Chapter 20:
Metabolism, Nutrition,
and Body Temperature
Overview
Key Terms
anabolism
glycogen
metabolic rate
basal metabolism
glycolysis
mineral
catabolism
hypothalamus
oxidation
cellular respiration
hypothermia
pyrogen
fever
kilocalorie
vitamin
glucose
malnutrition
Metabolism
Learning Outcomes
1. Differentiate between catabolism
and anabolism.
2. Differentiate between the
anaerobic and aerobic phases of
glucose catabolism and give the
end products and the relative
amount of energy released by
each.
Metabolism
Types of Metabolic Activities
• Catabolism
• Anabolism
Metabolism
Cellular Respiration
• Anaerobic glucose catabolism; glycolysis
– Location: Cytoplasm
– Yield:
– End product:
• Aerobic glucose catabolism
– Location: Mitochondria
– Yield:
– End products:
Figure 20-1 Cellular respiration.
What does pyruvic acid produce when it is metabolized anaerobically?
What does it produce when metabolized completely using oxygen?
Metabolism
Learning Outcomes
3. Define metabolic rate and name
several factors that affect the
metabolic rate.
4. Explain how carbohydrates, fats,
and proteins are metabolized for
energy.
5. Compare the energy contents of
fats, proteins, and carbohydrates.
6. Define essential amino acid.
7. Explain the roles of minerals and
vitamins in nutrition and give
examples of each.
Metabolism
Metabolic Rate
•
• Decreases with age
• Measured in kilocalories (kcal)
Metabolism
The Use of Nutrients for Energy
• Glucose is main source of energy
–
• Other energy sources
–
–
–
Metabolism
Minerals
•
• They are necessary for
–
–
–
–
– Blood clotting
Metabolism
Vitamins
• Vitamins are
– Water soluble
– Fat soluble
• Some are antioxidants.
–
Metabolism
Checkpoints
20-1 What are the two types of activities that make
up metabolism?
20-2 What name is given to the series of cellular
reactions that releases energy from nutrients?
20-3 What are the two main energy sources for cells?
20-4 What is meant when an amino acid or a fatty acid
is described as essential?
20-5 What is the difference between vitamins and
minerals?
Nutritional Guidelines
Learning Outcomes
8.
List the recommended
percentages of carbohydrate, fat,
and protein in the diet.
9.
Distinguish between simple and
complex carbohydrates, giving
examples of each.
10. Compare saturated and
unsaturated fats.
11. List some adverse effects of
alcohol consumption.
Nutritional Guidelines
Percentage of Calories in Daily Diet
• Carbohydrate:
• Fat:
• Protein:
Nutritional Guidelines
Carbohydrates
• Types
–
–
• Starches
• Plant fiber
Nutritional Guidelines
Carbohydrates
• Diet should be mainly complex, naturally occurring
carbohydrates
• Normal blood glucose range 85–125 mg/dL
• Glycemic effect measures how rapidly food raises blood
glucose level, stimulates release of insulin
Nutritional Guidelines
Fats
• Types
–
• Most are from animal sources
• Solid at room temperature
–
• Derived from plants
• Liquid at room temperature
Figure 20-2 Saturated and
unsaturated fats.
Nutritional Guidelines
Proteins
• Most animal proteins supply all essential amino acids
(complete).
• Most vegetable proteins lack one or more essential
amino acids (incomplete).
Figure 20-3 Combining foods to obtain the essential
amino acids.
Nutritional Guidelines
Vitamin and Mineral Supplements
• Supplements are controversial.
• Some populations may benefit from them.
• Some vitamins cause toxic effects when taken in
excess.
Figure 20-4 USDA dietary guidelines.
Nutritional Guidelines
Alcohol
• Not a nutrient
• Interferes with metabolism
Nutritional Guidelines
Checkpoints
20-6 What is the normal range of blood glucose?
20-7 What are typical recommendations for the relative
amounts of carbohydrates, fats, and proteins in the
diet?
20-8 What is the difference between saturated and
unsaturated fats?
20-9 What are some adverse effects of excess alcohol
consumption?
Nutritional Disorders
Learning Outcome
12. Describe some nutritional
disorders.
Nutritional Disorders
Food Allergies
• Allergens can be food or food additives.
• Allergic reactions involve
– Skin
– Respiratory tract
– Gastrointestinal tract
• Reactions can be fatal.n
Nutritional Disorders
Malnutrition
• Can occur from missing nutrients or too much of wrong
foods
• Protein and energy malnutrition (PEM)
• Marasmus
• Kwashiorkor
Figure 20-5 Effects of kwashiorkor.
Nutritional Disorders
Overweight and Obesity
• Causes are complex
• Incidence is increasing
• Shortens life span
• Measured by body mass index (BMI)
– Overweight is BMI of 25–30
– Obese is BMI greater than 30
• Increased risk of diabetes
Nutritional Disorders
Underweight
• Low reserves of energy
• Reproductive disturbances
• Nutritional deficiencies
• BMI less than 18.5
Figure 20-6 Calculation of body mass index (BMI).
What is the BMI of a man 5’10” in height who weighs 170 pounds?
(Round off to one decimal place.)
Nutrition and Aging
• Nutritional deficiencies may develop.
• Medications may interfere with appetite and absorption.
Body Temperature
Learning Outcomes
13. Explain how heat is produced
and lost in the body.
14. Describe the role of the
hypothalamus in regulating body
temperature.
15. Explain the role of fever in
disease.
16. Describe some adverse effects of
excessive heat and cold.
Body Temperature
• Heat is byproduct of chemical activities in body tissues
• Regulatory devices keep body temperature constant
within narrow limits
Heat Production
• Amount of heat produced by organs affected by
– Exercise
– Hormone production
– Food intake
– Age
Heat Loss
• More than 80% of heat loss occurs through skin
– Conduction
– Radiation
– Convection
– Evaporation
• 15%–20% heat loss through respiration and elimination
• Heat loss prevention
– Clothing
– Fat layer under skin
Figure 20-7 Mechanisms of heat loss.
What will happen in (B) if the fan speed is increased?
What will happen in (C) as environmental humidity increases?
Temperature Regulation
• Body has internal mechanisms for regulating
temperature
The Role of the Hypothalamus
• Regulation of heat loss
– Constrict skin blood vessels
– Shiver
– Increase cell metabolism
• Overheating
– Stimulate sweat glands
– Dilate skin blood vessels
– Muscle relaxation
Age Factors
• Newborns and elderly
• Reduced ability to produce heat
• Reduced ability to regulate overheating
Normal Body Temperature
• Normal range is 36.3°C to 37.6°C (97.8°F to
100.8°F)
• Varies with time of day
• Varies by body part
Fever
• Higher than normal body temperature
• Causes
– Infection
– Malignancies
– Brain injuries
– Toxic reactions
– Vaccine reactions
– Central nervous system diseases
• Crisis
• Lysis
Responses to Excessive Heat
• Heat cramps
– Localized muscle cramping
• Heat exhaustion
– Heat retention and fluid loss
• Heat stroke
– Medical emergency that can be fatal
Responses to Excessive Cold
• Hypothermia
– Excessively low body temperature
– Used in some types of surgery
• Frostbite
– Can cause permanent local tissue damage
– Likely areas are face, ears, extremities
Body Temperature
Checkpoints
20-10 What are some factors that affect heat production
in the body?
20-11 What part of the brain is responsible for regulating
body temperature?
20-12 What is normal body temperature?
20-13 What are some conditions brought on by excessive
heat?
20-14 What is the term for excessively low body
temperature?