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Names: Lieberman, Michael, 1950author. | Peet, Alisa, author.

Title: Marks’ basic medical biochemistry : a clinical approach / Michael Lieberman, Alisa Peet ; illustrations by Matthew Chansky.

Other titles: Basic medical biochemistry

Description: Fifth edition. | Philadelphia : Wolters Kluwer, [2018] | Includes bibliographical references and index.

Identifiers: LCCN 2017016094 | ISBN 9781496324818 Subjects: | MESH: Biochemical Phenomena | Clinical Medicine

Classification: LCC QP514.2 | NLM QU 34 | DDC 612.1/111—dc23 LC record available at https://lccn.loc.gov/2017016094

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This work is no substitute for individual patient assessment based upon healthcare professionals’ examination of each patient and

consideration of, among other things, age, weight, gender, current or prior medical conditions, medication history, laboratory data, and other

factors unique to the patient. The publisher does not provide medical advice or guidance and this work is merely a reference tool. Healthcare

professionals, and not the publisher, are solely responsible for the use of this work including all medical judgments and for any resulting

diagnosis and treatments.

Given continuous, rapid advances in medical science and health information, independent professional verification of medical diagnoses,

indications, appropriate pharmaceutical selections and dosages, and treatment options should be made and healthcare professionals should

consult a variety of sources. When prescribing medication, healthcare professionals are advised to consult the product information sheet (the

manufacturer’s package insert) accompanying each drug to verify, among other things, conditions of use, warnings and side effects and

identify any changes in dosage schedule or contraindications, particularly if the medication to be administered is new, infrequently used or has a

narrow therapeutic range. To the maximum extent permitted under applicable law, no responsibility is assumed by the publisher for any injury

and/or damage to persons or property, as a matter of products liability, negligence law or otherwise, or from any reference to or use by any

person of this work. LWW.comPreface to the Fifth Edition

It has been 5 years since the fourth edition was completed. The fifth edition has some significant

organizational changes, as suggested by extensive surveys of faculty and students who used the fourth

edition in their classes and studies. The major pedagogic features of the text remain. They have been

enhanced by the following changes for the fifth edition:

1.Every patient history has been reviewed and revised to reflect current standards of care (as of

2016). The patient names have also been changed to a first name and last initial. A key indicating

the “old” names and “new” names is available in the online supplement associated with the text.

2.The Biochemical Comments associated with each chapter have been updated, where appropriate,

to allow students to experience where current research efforts are headed.

3.The presentation of metabolism has been altered such that glycolysis is now the first topic

discussed, followed by the tricarboxylic acid cycle, and then oxidative phosphorylation. The

correlation between fourth edition chapters and fifth edition chapters are as follows:

a. Chapters 1 through 18, no change

b. Section IV is now entitled “Carbohydrate Metabolism, Fuel Oxidation, and the Generation of

Adenosine Triphosphate” and consists of Chapters 19 through 28.

i. Chapter 19 of the fifth edition (Basic Concepts in the Regulation of Fuel Metabolism by

Insulin, Glucagon, and Other Hormones) is based on Chapter 26 of the fourth edition. ii. Chapter 20 of the fifth edition (Cellular Bioenergetics: Adenosine Triphosphate and O2)

is based on Chapter 19 of the fourth edition.

iii. Chapter 21 of the fifth edition (Digestion, Absorption, and Transport of Carbohydrates) is

based on Chapter 27 of the fourth edition.

iv. Chapter 22 of the fifth edition (Generation of Adenosine Triphosphate from Glucose,

Fructose, and Galactose: Glycolysis) is based on Chapter 22 of the fourth edition and

also contains parts of Chapter 29 of the fourth edition (Pathways of Sugar Metabolism:

Pentose Phosphate Pathway, Fructose, and Galactose Metabolism).

v. Chapter 23 of the fifth edition (Tricarboxylic Acid Cycle) is based on Chapter 20 of the

fourth edition.vi. Chapter 24 of the fifth edition (Oxidative Phosphorylation and Mitochondrial Function) is

based on Chapter 21 of the fourth edition.

vii. Chapter 25 of the fifth edition (Oxygen Toxicity and Free-Radical Injury) is based on

Chapter 24 of the fourth edition.

viii. Chapter 26 of the fifth edition (Formation and Degradation of Glycogen) is based on

Chapter 28 of the fourth edition.

ix. Chapter 27 of the fifth edition (Pentose Phosphate Pathway and the Synthesis of Glycosides, Lactose, Glycoproteins, and Glycolipids) is based on Chapter 30 of the fourth edition, along with a section (The Pentose Phosphate Pathway) of Chapter 29 of the

fourth edition. This led to the deletion of old Chapter 29 from the Table of Contents of the

fifth edition.

x. Chapter 28 of the fifth edition (Gluconeogenesis and Maintenance of Blood Glucose Levels) is based on Chapter 31 of the fourth edition.

c. Section V (Lipid Metabolism) now consists of the following chapters:

i. Chapter 29 of the fifth edition (Digestion and Transport of Dietary Lipids) is based on

Chapter 32 of the fourth edition.

ii. Chapter 30 of the fifth edition (Oxidation of Fatty Acids and Ketone Bodies) is

based on

Chapter 23 of the fourth edition.

iii.Chapter 31 of the fifth edition (Synthesis of Fatty Acids, Triacylglycerols, and the Major

Membrane Lipids) is based on Chapter 33 of the fourth edition and also contains basic

information concerning the eicosanoids from Chapter 35 of the fourth edition. Material

from Chapter 35 of the fourth edition that was not incorporated into Chapter 31 of the fifth

edition is available as an online supplement. A separate chapter on eicosanoid metabolism is not present in the fifth edition.

iv.Chapter 32 of the fifth edition (Cholesterol Absorption, Synthesis, Metabolism, and Fate)

is based on Chapter 34 of the fourth edition.

v.Chapter 33 of the fifth edition (Metabolism of Ethanol) is based on Chapter 25 of

the

fourth edition.

vi.Chapter 34 of the fifth edition (Integration of Carbohydrate and Lipid Metabolism) is

based on Chapter 36 of the fourth edition.

d. Section VI (Nitrogen Metabolism) has the same chapter order as in the fourth edition, but

because two chapters have been deleted previously from the text, the chapter numbers in the

fifth edition are two less than in the fourth edition. Section VI in the fifth edition comprises

Chapters 35 through 40, whereas in the fourth edition, it is Chapters 37 through 42. e. Section VII (Tissue Metabolism) has the same chapter order as in the fourth edition, but the

chapter numbers in the fifth edition are two less than in the fourth edition. Section VII in the

fifth edition comprises Chapters 41 through 47, whereas in the fourth edition, it is Chapters 43

through 49.

4. The number of printed review questions at the end of each chapter has been increased to 10, up

from 5 questions per chapter in the fourth edition (470 total questions). The online question bank

associated with the text has also been increased to 560 questions, as compared to 468 questionsassociated with the fourth edition. Where possible, questions are presented in National Board of

Medical Examiners format.

As stated in previous editions, in revising a text geared primarily toward medical students, the authors

always struggle with new advances in biochemistry and whether such advances should be included in the

text. We have taken the approach of only including advances that will enable the student to better relate

biochemistry to medicine and future diagnostic tools. Although providing incomplete, but exciting,

advances to graduate students is best for their education, medical students benefit more from a more

directed approach—one that emphasizes how biochemistry is useful for the practice of medicine. This is

a major goal of this text.

Any errors are the responsibility of the authors, and we would appreciate being notified when such

errors are found.

The accompanying website for this edition of Marks’ Basic Medical Biochemistry: A Clinical

Approach contains the aforementioned additional multiple-choice questions for review, a table listing

patient names for the fifth edition and how they correspond to those of the fourth edition, summaries of all

patients described in the text (patient cases), all chapter references and additional reading (with links to

the article in PubMed, where applicable), a listing of diseases discussed in the book (with links to

appropriate websites for more information), and a summary of all of the methods described throughout the

text.How to Use This Book

Icons identify the various components of the book: the patients who are presented at the start of each

chapter; the clinical notes, methods notes, questions, and answers that appear in the margins; and the Key

Concepts, Clinical Comments, and Biochemical Comments that are found at the end of each chapter.

Each chapter starts with an abstract that summarizes the information so that students can recognize the

key words and concepts they are expected to learn. The next component of each chapter is The Waiting

Room, describing patients with complaints and detailing the events that led them to seek medical help.

indicates a female patient indicates a male patient

indicates a patient who is an infant or young child

As each chapter unfolds, icons appear in the margin, identifying information related to the material

presented in the text:

indicates a clinical note, usually related to the patients in The Waiting Room for that chapter. These

notes explain signs or symptoms of a patient or give some other clinical information relevant to the

text.

indicates a methods note, which elaborates on how biochemistry is required to perform, and

interpret, common laboratory tests.

Questions and answers also appear in the margin and should help to keep students thinking as they

read the text:indicates a question

indicates the answer to the question. The answer to a question is always located on the next page. If

two questions appear on one page, the answers are given in order on the next page. Each chapter ends with these three sections: Key Concepts, Clinical Comments, and Biochemical

Comments:

The Key Concepts summarize the important take-home messages from the chapter. The Clinical Comments give additional clinical information, often describing the treatment plan and

the outcome.

The Biochemical Comments add biochemical information that is not covered in the text or explore

some facet of biochemistry in more detail or from another angle.

Finally, Review Questions are presented. These questions are written in a United States Medical

Licensing Examination–like format, and many of them have a clinical slant. Answers to the review

questions, along with detailed explanations, are provided at the end of every chapter.Acknowledgments

The authors would like to thank Professor Kent Littleton of Bastyr University, for his careful reading of

the fourth edition and pointing out mistakes and errors that required correcting for the fifth edition. We

greatly appreciate his efforts in improving the text. Dr. Bonnie Brehm was instrumental in helping with the

nutrition aspects of the text, and Dr. Rick Ricer was invaluable in writing questions, both for the text and

the online supplement. We would also like to acknowledge the initial contributions of Dawn Marks,

whose vision of a textbook geared toward medical students led to the first edition of this book. Her vision

is still applicable today.Contents SECTION I

Fuel Metabolism

1 Metabolic Fuels and Dietary Components

2 The Fed or Absorptive State

3 Fasting

SECTION II

Chemical and Biologic Foundations of Biochemistry 4 Water, Acids, Bases, and Buffers

5 Structures of the Major Compounds of the Body

6 Amino Acids in Proteins

7 Structure–Function Relationships in Proteins

8 Enzymes as Catalysts

9 Regulation of Enzymes

10 Relationship between Cell Biology and Biochemistry

11 Cell Signaling by Chemical Messengers SECTION III

Gene Expression and the Synthesis of Proteins 12 Structure of the Nucleic Acids

13 Synthesis of DNA

14 Transcription: Synthesis of RNA15 Translation: Synthesis of Proteins

16 Regulation of Gene Expression

17 Use of Recombinant DNA Techniques in Medicine

18 The Molecular Biology of Cancer SECTION IV

Carbohydrate Metabolism, Fuel Oxidation, and the Generation of Adenosine Triphosphate

19 Basic Concepts in the Regulation of Fuel Metabolism by Insulin, Glucagon, and Other Hormones

20 Cellular Bioenergetics: Adenosine Triphosphate and O2

21 Digestion, Absorption, and Transport of Carbohydrates

22 Generation of Adenosine Triphosphate from Glucose, Fructose, and Galactose: Glycolysis

23 Tricarboxylic Acid Cycle

24 Oxidative Phosphorylation and Mitochondrial Function

25Oxygen Toxicity and Free-Radical Injury

26Formation and Degradation of Glycogen

27Pentose Phosphate Pathway and the Synthesis of Glycosides, Lactose, Glycoproteins, and

Glycolipids

28Gluconeogenesis and Maintenance of Blood Glucose Levels

SECTION V

Lipid Metabolism

29 Digestion and Transport of Dietary Lipids

30 Oxidation of Fatty Acids and Ketone Bodies

31 Synthesis of Fatty Acids, Triacylglycerols, and the Major Membrane Lipids 32 Cholesterol Absorption, Synthesis, Metabolism, and Fate

33 Metabolism of Ethanol

34 Integration of Carbohydrate and Lipid Metabolism SECTION VI

Nitrogen Metabolism

35 Protein Digestion and Amino Acid Absorption

36 Fate of Amino Acid Nitrogen: Urea Cycle

37 Synthesis and Degradation of Amino Acids38 Tetrahydrofolate, Vitamin B12, and S-Adenosylmethionine

39 Purine and Pyrimidine Metabolism

40 Intertissue Relationships in the Metabolism of Amino Acids SECTION VII

Tissue Metabolism

41 Actions of Hormones that Regulate Fuel Metabolism

42 The Biochemistry of Erythrocytes and Other Blood Cells

43 Blood Plasma Proteins, Coagulation, and Fibrinolysis

44 Liver Metabolism

45 Metabolism of Muscle at Rest and during Exercise

46 Metabolism of the Nervous System

47 The Extracellular Matrix and Connective Tissue Patient Index

Subject IndexF I

uel Metabolism SECTION I

n order to survive, humans must meet two basic metabolic requirements: We must be able to synthesize

everything our cells need that is not supplied by our diet, and we must be able to protect our internal

environment from toxins and changing conditions in our external environment. To meet these requirements,

we metabolize our dietary components through four basic types of pathways: fuel oxidative pathways, fuel

storage and mobilization pathways, biosynthetic pathways, and detoxification or waste disposal

pathways. Cooperation between tissues and responses to changes in our external environment are

communicated through transport pathways and intercellular signaling pathways (Fig. I.1).

The foods in our diet are the fuels that supply us with energy in the form of calories. This energy is

used for carrying out such diverse functions as moving, thinking, and reproducing. Thus, several of our

metabolic pathways are fuel oxidative pathways that convert fuels into energy that can be used forbiosynthetic and mechanical work. But what is the source of energy when we are not eating, such as

between meals, and while we sleep? How does a person on a hunger strike that you read about in the

morning headlines survive so long? We have other metabolic pathways that are fuel storage pathways.

The fuels that we store can be mobilized during periods when we are not eating or when we need

increased energy for exercise.

Our diet also must contain the compounds we cannot synthesize, as well as all the basic building

blocks for compounds we do synthesize in our biosynthetic pathways. For example, we have dietary

requirements for some amino acids, but we can synthesize other amino acids from our fuels and a dietary

nitrogen precursor. The compounds required in our diet for biosynthetic pathways include certain amino

acids, vitamins, and essential fatty acids.

Detoxification pathways and waste disposal pathways are metabolic pathways devoted to removing

toxins that can be present in our diets or in the air we breathe, introduced into our bodies as drugs, or

generated internally from the metabolism of dietary components. Dietary components that have no value to

the body, and must be disposed of, are called xenobiotics.

In general, biosynthetic pathways (including fuel storage) are referred to as anabolic pathways; that

is, pathways that synthesize larger molecules from smaller components. The synthesis of proteins from

amino acids is an example of an anabolic pathway. Catabolic pathways are those pathways that break

down larger molecules into smaller components. Fuel oxidative pathways are examples of catabolic

pathways.

In humans, the need for different cells to carry out different functions has resulted in cell and tissue

specialization in metabolism. For example, our adipose tissue is a specialized site for the storage of fat

and contains the metabolic pathways that allow it to carry out this function.

However, adipose tissue is

lacking many of the pathways that synthesize required compounds from dietary precursors. To enable our

cells to cooperate in meeting our metabolic needs during changing conditions of diet, sleep, activity, and

health, we need transport pathways into the blood and between tissues and intercellular signaling

pathways. One means of communication is for hormones to carry signals to tissues about our dietary

state. For example, a message that we have just had a meal, carried by the hormone insulin, signals

adipose tissue to store fat.

In the following section, we will provide an overview of various types of dietary components and

examples of the pathways involved in using these components. We will describe the fuels in our diet, the

compounds produced by their digestion, and the basic patterns of fuel metabolism in the tissues of our

bodies. We will describe how these patterns change when we eat, when we fast for a short time, and

when we starve for prolonged periods. Patients with medical problems that involve an inability to deal

normally with fuels will be introduced. These patients will appear repeatedly throughout the book and

will be joined by other patients as we delve deeper into biochemistry.

It is important to note that this section of the book contains an overview of basic metabolism, which

allows patients to be presented at an elementary level and to whet students’ appetites for the biochemistry

to come. The goal is to enable the student to taste and preview what biochemistry is all about. It is not

designed to be all-inclusive, as all of these topics will be discussed in greater detail in Sections IV, V,

VI, VII of the text. The next section of the text (Section II) begins with the basics of biochemistry and the

relationship of basic chemistry to processes that occur in all living cells.Metabolic Fuels and Dietary

Components 1

For additional ancillary materials related to this chapter, please visit thePoint. Fuel Metabolism. We obtain our fuel primarily from the macronutrients (i.e., carbohydrates, fats, and

proteins) in our diet. As we eat, our foodstuffs are digested and absorbed. The products of digestion

circulate in the blood, enter various tissues, and are eventually taken up by cells and oxidized to produce

energy. To completely convert our fuels to carbon dioxide (CO2) and water (H2O), molecular oxygen

(O2) is required. We breathe to obtain this oxygen and to eliminate the CO2 that is produced by the

oxidation of our foodstuffs.

Fuel Stores. Any dietary fuel that exceeds the body’s immediate energy needs is stored, mainly as

triacylglycerol (fat) in adipose tissue, as glycogen (a carbohydrate) in muscle, liver, and other cells, and,

to some extent, as protein in muscle. When we are fasting, between meals and overnight while we sleep,

fuel is drawn from these stores and is oxidized to provide energy (Fig. 1.1).

Fuel Requirements. We require enough energy each day to drive the basic functions of our bodies and tosupport our physical activity. If we do not consume enough food each day to supply that much energy, the

body’s fuel stores supply the remainder and we lose weight. Conversely, if we consume more food than

required for the energy we expend, our body’s fuel stores enlarge and we gain weight.

Other Dietary Requirements. In addition to providing energy, the diet provides

precursors for the

biosynthesis of compounds necessary for cellular and tissue structure, function, and survival. Among

these precursors are the essential fatty acids and essential amino acids (those that the body needs but

cannot synthesize). The diet must also supply vitamins, minerals, and water. Waste Disposal. Dietary components that we can use are referred to as nutrients. However, both the diet

and the air we breathe contain xenobiotic compounds, compounds that have no use or value in the human

body and may be toxic. These compounds are excreted in the urine and feces together with metabolic

waste products. THE WAITING ROOM

Percy V. is a 59-year-old school teacher who was in good health until his wife died suddenly.

Since that time, he has experienced an increasing degree of fatigue and has lost interest in many of

the activities he previously enjoyed. Shortly after his wife’s death, one of his married children moved far

from home. Since then, Mr. V. has had little appetite for food. When a neighbor found Mr. V. sleeping in

his clothes, unkempt, and somewhat confused, she called an ambulance. Mr. V. was admitted to the

hospital psychiatry unit with a diagnosis of mental depression associated with dehydration and

malnutrition.

Otto S. is a 25-year-old medical student who was very athletic during high school and college but

is now out of shape. Since he started medical school, he has been gaining weight. He is 5 ft 10 in

tall and began medical school weighing 154 lb, within his ideal weight range. By the time he finished his

last examination in his first year, he weighed 187 lb. He has decided to consult a physician at the student

health service before the problem gets worse, as he would like to reduce his weight (at 187 lb, his body

mass index [BMI] is 27] to his previous level of 154 lb (which would reduce his BMI to 23, in the

middle of the healthy range of BMI values).

Ivan A. is a 56-year-old accountant who has been obese for a number of years. He exhibits a

pattern of central obesity, called an “apple shape,” which is caused by excess adipose tissue being

disproportionally deposited in the abdominal area. His major recreational activities are watching TV

while drinking scotch and soda and doing occasional gardening. At a company picnic, he became very

“winded” while playing softball and decided it was time for a general physical examination. At the

examination, he weighed 264 lb at 5 ft 10 in tall. His blood pressure was elevated, 155 mm Hg systolic

and 95 mm Hg diastolic (for Ivan’s age, hypertension is defined as >140 mm Hg systolic and >90 mm Hg

diastolic). For a male of these proportions, a BMI of 18.5 to 24.9 would correspond to a weight between

129 and 173 lb. Mr. A. is almost 100 lb overweight, and his BMI of 37.9 is in the range defined as

obesity.

Ann R. is a 23-year-old buyer for a woman’s clothing store. Despite the fact that she is 5 ft 7 in talland weighs 99 lb, she is convinced she is overweight. Two months ago, she started a daily physical

activity program that consists of 1 hour of jogging every morning and 1 hour of walking every evening.

She also decided to consult a physician about weight loss. If patients are above

(like Ivan A.) or below

(like Ann R.) their ideal weight, the physician, often in consultation with a registered dietitian, prescribes

a diet designed to bring the weight into the ideal range. I. Dietary Fuels

The major fuels we obtain from our diet are the macronutrients—namely, carbohydrates, proteins, and

fats. When these fuels are oxidized to CO2 and H2O in our cells (the process of catabolism), energy is

released by the transfer of electrons to O2. The energy from this oxidation process generates heat and

adenosine triphosphate (ATP) (Fig. 1.2). CO2 travels in the blood to the lungs where it is expired, and

water is excreted in urine, sweat, and other secretions. Although the heat that is generated by fuel

oxidation is used to maintain body temperature, the main purpose of fuel oxidation is to generate ATP.

ATP provides the energy that drives most of the energy-consuming processes in the cell, including

biosynthetic reactions (anabolic pathways), muscle contraction, and active transport across membranes.

As these processes use energy, ATP is converted back to adenosine diphosphate (ADP) and inorganic

phosphate (Pi). The generation and use of ATP is referred to as the ATP–ADP cycle. The oxidation of fuels to generate ATP is called respiration (Fig. 1.3). Prior to oxidation,

carbohydrates are converted principally to glucose, fat to fatty acids, and protein to amino acids. The

pathways for oxidizing glucose, fatty acids, and amino acids have many features in common. They first

oxidize the fuels to acetyl coenzyme A (acetyl-CoA), a precursor of the tricarboxylic acid (TCA)

cycle. The TCA cycle is a series of reactions that completes the oxidation of fuels to CO2 (see Chapter

23). Electrons lost from the fuels during oxidative reactions are transferred to O2 by a series of proteins

in the electron transport chain (see Chapter 24). The energy of electron transfer is used to convert ADP

and Pi to ATP by a process known as oxidative phosphorylation.In discussions of metabolism and nutrition, energy is often expressed in units of calories. A calorie in

this context (nutritional calorie) is equivalent to 1 kilocalorie (kcal) in energy terms. “Calorie” was

originally spelled with a capital C, but the capitalization was dropped as the term became popular. Thus,

a 1-cal soft drink actually has 1 kcal of energy. Energy is also expressed in joules. One kilocalorie equals

4.18 kilojoules (kJ). Physicians tend to use units of calories, in part because that is what their patients use

and understand. One kilocalorie of energy is the amount of energy required to raise the temperature of 1 L

of water by 1°C. A. Carbohydrates

The major carbohydrates in the human diet are starch, sucrose, lactose, fructose, maltose, galactose, and

glucose. The polysaccharide starch is the storage form of carbohydrates in plants. Sucrose (table sugar),

maltose, and lactose (milk sugar) are disaccharides, and fructose, galactose, and glucose are

monosaccharides. Digestion converts the larger carbohydrates to monosaccharides, which can be

absorbed into the bloodstream. Glucose, a monosaccharide, is the predominant sugar in human blood

(Fig. 1.4).Oxidation of carbohydrates to CO2 and H2O in the body produces approximately 4 kcal/g (Table 1.1).

In other words, every gram of carbohydrate we eat yields approximately 4 kcal of energy. Note that

carbohydrate molecules contain a significant amount of oxygen and are already partially oxidized before

they enter our bodies (see Fig. 1.4). B. Proteins

Proteins are composed of amino acids that are joined to form linear chains (Fig. 1.5). In addition to

carbon, hydrogen, and oxygen, proteins contain approximately 16% nitrogen by weight. The digestive

process breaks down proteins to their constituent amino acids, which enter the blood. The complete

oxidation of proteins to CO2, H2O, and NH4+ in the body yields approximately 4 kcal/g (see Table 1.1).

C. Fats

Fats are lipids composed of triacylglycerols (also called triglycerides). A triacylglycerol molecule

contains three fatty acids esterified to one glycerol moiety (Fig. 1.6).Fats contain much less oxygen than is contained in carbohydrates or proteins. Therefore, fats are more

reduced and yield more energy when oxidized. The complete oxidation of triacylglycerols to CO2 and

H2O in the body releases approximately 9 kcal/g, more than twice the energy yield from an equivalent

amount of carbohydrate or protein (see Table 1.1).

An analysis of Ann R.’s diet showed that she ate 100 g of carbohydrate, 20 g of protein, and

15 g of fat each day. Approximately how many calories did she consume per day? Miss R. consumed

100 × 4 = 400 calories as carbohydrate

20 × 4 = 80 calories as protein

15 × 9 = 135 calories as fat for a total of 615 calories/day. D. Alcohol

Alcohol (ethanol, in the context of the diet) has considerable caloric content. Ethanol (CH3–CH2–OH) is

oxidized to CO2 and H2O in the body and yields approximately 7 kcal/g; that is, more than carbohydrate

or protein but less than fat.II. Body Fuel Stores

Humans carry supplies of fuel within their bodies (Table 1.2), which are similar to the fuel supplies in the

plants and animals we eat. These fuel stores are light in weight, large in quantity, and readily converted

into oxidizable substances. Most of us are familiar with fat, our major fuel store, which is located in

adipose tissue. Although fat is distributed throughout our bodies, it tends to increase in quantity in our

hips, thighs, and abdomens as we advance into middle age. In addition to our fat stores, we also have

important, although much smaller, stores of carbohydrate in the form of glycogen located primarily in our

liver and muscles. Glycogen consists of glucose molecules joined together to form a large, branched

polysaccharide (see Fig. 1.4). Body protein, particularly the protein of our large muscle masses, also

serves to some extent as a fuel store, and we draw on it for energy when we fast. Ivan A. ate 585 g of carbohydrate, 150 g of protein, and 95 g of fat each day. In addition, he

drank 45 g of alcohol daily. How many calories did he consume per day? Mr. A. consumed

585 × 4 = 2,340 calories as carbohydrate

150 × 4 = 600 calories as protein

95 × 9 = 855 calories as fat

45 × 7 = 315 calories as alcohol for a total of 4,110 calories/day.