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Chapter 25
Lecture Outline
25-1
Living Things as Chemical Factories:
Matter and Energy Manipulators
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All organisms need energy and building
blocks to live and grow.
Nutrients
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25-2
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All of the molecules required to support life
Includes inorganic elements and organic
molecules
Diet and Nutrition Defined
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Nutrition
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Diet
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The branch of science that studies food, its
nutrients, and how nutrients are used in the body
Also refers to the process by which we take in
food and utilize it
All of the food and drink consumed by an
organism
The Process of Nutrition
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Ingestion
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Digestion
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The movement of smaller molecules from the digestive
system to the circulatory system
Assimilation
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25-4
The breakdown of complex food molecules to smaller
molecules
Absorption
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Taking food into the body through eating
The modification and incorporation of absorbed
molecules into the structure of the organism
Kinds of Nutrients
and Their Function
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Nutrients are divided into six major
categories:
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25-5
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Carbohydrates
Lipids
Vitamins
Minerals
Water
Energy Content of Food
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25-6
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calorie is a unit of energy—the energy
needed to raise the temperature of a gram of
water one degree Celsius
Kilocalorie=1000 calories
The food calorie is a kilocalorie but is often
shown as Calorie (with a upper case C)
Kinds of Nutrients and Their
Function—Carbohydrates
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Nutritionally important kinds of carbohydrates
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Sugars
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25-7
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Simple sugars are the building blocks of complex
carbohydrates
Mono- and disaccharides
Glucose is a monosaccharide, sucrose is a
disaccharide
Starch is a large polysaccharide made of many
glucose molecules attached to one another.
Fiber—complex indigestible carbohydrates
Carbohydrates—Functions
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Sugars and starch provide energy.
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25-8
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Disaccharides and starch are broken down to
simple sugars.
4 Calories (kilocalories) in a gram of sugar
Sugars taste sweet and stimulate appetite.
Simple sugars are building blocks of other
important molecules—DNA.
Carbohydrates—Functions
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Dietary fiber
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Cellulose and other complex carbohydrates that
are Indigestible
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25-9
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Slows absorption
Stimulates peristalsis
Reduces absorption of cholesterol
Retains moisture in intestine—reduces incidence of
constipation
Carbohydrate Quality
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Foods made from refined flours and sugars
provide Calories but little else (“empty
Calories”)
Whole grain flours contain parts of seeds
other than just starch and sugar
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25-10
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Dietary fiber
Other nutrients
How the Body Manages
Carbohydrates
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Body stores the energy from carbohydrates in two
ways
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Glycogen
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Fat
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25-11
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Glycogen is stored in liver and muscles.
Glycogen consists of glucose molecules hooked together.
Glycogen can be broken down to glucose as needed.
Only small amounts of glycogen are stored.
Carbohydrates converted to fat for longer term storage.
Kinds of Nutrients and Their
Function—Lipids
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Three kinds of lipids
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Phospholipids are important parts of cell
membranes.
Steroids
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25-12
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Many steroids are hormones.
Cholesterol is a steroid.
True fats (triglycerides)
Function of Fats
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25-13
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Long term storage of energy
Excellent source of energy—release 9 Calories per
gram
Vitamins A, D, E, and K dissolve in fats and will not
be absorbed unless fat is present.
Fat under the skin serves as insulation.
Fat under skin and around organs is a shock
absorber.
Fats provide a pleasant “mouth feel” to food and
provide a feeling of fullness in the stomach.
Kinds of Fats Important in Nutrition
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Saturated fats
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Unsaturated
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25-14
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No double bonds in fatty acid portion of molecule
Typically found in foods of animal origin
Solids at room temperature
Double bonds in fatty acid portion of molecule
Typically found in foods of plant origin
Liquids at room temperature (oils)
Kinds of Fats Important in Nutrition
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Polyunsaturated fats
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Trans fats
Not normally found in natural foods
– Created when unsaturated fats are converted to
saturated fats industrially
Essential fatty acids (linoleic acid and linolenic acid)
must be obtain in the diet.
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25-15
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Have several double bonds in the fatty acid
portion of the molecule
How the Body Manages Fat
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25-16
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Fat is produced and stored when food consumption
exceeds energy needs.
Energy from stored fat can be released when
needed.
Originally this was a valuable mechanism to provide
energy in a time of food scarcity.
Today most people rarely experience food scarcity
and tend to permanently store fat (obesity).
Kinds of Nutrients and Their
Function—Proteins
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Composed of amino acids hooked end to end
Functions
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25-17
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Enzymes
Structure—connective tissue, muscles, skin
Component of cell membranes
Some are hormones
Antibodies
Sending and receiving signals
Emergency source of energy if the body runs out of
carbohydrate and fat
Kinds of Proteins
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Complete proteins
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Incomplete proteins
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Lack certain amino acids needed by the body
Typical of proteins from plant sources
Essential amino acids
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Contain all of the amino acids necessary for good
health
Most proteins from animal sources are complete
proteins
Cannot be made by the human body
Must be obtained from the diet
Sources of Essential Amino Acids
25-19
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How the Body Manages Protein
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Proteins cannot be stored and used later.
Only small amounts of protein are lost each
day.
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25-20
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Therefore, we only need a small amount of
protein in our diet every day.
Typically 50 grams is adequate.
Protein consumed in excess of needs are
metabolized to provide energy.
How the Body Manages Protein
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Protein-sparing mechanism
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During fasting or starvation our bodies oxidize
sugar and fats for energy before proteins.
Certain tissues cannot use fats for energy—red
blood cells, nerve cells.
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25-21
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Amino acids must be converted to glucose for their
use.
Long-term fasting or starvation is fatal because
proteins essential for other uses are metabolized
to provide glucose.
Starvation and Stored Foods
25-22
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Kinds of Nutrients and Their
Function—Vitamins
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Organic molecules needed in small amounts
to help enzymes work properly—cannot be
made by humans
Participate in various metabolic reactions
often as coenzymes
Many are antioxidants that destroy free
radicals.
Most are acquired from food
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25-23
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Vitamin D is made in our bodies when UV light
hits cholesterol.
Kinds of Vitamins
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Water soluble vitamins
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Fat soluble vitamins
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25-24
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Vitamin C and various B vitamins
Vitamins A, D, E, K, D
How Vitamins Are Managed
in the Body
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Water soluble vitamins are not stored.
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Fat soluble vitamins can be stored in liver.
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25-25
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Usually not needed if one eats a well-balanced diet
Megadoses of vitamins are not shown to be helpful.
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Released as needed
Vitamin supplements
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Must be obtain daily in the diet
Excess vitamins are excreted.
Some vitamins become toxic in high doses.
Vitamin-deficiency diseases are most common in
poor countries with poverty and starvation.
Sources and Functions of Vitamins
25-26
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Kinds of Nutrients and Their
Function—Minerals
Inorganic elements
 Cannot be synthesized by the body
 Not altered by cooking
 Present in various foods and drinking
water
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25-27
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Kinds of Nutrients and Their
Function—Minerals
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Functions
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Enzyme regulators and cofactors
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Involved in neurotransmission
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Iron
Anemia-iron deficiency
Bone structure
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25-28
Sodium, potassium
Oxygen transport
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Magnesium
Calcium
Osteoporosis-calcium deficiency
Management of Minerals in the Body
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25-29
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Minerals are constantly lost from the body
and must be replaced on a daily basis.
Most minerals are easily replaced with a
reasonable diet.
Iron and calcium supplements are often
needed, particularly in women.
Sources and Functions of Minerals
25-30
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Kinds of Nutrients and Their
Function—Water
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The human body is 65% water.
Primary component of blood, lymph, and
tissue fluid
Dissolves
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Inorganic ions (Na+, K+, Cl-)
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25-31
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Called electrolytes because they conduct electricity
when dissolved
Organic molecules
Many wastes are soluble in water, allowing for
easy elimination.
Kinds of Nutrients and Their
Function—Water
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Most chemical reactions in organisms occur
in water.
Water is involved as a reactant in many
important metabolic reactions.
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25-32
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Hydrolysis of carbohydrates, fats, proteins
Evaporation of water from skin provides
cooling.
Managing Water in the Body
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Water is constantly lost.
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25-33
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Perspiration
Evaporation from skin and lungs
Urine and feces
Must be replaced continuously by ingesting
water and foods containing water
Dietary Reference Intakes
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Published by the USDA
Guidelines for maintaining good health
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Used in preparing food labels
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25-34
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Specific guidelines for men, women, children,
pregnant, and nursing women, etc.
Provide guidelines about maximum amounts of
certain nutrients
Labels list ingredients from greatest to least in
quantity.
Dietary Reference Intakes
for Some Common Nutrients
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The Food Guide Pyramid
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A simple diet guide using food groups
The Food Guide Pyramid—Grains
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Includes vitamin-enriched or
whole-grain cereal
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Breads, bagels, cereals,
crackers, pasta, etc.
Recommended amounts
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Women - 6 oz.
Men - 8 oz.
1 slice of bread = 1 oz.
● Should provide most of Calories in the diet
● Whole grains are the best.
– Provide fiber that facilitates digestion
– Satisfy appetite
25-37
●Grains
also provide certain vitamins and minerals
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The Food Guide Pyramid—Fruits
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Fruit is a botanical term for an
enlarged or modified ovary of a plant
Nutritionally, a fruit is classified as any
plant product that is sweet and not
eaten during the main meal.
– Melons, berries, apples, oranges,
and bananas
1–2 cups per day are recommended.
Nutritional value
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Fiber
Water
Carbohydrate
Certain vitamins and minerals
The Food Guide Pyramid–Vegetables
Nutritionally defined as plant material that is not sweet
and is eaten with the main meal.
4.5 cups a day are recommended.
Include
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Significant value
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25-39
Broccoli, carrots, cabbage, corn, green beans, lettuce,
tomatoes, potatoes, etc
Raw leafy greens important
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Cancer protection
Vitamins and minerals
Provide fiber
Carbohydrate
The Food Guide Pyramid—Milk
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Includes milk, cheese, yogurt,
ice cream
2–3 cups/day recommended.
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Many milk products are high in
cholesterol and fat—use low fat
products
Significant nutrient value
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1.5 oz. cheese = to one cup.
Protein, carbohydrate, fat
Calcium, potassium
Vitamin D, some B vitamins
Vitamin A added to some
milk
The Food Guide Pyramid—Meat
and Beans
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Usually our main source of protein
Includes beef, chicken, fish, nuts, beans, peas,
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tofu, eggs
5.5–6.5 oz. per day are recommended.
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Daily intake is needed since protein cannot be stored.
Animal proteins are complete proteins.
Plant proteins are incomplete proteins.
Significant nutrient information
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Prepare meats to eliminate fats
Mix different plant proteins sources
to get complete protein
Essential fatty acids from plants and fish
Certain minerals and vitamins
The Food Guide Pyramid—Oils
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6–7 teaspoons per day needed to obtain
essential fatty acids
Have high caloric content
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Unsaturated is better than saturated
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Must be eaten in moderation
Fats should comprise 20–35%
of total calories eaten in a day.
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Fish, nuts, vegetable oils are unsaturated.
Saturated fats, trans fats, and cholesterol
should be as low as possible.
Use lean meats and cook to eliminate fat.
Fats are a source of vitamin E.
The Food Guide Pyramid—Exercise
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25-43
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2/3 of American adults are overweight and 1/3 are
obese.
Exercise affects the number of food calories that can
be consumed without gaining weight.
30 minutes of moderate exercise a day is
recommended.
Moderate exercise will elevate heart rate
significantly.
Longer and more vigorous exercise has additional
benefits.
Typical Energy Requirement for
Common Activities
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Basal Metabolic Rate, Diet, and
Weight Control
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Basal metabolic rate is the energy need to maintain
breathing, heart rate, digestion, and body
temperature while at rest.
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Highly variable
Most people have a basal metabolic rate in the range of
1,200–2,200 Calories per day.
Specific dynamic action is the energy needed to
process the food we eat.
Voluntary muscle activity is the energy needed to
perform all voluntary activities.
To maintain body weight the energy intake should be
equal to basal metabolism + specific dynamic action
+ voluntary muscle activity
Additional Kilocalories Needed
by Occupation
25-46
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Body Mass Index (BMI)
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The USDA has published guidelines that will help
people evaluate their weight.
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Body mass index
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A BMI of over 30kg/m2 is considered obese.
Drawback: BMI doesn’t measure fitness
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Evaluates weight based on height
Calculated by dividing weight in kilograms divided by height
in meters squared
Obesity
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Educates people about the dangers of obesity
A measure of how efficiently a person can function
physically and mentally
Eating Disorders
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Three most common problems associated
with diet and food consumption are
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25-48
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Obesity
Bulimia
Anorexia nervosa
All these conditions involve issues related to
metabolic rate, culture, and psychology.
Obesity
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Obesity is a condition of being overweight to the
point that a person’s health, quality of life, or life
span is adversely affected.
About 30% of U.S. population is obese.
Obesity is defined as having a body mass index of
30 kg/m2 or greater.
Body mass index (BMI) is determined by dividing a
person’s weight in kilograms (without clothes) by
their height in meters squared.
Body Mass Index
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Contributing Causes to Obesity
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Psychological factors
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Genetic and metabolic differences
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Eating is a pleasurable activity.
Overeating is often associated with depression.
“Obesity genes” have been identified in mice.
People differ in metabolic rates.
Some people have a faulty mechanism that
normally causes people to “turn off” their appetite
when they are full.
Obesity
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The condition of being overweight to the point where
a person’s health and lifespan are adversely
threatened
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Individuals who have a BMI of 30 or more are obese.
Incidence is increasing because our activity level is
decreasing.
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Occurs when people eat more calories than they use
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Sedentary death syndrome
Due to cultural and social factors
Genetic studies also indicate there may be a genetic
component to obesity.
May involve a chemical imbalance in the brain
Bulimia
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A disease involving a cycle of eating binges
followed by purging the body of food
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Caused by psychological factors
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Can involve depression
The binge-purge cycle has several negative
health effects.
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Purging may involve vomiting or the use of
laxatives or diuretics.
Dehydration, diminished blood volume, mineral
deficiencies, kidney malfunction, lethargy, etc.
Anorexia Nervosa
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A nutritional deficiency disease characterized by
severe, prolonged weight loss
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Caused by an extreme fear of becoming overweight
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Anorexics have a distorted perception of their body.
Severe caloric deficiency (starvation) results in
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25-54
Involves voluntary, severe restriction of caloric intake
Hair loss, constipation, amenorrhea, decreased heart rate,
osteoporosis, etc.
Nutrition During Infancy
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A person’s total energy needs per kg are
greatest during the first year of life.
50% of an infant’s caloric intake is used to
maintain its basal metabolic rate.
Infants triple their weight and increase 50%
in height over the first year of life.
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Therefore, they need nutritionally rich food with
high caloric value.
Human Breast Milk vs.
Cow’s Milk
25-56
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Osteoporosis
25-57
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Nutrition for Fitness and Sports
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Cellular respiration mobilizes the energy needed for
exercise.
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Makes the ATP needed for muscle contraction
Uses glucose, fatty acids, or amino acids
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Conditioning
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25-58
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Glucose from stored glycogen is used first.
Fatty acids from stored triglycerides is used next.
Amino acids are rarely utilized during exercise.
Improves strength of muscles and heart
Improves coordination of muscle movements
Increases metabolic rate
Anaerobic Exercise
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25-59
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Bouts of exercise that are so
intense that the muscles cannot
get oxygen as fast as they need it
Glycolysis provides the ATP
(since oxygen is not present).
Only glucose and glycogen can
be used.
Lactic acid buildup in muscles
Aerobic Exercise
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25-60
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When the level of exertion allows the heart
and lungs to keep up with the oxygen
demand of the muscles
Aerobic cellular respiration provides the ATP
needed.
Metabolic Changes during
Aerobic Exercise
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25-61
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Warm-up period increases metabolic rate, heart rate, and
temperature which provides better blood flow to muscles
At the beginning of exercise anaerobic respiration
provides ATP as glucose and glycogen is used.
Shift to aerobic exercise after initial anaerobic period
(second wind)
– Begin to metabolize triglycerides to provide ATP
– Continue to use glycogen
– When glycogen stores are depleted, athletes “hit the
wall”.
A cool-down period allows metabolic shifts back normal.
Diet and Training
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Water intake is very important during exercise.
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Long-term exercise requires the consumption of high
calorie foods.
Carbohydrate loading can help prevent “hitting the
wall”.
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25-62
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Needed to cool the body
Loss results in more viscous (thicker) blood
Eat high carbohydrate foods in days before event.
Used in conjunction with training exercise
High protein diets not necessary during training
Diet and Training
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Protein supplementation
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Water intake
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25-63
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Eating additional proteins will not result in an
increase in muscle mass unless one is exercising
and placing demands on the muscles.
Water loss can decrease muscular activity.
Drinking water before and during exercise is
necessary to prevent dehydration.