are organic compounds, minerals are inorganic compounds.
2. Discuss the concept that solubility determines how vitamins are absorbed, transported, excreted, and stored in
the body. Vitamins do not directly provide energy.
3. Describe the occurrence of minerals. Approximately 75% of the minerals are found in bones and teeth.
4. Explain that minerals in the ionized form are physiologically active.
Application Question(s)
1. Compare the chemical structures and characteristics of a selection of vitamins and minerals.
Answer: Vitamins are carbon-containing compounds and tend to be larger, more complex molecules. Minerals
are inorganic compounds and tend to be physiologically active in the ionized state. Illustrations which compare
structures would be beneficial, as would ball-and-stick models of the vitamins.
Critical Thinking Issue(s)
1. Is more vitamin C always better? Does vitamin C really prevent common cold symptoms? What are the
implications of hypervitaminosis with vitamin C?
Answer: Studies have shown that the human body will attempt to excrete excess vitamin C, which it cannot
use. Debate still exists as to the preventive effects of vitamin C against colds. A dietary excess of vitamin C
exacerbates gout and kidney stone formation.
LEARNING OBJECTIVE 14: List the major minerals and trace elements.
and
LEARNING OBJECTIVE 15: Describe the general functions of each mineral and trace element.
Lecture Suggestions and Guidelines
1. Discuss the major minerals found in the human body; give the name, functions, locations, consequences of
dietary excess, and consequences of dietary deficiency for each, including calcium, phosphorus, potassium,
sulfur, sodium, chlorine, and magnesium.
2. Discuss the trace elements found in the human body; give the name, functions, locations, consequences of
dietary excess, and consequences of dietary deficiency for each, including iron, manganese, copper, iodine,
cobalt, zinc, fluorine, selenium, and chromium.
Application Question(s)
1. Ask students to prepare index cards featuring the name of a major mineral or trace element on one side, and the
distribution, functions, sources, conditions associated with excesses, and conditions associated with
deficiencies on the other side.
Answer: When completed, the students will have a set of no fewer than sixteen index cards, which they may
use for future reference.
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Critical Thinking Issue(s)
1. What kinds of actions can students take to reduce their sodium intake?
Answer: Responses will probably include reducing salt intake gradually, reading food labels more carefully,
reduce snacking, add little or no salt when cooking, order more carefully at restaurants, limit the use of a salt
shaker, limit intake of processed cheeses, etc.
LEARNING OBJECTIVE 16: Describe an adequate diet.
Lecture Suggestions and Guidelines
1.
2.
3.
4.
Describe the food pyramid system.
Discuss the information available on food labels and interpret its meaning.
Define adequate diet.
Discuss devices, which are available to help consumers make healthy food choices.
Application Question(s)
1. Why is the food guide pyramid shaped like a pyramid?
Answer: The pyramidal shape is significant because it emphasizes that foods at the base of the pyramid should
be more abundant (more servings) than foods at the narrow peak. Bread, cereal, rice and pasta are at the base of
the pyramid, comprising 6 - 11 servings per day. Fruits and vegetables are at the next highest level at 3 - 5
servings, followed by milk, yogurt, cheese, meat, poultry, fish, dry beans, eggs, and nuts at 2 - 3 servings, and
finally fats, oils, and sweets at the pyramid’s apex, which should be used sparingly.
Critical Thinking Issue(s)
1. Ask students to bring in labels from some of their favorite foods. Analyze the nutrition facts stated on the label
regarding the container’s contents.
Answer: Responses will vary.
LEARNING OBJECTIVE 17: Distinguish between primary and secondary malnutrition.
Lecture Suggestions and Guidelines
1. Define malnutrition. Emphasize the fact that a person may eat too much, be overweight, or obese, and still be
malnourished.
2. Explain the difference between primary and secondary malnutrition.
3. Discuss the signs and symptoms of starvation.
4. Describe several nutritional disorders.
Application Question(s)
1. What health claims are advertisers making regarding their products? Are these claims supported by the Food
and Drug Administration? Collect some examples from magazines, newspapers, and television commercials to
discuss in class.
Critical Thinking Issue(s)
1. Compare and contrast anorexia nervosa and bulimia.
Answer: Anorexia nervosa is self-starvation. Its manifestations include amenorrhea, decreased blood pressure
and heart rate, anemia, dehydration, immunosuppression, and weight loss. An anorexic views himself as
overweight, even during starvation. Bulimia is a binge-purge syndrome. The manifestations include tooth
decay, sore throat, inflammation of the salivary glands, dehydration, electrolyte imbalance, heart irregularities,
and stomach rupture. Both anorexia nervosa and bulimia patients are treated for malnutrition and receive
psychological counseling.
LEARNING OBJECTIVE 18: What factors may lead to inadequate nutrition later in life?
Lecture Suggestions and Guidelines
1. Describe the effects of medical condition and socioeconomic circumstances that may affect nutrition of the
elderly.
2. Discuss the effects of aging on basal metabolic rate.
3. Identify the changes in energy balance and its effects upon activity levels later in life.
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Application Question(s)
1. Ask students to develop a food guide pyramid that would be appropriate for the elderly. How does it differ
from a similar pyramid for a teenager?
Answer: Responses will vary.
Critical Thinking Issue(s)
1. Compare and contrast the lasting effects of starvation with those of overeating.
Answer: Responses should include a discussion of the fact that both cases represent a form of malnutrition.
RELATED DISEASES OF HOMEOSTATIC INSTABILITY
1. Beriberi—A condition resulting from a thiamin (vitamin B1) deficiency. Its manifestations include
demyelination of nerve fibers, leading to extraneous perception of stimuli, weakening of appendages,
confusion, and paralysis of eye muscles.
2. Scurvy—Results from an ascorbic acid (vitamin C) deficiency. Manifestations include a separation of cells in
epithelial tissue, and an insufficient production of collagen. The gums may be severely affected. Scurvy can
usually be prevented with a proper diet, including citrus fruits and fresh vegetables.
3. Bulimia—A psycho-neurotic disorder in which the patient binges and purges. This condition may cause tooth
decay, sore throat, inflammation of salivary glands, dehydration, electrolyte imbalance, heart irregularities, or
stomach rupture. Treatment usually involves medications and psychological counseling.
SUGGESTIONS FOR ADDITIONAL READING
Elmer-Dewitt, Phillip. January 16, 1995. Fat Times. Time. Why are so many of us overweight? For most of us, the
environment plays a greater role than heredity.
Farley, Dixie. March 1992. Eating disorders require medical attention. FDA Consumer. Anorexia nervosa and
bulimia are serious, life-threatening disorders.
Foulke, Judith E. April 1992. Good news about good nutrition. FDA Consumer. You can eat in a way that promotes
good health.
Kurtzweil, Paula. January/February 1993. Nutrition information available for raw fruits, vegetables, fish. FDA
Consumer. We should eat more fruits, veggies, and fish.
Kurtzweil, Paula. March 1995. Labeling rules for young children’s food. FDA Consumer. Children under age four
years have different nutritional requirements.
Rink, Timothy J. December 1, 1994. In search of a satiety factor. Nature, vol. 372. Genes control the biochemical
pathways that control energy utilization—and therefore body weight.
Ronald, Pamela C. November, 1997. Making Rice Disease-Resistant. Scientific American.
Saltos, Etta. June 1993. The food pyramid-food label connection. FDA Consumer. Tips on how to implement the
food pyramid and read new food labels.
Spiller, Gene. 1003. The superpyramid eating program. New York: Times Books. Using the food pyramid plan.
Wagner, Bill. November 1993. Surprising sources for new foods. FDA Consumer. Eating a variety of foods helps
ensure that you meet nutritional needs.
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