Download Anatomy and Physiology, 5/e Chapter 27: Nutrition and Metabolism

Thibodeau: Anatomy and Physiology, 5/e
Chapter 27: Nutrition and Metabolism
This chapter begins by differentiating between the terms nutrition and metabolism. Proper
nutrition requires a balance of the three basic food types—carbohydrates, fats, and proteins—plus essential
vitamins and minerals. Metabolism, on the other hand, is basically the use the body makes of foods after
they have been digested, absorbed, and circulated to the cells. These two definitions are essential
distinctions to be made before moving into the heart of the digestive system physiology.
Metabolism can be further broken down into two major processes, catabolism and anabolism.
Catabolism breaks food molecules into smaller compounds to release energy from them, while anabolism
does the opposite, building nutrient molecules up into larger compounds and, in so doing, using energy.
Catabolism is decomposition; anabolism is a synthesis process. Anabolism in different cells produces
different compounds. Catabolism releases energy in two forms—heat and chemical energy—releasing the
heat in frequent, small bursts for the purpose of homeostasis of body temperature. At the same time, the
chemical energy is transferred to high-energy bonds of adenosine triphosphate (ATP) molecules. ATP, in
turn, supplies energy directly to the energy-using reactions of all cells.
The bulk of this chapter discusses concepts related to the many and varied metabolic pathways of
the human body. It is important to tell students that the text discussions and accompanying diagrams have
been simplified to facilitate understanding of the basic concepts.
Objectives
After students have completed this chapter, they should be able to:
1.
Define the terms nutrition and metabolism.
2.
Outline the processes of anabolism and catabolism and discuss the role of ATP, adenosine
triphosphate/adensosine diphosphate (ATP/ADP) system and its role in metabolism.
3.
Discuss the various dietary sources of carbohydrates.
4.
Discuss the steps involved in glycolysis.
5.
Explain the role of the electron transport system and oxidative phosphorylation in the citric acid
cycle.
6.
Explain what is meant by the terms anaerobic respiration and aerobic respiration.
7.
Discuss glycogenesis and glycogenolysis.
8.
Discuss glucose homeostasis.
9.
Discuss the dietary sources of lipids.
10.
Identify the major lipid constituents in blood and discuss their mechanisms of transport.
11.
Discuss the metabolism of lipids.
12.
Outline hormonal control of fat metabolism.
13.
Compare and contrast protein anabolism and catabolism.
14.
Discuss the two kinds of protein or nitrogen imbalance.
15.
Discuss the importance of vitamins and minerals.
16.
Define the term metabolic rate and discuss how it can be expressed.
17.
Discuss the major factors that influence basal metabolic rate (BMR).
18.
Discuss the relationship between body weight and energy intake, output, and balance.
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Chapter 27: Nutrition and Metabolism
19.
2
Discuss the mechanisms for regulating food intake.
Lecture Outline
I.
Overview of Nutrition and Metabolism (p. 795)
A.
B.
Nutrition
1.
The study of food
2.
Food groups
a.
Carbohydrates
b.
Fats
c.
Proteins
d.
Vitamins
e.
Minerals
Metabolism (Fig. 27-22; Table 27-2)
1.
The chemical reactions essential for life
2.
Two parts to metabolism
a.
Catabolism (a decomposition process)
1)
Large molecules broken down into small molecules
2)
Energy release
3)
b.
a)
Heat (helps maintain body temperature)
b)
Chemical energy (in the form of ATP)
ATP/ADP system (Fig. 27-1)
Anabolism (a synthesis process)
1)
Small molecules built up into larger molecules
2)
Energy taken in
a)
II.
Chemical energy used to build bonds (ATP
used)
Carbohydrates (p. 797)
A.
Dietary sources of carbohydrates
1.
Complex carbohydrates (polysaccharides)
a.
2.
Disaccharides (Fig. 2-15)
a.
3.
Example: sucrose
Monosaccharides (Figs. 2-14, 27-2)
a.
B.
Examples: starches and cellulose
Example: glucose
Carbohydrate metabolism (p. 797)
1.
The most prevalent form of carbohydrate metabolized is glucose. (Fig.
27-2)
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Chapter 27: Nutrition and Metabolism
a.
2.
The ultimate goal of catabolism is to yield energy to form
ATP
Glucose transport and phosphorylation (Fig. 27-3)
a.
3.
3
When glucose enters the cell, it reacts with ATP and is
immediately phosphorylated, yielding glucose-6-phosphate
Glycolysis (Fig. 27-3)
a.
First series of reactions in glucose catabolism
b.
Result is a gain of two ATP molecules and production of two
pyruvic acid molecules
4.
c.
An anaerobic process
d.
Occurs in the cytoplasm of the cell (Fig. 27-7)
Citric acid cycle (Fig. 27-5)
a.
Second series of reactions in glucose catabolism
b.
Result is a release of six CO2 molecules and H atoms attached
to carrier molecules
5.
6.
c.
An aerobic process linked absolutely to the electron transport
system
d.
Occurs in the mitochondria of the cell (Fig. 27-7)
Electron transport system and oxidative phosphorylation (Fig. 27-6)
a.
Third and final series of reactions in glucose catabolism
b.
Results in production of 34 ATP and production of water
c.
An aerobic process
d.
Occurs in the mitochondria of the cell (Fig. 27-7)
Energy from one glucose molecule (Fig. 27-8)
a.
7.
8.
9.
Anaerobic pathway (p. 802)
a.
In the absence of oxygen, the glucose catabolism proceeds
only through glycolysis.
b.
Produces two ATP molecules and lactic acid instead of
pyruvic acid (Fig. 27-9)
Glycogenesis (Figs. 27-9, 27-10, 27-11)
a.
If glucose enters the cell faster than it can be catabolized, the
excess is stored as glycogen.
b.
Most glycogen is stored in the liver and muscles.
Glycogenolysis (Figs. 27-9, 27-12)
a.
10.
During aerobic conditions, enough energy to synthesize 36
ATP molecules
The process of breaking glycogen into individual glucose
molecules that can be metabolized
Gluconeogenesis (Figs. 27-11, 27-13)
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Chapter 27: Nutrition and Metabolism
a.
11.
4
Occurs when there is not enough glucose in the cell and the
cell converts fat and protein to glucose
Control of glucose metabolism (p. 806)
a.
Beta cells of the pancreas secrete insulin, which moves
glucose from blood into cells.
(Figs. 27-14, 27-15)
b.
Alpha cell of pancreas secrete glucagon, which increases
glycogenolysis and thus increases blood glucose levels (Fig. 27-15)
c.
Epinephrine increases glycogenolysis and thus increases blood
glucose levels. (Fig. 27-15)
d.
Adrenocorticotropic hormone (ACTH) and glucocorticoids
increase blood glucose levels (Fig. 27-15)
e.
Growth hormone (GH) switches metabolism to fat use from
glucose; thus it increases blood glucose levels (Fig. 27-15)
f.
Thyroid stimulating hormone (TSH) may result in elevated or
depressed blood glucose levels (Fig. 27-15).
III.
Lipids (p. 808)
A.
Dietary sources of lipids (fats and oils)
1.
Triglycerides (fats)
a.
Composed of three fatty acids and one glycerol subunit
2.
Phospholipids (all cell membranes)
3.
Cholesterol (only from animal cells, not plants)
4.
Saturated and unsaturated fats
a.
Saturated fats have no double bonds in the fatty acids
(saturated with hydrogen)
b.
Unsaturated fats have double bonds in the fatty acids
(therefore, could have more hydrogens, if the double bonds were
missing)
B.
Transport of lipids
1.
Chylomicrons
a.
2.
3.
Lipoproteins (Box 27-7)
a.
Most common form of lipid in the blood, except immediately
after a meal
b.
Three major forms
1)
VLDL (very-low-density lipoprotein)
2)
LDL (low-denisty lipoprotein)
3)
HDL (high-density lipoprotein)
Free fatty acids
a.
C.
In blood following fat absorption; levels drop within 4 hours
Found in blood when rate of fat metabolism increases
Lipid metabolism (p. 810)
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Chapter 27: Nutrition and Metabolism
1.
5
Lipid catabolism (Fig. 27-16)
a.
Triglycerides are broken into glycerol and fatty acids
1)
Glycerol enters a step of glycolysis (Fig. 27-19)
2)
Fatty acids undergo beta-oxidation and enter the
citric acid cycle (Fig. 27-19)
b.
2.
3.
IV.
Ketogenesis (production of ketone bodies) occurs during
accelerated fat metabolism, such as with starvation
Lipid anabolism
a.
Lipogenesis
b.
Essential fatty acids
1)
Cannot be produced by the body
2)
Needed to produce prostaglandins
Control of lipid metabolism
a.
Insulin
b.
Growth hormone
c.
ACTH
d.
Glucocorticoids
Proteins (p. 811)
A.
Sources of proteins
1.
2.
B.
Amino acids (Table 27-1)
a.
Essential (9; not produced by the body)
b.
Nonessential (11; produced by the body)
Dietary sources
Protein metabolism
1.
Protein anabolism (Fig. 27-17)
a.
2.
Protein synthesis (Chapter 2)
Protein catabolism (Fig. 27-18)
a.
Steps to the process
1)
Break individual amino acids from protein
2)
Deamination (removal of amine group)
3)
Keto acid
a)
Oxidized via citric acid cycle (Fig. 27-19)
b)
Converted to glucose
c)
Converted to fat
4)
Gluconeogenesis
5)
Lipogenesis
6)
Ammonia conversion to urea
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Chapter 27: Nutrition and Metabolism
3.
Protein balance and nitrogen balance
a.
4.
V.
Usually, rate of protein catabolism equals rate of protein
anabolism
Control of protein metabolism (Table 27-2)
a.
Growth hormone stimulates anabolism
b.
Testosterone stimulates anabolism
c.
Glucocorticoids stimulate catabolism
d.
Thyroid hormone stimulates anabolism or catabolism
Vitamins and Minerals (p. 813)
A.
Vitamins (Fig. 27-20; Table 27-3)
1.
Molecules that the body cannot produce; needed in small quantities
2.
Usually attach to coenzymes
3.
Two types of vitamins
a.
b.
B.
Fat-soluble vitamins
1)
Vitamin A—retinal
2)
Vitamin D—calcitriol
3)
Vitamin E—antioxidant (Fig. 27-21)
4)
Vitamin K—produced by bacteria in colon
Water-soluable vitamins
1)
Vitamin C—ascorbic acid
2)
Vitamin B—several different ones
Minerals (Table 27-4)
1.
VI.
6
Function
a.
Attach to enzymes, allowing them to function
b.
Assist other chemical reactions in body
Metabolic Rates (p. 817)
A.
Expressed as number of kilocalories expended per hour or day (catabolism)
B.
Expressed as normal or as a percentage above or below normal
C.
Basal metabolic rate (BMR) (Table 27-5)
1.
Factors affecting basal metabolic rate (Fig. 27-22))
a.
Size
b.
Sex
c.
Age
d.
Thyroid hormone
e.
Body temperature
f.
Drugs
g.
Other factors
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Chapter 27: Nutrition and Metabolism
D.
E.
VII.
VIII.
Basic metabolic rate
2.
Skeletal muscle work
3.
Thermic effect of food
Energy balance and body weight (p. 819)
A.
Appetite center
B.
Satiety center
C.
Thermostat theory
D.
Glucostat theory
Cycle of Life: Nutrition and Metabolism (p. 821)
B.
Childhood—critical nutrients
1.
Protein
2.
Calcium
Late adulthood
1.
Decrease in metabolic rate
2.
Calcium requirements
The Big Picture: Nutrition, Metabolism, and the Whole Body (p. 822)
A.
X.
1.
Mechanisms for Regulating Food Intake (Fig. 27-23)
A.
IX.
Total metabolic rate (Box 27-12)
Other body systems involved in nutrition and metabolism
1.
Nervous
2.
Skeletal
3.
Muscular
4.
Digestive
5.
Circulatory
6.
Lymphatic
7.
Respiratory
8.
Urinary
9.
Integumentary
Mechanisms of Disease: Metabolic and Nutritional Disorders (p. 822)
A.
Inborn errors of metabolism
1.
B.
C.
Phenylketonuria
Complications from other conditions
1.
BMR—hypothyroidism or hyperthyroidism
2.
Metabolism—diabetes mellitus
Eating disorders
1.
Anorexia nervosa
2.
Bulimia
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7
Chapter 27: Nutrition and Metabolism
3.
D.
Obesity
Nutritional disorders
1.
2.
Protein-calorie malnutrition
a.
Marasmus (Fig. 27-24 B)
b.
Kwashiorkor (Fig. 27-24 A)
Vitamin disorders
a.
Avitaminosis C—scurvy
b.
Hypervitaminosis A (Fig. 27-25)
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