Chapter 20:Metabolism, Nutrition, and Body Temperature

Overview

Key Termsanabolism glycogen metabolic ratebasal metabolism glycolysis mineralcatabolism hypothalamus oxidationcellular respiration hypothermia pyrogenfever kilocalorie vitaminglucose malnutrition

MetabolismLearning Outcomes1. 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.

MetabolismTypes of Metabolic Activities• Catabolism

• Anabolism

MetabolismCellular 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?

MetabolismLearning Outcomes3. 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.

MetabolismMetabolic Rate• • Decreases with age• Measured in kilocalories (kcal)

MetabolismThe Use of Nutrients for Energy• Glucose is main source of energy

– • Other energy sources

– – –

MetabolismMinerals• • They are necessary for

– – – – – Blood clotting

MetabolismVitamins• Vitamins are

– Water soluble– Fat soluble

• Some are antioxidants.–

Metabolism ✓Checkpoints20-1 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 GuidelinesLearning Outcomes8. 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 GuidelinesPercentage of Calories in Daily Diet• Carbohydrate: • Fat: • Protein:

Nutritional GuidelinesCarbohydrates• Types

– –

• Starches• Plant fiber

Nutritional GuidelinesCarbohydrates• 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 GuidelinesFats• 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 GuidelinesProteins• 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 GuidelinesVitamin 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 GuidelinesAlcohol• Not a nutrient• Interferes with metabolism

Nutritional Guidelines✓Checkpoints20-6 What is the normal range of blood glucose?20-7 What are typical recommendations for the relative

amounts of carbohydrates, fats, and proteins in thediet?

20-8 What is the difference between saturated andunsaturated fats?

20-9 What are some adverse effects of excess alcoholconsumption?

Nutritional DisordersLearning Outcome12. Describe some nutritional

disorders.

Nutritional DisordersFood Allergies• Allergens can be food or food additives.• Allergic reactions involve

– Skin– Respiratory tract – Gastrointestinal tract

• Reactions can be fatal.n

Nutritional DisordersMalnutrition• 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 DisordersOverweight 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 TemperatureLearning Outcomes13. 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✓Checkpoints20-10 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

excessiveheat?

20-14 What is the term for excessively low bodytemperature?