Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017)

Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017) Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017) Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017) Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017) Preview Marks’ Basic Medical Biochemistry A Clinical Approach (5th Edition) by Michael A. Lieberman Alisa Peet (2017)

Acquisitions Editor: Shannon Magee Development Editor: Andrea Vosburgh Editorial Coordinator: Lauren Pecarich Marketing Manager: Michael McMahon Production Project Manager: David Orzechowski Design Coordinator: Joan Wendt Prepress Vendor: Absolute Service, Inc Fifth Edition Copyright © 2018 Wolters Kluwer Copyright © 2013, 2009 by Lippincott Williams & Wilkins, a Wolters Kluwer business All rights reserved This book is protected by copyright No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews Materials appearing in this book prepared by individuals as part of their official duties as U.S government employees are not covered by the abovementioned copyright To request permission, please contact Wolters Kluwer at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email at permissions@lww.com, or via our website at lww.com (products and services) Printed in China Library of Congress Cataloging-in-Publication Data Names: Lieberman, Michael, 1950- author | 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 This work is provided “as is,” and the publisher disclaims any and all warranties, express or implied, including any warranties as to accuracy, comprehensiveness, or currency of the content of this work 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.com Preface 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: 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 The Biochemical Comments associated with each chapter have been updated, where appropriate, to allow students to experience where current research efforts are headed 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 FreeRadical 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 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 questions associated 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 also called vitamin B6) (Fig 5.23) The suffix “-ine” denotes the presence of nitrogen (amine) in the ring The pyrimidine uracil is an exception to this general type of nomenclature The utility of these nitrogen-containing ring structures lies in the ability of the nitrogen to form hydrogen bonds and to accept and donate electrons while still part of the ring In contrast, the unsubstituted aromatic benzene ring, in which electrons are distributed equally among all six carbons (see Fig 5.1), is nonpolar, hydrophobic, and relatively unreactive Nucleosides and Nucleotides Nitrogenous bases form nucleosides and nucleotides A nucleoside consists of a nitrogenous base joined to a sugar, usually ribose or deoxyribose, through an Nglycosidic bond (see Fig 5.16) If phosphate groups are attached to the sugar, the compound becomes a nucleotide In the name of the nucleotide ATP, the addition of the ribose is indicated by the name change from adenine to adenosine (for the glycosidic bond) Monophosphate, diphosphate, or triphosphate is added to the name to indicate the presence of one, two, or three phosphate groups in the nucleotide The structures of the nucleotides that serve as precursors of DNA and RNA are discussed in more detail in Section III, Chapter 12 Tautomers In many of the nitrogen-containing rings, the hydrogen can shift to produce a tautomer, a compound in which the hydrogen and double bonds have changed position (i.e., –N=C–OH → –NH–C=O) (Fig 5.24) Tautomers are considered the same compound, and the structure may be represented either way Generally, one tautomeric form is more reactive than the other For example, in the two tautomeric forms of uric acid, a proton can dissociate from the enol form to produce urate Lotta T has gouty arthritis (podagra) involving her great right toe Polarized light microscopy of the fluid aspirated from the joint space showed crystals of monosodium urate phagocytosed by white blood cells The presence of the relatively insoluble urate crystals within the joint space activates an inflammatory cascade leading to the classic components of joint inflammation (pain, redness, warmth, swelling, and limitation of joint motion) Uric acid is produced from the degradation of purines (adenine and guanine) At a blood pH of 7.4, all of the uric acid has dissociated a proton to form urate, which is not very water-soluble and forms crystals of the Na+ salt In the more acidic urine generated by the kidney, the acidic form, uric acid, may precipitate to form kidney stones V Free Radicals Radicals are compounds that have a single electron, usually in an outer orbital Free radicals are radicals that exist independently in solution or in a lipid environment Although many enzymes generate radicals as intermediates in reactions, these are not usually released into the cell to become free radicals Many of the compounds in the body are capable of being converted to free radicals by natural events that remove one of their electrons or by radiation Radiation, for example, dissociates water into the hydrogen atom and the hydroxyl radical: H2O ↔ H● + OH● In contrast, water normally dissociates into a proton and the negatively charged hydroxyl ion The hydroxyl radical forms organic radicals by taking one electron (as H●) from a compound such as an unsaturated membrane lipid, which then has a single unpaired electron and is a new radical Compounds that are radicals may be written with, or without, the radical showing For example, nitrogen dioxide, a potent, reactive, toxic radical present in smog and cigarette smoke, may be designated in medical and lay literature as NO2 rather than NO2● Superoxide, a radical produced in the cell and that is the source of much destruction, is correctly written as the superoxide anion, O2− However, to emphasize its free radical nature, the same compound is sometimes written as O2−● If a compound is designated as a radical in the medical literature, you can be certain that it is a reactive radical and that its radical nature is important for the pathophysiology under discussion Reactive oxygen- and nitrogen-containing free radicals are discussed in more detail in Chapter 25 Free radicals are not just esoteric reactants; they are the agents of cell death and destruction They are involved in many chronic disease states (e.g., coronary artery disease, diabetes mellitus, arthritis, emphysema) as well as acute injury (e.g., radiation, strokes, myocardial infarction, spinal cord injury) Through free radical defense mechanisms in our cells, we can often restrict the damage attributed to the “normal” aging process CLINICAL COMMENTS Dianne A The severity of clinical signs and symptoms in patients with DKA, such as Dianne A., is correlated directly with the concentration of ketone bodies in the blood Direct quantitative methods for measuring acetoacetate and β-hydroxybutyrate are not routinely available As a result, clinicians usually rely on semiquantitative reagent strips (Ketostix, Bayer Corporation, Pittsburgh, PA) or tablets (Acetest, Bayer Corporation) to estimate the level of acetoacetate in the blood and the urine The nitroprusside on the strips and in the tablets reacts with acetoacetate and to a lesser degree with acetone (both of which have ketone groups) but does not react with βhydroxybutyrate (which does not have a ketone group) β-Hydroxybutyrate is the predominant ketone body present in the blood of a patient in DKA, and its concentration could decline at a disproportionately rapid rate compared with that of acetoacetate and acetone Therefore, tests employing the nitroprusside reaction to monitor the success of therapy in such a patient may be misleading As a result, clinicians will follow the “anion gap” in the blood, which in DKA represents the increase in ketone bodies In contrast to the difficulty of ketone body measurements, patients with diabetes can self-monitor blood glucose levels at home, thereby markedly decreasing the time and expense of the many blood glucose determinations they need Capillary blood obtained from a finger prick is placed on the pad of a plastic strip The strip has been impregnated with an enzyme (usually the bacterial enzyme glucose oxidase) that specifically converts the glucose in the blood to an oxidized sugar (gluconate) and a reduced compound (hydrogen peroxide, H2O2) The H2O2 reacts with a dye to produce a color The intensity of the color, which is directly proportionate to the concentration of glucose in the patient’s blood, is read on an instrument called a blood glucose monitor The anion gap refers to the difference in concentration between routinely measured anions (chloride and bicarbonate) and cations (sodium and potassium) in the blood Because these cations are in most cases in greater concentration than the measured anions, the difference in value is known as the anion gap The normal value for the anion gap is 12 (range = 8–16) If the anion gap is greater than normal, it is indicative of unknown anions being present in excess and, in the case of type 1 diabetes, most often reflects the production of ketone bodies The reducing sugar test The reducing sugar test was used for detection of sugar in the urine long before specific enzymatic assays for glucose and galactose became available In this test, the aldehyde group of a sugar is oxidized as it donates electrons to copper; the copper becomes reduced and produces a blue color In alkaline solution, keto sugars (e.g., fructose) also react in this test because they form tautomers that are aldehydes Ring structures of sugars also react but only if the ring can open (i.e., it is not attached to another compound through a glycosidic bond) Until a specific test for fructose becomes available, a congenital disease resulting in the presence of fructose in the urine is indicated by a positive reducing sugar test and negative results in the specific enzymatic assays for glucose or galactose Lotta T Ms T has acute gouty arthritis (podagra) involving her right great toe Lotta was treated with colchicine (acetyltrimethyl colchinic acid methyl ether) for the acute attack of gout affecting her great right toe After having two doses of colchicine, the throbbing pain in her toe had abated significantly The redness and swelling also seemed to have lessened slightly Colchicine will reduce the effects of the inflammatory response to the urate crystals Several weeks later, Lotta was started on allopurinol (150 mg twice daily), which inhibits the enzyme that produces uric acid Within several days of starting allopurinol therapy, Lotta’s uric acid levels began to decrease BIOCHEMICAL COMMENTS Chlorinated Aromatic Hydrocarbon Environmental Toxins As a result of human endeavor, toxic compounds containing chlorinated benzene rings have been widely distributed in the environment The pesticide dichlorodiphenyltrichloroethane (DDT), the class of chemicals called dioxins, and polychlorinated biphenyls (PCBs) provide examples of chlorinated aromatic hydrocarbons and structurally related compounds that are very hydrophobic and poorly biodegraded (Fig 5.25) As a consequence of their persistence and lipophilicity, these chemicals are concentrated in the adipose tissue of fish, fisheating birds, and carnivorous mammals, including humans DDT, a chlorinated biphenyl, was widely used in the United States as a herbicide from the 1940s through the 1960s (see Fig 5.25) Although it has not been used in this country since 1972, the chlorinated benzene rings are resistant to biodegradation, and US soil and water are still contaminated with small amounts DDT continues to be used in other parts of the world Because this highly lipophilic molecule is stored in the fat of animals, organisms accumulate progressively greater amounts of DDT at each successive stage of the food chain Fish-eating birds, one of the organisms at the top of the food chain, have declined in population because of the effect of DDT on the thickness of their eggshells DDT is not nearly as toxic in the human, although long-term exposure or exposure to high doses may cause reversible neurologic symptoms, hepatotoxic effects, or cancer Dioxins, specifically polychlorinated dibenzo-p-dioxins (PCDDs), constitute another class of environmental toxins that are currently of great concern (see Fig 5.25) They have been measured at what is termed background levels in the blood, adipose tissue, and breast milk of all humans tested PCDDs are formed as a by-product during the production of other chlorinated compounds and herbicides and from the chlorine bleaching process used by pulp and paper mills They are released during the incineration of industrial, municipal, and domestic waste and during the combustion of fossil fuels, and they are found in cigarette smoke and the exhaust from engines that burn gasoline and diesel fuels PCDDs can also be formed from the combustion of organic matter during forest fires They enter the atmosphere as particulate matter, are vaporized, and can spread large distances to enter soil and water The accumulation of DDT in adipose tissue may be protective in humans because it decreases the amount of DDT available to pass through nonpolar lipid membranes to reach neurons in the brain or to pass through placental membranes to reach the fetus Eventually, we convert DDT to more polar metabolites that are excreted in the urine However, some may pass with lipid into the breast milk of nursing mothers PCBs were originally synthesized for use as nonflammable material for cooling and insulating industrial transformers and capacitors As a result of accidents in the chemical plants producing the PCBs, it became evident that these chemicals can cause adverse health effects in humans Production of PCBs stopped in the United States in 1979, although they may still be found in enclosed containers for electrical transformers All of the chlorinated compounds thus far discussed may have as their mechanism of action an alteration of gene expression via binding to the cytoplasmic arylhydrocarbon receptor (see Section III of this text) PCB exposure has been linked to cancer and to disorders of the immune, reproductive, nervous, and endocrine systems All of the polychlorinated derivatives are difficult to remove from the environment One promising approach is to use genetically engineered bacteria that can use these compounds as a food source and safely metabolize the toxins This approach, however, has the drawback of introducing genetically engineered organisms into the environment, which has its own potential problems (see Chapter 17) As humans at the top of the food chain, we have acquired our background levels of dioxins principally through the consumption of food—primarily meat, dairy products, and fish Once in the human body, dioxins are stored in human fat and adipose tissue and have an average half-life of approximately 5 to 15 years They are unreactive, poorly degraded, and not readily converted to more water-soluble compounds that can be excreted in the urine They are slowly excreted in the bile and feces and together with lipids enter the breast milk of nursing mothers Most of what is known about the toxicity of dioxins in humans comes from individuals exposed incidentally or chronically to higher levels (e.g., industrial accidents or presence in areas sprayed with Agent Orange or other herbicides contaminated with dioxins) The lowest dose effects are probably associated with thymic atrophy and decreased immune response, chloracne and related skin lesions, and neoplasia (cancer) Dioxins can cross into the placenta to cause developmental and reproductive effects, decreased prenatal growth, and prenatal mortality KEY CONCEPTS Carbohydrates, commonly known as sugars, can be classified by several criteria: Type of carbonyl group (aldo- or ketosugars) Number of carbons (pentoses [five carbons], hexoses [six carbons]) Positions of hydroxyl groups on asymmetric carbon atoms (D- or Lconfiguration, stereoisomers, epimers) Substituents (amino sugars) Number of monosaccharides joined through glycosidic bonds (disaccharides, oligosaccharides, polysaccharides) Lipids are structurally diverse compounds that are not very soluble in water (i.e., they are hydrophobic) The major lipids are fatty acids Triacylglycerols (triglycerides) consist of three fatty acids esterified to the carbohydrate glycerol Phosphoacylglycerols (phosphoglycerides or phospholipids) are similar to triacylglycerol but contain a phosphate in place of a fatty acid Sphingolipids are built on sphingosine Cholesterol is a component of membranes and a precursor for molecules that contain the steroid nucleus, such as bile salts and steroid hormones Nitrogen is found in a variety of compounds, in addition to amino sugars Amino acids and heterocyclic rings contain nitrogens, which carry a positive charge at neutral pH Amino acids contain a carboxyl group, an amino group, and a side chain attached to a central carbon Proteins consist of a linear chain of amino acids Purines, pyrimidines, and pyridines have heterocyclic nitrogencontaining ring structures Nucleosides consist of a heterocyclic ring attached to a sugar A nucleoside plus phosphate is a nucleotide Glycoproteins and proteoglycans have sugars attached to protein components Diseases discussed in this chapter are summarized in Table 5.1 REVIEW QUESTIONS—CHAPTER 5 Select the single best answer for each of the following questions Base your answers on your knowledge of nomenclature You need not recognize any of the structures shown to answer the questions A component of a “lipid panel” for a patient is triglyceride, which is best described by which one of the following? A Contains a steroid nucleus B Three fatty acids esterified to sphingosine C Three fatty acids esterified to a carbohydrate D Two fatty acids and a phosphate esterified to a sphingosine E Two fatty acids and a phosphate esterified to a carbohydrate A patient was admitted to the hospital emergency department in a coma Laboratory tests found high levels of the compound shown below in her blood: CH2OH—CH2—CH2—COO− On the basis of its structure (and your knowledge of the nomenclature of functional groups), you identify the compound as which one of the following? A Methanol (wood alcohol) B Ethanol (alcohol) C Ethylene glycol (antifreeze) D β-Hydroxybutyrate (a ketone body) E γ-Hydroxybutyrate (the “date rape” drug) A patient was diagnosed with a deficiency of the lysosomal enzyme αglycosidase The name of the deficient enzyme suggests that it hydrolyzes a glycosidic bond, which is best described as a bond formed via which one of the following? A Through multiple hydrogen bonds between two sugar molecules B Between the anomeric carbon of a sugar and an O–H (or N) of another molecule C Between two anomeric carbons in polysaccharides D Internal bond formation between the anomeric carbon of a monosaccharide and its own fifth carbon hydroxyl group E Between the carbon containing the aldol or keto group and the α-carbon of the sugar In the congenital disease galactosemia, high concentrations of galactose and galactitol accumulate in the blood On the basis of their names, you would expect which one of the following statements to be correct? A Galactitol is an aldehyde formed from the keto sugar galactose B Galactitol is the oxidized form of galactose C Galactitol is the sugar alcohol of galactose D Both galactose and galactitol are sugars E Both galactose and galactitol would give a positive reducing sugar test A patient was diagnosed with one of the types of sphingolipidoses, which are congenital diseases involving the inability to degrade sphingolipids All sphingolipids have in common which one of the following? A A glycerol backbone B Ceramide C Phosphorylcholine D N-Acetylneuraminic acid (NANA) E A steroid ring structure to which sphingosine is attached In DKA, a metabolic acidosis results from increased hepatic production of ketone bodies (β-hydroxybutyrate, acetoacetate, and acetone) Which one of the following terms best describes all three of these ketone bodies? A Butyl structure B Aromatic structure C Aliphatic structure D Hydroxyl-containing structure E Amine-containing structure Omega-3 fatty acids are found in “oily” fish and are considered beneficial for heart health A food containing which one of the following would fall into this category? A Cis, Δ9,12,15, C18:3 B Cis, Δ9,12, C18:2 C Cis, Δ6,9,12, C18:3 D Cis, Δ9,12,15, C20:3 E Cis, Δ6,9, C16:2 A patient has had viral gastroenteritis for 3 days and has been unable to keep any oral intake down, such that the patient is now dehydrated In the emergency department, he is given 2 L of intravenous (IV) D5 0.9% NaCl solution Which of the following best describes this IV solution? A It is hypotonic B It is hypertonic C It contains D-glucose D It contains L-glucose E It contains D-galactose A patient with hyperlipidemia has been counseled to reduce the saturated fats in his diet, so he has replaced butter with a butter substitute that he knows is made from a polyunsaturated oil The manufacturer of this butter substitute has partially hydrogenated this product Which one of the following is the best description of why this product was partially hydrogenated? A The trans-fatty acids produced by commercial hydrogenation are very healthy in humans B Hydrogenation reduces the double bonds, creating a more saturated product, which is more marketable C Hydrogenation makes the product less expensive to produce D Hydrogenation reduces the cholesterol content of the oil E Hydrogenation increases the cholesterol content of the oil 10 A researcher is trying to design an antibiotic to kill bacteria but not harm any human cells Which one of the following theoretically could be used for this purpose? A A medication that inhibits reactions using only D-amino acids B A medication that inhibits reactions using only L-amino acids C A medication that inhibits reactions using only amino acids containing a β-amino group D A medication that inhibits reactions using only amino acids containing a γ-amino group E A medication that only inhibits reactions using only aromatic amino acids ANSWERS TO REVIEW QUESTIONS The answer is C Triglyceride (triacylglycerol) consists of three fatty acids esterified to the carbohydrate glycerol Phosphoacylglycerols are similar to triacylglycerol but contain a phosphate in place of a fatty acid Cholesterol contains a steroid nucleus Sphingolipids are built on sphingosine, but triglycerides are not The answer is E The compound contains an –OH group, which should appear in the name as an “-ol” or a “hydroxyl-” group All answers fit this criterion The structure also contains a carboxylate group (–COO−), which should appear in the name as an “-ate” or “acid.” Only D and E fit this criterion Counting backward from the carboxylate group (carbon 1), the second carbon is α, the third carbon is β, and the fourth carbon, containing the hydroxyl group, is γ Thus, the compound is γhydroxybutyrate A, B, and C can also be eliminated because “meth-” denotes a single carbon, “eth-” denotes two carbons, and the “-ene” in ethylene denotes a double bond The answer is B The term “glycosidic bond” refers to a covalent bond formed between the anomeric carbon of one sugar, when it is in a ring form, and a hydroxyl group or nitrogen of another compound (see Fig 5.16) (thus, A, D, and E are incorrect) Disaccharides can be linked through their anomeric carbons, but polysaccharides cannot because there would be no anomeric carbon left to form a link with the next sugar in the chain (thus, C is incorrect) The answer is C The keto or aldehyde group is necessary for a positive reducing sugar test (a nonspecific test used to identify the presence of sugar in the urine) Because galactitol has had its aldehyde group already reduced to form the alcohol group, it would no longer give a positive result in a reducing sugar test An “ol” in the name denotes that the compound is an alcohol (has an –OH group) and an “ose” denotes a sugar Thus, the alcohol that is derived from galactose is galactitol All sugars have a keto or aldehyde group, which is reduced when the compound becomes an alcohol (a gain of electrons, as indicated by an increase of hydrogen relative to oxygen) Oxidation of the keto or aldehyde group would lead to an acid group being generated, not an alcohol group Galactose is an aldose sugar, not a keto sugar The answer is B Sphingolipids contain a ceramide group, which is sphingosine with an attached fatty acid They do not contain a glycerol moiety (thus, A is incorrect) However, different sphingolipids have different substituents on the –CH2OH group of ceramide For example, sphingomyelin contains phosphorylcholine, and gangliosides contain NANA (thus, C and D are incorrect) No known sphingolipids contain a steroid (thus, E is incorrect) The answer is C None of these ketone bodies contains a benzene or similar ring (aromatic), so they are all defined as aliphatic Two of these have four carbons (butyl), but acetone has only three carbons (propyl structure) Only β-hydroxybutyrate contains a hydroxyl group (–OH), and none contains a nitrogen atom or group (amine) The answer is A The ω-series of fatty acids refers to counting carbons from the ω-end of the fatty acid (usually the methyl carbon end) until a double bond is reached For the cis Δ9,12,15 C18:3 fatty acid, the double bonds are between carbons 9 and 10, 12 and 13, and 15 and 16 If one counts backward from carbon 18, one counts three carbons (18, 17, and 16) before the double bond is reached, indicating that this fatty acid belongs to the ω-3 family The cis Δ,12 C18:2 fatty acid belongs to the ω-6 group, as does the cis Δ6,9,12 C18:3 fatty acid The cis Δ9,12,15 C20:3 fatty acid belongs to the ω-5 group, whereas the cis Δ6,9 C16:2 fatty acid belongs to the ω-7 group The answer is C Saline 0.9% is considered “normal” saline (NS) and is isotonic This is a very common solution in IV fluids used to treat dehydration D5 refers to 5% dextrose solution or 50 g/L dextrose given as a means of parenteral nutrition because the patient cannot take oral nutrition Dextrose is another name for D-glucose L-Glucose is not commonly found in the human body The glucose is completely metabolized and does not contribute to tonicity Galactose is not present in this type of solution The answer is B Polyunsaturated fatty acids have a lower melting point than more saturated fats Butter is a highly saturated fat and is a solid around room temperature Polyunsaturated fats melt at room temperature Most consumers do not want a butter substitute that melts at room temperature, so such a product would not sell as well as natural butter Hydrogenation reduces the double bonds in the polyunsaturated fats and makes the product more saturated, which raises the melting point of the oil as well as increasing the shelf life of the product Hydrogenated oils are less expensive to produce than animal fats, but hydrogenation introduces an extra step in manufacturing and increases costs as compared to not changing the product at all Unfortunately, commercial hydrogenation creates trans double bonds in the fats, whereas all naturally occurring unsaturated fatty acids contain double bonds in the cis-configuration The presence of trans fats in American diets has been linked to the development of cardiovascular disease Hydrogenation of fatty acids has nothing to do with cholesterol 10 The answer is A In human proteins, the amino acids are always L-αamino acids (in the L-configuration) D-Amino acids are not used for synthesizing proteins in humans but are used to generate products in bacteria Inhibiting the use of D-amino acids would inhibit bacterial growth but does not affect human cell growth Some human products contain β- and γ-amino groups, so drugs inhibiting their production would not be beneficial for human use ... Library of Congress Cataloging-in-Publication Data Names: Lieberman, Michael, 1950- author | Peet, Alisa, author Title: Marks’ basic medical biochemistry : a clinical approach / Michael Lieberman, Alisa Peet ; illustrations by Matthew Chansky... 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... The RDA is intended to serve as a goal for intake by individuals The AI is a recommended intake value that is used when not enough data are available to establish an RDA A Carbohydrates The RDA for carbohydrate is 130 g/day for children and adults and is based on