25-1 Chapter 25 Lecture Outline. . 25-2 Living Things as Chemical Factories: Matter and Energy...
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Transcript of 25-1 Chapter 25 Lecture Outline. . 25-2 Living Things as Chemical Factories: Matter and Energy...
.25-2
Living Things as Chemical Factories: Matter and Energy Manipulators
All organisms need energy and building blocks to live and grow.
Nutrients– All of the molecules required to support life– Includes inorganic elements and organic
molecules
.25-3
Diet and Nutrition Defined
Nutrition– 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
Diet– All of the food and drink consumed by an
organism
.25-4
The Process of Nutrition
Ingestion– Taking food into the body through eating
Digestion– The breakdown of complex food molecules to smaller
molecules
Absorption– The movement of smaller molecules from the digestive
system to the circulatory system
Assimilation– The modification and incorporation of absorbed
molecules into the structure of the organism
.25-5
Kinds of Nutrients and Their Function
Nutrients are divided into six major categories:– Carbohydrates– Lipids– Vitamins– Minerals– Water
.25-6
Energy Content of Food
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)
.25-7
Kinds of Nutrients and Their Function—Carbohydrates
Nutritionally important kinds of carbohydrates– Sugars
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
.25-8
Carbohydrates—Functions
Sugars and starch provide energy.– 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.
.25-9
Carbohydrates—Functions
Dietary fiber– Cellulose and other complex carbohydrates that
are Indigestible Slows absorption Stimulates peristalsis Reduces absorption of cholesterol Retains moisture in intestine—reduces incidence of
constipation
.25-10
Carbohydrate Quality
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– Dietary fiber– Other nutrients
.25-11
How the Body Manages Carbohydrates
Body stores the energy from carbohydrates in two ways
– Glycogen 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.
– Fat Carbohydrates converted to fat for longer term storage.
.25-12
Kinds of Nutrients and Their Function—Lipids
Three kinds of lipids– Phospholipids are important parts of cell
membranes.– Steroids
Many steroids are hormones. Cholesterol is a steroid.
– True fats (triglycerides)
.25-13
Function of Fats
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.
.25-14
Kinds of Fats Important in Nutrition
Saturated fats– No double bonds in fatty acid portion of molecule– Typically found in foods of animal origin– Solids at room temperature
Unsaturated– Double bonds in fatty acid portion of molecule– Typically found in foods of plant origin– Liquids at room temperature (oils)
.25-15
Kinds of Fats Important in Nutrition
Polyunsaturated fats– Have several double bonds in the fatty acid
portion of the molecule 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.
.25-16
How the Body Manages Fat
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).
.25-17
Kinds of Nutrients and Their Function—Proteins
Composed of amino acids hooked end to end Functions
– 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
.25-18
Kinds of Proteins
Complete proteins– Contain all of the amino acids necessary for good
health– Most proteins from animal sources are complete
proteins Incomplete proteins
– Lack certain amino acids needed by the body– Typical of proteins from plant sources
Essential amino acids– Cannot be made by the human body– Must be obtained from the diet
.25-20
How the Body Manages Protein
Proteins cannot be stored and used later. Only small amounts of protein are lost each
day.– 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.
.25-21
How the Body Manages Protein
Protein-sparing mechanism– 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. 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.
.25-23
Kinds of Nutrients and Their Function—Vitamins
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– Vitamin D is made in our bodies when UV light
hits cholesterol.
.25-24
Kinds of Vitamins
Water soluble vitamins– Vitamin C and various B vitamins
Fat soluble vitamins– Vitamins A, D, E, K, D
.25-25
How Vitamins Are Managed in the Body
Water soluble vitamins are not stored.– Must be obtain daily in the diet
Fat soluble vitamins can be stored in liver.– Released as needed
Vitamin supplements – Usually not needed if one eats a well-balanced diet
Megadoses of vitamins are not shown to be helpful.– Excess vitamins are excreted.– Some vitamins become toxic in high doses.
Vitamin-deficiency diseases are most common in poor countries with poverty and starvation.
.25-27
Kinds of Nutrients and Their Function—Minerals
Inorganic elementsCannot be synthesized by the bodyNot altered by cookingPresent in various foods and drinking
water
.25-28
Kinds of Nutrients and Their Function—Minerals
Functions– Enzyme regulators and cofactors
Magnesium– Involved in neurotransmission
Sodium, potassium– Oxygen transport
Iron Anemia-iron deficiency
– Bone structure Calcium Osteoporosis-calcium deficiency
.25-29
Management of Minerals in the Body
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.
.25-31
Kinds of Nutrients and Their Function—Water
The human body is 65% water. Primary component of blood, lymph, and
tissue fluid Dissolves
– Inorganic ions (Na+, K+, Cl-) Called electrolytes because they conduct electricity
when dissolved Organic molecules
– Many wastes are soluble in water, allowing for easy elimination.
.25-32
Kinds of Nutrients and Their Function—Water
Most chemical reactions in organisms occur in water.
Water is involved as a reactant in many important metabolic reactions. – Hydrolysis of carbohydrates, fats, proteins
Evaporation of water from skin provides cooling.
.25-33
Managing Water in the Body
Water is constantly lost.– Perspiration– Evaporation from skin and lungs– Urine and feces
Must be replaced continuously by ingesting water and foods containing water
.25-34
Dietary Reference Intakes
Published by the USDA Guidelines for maintaining good health
– Specific guidelines for men, women, children, pregnant, and nursing women, etc.
– Provide guidelines about maximum amounts of certain nutrients
Used in preparing food labels– Labels list ingredients from greatest to least in
quantity.
.25-37
The Food Guide Pyramid—Grains
Includes vitamin-enriched or whole-grain cereal
– Breads, bagels, cereals, crackers, pasta, etc.
Recommended amounts– 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
●Grains also provide certain vitamins and minerals
.25-38
The Food Guide Pyramid—Fruits
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
– Fiber– Water– Carbohydrate– Certain vitamins and minerals
.25-39
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
– Broccoli, carrots, cabbage, corn, green beans, lettuce, tomatoes, potatoes, etc
– Raw leafy greens important Significant value
– Cancer protection– Vitamins and minerals– Provide fiber– Carbohydrate
.25-40
The Food Guide Pyramid—Milk
Includes milk, cheese, yogurt, ice cream
2–3 cups/day recommended.– 1.5 oz. cheese = to one cup.
Many milk products are high in cholesterol and fat—use low fat products
Significant nutrient value– Protein, carbohydrate, fat– Calcium, potassium– Vitamin D, some B vitamins– Vitamin A added to some
milk
.25-41
The Food Guide Pyramid—Meatand Beans
Usually our main source of protein Includes beef, chicken, fish, nuts, beans, peas,
tofu, eggs 5.5–6.5 oz. per day are recommended. Daily intake is needed since protein cannot be stored. Animal proteins are complete proteins. Plant proteins are incomplete proteins. Significant nutrient information
– 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
.25-42
The Food Guide Pyramid—Oils
6–7 teaspoons per day needed to obtain essential fatty acids
Have high caloric content– Must be eaten in moderation– Fats should comprise 20–35%
of total calories eaten in a day. Unsaturated is better than saturated
– 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.
.25-43
The Food Guide Pyramid—Exercise
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.
.25-45
Basal Metabolic Rate, Diet, and Weight Control
Basal metabolic rate is the energy need to maintain breathing, heart rate, digestion, and body temperature while at rest.
– 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
.25-47
Body Mass Index (BMI)
The USDA has published guidelines that will help people evaluate their weight.
– Educates people about the dangers of obesity Body mass index
– Evaluates weight based on height– Calculated by dividing weight in kilograms divided by height
in meters squared Obesity
– A BMI of over 30kg/m2 is considered obese. Drawback: BMI doesn’t measure fitness
– A measure of how efficiently a person can function physically and mentally
.25-48
Eating Disorders
Three most common problems associated with diet and food consumption are– Obesity– Bulimia– Anorexia nervosa
All these conditions involve issues related to metabolic rate, culture, and psychology.
.25-49
Obesity
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.
.25-51
Contributing Causes to Obesity
Psychological factors– Eating is a pleasurable activity.– Overeating is often associated with depression.
Genetic and metabolic differences– “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.
.25-52
Obesity
The condition of being overweight to the point where a person’s health and lifespan are adversely threatened
– Occurs when people eat more calories than they use Individuals who have a BMI of 30 or more are obese. Incidence is increasing because our activity level is
decreasing.– 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
.25-53
Bulimia
A disease involving a cycle of eating binges followed by purging the body of food– Purging may involve vomiting or the use of
laxatives or diuretics. Caused by psychological factors
– Can involve depression The binge-purge cycle has several negative
health effects.– Dehydration, diminished blood volume, mineral
deficiencies, kidney malfunction, lethargy, etc.
.25-54
Anorexia Nervosa
A nutritional deficiency disease characterized by severe, prolonged weight loss
– Involves voluntary, severe restriction of caloric intake
Caused by an extreme fear of becoming overweight– Anorexics have a distorted perception of their body.
Severe caloric deficiency (starvation) results in– Hair loss, constipation, amenorrhea, decreased heart rate,
osteoporosis, etc.
.25-55
Nutrition During Infancy
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.– Therefore, they need nutritionally rich food with
high caloric value.
.25-58
Nutrition for Fitness and Sports
Cellular respiration mobilizes the energy needed for exercise.
– Makes the ATP needed for muscle contraction– Uses glucose, fatty acids, or amino acids
Glucose from stored glycogen is used first. Fatty acids from stored triglycerides is used next. Amino acids are rarely utilized during exercise.
Conditioning– Improves strength of muscles and heart – Improves coordination of muscle movements– Increases metabolic rate
.25-59
Anaerobic Exercise
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
.25-60
Aerobic Exercise
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.
.25-61
Metabolic Changes during Aerobic Exercise
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.
.25-62
Diet and Training
Water intake is very important during exercise.– Needed to cool the body– Loss results in more viscous (thicker) blood
Long-term exercise requires the consumption of high calorie foods.
Carbohydrate loading can help prevent “hitting the wall”.
– Eat high carbohydrate foods in days before event.– Used in conjunction with training exercise
High protein diets not necessary during training
.25-63
Diet and Training
Protein supplementation– Eating additional proteins will not result in an
increase in muscle mass unless one is exercising and placing demands on the muscles.
Water intake– Water loss can decrease muscular activity.– Drinking water before and during exercise is
necessary to prevent dehydration.