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(BQ) Part 1 book Essentials of biochemistry has contents: Cell and membrane transport, carbohydrate chemistry, chemistry of lipids, chemistry of proteins, plasma proteins and immunoglobulins, enzymes, chemistry of hemoglobin,... and other contents.
m m co co m e co e e fre ks ks fre oo oo eb m eb m fre ks oo eb m e co m fre ok s eb o m m co m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m e fre fre ks oo eb m ks oo eb m co m om e c m co e re re oo ks f eb m ks f oo eb m co m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m e co fre oo ks eb m m co e m e m e m e m m m co co m e co e e fre ks ks fre oo oo eb m eb m fre ks oo eb m e co m fre ok s eb o m m co m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m e fre fre ks oo eb m ks oo eb m co m om e c m co m co e re re oo ks f eb m ks f oo eb m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m m co e co fre oo ks eb m BIOCHEMISTRY ESSENTIALS OF e m e m e m e m m m co co m e co e e fre ks ks fre oo oo eb m eb m fre ks oo eb m e co m fre ok s eb o m m co m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m e fre fre ks oo eb m ks oo eb m co m om e c m co e re re oo ks f eb m ks f oo eb m co m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m e co fre oo ks eb m m co e m e m e m e m New Delhi | London | Philadelphia | Panama m co e fre ks m co e fre ks oo m co e fre ks oo eb m co m e fre ks oo co m e fre oo ks eb m m co e Professor Department of Biochemistry SMBT Institute of Medical Sciences and Research Center Nashik, Maharashtra, India PhD oo eb m eb m m e co co m e fre fre ks oo eb m ks oo eb m co m Pankaja Naik eb m co m e The Health Sciences Publisher ks fre oo co e ks fre oo eb m co m e fre oo ks eb m co m om e c m co m co e re re oo ks f eb m ks f oo eb m m m co e co e ks fre oo eb m re sf oo k eb m Second Edition m eb m fre ks oo eb m e co m fre ok s eb o m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m m co e co fre oo ks eb m BIOCHEMISTRY ESSENTIALS OF e m e m e m e m e m e co oo ks f re fre ks oo oo m m eb eb eb m m m om e ks fre fre oo ks eb e c co e co m m m m e e e m m co Jaypee Brothers Medical Publishers (P) Ltd Headquarters om e c co e oo ks f re re eb m e fre ks oo oo oo ks ks fre fre e e co m co co m m co m e The views and opinions expressed in this book are solely those of the original contributor(s)/author(s) and not necessarily represent those of editor(s) of the book eb m m m eb eb eb © 2017, Jaypee Brothers Medical Publishers m Jaypee Medical Inc 325 Chestnut Street Suite 412, Philadelphia, PA 19106, USA Phone: +1 267-519-9789 Email: support@jpmedus.com Jaypee Brothers Medical Publishers (P) Ltd Bhotahity, Kathmandu, Nepal Phone +977-9741283608 Email: kathmandu@jaypeebrothers.com fre ks Website: www.jaypeebrothers.com Website: www.jaypeedigital.com oo ks f eb oo Jaypee-Highlights Medical Publishers Inc City of Knowledge, Bld 235, 2nd Floor, Clayton Panama City, Panama Phone: +1 507-301-0496 Fax: +1 507-301-0499 Email: cservice@jphmedical.com m Jaypee Brothers Medical Publishers (P) Ltd 17/1-B Babar Road, Block-B, Shaymali Mohammadpur, Dhaka-1207 Bangladesh Mobile: +08801912003485 Email: jaypeedhaka@gmail.com co m m co m e oo eb J.P Medical Ltd 83 Victoria Street, London SW1H 0HW (UK) Phone: +44 20 3170 8910 Fax: +44 (0)20 3008 6180 Email: info@jpmedpub.com m m eb oo k Overseas Offices ks fre sf re e co co m m Jaypee Brothers Medical Publishers (P) Ltd 4838/24, Ansari Road, Daryaganj New Delhi 110 002, India Phone: +91-11-43574357 Fax: +91-11-43574314 Email: jaypee@jaypeebrothers.com All rights reserved No part of this publication may be reproduced, stored or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission in writing of the publishers fre e co co e fre ks ks oo ks ks fre fre e e co Medical knowledge and practice change constantly This book is designed to provide accurate, authoritative information about the subject matter in question However, readers are advised to check the most current information available on procedures included and check information from the manufacturer of each product to be administered, to verify the recommended dose, formula, method and duration of administration, adverse effects and contraindications It is the responsibility of the practitioner to take all appropriate safety precautions Neither the publisher nor the author(s)/editor(s) assume any liability for any injury and/or damage to persons or property arising from or related to use of material in this book m m m co m co m All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners The publisher is not associated with any product or vendor mentioned in this book oo oo oo m m eb eb eb Every effort has been made where necessary to contact holders of copyright to obtain permission to reproduce copyright material If any have been inadvertently overlooked, the publisher will be pleased to make the necessary arrangements at the first opportunity m m eb This book is sold on the understanding that the publisher is not engaged in providing professional medical services If such advice or services are required, the services of a competent medical professional should be sought Inquiries for bulk sales may be solicited at: jaypee@jaypeebrothers.com Essentials of Biochemistry m co e e fre oo eb m m eb oo ks ks oo eb m eb o ok s Printed at ks fre fre fre e ISBN 978-93-86150-30-1 m co m m co co e co m m First Edition: 2012 Second Edition: 2017 m m co co m e e fre ks oo eb ks fre oo co e m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m co m e fre fre ks oo eb m ks oo eb m My Parents m eb m fre ks oo eb m e co m fre ok s eb o m m co Dedicated to om e c m co e re re oo ks f eb m ks f oo eb m co m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m e co fre oo ks eb m m co e m e m e m e m m m co co m e co e e fre ks ks fre oo oo eb m eb m fre ks oo eb m e co m fre ok s eb o m m co m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m e fre fre ks oo eb m ks oo eb m co m om e c m co e re re oo ks f eb m ks f oo eb m co m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m e co fre oo ks eb m m co e m e m e m e m e m m e co oo ks f re fre ks oo oo m m eb eb co m fre ks oo eb eb m m m m co co e e fre fre ks ks oo oo eb eb m m oo eb m m eb oo ks fre ks fre e e co m co m m co e fre ks oo eb m om re oo ks f eb m co m e fre oo ks Pankaja Naik m e co ks fre oo eb m e co m fre ok s e c co e re ks f oo eb m m co e fre ks oo eb m co m e fre oo ks eb m eb o m co m e ks fre oo eb m co m e fre ks oo eb m co m m e eb m m e co re sf oo k eb m om e ks fre fre oo ks eb m This second edition of Essentials of Biochemistry is a clear, concise, comprehensive and in full color, exam oriented ideal textbook for medical, dental, physiotherapy, occupational therapy, nursing and other health sciences students This book is revised and updated keeping in view all categories of students and it addresses their needs in a simple manner Essentials of Biochemistry has been streamlined to focus on only the most essential biochemical concepts and avoids details not required by undergraduate students Additional information has been given in the form of diagrams, tables, and flowcharts to understand the topics and its proper perspective The text has been so presented that the students would find it easy to attempt any question in the form of objective type or essay type after going through the text To facilitate the student learning, I have added new features: • Exam questions in the form of long answer questions (LAQs), short answer questions (SAQs), multiple choice questions (MCQs), and clinical case studies • A glossary with precise definitions of the most common words of biochemical sciences • A list of reference/normal values for selected biochemical laboratory tests After reading this book, reader suggestion and healthy criticism will be of great help in the future improvement of the book I would like you to send me your feedback at pankajanaik@hotmail.com/ pankajanaik@gmail.com co m e c co e co m m m m e e e m m co m co co m Preface m m co co m e co e e fre ks ks fre oo oo eb m eb m fre ks oo eb m e co m fre ok s eb o m m co m co e fre ks m co e fre ks oo oo eb m eb m m e co ks fre oo eb m co m e fre oo ks eb m co m eb m co m e fre ks oo co m e fre oo ks eb m m co e co m e fre fre ks oo eb m ks oo eb m co m om e c m co e re re oo ks f eb m ks f oo eb m co m m e co e ks fre oo eb m re sf oo k eb m m co ks re m om e c e co fre oo ks f eb m oo eb m m co e ks fre oo eb m m e co fre oo ks eb m m co e m e m e m e m e m e co re oo ks f eb eb m m co m m co e fre ks ks oo oo eb eb m m oo eb m m eb oo ks fre ks fre e e co m co m m co e fre ks oo eb m e fre ks oo eb m m co e fre ks fre oo eb m e co m fre ok s om re oo ks f eb m co m e fre oo ks eb m m e co e fre oo ks eb m e c co e re ks f oo eb m m co e fre ks oo eb m co m co m m eb o m co m e ks fre oo eb m co m e fre ks oo m eb m fre ks oo oo eb m m e co re sf oo k eb m om e ks fre fre oo ks eb m co co m e c co e co m m m m e e e m m co m I express my profound gratitude to Honorable Shri Balasaheb Thorat (MLA and Trustee), and Honorable Dr Sudhirji Tambe (MLA and Trustee), SMBT Sevabhavi Trust, Nashik, Maharashtra, India for their keen interest in all the academic activities of the faculty members I sincerely express my gratitude to Dr Harshal Tambe, the dynamic Managing Trustee, SMBT Sevabhavi Trust, Nashik, Maharashtra, India, for his continuous support and encouragement I am grateful to all my colleagues and students from various institutes and universities across the world as reviewers Their suggestions and thoughtful comments have been of immense help to me in maintaining the excellence of the second edition I would like to acknowledge and thank the help rendered by Dr Pankaj Kamble, Dr Sandip Lambe and Ms Asmita Patil, my colleagues in the department Special thanks to Mr SD Kurhe (Chief Officer) and Dr BM Deshpande (Administrative Officer), SMBT Sevabhavi Trust for all the cooperation extended by them to me I profusely thank Mr Mukesh Kale, artist/DTP operator, Nashik, Maharashtra, India for his help in completing the script within the due period I am grateful to Shri Jitendar P Vij (Group Chairman) and Mr Ankit Vij (Group President), M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India for their motivating passion and all the timely help extended in bringing out the second edition I wish to thank Mr Chandrashekhar S Gawade, Branch Manager, Mumbai, Maharashtra, India for his unfailing personal support in the preparation of the second edition I also wish to thank Ms Payal Bharti (Project Manager), Mr Umar Rashid (Development Editor) and staff of Jaypee Brothers Medical Publishers for their cooperation and patience during the preparation and publication of the second edition Last but not least, I thank my husband Mr Shekhar and my son Mr Sushrut for understanding and supporting me to complete the task successfully co m Acknowledgments Melatonin Tryptophan Vasoconstrictor GABA Glutamate Neurotransmitter e m e co re oo ks f m om m e c re oo ks f oo m fre e co m co m e fre oo ks oo ks eb m m m fre e co co oo eb m co m e oo eb m m eb oo ks fre ks fre co e ks oo eb m eb eb oo Growth factor, regulator of transcription and translation fre m eb Ornithine and methionine m Vasodilator Neurotransmitter fre Catabolism and excretion of polyamines • The enzyme polyamine oxidase present in liver peroxisomes oxidizes spermine to spremidine and spermidine to putrescine • Putrescine is then oxidized by a copper containing diamine oxidase to CO2 and NH3 • Major portions of putrescine and spermidine are excreted in urine after conjugation with acetyl-CoA as acetylated derivatives m eb m Histidine Cysteine e co m Histamine Taurine ok s eb o Vasoconstrictor m Tryptophan co Serotonin fre Hormone Vasoconstrictor e Tyrosine ks Tyrosine oo Epinephrine Tyramine ks Neurotransmitter Biosynthesis of polyamines • Putrescine, spermidine and spermine are derived from ornithine and methionine • Ornithine is derived from arginine Arginine undergoes a decarboxylation to form putrescine and carbon dioxide (Fig 14.48) by an enzyme ornithine decarboxylase • S-Adenosylmethionine undergoes a decarboxylation to form 5-adenosylmethiopropylamine, by an enzyme S-adenosylmethionine decarboxylase • S-Adenosylmethiopropylamine donates aminopropyl group to putrescine and then to spermidine to form spermine • It is presumed that the 15% of methionine which cannot be used for cysteine synthesis in minimal diets is used for polyamine synthesis e Tyrosine oo ks eb m m co e re ks f m e co Norepinephrine ks fre Function Neurotransmitter Functions of polyamines • Polyamines are involved in regulation of transcription and translation • They act as a growth factor and function in cell prolife ration and growth • Polyamines are involved in stabilization of intact cells, subcellular organelles and membranes eb m co e fre ks oo eb m co m e fre Amino acid precursor Tyrosine Dopamine • Polyamines are positively charged at physiological pH and associate with negatively charged nuclear DNA These are present in high concentration in semen The concentration of polyamines in brain is about mm m oo eb m co m e fre ks oo eb co m Table 14.6: Some important biogenic amines and their function m eb eb m co m e ks fre re sf oo k eb m m • Biological amines made up of multiple amino acids called polyamines, e.g –– Putrescine –– Spermidine –– Spermine Spermine m fre ks oo oo eb m m e co co co m Polyamines co om e ks fre fre oo ks eb m Fig 14.47: Synthesis of biogenic amines by PLP dependent decarboxylation of amino acids • Histamine: Histamine is produced by decarboxylation of histidine It is a vasodilator and lowers blood pressure It is involved in allergic reactions • Catecholamines (dopamine, norepinephrine and epinep hrine) Synthesis of catecholamines from tyrosine requires PLP-dependent DOPA decarboxylase Catecholamines are neurotransmitters and involved in metabolic and nervous regulation Some of the most important biogenic amines and their functions are given in Table 14.6 Amine e c co e co m m m m e e e m m Essentials of Biochemistry m co 272 e om co m e fre ks oo eb m m m fre e co co e fre m Short Notes e e co m co m Transamination Nitrogen balance Deamination Metabolic disorders of urea cycle Phenylketonuria Alkaptonuria m eb oo ks ks oo eb 10 Describe formation and fate of ammonia fre oo eb m m eb oo ks ks ks fre m co e fre Describe the metabolism of amino acid tryptophan and associated disorders Describe metabolic disorders of aromatic and sulfur containing amino acids oo eb m e c re oo ks f eb m co m e fre oo ks eb m m e co ks fre oo eb m e co m fre m m m co e re ks f oo eb m m co e fre ks oo eb m co m e fre oo ks ok s e co re oo ks f eb eb m co m e ks fre oo eb m co m e fre ks oo • Their concentration is elevated in body fluids of cancer patients • Assays of urinary and blood polyamines have been used to detect cancer and to determine the success of therapy (diagnostic indicator) EXAM QUESTIONS Describe the metabolism and inherited disorders of phenylalanine and tyrosine Explain the routes of ammonia disposal via: (i) Glutamate (ii) Glutamine (iii) Urea Mention the disorders associated with the urea cycle Describe the digestion and absorption of proteins Briefly mention the fate of amino acids What is the fate of ammonia and describe urea cycle? Describe the metabolism of sulfur containing amino acids and associated inherited disorders Describe one carbon metabolism Describe the metabolism of glycine and associated disorders eb o m fre ks oo oo eb m m e co re sf oo k eb eb eb m m om e ks fre fre oo ks eb m m Clinical significance of polyamines • Polyamines and their derivatives have application in diagnosis and treatment of cancer • Their levels have been shown to increase in response to cell growth and differentiation m co m m co e c co e co m m m m e e e m m co m co co m Fig 14.48: Biosynthesis of polyamines (SAM: S-Adenosylmethionine) Long Answer Questions (LAQs) 273 Protein Metabolism e m e co m om re oo ks f ks oo eb eb m co m e fre ks oo eb m m m fre e co co e fre ks ks m eb oo oo e e co m co m Histidine is converted to histamine by: a Transamination b Decarboxylation c Hydroxylation d Reduction fre oo eb m m eb oo ks ks oo eb m e c re oo ks f eb m co m e fre oo ks eb m Multiple Choice Questions (MCQs) ks fre m co e fre Questions a Outline the biochemical pathway and point out metabolic defect which leads to this condition b State the changes in urine, on standing, in such patients Why? c What is ochronosis? d What is the treatment? eb m e co ks fre oo eb m e co m A patient was diagnosed as having alkaptonuria m ks oo eb m co m e fre fre ok s om m co e re eb m m co e fre fre ks Questions a Name the probable disorder b What is the cause of the disorder? c Name the transport form of ammonia d What will be the nutritional therapy for the patient? A full term infant was observed to have a lack of pigmen tation, blue eyes, white hair and confirmed as a case of albinism eb o ks f oo eb m co m Case History e Case History oo ks eb m Case History Questions a Name the defective enzyme of classic phenyl ketonuria b Name the other types of PKU with their defective enzymes c What are the characteristics of PKU? d Name diagnostic test for PKU Case History m Questions a What is the cause of cystinuria? b Why is there formation of kidney stone? c How is the condition to be treated? d Name the biosynthetic precursor of cysteine Questions a What is the cause of Hartnup disease? b Why does it show mental retardation and pellagra like symptoms? c How will you treat pellagra like symptoms? d Can aminoaciduria be treated? oo eb m co m A 20-year-old man came to the emergency room with severe pain in his right side and back Subsequent examination and evaluation indicated a kidney stone and increased excretion of cystine, arginine and lysine in the urine and diagnosed as a case of cystinuria A 5-month-old female infant was hospitalized A diagnosis of classic phenylketonuria (PKU) was made A 5-month-old female infant was admitted to hospital with a complaint of vomiting and a failure to gain weight The mother also reported that the child would oscillate between periods of irritability and lethargy, biochemical investigations of the patient indicated markedly increased concentration of plasma ammonia (550 µg/dL) m Case History oo co m e ks fre re sf oo k eb m co m A 3-year-old boy was admitted to hospital with the symptoms of pellagra, accompanied by mental retardation and excessive excretion of neutral amino acids He was diagnosed as having Hartnup disease co Questions a Name the deficient pigment b Name the enzyme responsible for the defect c Write biochemical reaction catalyzed by the enzyme d Name the amino acid, from which the pigment is synthesized m oo eb m m e co co Case History fre e ks fre fre m eb oo ks Disorders of sulfur containing amino acids Hartnup disease Absorption of amino acids 10 Glycine 11 Tyrosinemia 12 Albinism 13 Serotonin 14 Transmethylation 15 Importance of histidine 16 Formation of ammonia and its toxicity in brain 17 Proteolytic enzymes and their specificity 18 Give significance of urea cycle 19 Biologically important compound derived from tyrosine and tryptophan 20 Maple-syrup urine disease Solve the Following e c co e co m m m m e e e m m Essentials of Biochemistry m co 274 e m e co re oo ks f eb m re e c om m co e re oo ks f ks f oo eb eb m fre e co m co m e fre oo ks oo ks eb eb m m m fre e co co e fre ks ks oo eb m 20 The following enzymes are involved in digestion and absorption of protein, except: a Trypsinogen b Amylase c Pepsin d Chymotrypsin m co e fre ks oo eb m m eb oo oo eb m m om ks oo eb m 19 Which of the following amino acid is involved in the synthesis of carnitine? a Lysine b Phenylalanine c Tryptophan d Threonine co m m co e 18 Which of the following pathways occurs in part in the mitochondria and in part in the cytoplasm? a Urea cycle b TCA cycle c Glycolysis d Oxidative phosphorylation ks fre fre ok s eb o m 17 Tetrahydrobiopterine is used as a coenzyme in the metabolism of: a Folic acid b Phenylalanine c Glycine d Aspargine e eb m e co m m 10 The fate of ammonia in brain is: a Conversion to urea b Conversion to glutamate c Conversion to aspartate d Remains as such 16 All of the following statements are true in the trans amination of amino acids, except: a Ammonia is neither consumed nor produced b Requires pyridoxal phosphate c The amino group acceptor is α-keto acid d All amino acids can undergo transamination ks fre ks fre oo oo ks eb m All of the following are synthesized from tyrosine, except: a Melanin b Serotonin c Dopamine d Epinephrine 15 The reactions of urea cycle occur in: a THe cytosol b THe mitochondria c THe mitochondrial matrix and the cytosol d Lysosomes oo m e co e fre The amino acid required for synthesis of heme is: a Glutamine b Glutamic acid c Glycine d Lysine 14 In alkaptonuria, which of the following accumulates abnormally in the urine? a Phenylalanine b Acetoacetate c Homogentisated Fumarate eb m co e fre ks oo eb m co m co m Which of the following amino acid cannot undergo transamination? a Lysine b Alanine c Aspartic acid d Glutamic acid 13 All of the following are intermediates formed by amino acid degradation, except: a α-Ketoglutarate b Oxaloacetate c Fumarate d Citrate m oo eb m co m e fre ks m eb oo Phenylketonuria results due to the absence of the enzyme: a Phenylalanine oxidase b Phenylalanine hydroxylase c Phenylalanine transaminase d Phenylalanine oxygenase 12 Transamination of oxaloacetate results in the formation of: a Aspartic acid b Valine c Alanine d Serine m co m e ks fre re sf eb m co m Which type of reaction is conversion of norepi nephrine to epinephrine? a Transamination b Decarboxylation c Transmethylation d Phosphorylation 11 Which of the following amino acids can undergo deamination by dehydration? a Threonine b Alanine c Tryptophan d Glycine m oo eb m m e co co oo k Which of the following does not take part in the human urea cycle? a Arginine b Aspartate c Arginosuccinate d Urease fre e ks fre fre oo ks eb m m The methylene group, transferred to glycine in converting it to serine, comes from: a S-Adenosylmethionine b Methylene-B12 c Carboxybiotin d N5,N10-methylene-THF co e c co e co m m m m e e e m m co In Maple-syrup urine disease, which of the following compounds is accumulated? a Homogentisate b Methylmalonyl-CoA c Branched chain α-keto acids d Homocysteine 275 Protein Metabolism e m e co re oo ks f eb m re e c om m co e re oo ks f ks f oo eb eb m fre e co m co m e fre oo ks oo ks eb m m m fre e co co e fre ks ks oo eb m co m co m 37 Free ammonia is released during: a Oxidative deamination of glutamate b Catabolism of purines c Catabolism of pyrimidines d All of these e fre oo eb m m eb oo ks ks oo eb m m om ks oo eb m 36 Methionine is synthesized in human body from: a Cysteine and homoserine b Homocysteine and serine c Cysteine and serine d None of these e m co e fre 35 Cysteine is synthesized from methionine and which of the following amino acid a Serine b Homoserine c Homocysteine d Threonine ks fre ks fre oo eb m e co m fre ok s eb o m 34 A coenzyme required for the synthesis of glycine from serine is: a ATP b Pyridoxal phosphate c Tetrahydrofolate d NAD oo m e co e fre oo ks eb m m 28 Following components are required for the urea formation, except: a Ammonia b α-amino group of aspartate c CO2 d NADPH 33 The two nitrogen atoms in urea are contributed by: a Ammonia and glutamate b Glutamine and glutamate c Ammonia and aspartate d Ammonia and alanine eb m co e fre ks oo eb m co m co m 27 In the formation of urea from ammonia all of the following are true, except: a Ornithine transcarbamoylase catalyzes the rate limiting step b Aspartate supplies one of the nitrogen found in urea c This is an energy required process d Fumarate is produced 32 A compound that link citric acid cycle and urea cycle is: a Malate b Citrate c Succinate d Fumarate eb oo eb m co m e fre ks m eb oo 26 Select incorrect statement of the following: a Threonine contribute to biosynthesis of coenzyme A b Histamine arises by decarboxylation of histidine c Serotonin and melatonin are metabolites of tryptophan d Glycine, arginine and methionine each contribute atoms for biosynthesis of creatine 31 The number of ATP required for urea synthesis is: a b c d m e ks fre re sf eb m co m 25 For metabolic disorder of urea cycle which statement is not correct? a Ammonia intoxication is most severe when the metabolic block occurs prior to reactions of the urea cycle b Clinical symptoms include mental retardation c Clinical signs include hyperammonemia d Glutamate provides the second nitrogen of arginosuccinate 30 Which of the following statements are true for the reaction catalyzed by glutamate dehydrogenase? Except: a It catalyzes oxidative deamination b Requires NADH or NADPH c Net removal of α-amino group of amino acid to ammonia d Is an irreversible reaction m co m m e co co oo k 24 Carboxypeptidase contains which of the following mineral? a Fe b Cu c Ca d Zn 29 Which of the following is true for aminotransferase? a Catalyze irreversible reaction b Require pyridoxal phosphate as a cofactor c Catalyze reaction that result in net loss of amino group in the form of ammonia d Usually require glutamine as one of the reacting pair m oo eb m 22 Following enzymes are endopeptidase, except: a Pepsin b Trypsin c Chymotrypsin d Aminopeptidase fre e ks fre fre m eb oo ks 21 Norepinephrine is converted to epinephrine by: a Transamination b Transmethylation c Transcarboxylation d Decarboxylation 23 Which of the following enzyme is secreted by mucosal cell? a Trypsin b Proelastase c Aminopeptidase d Carboxypeptidase co e c co e co m m m m e e e m m Essentials of Biochemistry m co 276 e m om e c re oo ks f eb m fre e co m co m e ks oo eb m m m co co e e fre fre ks eb oo m co ks fre e e m eb oo oo eb m c 16 d 24 d 32 d 40 d 48 a ks fre ks a 15 c 23 c 31 d 39 c 47 c m b 14 c 22 d 30 d 38 d 46 b m c 13 d 21 b 29 b 37 a 45 d 53 c co m eb oo e co m d 12 a 20 b 28 d 36 d 44 d 52 b e co re oo ks f eb m m co e re fre oo ks eb 53 Ochronosis occurs in: a Tyrosinemia b Tyrosinosis c Alkaptonuria d Richner Hanhart syndrome oo eb m m om ks oo m 52 Alkaptonuria occurs due to deficiency of the enzyme: a Maleylacetoacetate isomerase b Homogentisate oxidase c P-hydroxyphenylpyruvate hydroxylase d Fumarylacetoacetate hydrolase ks ks fre 51 An inborn error, maple syrup urine disease is due to deficiency of the enzyme: a Glycinase b Phenylalanine hydroxylase c Fumarylacetoacetate hydrolase d α-Ketoacid dehydrogenase oo d 11 a 19 a 27 a 35 a 43 d 51 d fre fre e co m m c 10 b 18 a 26 a 34 b 42 a 50 b eb Answers for MCQs ok s eb o m eb eb m e co e fre oo ks eb m m 50 Increased urinary indole acetic acid is diagnostic of: a Maple syrup urine disease b Hartnup disease c Homocystinuria d Phenylketonuria m m co oo eb co m co m m m eb oo ks ks fre fre e e 43 The milk protein in the stomach of the infants is digested by: a Pepsin b Trypsin c Chymotrypsin d Rennin 44 Rennin acts on casein of milk in infants in presence of: b Zn++ a Mg++ ++ c Co d Ca++ 45 Neonatal tyrosinemia improves on administration of: a Thiamin b Riboflavin c Pyridoxine d Ascorbic acid 46 Absence of phenylalanine hydroxylase causes: a Neonatal tyrosinemia b Classic phenylketonuria c Primary hyperoxaluria d Albinism co 49 An important finding in glycinuria is: a Excess excretion of oxalate in the urine b Deficiency of enzyme glycinase c Significantly increased serum glycine level d Defect in renal tubular reabsorption of glycine ks f ks fre oo eb m co m co m 42 The symptom of ammonia intoxication includes: a Blurring of vision b Constipation c Skin lesion d Diarrhea b b 17 b 25 d 33 c 41 c 49 d 48 Tyrosinosis is due to defect in the enzyme: a Fumarylacetoacetate hydrolase b P-hydroxyphenylpyruvate hydroxylase c Tyrosine transaminase d Tyrosine hydroxylase oo co m e e co re sf oo k eb m 41 Normal range of serum urea is: a 0.6–1.5 mg/dL b 9–11 mg/dL c 20–40 mg/dL d 60–100 mg/dL 47 Richner-Hanhart syndrome is due to defect in: a Tyrosinase b Phenylalanine hydroxylase c Hepatic tyrosine transaminase d Fumarylacetoacetate hydrolase m oo eb m m m co 40 Pancreatic juice contains of all of the following, except: a Trypsin b Chymotrypsin c Carboxypeptidase d Aminopeptidase fre e ks fre fre oo ks eb m 39 Maple syrup urine disease is an inborn error of metabolism of: a Sulfur-containing amino acids b Aromatic amino acids c Branched chain amino acids d Dicarboxylic amino acids e c co e co m m m m e e e m m co 38 Ammonia is transported from muscles to liver mainly in the form of: a Free ammonia b Glutamine c Asparagine d Alanine 277 Protein Metabolism e m e co re oo ks f eb m co m e fre ks oo eb eb m m co m co m m m m eb eb oo oo ks ks fre fre e e co co m m m e co co ks m eb oo oo eb m fre ks fre e e e fre ks oo eb m om e c re oo ks f eb m oo ks ks ks fre oo eb m e co m Fig 15.1: Inter-relationship between metabolism of three principal nutrients The amino acids, glucose and fatty acids catabolized to a common degradative product, acetyl-CoA, which in turn is degraded to CO2 and H2O with formation of ATP ok s fre co m e fre The various anabolic and catabolic pathways by which carbohydrates, lipids and proteins are processed for energy supply or for the biosynthesis of compounds required by the cell (for maintenance or growth) are closely co-ordinated oo eb m co m e fre oo ks eb m eb o Definition fre m co e e fre ks oo eb m co m m m m INTEGRATION OF METABOLISM co m co m co e re ks f m m eb eb oo oo ¾¾ Metabolism in Starvation ¾¾ Metabolic Changes occur during Short-term Starvation ¾¾ Metabolic Changes occur during Prolonged Starvation Carbohydrates, lipids and proteins are the principal foods providing necessary nutrients to the body The metabolism of all of them is inter-related, and occurs simultaneously (Fig 15.1) The deficiency of one is made up by another to some extent co m fre ks eb m co m e ks fre re sf oo k ¾¾ Integration of Metabolism ¾¾ Integration of Metabolism at Cellular Level ¾¾ Integration of Metabolism at Tissue or Organ Level eb m oo oo eb m m e co co Integration of Metabolism and Metabolism in Starvation Chapter outline INTRODUCTION om e ks fre fre oo ks m m eb 15 e c co e co m m m m e e e m m co CHAPTER e m e co re oo ks f eb m re e c om m co e re oo ks f ks f oo eb eb m fre e co m co m e fre ks oo ks oo eb m m m fre e co co e fre ks ks • Skeletal muscle maintains large stores of glycogen, which provide energy during exertion • During starvation, free fatty acids and ketone bodies supplied by liver are oxidized in preference to glucose in muscle • The protein present in muscle may be used as a fuel source, if no other fuel is available • Pyruvate, the product of glycolysis in the skeletal muscle, may be converted to either lactate or alanine and transported to the liver, where it is used to regenerate glucose via gluconeogenesis (See Fig 12.11) oo eb m co e fre ks m eb oo oo eb m m co m ks oo eb m m om e c fre ks oo eb m Role of Skeletal Muscle e m co e fre Major roles of the liver include the following: • Maintenance of blood glucose levels • During the fed state, the liver takes up excess glucose and stores it as glycogen or converts it to fatty acids • During the fasting state, liver provides glucose for the body by the glycogenolysis and gluconeogenesis • The liver serves as the major site of fatty acid synthesis • The liver synthesizes ketone bodies during starvation and supplies to the peripheral tissues as a source of energy ks fre m e co ks fre oo eb m e co m fre ok s eb o m Role of Liver oo ks oo eb m co m e fre oo ks eb m co • Many carbon skeletons of the nonessential amino acids can be produced from carbohydrate via the intermediates of citric acid cycle and transamination Integration of metabolism at tissue or organ level includes the inter-relationship of different tissues and organs to meet metabolic demands for the whole body (Fig 15.3) The major organs along with their most important metabolic functions are discussed here eb m co e fre fre ks oo eb m co m m Conversion of Carbohydrates into Proteins and Proteins into Carbohydrates INTEGRATION OF METABOLISM AT TISSUE OR ORGAN LEVEL eb oo eb m co m e • Carbohydrates (glucose) are metabolized via glycolytic pathway to pyruvate and then pyruvate to acetyl-CoA • Acetyl- CoA is the starting material for synthesis of fatty acids Fatty acids, that are produced, combine with glycerol to form triacylglycerol • Glycerol may also be supplied from the glucose by glycolysis as glycerol-3-phosphate Thus, carbohydrates can easily form fat • There cannot be a net conversion of fatty acids having an even number of carbon atoms (which form acetyl-CoA) to glucose or glycogen • Only a fatty acid having an odd number of carbon atoms is glucogenic (i.e can form glucose) as it forms a molecule of propionyl-CoA upon β-oxidation • Propionyl-CoA can be converted to succinyl-CoA, an intermediate of citric acid cycle, which can be converted to glucose by gluconeogenesis • The glycerol moiety of triacylglycerol is converted to glucose by gluconeogenesis after activation to glycerol3-phosphate and this is an important source of glucose in starvation • Conversion of carbon skeletons of glucogenic amino acids to fatty acids is possible either by formation of pyruvate and acetyl-CoA • Generally, however, the net conversion of amino acids to fat is not a significant process • It is not possible for a net conversion of fatty acids to amino acids to take place m e ks fre re sf oo k eb m co m Conversion of Carbohydrates into Fats and Fat to Carbohydrate Conversion of Proteins to Fats and Fats into Proteins m m Integration of metabolism at cellular level includes the different metabolic pathways of glucose, fatty acids, glycerol and amino acids, at the cellular level which results in: (Fig. 15.2) Conversion of carbohydrates into fats and fats into carbohydrates Conversion of carbohydrates into proteins and proteins into carbohydrates Conversion of proteins into fats and fats into proteins e co co co m m eb oo oo ks eb m m INTEGRATION OF METABOLISM AT CELLULAR LEVEL • By reversal of these processes, glucogenic amino acids yield intermediates of the citric acid cycle They are therefore readily converted by gluconeogenesis to glucose and glycogen m ks fre fre e co e co m m m m e e e m m co This coordination between three metabolites is called integration of metabolism Integration of metabolism is considered at two levels: Cellular level Tissue or organ level 279 Integration of Metabolism and Metabolism in Starvation e m m om m e c co e re re oo ks f ks f oo eb eb m m m e ks ks fre fre ks fre e co co e co m m m m eb eb oo ks oo ks fre fre e e co m co m m co e fre ks oo m e • Brain tissue normally uses glucose as an exclusive fuel, except during starvation, when it can adapt to use ketone bodies as an energy source fre oo eb m m eb oo ks ks co m co m Role of Brain oo eb m eb eb m Heart muscle contains essentially no fuel reserves and must be continuously supplied with fuel from liver and adipose tissue ks fre fre fre e co m e co m m • The primary function of the adipose tissue is the storage of metabolic fuel in the form of triacylglycerols • During the fed state, the adipose tissue synthesizes triacylglycerols from glucose and free fatty acids • During the fasting state, triacylglycerols are converted to glycerol and fatty acids, which are exported to the liver and other tissues ok s oo oo oo eb Role of Heart Muscle e eb m co m e fre oo ks e co re oo ks f eb eb m co m e ks fre oo eb m co m e fre ks oo eb eb Fig 15.2: Integration of three metabolisms at cellular level Role of Adipose Tissue eb o m fre ks oo oo eb m m e co re sf oo k eb m m m m om e ks fre fre oo ks eb m co co m co m m co e c co e co m m m m e e e m m Essentials of Biochemistry m co 280 e m e co m om re oo ks f eb m om m e c re oo ks f eb m co m e fre oo ks oo ks eb eb e co co e fre fre ks ks oo eb m co e fre oo eb m m eb oo ks ks ks fre e co m m m m m m m m • In starvation, energy has to be derived from the body’s own stores A typical well-nourished 70 kg man has fuel reserve of: –– 1600 kcal in glycogen –– 2400 kcal in mobilizable protein –– 135000 kcal in triacylglycerols • The energy, needed for 24-hr period, ranges from about 1600 kcal in the basal state to 6000 kcal depending on the extent of activity • Thus, stored fuels are enough to meet caloric needs in starvation for one to three months and in the case of some obese individuals, much longer oo eb m eb o ok s fre fre e co • Starvation is the deprivation of the food and thereby deprivation of exogenous supply of calories to meet the energy demands of the body for basal metabolism and other activities m Fuel Reserve of a Normal Healthy Person oo ks fre oo eb m e co m m • Starvation is not always the result of unavailability or scarcity of food • Any medical condition, which prevents consumption or utilization of available food will lead to starvation, e.g trauma, surgery, cancer cachexia, infections, malabsorption, etc eb m e co e fre METABOLISM IN STARVATION Definition co co m e fre fre ks oo eb m co m Integration of metabolism ensures a supply of suitable fuel for all tissues, at all times from the fully fed state to the totally starved state Under positive caloric balance, i.e in well fed state, a significant proportion of the food energy intake is stored as either glycogen or fat Under negative caloric balance, i.e in starvation, fatty acids are oxidized in preference to glucose, to spare glucose for those tissues, (e.g brain and erythrocytes) that require it under all conditions oo ks m eb • co e re ks f oo co e e fre ks oo eb m co m Significance of Integration of Metabolism • e c fre ks oo eb eb m co m m m m eb eb oo oo k sf ks fre re e e co co m m m m m eb eb oo oo ks ks fre fre e co e co m m m m e e e m m co m co co m Fig 15.3: Integration of metabolism among major tissues of the body • The brain contains essentially no fuel reserves and must be continuously supplied with fuel from the liver • 281 Integration of Metabolism and Metabolism in Starvation m e co re om co m m m m co co e e fre fre ks ks oo oo eb eb m m co m co m m e e oo eb m m eb oo ks fre ks fre fre ks oo eb m e fre ks oo eb eb m m e co co e Fig 15.4: Metabolic changes occurring during starvation The circled number indicates the approximate order in which processes begin to occur (TG: Triacylglycerol; FA: Fatty acid; KB: Ketone bodies) ok s e c re oo ks f eb m co m fre oo ks ks ks fre oo eb m e co m oo ks f eb m m co ks f oo eb fre e e • As the liver glycogen store begins to be depleted, gluconeogenesis becomes active, which ensures a continuous supply of glucose to the brain and other tissues The sources of substrates for gluconeogenesis are: oo eb m co m e fre oo ks eb m fre e ks oo eb re co m co m e fre ks oo eb m co m eb o The liver glycogen is capable of maintaining the blood glucose concentration at normal values for to 12 hours m m eb oo • The first phase of starvation begins four to five hours after a meal Within about hr after a meal, blood glucose levels begin to fall Consequently, insulin levels decline and glucagon, epinephrine levels rise • The brain, the erythrocytes, the bone marrow, the renal medulla and peripheral nerves have to be supplied with glucose, for their energy needs However, the tissues such as muscle can readily use free fatty acids, released from adipose tissue m m • In this phase, the main source of blood glucose is liver glycogen The liver first uses glycogenolysis (glycogen degradation) then gluconeogenesis to maintain blood glucose levels and provide sufficient glucose to the brain and other glucose requiring tissues • The fall of blood glucose and insulin concentration and rise of glucagon stimulates glycogenolysis Glucagon stimulates c-AMP formation, essential for degradation of glycogen e e ks fre re m eb oo k sf Changes in Carbohydrate Metabolism and Role of Liver co m fre co m m METABOLIC CHANGES OCCUR DURING SHORT-TERM STARVATION The first priority of metabolism in starvation is to provide sufficient glucose to the brain and other tissues that are absolutely dependent on glucose m m eb oo Starvation can be divided into two phases characterized by distinct metabolic changes In starvation, the changes in metabolism are not abrupt but gradual (Fig 15.4) Short-term starvation, which covers the 12 hour overnight fast and can extend to 24 hour Prolonged starvation, which lasts longer than 24 hour and can extend to several days or weeks e co co om e ks fre fre m eb oo ks Phases of Starvation co m e c co e co m m m m e e e m m Essentials of Biochemistry m co 282 e m e co re om e c re co m e fre ks m co e fre ks oo eb m fre ks m eb oo oo eb m e co m co m e ks fre ks Fig 15.5: Changes in the concentration of fuels in the blood during prolonged fasting (1 mm glucose = 18 mg/dL glucose) oo eb m oo ks f oo eb m m co eb m m co e fre fre ok s oo ks f eb eb m co m e fre fre ks oo oo eb e co m m • The processes which take place in short-term starvation cannot go on indefinitely, because, although gluconeogenesis provides glucose efficiently for the body’s energy requirements, it will soon deplete the substantial proportion of body protein and it is known that death results when 30 to 50% of the body protein is lost • Adjustments to metabolism are made after 24 to 48 hr, which conserve body protein eb o m m e re ks f ks fre e e fre oo ks m m eb METABOLIC CHANGES OCCUR DURING PROLONGED STARVATION co m om e c fre ks oo oo eb m Ketosis is a metabolic adaptation to starvation, arises as a result of deficiency in available carbohydrate e co m oo ks fre ks oo eb m co m • During prolonged fasting, adipose tissue continues to breakdown its triacylglycerol store to fatty acids and glycerol These fatty acids serve as the major source of fuel for the body The glycerol is converted to glucose while fatty acids are oxidized to CO2 and H2O by muscle and in the liver where they are converted into ketone bodies • The synthesis of ketone bodies from acetyl-CoA increases markedly producing the state of ketosis (Fig 15.5) As the citric acid cycle is unable to oxidize all of the acetyl-CoA generated by the degradation of fatty acids, these are converted to ketone bodies Gluconeogenesis depletes the supply of oxaloacetate, which is essential for the entry of acetyl-CoA into the citric acid cycle Consequently, liver produces large quantities of ketone bodies eb m co e e fre ks oo eb m • Increased levels of epinephrine stimulates breakdown of triacylglycerol of adipose tissue to free fatty acids and glycerol Free fatty acids can be used by some tissues such as skeletal muscle, as an alternative source of fuel, and glucose is spared for the brain and other glucose requiring tissues • The glycerol derived from the cleavage of triacylglycerol is a source for the synthesis of glucose by gluconeogenesis by the liver Changes in Fat Metabolism in Prolonged Starvation m oo eb m co m co m co m • The blood glucose levels drop from about 100 mg/dL to about 70 mg/dL after 24 h but, are thereafter maintained (Fig 15.5) • Conservation of body proteins is accomplished by a reduction in glucose production by gluconeogenesis m co m e ks fre re m eb oo k sf • The decrease in plasma insulin and increase in epinephrine inhibits glycolysis and the uptake of glucose by muscle, whereas fatty acids enter freely in muscle • Increased proteolytic activity occurs due to decreased concentration of insulin The main precursor for gluconeogenesis is, however, tissue protein, in the form of amino acids, released after proteolytic degradation • During short-term starvation there is a rapid breakdown of muscle protein, providing amino acids that are used by the liver for synthesis of glucose by gluconeogenesis The major gluconeogenic amino acids, coming from muscle, are alanine and glutamine Changes in Fat Metabolism and Role of Adipose Tissue Changes in Carbohydrate Metabolism in Prolonged Starvation co m m e co co Changes in Protein Metabolism and Role of Muscles eb eb oo oo ks eb m m Gluconeogenesis plays an essential role in maintaining blood glucose during both short-term and prolonged starvation Thus, the second priority of metabolism in starvation is to preserve protein This is accomplished by using fatty acids and ketone bodies in place of glucose as a fuel m ks fre fre e co e co m m m m e e e m m co –– Pyruvate –– Lactate which is a product of glycolysis in red blood cell and exercising muscle –– Glucogenic amino acids released from muscle –– Glycerol released by degradation of triacylglycerols 283 Integration of Metabolism and Metabolism in Starvation e m m e co oo ks f eb m om m e c co e re re oo ks f ks f oo eb m Short Notes Significance of integration metabolism eb m co m Prolonged starvation co Role of liver in integration metabolism e fre oo eb m m eb oo ks ks ks fre fre What is short-term and prolonged starvation? oo eb m m Short-term starvation e m co e m m e co m fre m co e fre ks oo Integration metabolism at tissue or organ level ok s e fre ks oo eb m m co e fre oo Define integration metabolism Discuss integration of metabolism at various levels and its significance Define starvation Describe metabolic changes occur during starvation eb Integration metabolism at cellular level eb Long Answer Questions (LAQs) eb o co m co m e fre oo ks ks fre oo ks e fre re fre ks eb eb m • Apart from increase in the ratio of glucagon to insulin concentrations thyroxine (T3), production is reduced and that leads to the decreased: –– BMR –– Body temperature –– Pulse rate –– BP • The body is more susceptible to infections, all these lead death in prolonged starvation e co m Effect on BMR eb e fre ks oo eb m co m • During the conversion of amino acid to glucose by gluconeogenesis, the nitrogen of the amino acid is converted to urea and so production of urea decreases during prolonged starvation, as compared to its production in short-term starvation (Fig 15.6) m co m co m e fre ks Fig 15.6: Changes in urea excretion during starvation EXAM QUESTIONS oo ks eb m co m e ks fre oo eb m • During the first few days of starvation, there is a rapid breakdown of muscle protein, providing amino acids, alanine and glutamine for gluconeogenesis • After several weeks of starvation, the rate of muscle breakdown decreases due to decreased need of glucose as a fuel for brain which has begun using ketone bodies as a source of energy • Because of these adaptive mechanisms the duration of starvation of the adult human is determined by the size of the triacylglycerol depot When the stored triacylglycerol are completely exhausted, muscle proteins the largest single source of energy are heavily drained • At that time, the protein stores once again enter a stage of rapid depletion As proteins are also essential for the maintenance of cellular function, death ordinarily results when the proteins of the body have been depleted to about half their normal level oo eb m m oo oo eb m m e co re sf oo k eb m Changes in Protein Metabolism in Prolonged Starvation Biochemical changes in starvation m om e ks fre fre • As the supply of ketone bodies increases and the supply of glucose diminish, the brain reduces its utilization of glucose and begins to consume appreciable amounts of ketone bodies in place of glucose Although the brain still has a residual glucose requirement, not only for provision of energy, but also for synthesis of neurotransmitters • After several weeks of starvation, ketone bodies become the major fuel of the brain which diminishes the need for glucose Therefore, in prolonged starvation, less muscle is degraded than in the first days of starvation This sequence of events leads to at least partial preservation of the protein stores of the body oo ks eb m co co m co m m co e c co e co m m m m e e e m m Essentials of Biochemistry m co 284 e m e co m om e c re oo ks f eb eb m re e c om m co e re oo oo ks f ks f eb eb m m fre e co m co m e fre ks oo ks oo eb m m m fre e co co e fre ks ks oo eb m co e fre oo eb m m eb oo ks ks m co m 15 After overnight fast one would expect glucose transporter activity to be what? a Decreased in brain cell b Enhanced in adipocytes c Decreased in red blood cells d Decreased in muscle cells e m co 14 After overnight fast one would expect increased activity of what? a Hepatic glycogen synthase b Pyruvate dehydrogenase c Hormone sensitive lipase d Pancreatic lipase oo eb m m eb o ok s fre fre e During early fasting glucose is derived from: a Glycogen b Amino acids c Fatty acids d Ketone bodies 13 On prolonged fasting which of the following metabolites will be elevated in blood after days? a Ketone bodies b Glycogen c Triacylglycerol d Glucose ks fre oo eb e co m m The major glucogenic amino acid coming from muscle to liver for gluconeogenesis during starvation is: a Threonine b Methionine c Alanine d Glycine 12 In fasting which of the following metabolites will be elevated in blood after 24 hours? a Triacylglycerol b Glucose c Free fatty acid d Glycogen oo In prolonged starvation, the main energy source of brain is: a Glucose b Ketone bodies c Fructose d Fatty acids oo ks eb m m ks fre fre e e co co m co m In starvation, muscle protein is spared by: a Using fatty acids and ketone bodies b By increasing rate of gluconeogenesis c By inhibiting glucose utilization d By stimulating protein synthesis 11 Synthesis of the following enzymes is increased during starvation: a Digestive enzymes b Gluconeogenic enzymes c Glycolysis enzymes d Glycogenesis enzymes eb oo eb m m eb oo ks ks Which of the following processes plays an essential role in maintaining blood glucose during early and prolonged starvation? a Glycolysis b Gluconeogenesis c Ketogenesis d Glycogenolysis 10 During starvation, the first reserve nutrient to be depleted is: a Glycogen b Proteins c Triglycerides d Cholesterol eb fre fre e e co m co m co m During starvation, blood or tissue levels of all of the following are elevated, except: a Free fatty acids b Ketone bodies c Glucagon d Insulin m During starvation free fatty acids and ketone bodies are oxidized in preference to glucose in muscle by impairing, except: a Uptake of glucose by the cell b Phosphorylation by hexokinase and phosphofructokinase c Pyruvate dehydrogenase activity d Lactate dehydrogenase activity m oo eb The first priority of metabolism in starvation is to provide which of the following substances to the brain and other tissue? a Fatty acids b Ketone bodies c Glucose d Cholesterol m m eb oo k Multiple Choice Questions (MCQs) co oo ks co m sf ks fre re e e co co m m m m eb eb A patient attending an obesity clinic is found to have ketonuria The patient is on a low carbohydrate diet in order to lose weight There is no glycosuria Blood glucose level was, found 80 mg/100 mL: a Explain the cause of ketonuria b What is ketoacidosis? c Name ketone bodies d What is ketonemia? e What is ketosis? m Case History Fatty acid or ketone bodies are used as energy source in: a Intraprandial phase b Post absorptive phase c Prolonged starvation d Fully fed state m oo oo ks fre ks fre fre e co e co m m m m e e e m m co Solve the Following 285 Integration of Metabolism and Metabolism in Starvation e m om e c re oo ks f c 16 b co m e e fre fre oo ks oo ks eb eb m m m co e fre ks oo eb m m eb oo oo ks ks fre fre e e co co m m m m eb eb oo oo ks ks fre fre e e co co m m m e co ks fre oo eb m eb m eb m a 15 d co m m co fre ks oo eb m co m e e co m fre e co re oo ks f eb m m co ks f oo eb c 14 c m b 13 a e e fre fre oo ks ok s m om ks oo eb oo eb m a 12 c co m b 11 b 19 b ks oo eb eb m eb o 19 During starvation, ketone bodies are used as a fuel by: a Erythrocytes b Brain c Liver d All of these e e ks fre re sf oo k eb m d 10 a 18 a m co m m co m 18 Which of the following occurs in cardiac muscle but not in the brain, even in the fasted state? a Fatty acid oxidation b Glycolysis c TCA cycle d Glucose uptake via a glucose transporter re co m m e co co Answers for MCQs co m b Glucose is preserved for the brain c Alanine is utilized for glucose synthesis d Alanine is utilized for protein synthesis m oo eb m 17 Which of the following statements are correct for amino acid metabolism during the fasting state compared with the fed state? Except: a Glutamine and alanine are released in increased amounts fre e ks fre fre m eb oo ks 16 Which one of the following statements is correct for metabolism during prolonged starvation compared to early or short term starvation? a The degradation of proteins is increased b The rate of gluconeogenesis in liver is decreased c The formation of ketone bodies is deceased d Heart generates more of its energy from glucose c a 17 d e c co e co m m m m e e e m m Essentials of Biochemistry m co 286 ... m 7, 10 ,13 , 16 , 19 co e co ks fre oo eb m e co m ω-6 e m co m e fre Straight Chain Fatty Acids fre 5, 8, 11 , 14 4,7 ,10 ,13 ,16 ,19 Fatty acids are classified into four major classes (Fig 3 .1) Straight... m 19 PURINE AND PYRIMIDINE NUCLEOTIDE METABOLISM 3 21 m co e Synthesis of Heme 312 Disorder of Heme Biosynthesis 313 Breakdown of Hemoglobin 314 Fate of Bilirubin 315 Jaundice 315 ... Functions of Carbohydrates 13 Structure of Glucose 15 Isomerism 16 Mutarotation 18 Chemical Properties of Monosaccharides 18 Glycoside Formation 20 Derivatives of Monosaccharides 21 Disaccharides