Biochemistry 1 for Technologists (Menoufia University 2024-2025) PDF

1 Faculty of Applied Health Sciences Technology of Medical Laboratory Department Second year Biochemistry 1 For Technologists By Staff members of medical Biochemistry and Molecular Biology...

1 Faculty of Applied Health Sciences Technology of Medical Laboratory Department Second year Biochemistry 1 For Technologists By Staff members of medical Biochemistry and Molecular Biology Department Faculty of Medicine Menoufia University 2024 - 2025 Table Content 2 Table Content ‫رؤﯾﺔ اﻟﻛﻠﯾﺔ‬ 13 ‫رﺳﺎﻟﺔاﻟﻛﻠﯾﺔ‬ 13 Overall Aims of the Course............................................................................................... 14 Chapter I: Carbohydrate metabolism............................................................................... 15 Chapter Content................................................................................................................ 15 Learning Objectives..................................................................................................... 15 Introduction to metabolism........................................................................................ 15 Digestion and absorption of CHO.............................................................................. 15 Glycolysis...................................................................................................................... 15 Oxidative decarboxylation.......................................................................................... 15 Kreb’s cycle.................................................................................................................. 15 HMP shunt................................................................................................................... 15 Uranic acid pathway.................................................................................................... 15 Glycogen metabolism.................................................................................................. 15 Gluconeogenesis........................................................................................................... 15 Metabolism of other hexoses....................................................................................... 15 Blood glucose................................................................................................................ 15 Revision questions........................................................................................................ 15 Learning Objectives......................................................................................................... 16 Introduction to metabolism............................................................................................. 17 Definition..................................................................................................................... 17 Metabolic pathways of metabolism include................................................................. 17 1- Anabolic pathways................................................................................................ 17 2- Catabolic pathways:.............................................................................................. 17 3- Amphibolic pathways:........................................................................................... 17 Carbohydrate Metabolism............................................................................................... 18 Sources of CHO in food:................................................................................................ 18 Digestion of CHO:......................................................................................................... 18 Note:........................................................................................................................... 18 Metabolic pathways of carbohydrates......................................................................... 19 A. Catabolic pathways............................................................................................... 19 B. Anabolic pathways................................................................................................ 19 Table Content 3 C. Amphibolic pathways............................................................................................ 19 Glycolysis......................................................................................................................... 20 Definition..................................................................................................................... 20 Site:............................................................................................................................. 20 Steps............................................................................................................................ 20 1- Stage 1:................................................................................................................. 20 2- Stage 2:................................................................................................................. 20 Importance of glycolysis:.............................................................................................. 22 Energy production of glycolysis:................................................................................... 22 In case of aerobic glycolysis.......................................................................................... 23 In case of anaerobic glycolysis...................................................................................... 23 Substrate level phosphorylation:.................................................................................. 23 Discuss glycolysis in the RBCs?..................................................................................... 24 Regulation of glycolysis:............................................................................................... 24 Note:............................................................................................................................... 25 Oxidative decarboxylation of pyruvate............................................................................ 26 Pyruvate...................................................................................................................... 26 Oxidative..................................................................................................................... 26 Site:............................................................................................................................. 26 PDH-complex:.............................................................................................................. 26 5 coenzymes are needed;............................................................................................. 26 Summary of oxidative decarboxylation of pyruvate:.................................................... 27 Regulation of oxidative decarboxylation;..................................................................... 27 Krebs cycle = Citric Acid Cycle (CAC)................................................................................. 29 Tricarboxylic Acid Cycle (TCA).......................................................................................... 29 Definition:.................................................................................................................... 29 Site:............................................................................................................................. 29 Steps: - See the next page............................................................................................ 29 Energy production by CAC:....................................................................................... 29 Regulation of CAC:.................................................................................................... 29 Importance of TCA:...................................................................................................... 31 A. Production of energy:........................................................................................... 31 B. TCA has amphibolic........................................................................................... 31 Table Content 4 C. Production of CO2................................................................................................ 32 Inhibitors of CAC in vitro:............................................................................................. 33 Hexose monophosphate shunt........................................................................................ 33 (HMP shunt).................................................................................................................... 33 Definition:.................................................................................................................... 33 Site:............................................................................................................................. 33 Steps:........................................................................................................................... 33 1-Oxidative (irreversible) phase:............................................................................... 33 2- non-oxidative (reversible) phase:.............................................................................. 33 Functions of HMP shunt:.............................................................................................. 33 A. Production of pentoses......................................................................................... 33 B. Production of NADPH+H+..................................................................................... 33 Regulation of HMP shunt:............................................................................................ 34 Uranic acid pathway........................................................................................................ 35 Definition:.................................................................................................................... 35 Site:............................................................................................................................. 35 Importance of uranic acid pathway.............................................................................. 35 A. Production of glucuronic acid in the form of UDP................................................. 35 B. Production of pentoses........................................................................................ 35 Glycogen Metabolism...................................................................................................... 36 Glycogenesis.................................................................................................................... 37 Definition..................................................................................................................... 37 Site:............................................................................................................................. 37 Sources of glucose units:.............................................................................................. 37 For liver glycogen: it includes................................................................................... 37 -For muscle glycogen:............................................................................................... 37 Steps:........................................................................................................................... 37 1- Formation of UDP - glucose (UDP-G)...................................................................... 37 2- Formation of glycogen from UDP - G units needs................................................... 37 Glycogenolysis................................................................................................................. 39 Fate of glucose -6- phosphate:..................................................................................... 40  In liver.............................................................................................................. 40  In muscle...................................................................................................... 40 Table Content 5 Regulation of glycogenesis and glycogenolysis................................................................. 41 During fasting:............................................................................................................. 41 After meals:................................................................................................................. 42 Gluconeogenesis.............................................................................................................. 44 Gluconeogenic substances............................................................................................... 47 1) Gluconeogenic amino acids...................................................................................... 47 2) Lactate..................................................................................................................... 47 3) Propionate:.............................................................................................................. 47 4) Glycerol:.................................................................................................................. 47 Energy cost of gluconeogenesis:................................................................................... 47 Regulation of gluconeogenesis:.................................................................................... 48 Metabolism of other hexoses........................................................................................... 49 A-Fructose metabolism................................................................................................ 49 Sources of fructose:..................................................................................................... 49 Importance of fructose................................................................................................. 49 A-Fructose metabolism in the liver, kidney and intestine............................................. 49 B-Fructose metabolism in muscles and adipose tissues:............................................... 50 C-In the testis, lens, peripheral nerves and renal glomeruli:......................................... 50 Galactose metabolism..................................................................................................... 51 Blood Glucose.................................................................................................................. 52 Normal blood glucose:................................................................................................. 52 Sources of blood glucose:............................................................................................. 52 Variations in blood glucose.............................................................................................. 53 Hypoglycemia.................................................................................................................. 53 Definition..................................................................................................................... 53 Symptoms:................................................................................................................... 53 Causes:........................................................................................................................ 53 1)Stimulative hypoglycemia..................................................................................... 53 2)Fasting hypoglycemia............................................................................................ 53 Glucosuria....................................................................................................................... 55 Definition..................................................................................................................... 55 Glucosuria.................................................................................................................... 55 Causes:........................................................................................................................ 55 Table Content 6 Revision questions........................................................................................................... 56 Chapter II: Lipid Metabolism............................................................................................ 58 Chapter Content.......................................................................................................... 58 Learning Objectives..................................................................................................... 58 Digestion and absorption of lipids.............................................................................. 58 Fatty acid synthesis (lipogenesis)................................................................................ 58 Fatty acid oxidation..................................................................................................... 58 Metabolism of Ketone bodies...................................................................................... 58 Metabolism of Acylglycerols & PLs........................................................................... 58 Metabolism of Eicosanoids.......................................................................................... 58 Metabolism of Cholesterol.......................................................................................... 58 Metabolism of Bile acids............................................................................................. 58 Lipid transport and storage........................................................................................ 58 Fallow up Activity........................................................................................................ 58 Learning Objectives......................................................................................................... 59 Lipid metabolism............................................................................................................. 60 Digestion of dietary lipids................................................................................................ 60 A.Digestion of triacylglycerols (TAGs):.......................................................................... 60 B.Digestion of cholesterol esters:................................................................................. 61 C.Digestion of phospholipids (PLs):............................................................................... 61 Absorption of lipids......................................................................................................... 62 1- Short and medium chain FAs..................................................................................... 62 2- Hydrophobic lipids.................................................................................................... 62 Secretion of lipids............................................................................................................ 62 Fatty acid synthesis (Lipogenesis).................................................................................... 63 Cytoplasmic system (Extramitochondrial)........................................................................ 63 Site:............................................................................................................................. 63 Requirements.............................................................................................................. 63 1). Acetyl CoA:.......................................................................................................... 63 2). Sources of reducing equivalents (NADPH+H+) for lipogenesis............................... 63 3). Fatty acid synthase complex:............................................................................... 64 Steps:........................................................................................................................... 64 1.Carboxylation of acetyl CoA to form malonyl CoA.................................................. 64 Table Content 7 2.Steps of FA synthesis:............................................................................................ 64 Note:............................................................................................................................... 65 The overall reaction of synthesis of palmitic acid is summarized as follow:.................. 65 Fate of palmitate:........................................................................................................ 66 Regulation of FA synthesis:.......................................................................................... 66 Microsomal pathway for FA synthesis.............................................................................. 67 Requirements:............................................................................................................. 67 Importance:................................................................................................................. 67 Fatty acid desaturation.................................................................................................... 68 Sources and fates of acetyl CoA....................................................................................... 69 Sources of acetyl COA:................................................................................................. 69 1.Carbohydrates....................................................................................................... 69 2. Fat........................................................................................................................ 69 3.Protein.................................................................................................................. 69 Fates of acetyl CoA:...................................................................................................... 69 Fatty acid oxidation......................................................................................................... 70 Types of fatty acid oxidation include:........................................................................... 70 1- Beta (β) oxidation (the most common type)......................................................... 70 2- Alpha (α) oxidation............................................................................................... 70 3- Omega (ω) oxidation............................................................................................ 70 β-Oxidation..................................................................................................................... 70 Regulation of FA oxidation........................................................................................... 74 Energy produced from β-oxidation of palmitic acid:..................................................... 74  Note;................................................................................................................................ 74 Oxidation of odd number fatty acids............................................................................ 75 α – oxidation................................................................................................................... 76 It is characterized by:................................................................................................... 76 Importance:................................................................................................................. 76 Metabolism of ketone bodies.......................................................................................... 77 The ketone bodies include 3 substances....................................................................... 77 1- Acetoacetic acid CH3-CO-CH2-COOH.................................................................... 77 2- β-hydroxybutyric acid CH3-CHOH-CH2-COOH........................................................ 77 3- Acetone CH3-CO-CH3......................................................................................................................... 77 Table Content 8 Importance of ketone bodies....................................................................................... 77 Notes:.......................................................................................................................... 77 Ketone body synthesis (Ketogenesis)............................................................................... 78 Definition..................................................................................................................... 78 Site:............................................................................................................................. 78 Steps:........................................................................................................................... 78 1- Formation of acetoacetyl CoA............................................................................... 78 2- Formation of acetoacetic acid from acetoacetyl CoA................................................ 78 3- Acetoacetic acid is then undergoing...................................................................... 79 Regulation of ketogenesis............................................................................................ 79 1- Lipolysis of triacylglycerol in adipose tissue........................................................... 79 2- Increased activity of carnitine palmitoyl transferase -I in the liver......................... 80 3- Increased level of serum free fatty acids................................................................ 80 Catabolism of ketone bodies (Ketolysis)........................................................................... 81 Definition..................................................................................................................... 81 Site:............................................................................................................................. 81 Steps of ketolysis:........................................................................................................ 81 1.Activation of acetoacetate to acetoacetyl COA........................................................... 81 Acetoacetic acid CH2-CO-SCOA............................................................ 81 2.Splitting of the acetoacetyl COA to acetyl COA...................................................... 82 Relation between ketolysis and citric acid cycle........................................................... 82 Importance of ketolysis................................................................................................ 82 Metabolism of Acylglycerol and....................................................................................... 83 Phospholipids.................................................................................................................. 83 1) Biosynthesis of triacylglycerols.................................................................................... 83 2) Lipolysis....................................................................................................................... 84 Definition:.................................................................................................................... 84 Steps:........................................................................................................................... 84 Fate of products of lipolysis:........................................................................................ 84 Regulation of lipolysis:................................................................................................. 85 During fasting:.......................................................................................................... 85 After meals:............................................................................................................. 85 Degradation of phospholipids.......................................................................................... 86 Table Content 9 A. Degradation of phosphoglycerols............................................................................. 86 B. Degradation of sphingolipids.................................................................................... 87 Eicosanoids...................................................................................................................... 87 Definition..................................................................................................................... 87 Sources of arachidonic acid:......................................................................................... 87 Differences between eicosanoids and hormone;.......................................................... 87 Cholesterol Metabolism................................................................................................... 88 Structure...................................................................................................................... 88 Importance of Cholesterol............................................................................................ 88 Synthesis of cholesterol:.............................................................................................. 88 Blood Cholesterol......................................................................................................... 90 Factors controlling blood cholesterol concentration:.................................................... 90 Degradation of Cholesterol.......................................................................................... 91 Bile Acids......................................................................................................................... 92 There are 2 Types of bile acids..................................................................................... 92.1The primary bile acids............................................................................................ 92 2.The secondary bile acids........................................................................................ 92 Synthesis of Bile Acids.................................................................................................. 92 Conjugation:................................................................................................................ 92 Enterohepatic circulation............................................................................................. 92 Functions of Bile Acids................................................................................................. 93 Lipid transport & storage................................................................................................. 94 Lipids........................................................................................................................... 94 The typical lipoprotein consists of................................................................................ 94 Lipid part................................................................................................................ 94 Protein part............................................................................................................ 94 Classification of lipoproteins........................................................................................ 95 The lipids present in lipoproteins include..................................................................... 96 Apolipoproteins or apoproteins................................................................................... 96 Functions of apolipoproteins........................................................................................ 97 Metabolism of plasma lipoproteins.................................................................................. 98 A. Metabolism of Chylomicrons.................................................................................... 98 B. Metabolism of very low-density lipoproteins (VLDL)................................................100 Table Content 10 C. Metabolism of low-density lipoproteins (LDL)..........................................................101 Metabolism of high-density lipoprotein (HDL)................................................................103 Site of synthesis: - liver and intestine............................................................................... 103 Function:.....................................................................................................................103 Structure:....................................................................................................................103 Metabolism:...............................................................................................................103 Clinical Significance of HDL..........................................................................................105 LDLc / HDLc Ratio........................................................................................................105 Role of lipoprotein (a)(LPa) in heart disease................................................................105 Role of the liver in lipid transport and metabolism......................................................106 Fatty liver.......................................................................................................................107 Definition....................................................................................................................107 Causes:.......................................................................................................................107 Mechanism:................................................................................................................107 Revision questions..........................................................................................................108 Chapter III: Protein metabolism......................................................................................111 Chapter Content.........................................................................................................111 Learning Objectives...............................................................................................111 Protein digestion & Absorption..............................................................................111 Catabolism of a.a. nitrogen....................................................................................111 Urea cycle..............................................................................................................111 Glycine..................................................................................................................111 Phenyl alanine & Tyrosine.....................................................................................111 Tryptophan............................................................................................................111 Histidine................................................................................................................111 Arginine & Ornithine.............................................................................................111 Lysine & Proline.....................................................................................................111 Serine....................................................................................................................111 Threonine & Sulfur containing amino acids............................................................111 Branched chain a.a., Glutamic acid & Aspartic acid................................................111 Alanine & β-Alanine.............................................................................................. 111 Revision questions.................................................................................................111 Learning Objectives........................................................................................................112 Table Content 11 Protein digestion............................................................................................................113 In the stomach............................................................................................................113 In the intestine............................................................................................................113 Absorption of proteins....................................................................................................114 Catabolism of amino acid nitrogen..................................................................................114 Synthesis of urea is divided into 4 stages:....................................................................115 1- Transamination....................................................................................................115 2- Deamination........................................................................................................115 3- Ammonia transport..............................................................................................115 4- Reactions of urea cycle.........................................................................................115 Transamination..............................................................................................................115 Definition:...................................................................................................................115 Examples:...................................................................................................................116 Importance of transamination:...................................................................................116 Clinical importance of ALT and AST.............................................................................116 Deamination...................................................................................................................117 Definition..................................................................................................................117 Site:...........................................................................................................................117 Types:.........................................................................................................................117 1.Oxidative deamination.........................................................................................117 2.Non- oxidative deamination.................................................................................117 Ammonia transport........................................................................................................119 Urea cycle.......................................................................................................................120 Urea is the major end product of nitrogen catabolism in human.................................120 Steps of urea cycle:.....................................................................................................120 Important notes:.........................................................................................................121 Regulation of urea cycle:.............................................................................................122 Causes of abnormal plasma urea:................................................................................122 Metabolism of individual amino acids.............................................................................123 Glycine...........................................................................................................................123 Phenylalanine.................................................................................................................126 Tyrosine..........................................................................................................................127 Catabolism of tyrosine:...............................................................................................127 Table Content 12 Important derivatives of tyrosine................................................................................127 Tryptophan.....................................................................................................................128 Catabolism and important derivatives of tryptophan:.................................................129 1- Biosynthesis of alanine and acetoacetyl CoA........................................................129 2- Biosynthesis of niacin:..........................................................................................129 3. Biosynthesis of serotonin:...................................................................................129 4. Biosynthesis of melatonin:..................................................................................129 5.Synthesis of indol and skatol:...............................................................................130 Histidine.........................................................................................................................130 Arginine..........................................................................................................................131 Ornithine........................................................................................................................132 Lysine and hydroxylysine................................................................................................132 Proline and hydroxyproline.............................................................................................133 Serine.............................................................................................................................133 Threonine.......................................................................................................................134 Sulfur containing amino acids Methionine......................................................................135 Functions..................................................................................................................135 1.Methyl donor.......................................................................................................135 2.Glucose:...............................................................................................................135 3.Cysteine...............................................................................................................135 4.Polyamines:..........................................................................................................135 Cysteine & Cystine..........................................................................................................135 Branched chain amino acids............................................................................................136 Glutamic acid..................................................................................................................137 Aspartic acid...................................................................................................................138 Alanine...........................................................................................................................139 β-alanine and related dipeptides............................................................................... 139 Revision questions..........................................................................................................141 Link of Biochemistry 1 For Technologists.........................................................................144 References:.....................................................................................................................145 Table Content ‫‪13‬‬ ‫رؤﯾﺔ اﻟﻜﻠﯿﺔ‬ ‫ﺗﺘﻤﯿﺰ ﺑﺘﺨﺮﯾﺞ ﺗﻜﻨﻮﻟﻮﺟﻲ ﺻﺤﻰ ذو ﻛﻔﺎءة ﻋﺎﻟﯿﺔ ﻗﺎدر ﻋﻠﻰ اﻟﻤﻨﺎﻓﺴﺔ ﻓﻲ ﺳﻮق‬ ‫اﻟﻌﻤﻞ ﻣﺤﻠﯿﺎ وإﻗﻠﯿﻤﯿﺎ ﻟﻼرﺗﻘﺎء ﺑﻤﺴﺘﻮى اﻟﺨﺪﻣﺎت اﻟﺼﺤﯿﺔ‪.‬‬ ‫رﺳﺎﻟﺔ اﻟﻜﻠﯿﺔ‬ ‫ﺗﺨﺮﯾﺞ ﺗﻜﻨﻮﻟﻮﺟﻲ ﺻﺤﻰ‪ ,‬ﻣﻠﺘﺰم ﺑﺎﻷﺧﻼﻗﯿﺎت اﻟﻤﮭﻨﯿﺔ ﻣﺘﻘﻦ ﻟﻠﻤﮭﺎرات اﻟﺘﻘﻨﯿﺔ‬ ‫اﻟﻤﺘﺨﺼﺼﺔ اﻟﺘﻰ ﺗﺆھﻠﮫ ﻟﻠﻤﺴﺎﻋﺪة ﻓﻰ ﺗﻘﺪﯾﻢ رﻋﺎﯾﺔ ﺻﺤﯿﺔ ﻣﺘﻤﯿﺰة وأﻣﻨﺔ ﻣﺒﻨﯿﺔ ﻋﻠﻰ‬ ‫اﻷدﻟﮫ واﻟﺒﺮاھﯿﻦ ﺗﺨﺪم ﻣﺨﺘﻠﻒ اﻟﻤﺆﺳﺴﺎت اﻟﺼﺤﯿﺔ‪ ,‬وأن ﯾﻜﻮن اﻟﺨﺮﯾﺞ ﻗﺎدر ﻋﻠﻰ‬ ‫اﻟﻤﺸﺎرﻛﺔ ﻓﻲ اﻟﺒﺤﺚ اﻟﻌﻠﻤﻰ وﺧﺪﻣﮫ اﻟﻤﺠﺘﻤﻊ وﻣﮭﯿﺄ ﻟﻠﺘﻌﻠﯿﻢ اﻟﻤﺴﺘﻤﺮ واﻟﻌﻤﻞ اﻟﺠﻤﺎﻋﻰ‬ ‫ﻣﺘﻤﺘﻌﺎ ﺑﻤﮭﺎرات اﻻدارة ﻣﻦ ﺧﻼل ﺗﻘﺪﯾﻢ ﺑﺮاﻣﺞ ﻣﺘﻨﻮﻋﺔ ﺗﻠﺘﺰم ﺑﻤﻌﺎﯾﯿﺮ اﻟﺠﻮدة اﻟﺘﻌﻠﯿﻤﯿﺔ‪.‬‬ ‫‪Table Content‬‬  14 Course Specification Facult Applied Health Sciences Technology y: Administrative information: Program(s) on which the course is Medical Biochemistry Program given Department offering the course: Medical Laboratory Academic year / level: 2 Date of specification approval: April 2021 Course coordinator Prof/ Dr. Abeer Ahmed Alrefai- Assit Prof/ Dr. Shereen Sobhy A- Basic information Title of course Medical Biochemistry Code: MLBC20 Lecture: 2h/w Practical 1 Tutorial 0 field 0h/w Total 3h/w B. Professional Information 1. Overall Aims of the Course: By the end of this course, the student should be able to: 1- Describes how dietary carbohydrates (CHO), lipids and proteins are digested and absorbed 2- Explain the different metabolic pathways related to carbohydrates, lipids and proteins metabolism and how the body can control these pathways. 3- Identify the normal level of blood glucose and understand the causes of hyperglycemia, hypoglycemia and glucosuria. 4- Discuss the importance of carbohydrates and lipids as a source of energy. 5- Describes how lipids are transported inside the body and the causes of hypercholesterolemia and fatty liver. 6- Clarify the importance of individual amino acids, the biochemical causes of hyperammonemia and abnormal blood urea. 2. Intended Learning Outcomes of the Course (ILOS ) a- Knowledge and Understanding By the end of this course, the student should be able to: a1. Explain how dietary CHO are digested and absorbed. a1*. Understand the mean of metabolism, anabolism and catabolism. a2. Describes how glucose is oxidized by glycolysis and oxidative decarboxylation. a3. Describes the steps. regulatory mechanisms and importance of kreb's cycle. a3*. Describes the steps of glucose oxidation by uronic acid pathway and HMP shunt a4. Understand how glycogen is synthesized (glycogenesis) and degraded (glycogenolysis) and their regulatory mechanisms. Table Content 15 a5. Describes how the body can synthesize glucose from non-carbohydrate source by gluconeogenesis a6. Explain the metabolism of galactose and fructose and how can be converted to glucose a6*. Identify the normal level of blood glucose and the causes of abnormal levels. a7. Explain how dietary lipids are digested and absorbed. a8. Understand the steps and regulatory mechanisms of fatty acid synthesis and oxidation. a9. Identify ketone bodies and how they are synthesized (ketogenesis) and degraded (ketolysis). a10. Understand steps of cholesterol synthesis from acetyl CoA and its metabolic importance. a11. Discuss the metabolism of lipoproteins and lipid transport. a12. Explain the digestion and absorption of dietary proteins. a12*. Understand how ammonia is converted into urea by urea cycle. a13. Discuss the derivatives of individual amino acids and their importance. b- Intellectual Skills b1. Diagnose how the deficiency of some digestive enzymes can cause disease (lactose intolerance) b2. Calculate the energy produced by oxidation of one molecule of glucose by glycolysis and oxidative decarboxylation. b2*. Compare between aerobic and anaerobic glycolysis. b3. Calculate the energy produced by oxidation of acetyl CoA by Kreb's cycle b3*. Evaluate the importance of uronic acid pathway and HMP shunt in producing glucouronic acid, ribose-5-phosphate and NADPH+H+ b4. Compare between glycogenesis and glycogenolysis during feeding and fasting. b5. Point out the mechanisms of synthesis of glucose in cases of fasting b6. Calculate the energy produced by oxidation of fatty acids. b6*. Compare between energy produced from oxidation of one molecule of glucose and fatty acids. b7. Correlate between ketogenesis and ketolysis during fasting and feeding. b8. Conclude how hypercholesterolemia can be a risk factor for atherosclerosis b9. Interpret a sheet of lipid profile. c- Professional and Practical Skills c1- Perform physical examination of urine. c2- Perform chemical examination of urine for glucose and proteins. c3- Perform microscopic examination of urine and CSF d- General and Transferable Skills The student will also be : d1- Develop writing and oral communication capability d.2 Use E-learning University platform melc.menofia.edu.eg. 3. Course Weekly Detailed Topics/Hours Topic Number of Number of Practical/week hours lectures 1st Week: Digestion and absorption of 3 1 1 CHO Table Content 16 2st Week: Glycolysis and 3 1 1 Oxidative decarboxylation 3st Week: Kreb’s cycle & HMP 3 1 1 shunt and Uronic acid pathways 4st Week: Glycogen metabolism 3 1 1 5st Week : Gluconeogenesis 3 1 1 6st Week: Metabolism of other hexoses 3 1 1 and Blood glucose st 7 Week: Mid-Term Exam 3 1 1 8st Week: Lipid digestion and absorption 3 1 1 9st Week: Fatty acid synthesis and 3 1 1 oxidation 10th Week: Metabolism of ketone bodies 3 1 1 11st Week : Cholesterol metabolism 3 1 1 12st Week: Lipid transport and fatty liver 3 1 1 13st Week: Digestion and absorption of 3 1 1 proteins & urea cycle st 14 Week: Importance and derivatives of amino acids 15th Week: Final term Exams 2 4. Course Matrix Contents Contents Course ILOs Covered by content (By ILO Code) K&U S. I/C S. P&P S. G&T S. 1 Digestion and absorption of CHO a1, a1* b1 d1,d2 2Glycolysis and Oxidative decarboxylation a2 b2, b2* c1 d1,d2 3 Kreb’s cycle & HMP shunt and a3, a3* b3, b3* c1 d1,d2 Uronic acid pathways 4 Glycogen metabolism a4 b4 c1 d1,d2 5 Gluconeogenesis a5 b5 c2 d1,d2 6 Metabolism of other hexoses and Blood a6, a6* c2 d1,d2 glucose 7 Lipid digestion and absorption a7 d1,d2 8 Fatty acid synthesis and oxidation a8 b6, b6* c2 d1,d2 9 Metabolism of ketone bodies a9 b7 c2 d1,d2 10 Cholesterol metabolism a10 b8 c2 d1,d2 11 Lipid transport and fatty liver a11 b9 c3 d1,d2 Table Content 17 12 Digestion and absorption of proteins & a12, a12* c3 urea cycle 13 Importance and derivatives of amino acids a13 5- Teaching and learning methods Course ILO Covered by Method (By ILO Code) Teaching/Learning Method G&T K&U S. I/C S. P&P S. S. Lectures a1-a13 d1, d2 Discussion (Brain Storming) Practical / Tutorials a1, a13 c1-c3 d1, d2 Reading Materials Research & Reporting a3, a4, a5, a10, a11 b3, b4, b5, b8, b9 d1, d2 Problem Solving-based Learning Projects Individual Work Group Work d1 E-learning a1, a13 d1 ,d2 Presentations 6 -Teaching and Learning Methods for Low Capacity and Outstanding Students: For low Assign a portion of the office hours for those students. capacity Give them specific tasks. students Repeat the explanation of some of the material. Assign a teaching assistance to follow up the performance of this group of students. For Give them some research topics to be searched using the internet and outstanding conduct presentation students Encourage them to take parts in the running research projects. 7- Student assessment methods Course ILOs Covered by Method (By ILO Code) Assessment Week Assessment Method Weight / No. K&U I/C S. P&P S. G&T S. Percentage Final written Exam a1-a13 b1-b9 d1-d2 (60 %) Practical exam c1-c3 d1-d2 (20 %) Continuous semester assessment (CSA) Formative (10 %) assessment a1-a5 b1,b5 C1-c6 d1-d2 Midterm exam Quizzes Table Content 18 Course Work a1-a13 Oral Assessment Report Writing a3-a4, a11 b2-b3,b4 d1,d2 Online assignment 6- List of references 1. Lecture Notes: prepared in the form of a book , authorized by the department 2. Harper's illustrated biochemistry,31th edition 2018 7- Facilities required for teaching and learning - Data show - Photo projector - Laser pointer Course coordinator: Prof. Dr. Abeer Ahmed Alrefai- Assistant Prof/ Dr. Shereen Sobhy Head of Department: Prof. Dr. Abeer Ahmed Alrefai- Assistant Prof/ Dr. Shereen Sobhy Table Content 19 Chapter I: Carbohydrate metabolism Chapter Content Learning Objectives Introduction to metabolism Digestion and absorption of CHO Glycolysis Oxidative decarboxylation Kreb’s cycle HMP shunt Uranic acid pathway Glycogen metabolism Gluconeogenesis Metabolism of other hexoses Blood glucose Revision questions Table Content 20 Learning Objectives By the end of this course, the student should be able to: 1. Understand the mean of metabolism, anabolism, and catabolism. 2. Explain how dietary CHO are digested and absorbed. 3. Understand the mean of metabolism, anabolism, and catabolism. 4. Describes how glucose is oxidized by glycolysis and oxidative decarboxylation. 5. Describes the steps. regulatory mechanisms and importance of kreb's cycle. 6. Describes the steps of glucose oxidation by uronic acid pathway and HMP shunt 7. Understand how glycogen is synthesized (glycogenesis) and degraded (glycogenolysis) and their regulatory mechanisms. 8. Describes how the body can synthesize glucose from non-carbohydrate source by gluconeogenesis 9. Explain the metabolism of galactose and fructose and how can be 10. Identify the normal level of blood glucose and the causes of abnormal levels. Table Content 21 Introduction to metabolism Metabolism means the fate of food molecules after digestion and absorption. Definition: - It is the chemical enzymatic reactions occurring inside the body and concerned with synthesis and breakdown of various substances. Metabolic pathways of metabolism include: - 1- Anabolic pathways: - - It means synthesis of complex molecules from simpler ones. - It is endergonic i.e requires free energy. - Example, synthesis of proteins. 2- Catabolic pathways: - - It means breakdown of complex molecules into simpler ones. - It is exergonic i.e releases free energy. - Example, oxidative processes that releases free energy. 3- Amphibolic pathways: - - These pathways act as link between anabolic pathways and catabolic pathways. - Example, citric acid cycle. Food molecules Digestion Simpler molecules Absorption Amphibolic pathways Anabolic pathways Catabolic pathways 2H ~P Proteins, carbohydrates CO2 + Water Lipids, Nucleic acids….etc Table Content 22 Carbohydrate Metabolism ✓ CHO provides 50% of daily calories in our body. ✓ Complete oxidation of 1gm CHO gives 4 kcal. Sources of CHO in food: - 1. Starch constitutes about 50% of dietary CHO e.g from potatoes. 2. Sucrose and lactose constitute most of the rest of CHO. 3. Fructose and glucose, from fruits and honey. Digestion of CHO: - Polysaccharides and disaccharides must be converted to monosaccharides to be absorbed. The following enzymes are involved: 1- Salivary amylase; converts starch and glycogen into dextrins 2- Pancreatic amylase; converts dextrins into maltose. 3- Intestinal disaccharidases: - Maltase converts maltose into 2 molecules of glucose - Sucrase converts sucrose into glucose and fructose - Lactase converts lactose into glucose and galactose Note: - 1) Lactose intolerance: - Definition: It is a disease which may be congenital or acquired. Cause: Deficiency of lactase enzyme. Effects: - Absence of intestinal lactase → lactose is not digested and accumulated in the intestine leading to; Intestinal bacteria Lactose Acids + Gases Fermentation Symptoms: - Abdominal distension, abdominal cramps (due to release of gases) and diarrhea (due to ↑ intestinal osmotic pressure). Treatment: Lactose free milk formula. Table Content 23 Metabolic pathways of carbohydrates These include the following: A. Catabolic pathways: - involving oxidative pathways and include Glycolysis, Glycogenolysis, Hexose monophosphate shunt and Uronic acid pathway. B. Anabolic pathways: - these include Gluconeogenesis and Glycogenesis. C. Amphibolic pathways: - Only citric acid cycle. Table Content  24 Glycolysis Definition: - It means oxidation of glucose to give pyruvate in the presence of oxygen or lactate in absence of oxygen. - It is one of the major pathways of glucose oxidation. Site: - It occurs in the cytoplasm of all tissue cells, but it is of specific importance in the following tissues. 1. Tissues with no mitochondria e.g RBCs, cornea and lens. 2. Tissues with frequent oxygen lack e.g skeletal muscles especially during exercise. Steps: - It occurs in 2 stages 1- Stage 1: - Is the energy requiring step were - One molecule of glucose is converted into 2 molecules of glyceraldhyde-3-P. It needs energy. 2- Stage 2: - Is the energy producing stage were - Two molecules of glyceraldhyde-3-P are converted into pyruvate or lactate. It produces energy. Table Content 25 Table Content 26 Importance of glycolysis: - 1- Energy production - Anaerobic glycolysis gives 2 ATP. - Aerobic glycolysis gives 6-8 ATP. 2- Provides the main pathway for metabolism of fructose and galactose derived from diet. 3- Good oxygenation of tissues by formation of 2,3 diphosphoglycerate which decreases the affinity of Hb to oxygen. 4- Provides important intermediates e,g - Dihydroxy acetone phosphate gives glycerol-3-P that is used for lipogenesis. - Provides pyruvate for synthesis of alanine amino acid. Energy production of glycolysis: - 1- ATP consumed in both aerobic and an aerobic glycolysis - 1 ATP for conversion of glucose to G-6-P. - 1 ATP for conversion of fructose-6-P to fructose 1,6 biphosphate Net energy consumed = 2 ATP. 2- ATP produced: - Table Content 27 In case of aerobic glycolysis a. 4 ATP by substrate level phosphorylation; o 2ATP for conversion of 1,3 biphosphoglycerate to 3-phosphoglycerate. o 2ATP for conversion of phosphenol pyruvate into enolpyruvate. b. 4 or 6 ATP by oxidative phosphorylation in mitochondria from oxidation of 2 NADH+H+ by respiratory chain. Net energy gain in case of aerobic glycolysis = 4 (substrate level) + 4 or 6 (respiratory chain) = 8 - 10 ATP Net energy = ATP gained - ATP consumed = (8 - 10) - 2 = 6-8 ATP. In case of anaerobic glycolysis o The 2 NADH+H+ are consumed in conversion of pyruvate to lactate so the energy gained is only obtained from substrate level phosphorylation Net energy = 4 ATP - 2 ATP = 2 ATP. Substrate level phosphorylation: - Definition; - It means phosphorylation of ADP to ATP at the level of the reaction itself without the need for the respiratory chain. e.g 1,3 biphosphoglycerate + ADP → 3 phosphoglycerate + ATP. Table Content 28 Discuss glycolysis in the RBCs? A. Mature RBCs contains no mitochondria, so -They depend completely upon glycolysis for energy production. -Lactate is always the product. -The net energy = 2 ATP B. Glucose uptake by the RBCs doesn’t depend on insulin hormone. C. Production of 2,3 biphosphoglycerate (BPG). Regulation of glycolysis: - ✓ The key enzymes of glycolysis are the 3 irreversible enzymes which include: - 1- Hexokinase or glucokinase. 2- Phosphofructokinase-l (PFK-1). 3- Pyruvate kinase. 1- Hormonal regulation: - Insulin stimulates the synthesis of all 3 key enzymes while glucagon inhibits their synthesis. 2- Allosteric regulation: - o G-6-F allosterically inhibits hexokinase and not glucokinase. o Fructose 2,6 biphosphate stimulates PFK-1. o Citrate inhibits PFK-1. o Fructose 1,6 biphosphate stimulates pyruvate kinase. 3- Covalent modification: - Pyruvate kinase is inactivated by phosphorylation. 4- Energy regulation: - o ATP inhibits PFK-1 and pyruvate kinase. Table Content  29 o ADP and AMP stimulate PFK-1. Note: - Fructose 2,6 biphosphate: - It is formed from fructose-6-P by the effect of phosphofructokinase-2 as follow. PFK-2 Fructose-6-P Fructose2,6 biphosphate o Fructose 2,6 biphosphate: - 1. Stimulate glycolysis by stimulation of phosphofructokinase 1. 2. It also inhibits gluconeogenesis by inhibiting fructose 1,6 biphosphatase. ❖ In vitro inhibition of glycolysis: - 1. Arsenate competes with inorganic phosphate in the reaction Glyceraldhyde-3-P 1,3 biphosphoglycerate 2. Iodoacetate inhibits glyceraldhyde-3-P Dehydrogenase. 3. Fluoride inhibits enolase and used in clinical laboratories to inhibit glycolysis before measurement of blood glucose. ❖ Important: Hemolytic anemia caused by deficiency of glycolysis in RBCs is most commonly due to deficiency of pyruvate kinase enzyme. Table Content 30 Oxidative decarboxylation of pyruvate Pyruvate is α-keto acid produced from glucose by glycolysis inside cytoplasm. To undergo oxidative decarboxylation into acetyl CoA it must be transported into the mitochondria by special pyruvate transporter. Oxidative decarboxylation is carried out by pyruvate dehydrogenase complex (PDH-complex). Site: - Mitochondria. PDH-complex: - Is a multienzyme complex consisting of 3 enzymes 1- Pyruvate dehydrogenase enzyme. 2- Dihyrdolipoyl-transacetylase enzyme. 3- Dihydrolipoyl Dehydrogenase. 5 coenzymes are needed; for the action of PDH-complex; TPP= Thiamin pyrophosphate, Lipoic acid, COASH, FAD and NAD. Table Content 31 Summary of oxidative decarboxylation of pyruvate: - Pyruvate DH complex CH3-CO-COOH CH3-CO~SCoA Pyruvate COASH CO2 Acetyl CoA TPP, FAD, Lipoic acid NAD NADH+H+ Regulation of oxidative decarboxylation; - - PDH is regulated by the following 1- Feedback inhibition: - It is inhibited by its end product which is acetyl CoA + NADH+H+ and stimulated by pyruvate + NAD+. 2- Covalent modification: - PDH is present in 2 forms - PDH - a = Dephosphorylated form (active form). - PDH- b = Phosphorylated form (inactive form). Table Content 32 ✓ Phosphorylation is activated by PDH kinase enzyme that is stimulated by increased acetyl CoA/CoA, NADH/NAD or ATP/ADP. ✓ Dephosphorylation is activated by PDH phosphatase enzyme that is stimulated by Mg2+, Ca2+ and insulin. 3- Pyruvate DH is inhibited by arsenate or mercuric ions and by thiamin deficiency, leading to accumulation of pyruvic acid in blood and lactic acidosis. Table Content 33 Krebs cycle = Citric Acid Cycle (CAC) Tricarboxylic Acid Cycle (TCA) Definition: - TCA is a series of reactions in which acetyl CoA is completely oxidized into CO2, H2O and energy. Site: - Mitochondria as all enzymes of CAC are present in the mitochondrial matrix except succinate dehydrogenase which is attached to the inner mitochondrial membrane and considered also as one of the components of the respiratory chain. Steps: - See the next page Energy production by CAC: - ✓ Oxidation of one molecule of acetyl CoA in TCA produces 12 ATP (11 ATP by respiratory chain and 1 by substrate level phosphorylation) as follow; - o 3NADH+H+ by isocitrate dehydrogenase, α-ketoglutarate dehydrogenase and malate dehydrogenase. o 1 FADH2 by succinate dehydrogenase. o 1 ATP by succinate thiokinase (substrate level Phosphorylation). ✓ Every NADH+H+ gives 3 ATP while every FADH2 gives only 2 ATP by the respiratory chain. ✓ So, Net energy by one cycle of Krebs’ = (3 x 3) + 2 +1 = 12 ATP Regulation of CAC: - ✓ CAC is the major route for ATP generation and its regulation depends on supply of. 1. Oxidized cofactors e.g NAD+. Table Content 34 2. Availability of ADP. Table Content 35 ✓ The 3 key enzymes of CAC include citrate synthase, isocitrate DH and α-ketoglutarate DH are regulated as follow; 1. Citrate synthase is o Allosterically inhibited by long chain FAs and competitively inhibited by succinyl CoA. o And stimulated by Ca2+ which increases during muscle contraction (there is increased energy demand). 2. All 3 enzymes are - Stimulated by ADP, NAD and Ca2+. - And inhibited by ATP and NADH+H+. 3. Respiratory control via the respiratory chain and oxidative phosphorylation which ensures oxidation of reduced coenzymes e.g. NADH+H+ and FADH2. 4. Alpha-ketoglutarate DH: as pyruvate DH complex. Importance of TCA: - A. Production of energy: - Each molecule of acetyl CoA gives 12 ATP by TCA. B. TCA has amphibolic function i.e it has a catabolic (breakdown) and anabolic (synthetic) functions. I. Catabolic function: - Complete oxidation of acetyl CoA derived from CHO, lipid and proteins into CO2 and water. II. Anabolic (synthetic) function includes: - 1- Synthesis of non-essential amino acids by transamination. 2- Role of citric acid cycle in gluconeogenesis: - Intermediates as Citrate, α- ketoglutarate and succinyl CoA are glucogenic substance. Table Content 36 3- Succinyl CoA is used in hem synthesis, Ketolysis (breakdown of ketone bodies) and detoxification reactions. 4- Role of CAC in fatty acid and cholesterol synthesis: - C. Production of CO2 which is used in: - 1. Carboxylation of pyruvate to give oxaloacetate that is important for gluconeogenesis. 2. Formation of malonyl CoA during fatty acid synthesis. 3. Formation of carbamoyl phosphate which is used in urea and pyrimidine synthesis. 4. Formation of C6 of purine bases. 5. Synthesis of bicarbonate buffer used in acid base balance. Table Content 37 Inhibitors of CAC in vitro: - 1- Fluoroacetate inhibits aconitase. 2- Arsenate inhibits α-ketoglutarate DH. 3- Malonate competitively inhibits succinate DH due to structural similarity between malonate and succinic acid. Hexose monophosphate shunt (HMP shunt) Definition: - It is an alternative pathway of glucose oxidation in which ATP is neither produced nor utilized. Site: - Cytoplasm of many tissues Steps: - The reactions of HMP-shunt occur in 2 phases 1- Oxidative (irreversible) phase: - ✓ Where 3 molecules of glucose are converted into 3 molecules of ribulose-5-P with production of NADPH+H+ and CO2. 2- non-oxidative (reversible) phase: - ✓ Where 3 molecules of ribulose-5-P are converted into 2 molecules of glucose-6-P and 1 molecule of glyceraldhyde-3-P. Functions of HMP shunt: - A. Production of pentoses (ribose-5-p) used for synthesis of - DNA, RNA - ATP, GTP..... etc - NAD, FAD.... etc B. Production of NADPH+H+: - It is important for synthesis of o Fatty acids and steroid hormones. o Non-essential amino acids. Table Content 38 o Malate from pyruvate by malic enzyme. o Reduced glutathione in erythrocytes; Glutathione reductase G-S-S-G 2 G-SH NADPH+H+ NADP (Oxidized glutathione) (Reduced glutathione) o Reduced glutathione is needed for; 1. Maintenance of the normal integrity of RBCs by removal of hydrogen peroxide (H2O2), which is a toxic compound that increases cell membrane fragility. Glutathione peroxidase 2 G-SH + H2O2 2 H2O + G-S-S-G Glutathione reductase NADP NADPH+H+ 2. Maintenance of SH group of RBCs enzymes. 3. Detoxification of many drugs and carcinogens. Regulation of HMP shunt: - Glucose-6-phosphate DH is the key enzyme of HMP shunt. It is stimulated by insulin and NADP+ and inhibited by NADPH+H+ and acetyl CoA. Table Content 39 Uranic acid pathway Definition: - It is an alternative pathway of glucose oxidation in which glucose is converted into glucuronic acid. Site: - It occurs in the cytoplasm of many tissues. Importance of uranic acid pathway: A. Production of glucuronic acid in the form of UDP-glucuronic acid which is used in: - 1) Synthesis of substrates as o Glycosaminoglycans. o Vitamin C (L-ascorbic acid) in animals only not in human. (Humans can't convert glucuronic acid into ascorbic acid due to absence of L-gluconolactone oxidase) 2) Conjugation reactions: - with many substances e.g bilirubin to make them more water soluble and easily excreted. 3) Detoxification reactions: - to make the toxic compounds less toxic. B. Production of pentoses Table Content 40 Glycogen Metabolism Glycogen: - is the storage from of carbohydrates in animals. ✓ It is formed of α-D glucose units linked together by α1-4 glucosidic bonds and by α 1-6 glucosidic bonds at the branch points. ✓ It is stored mainly in the liver and muscles. Liver glycogen Muscle glycogen o Occurs in the liver. o Occurs in muscles. o Constitutes up to 6% of liver o Rarely exceeds 1% of ms mass. mass. o Its function is to maintain blood o Acts as a source of glucose - glucose during fasting. 6-P for glycolysis of muscle o Depletes after 12-18 hrs of only. fasting. o Depletes after prolonged vigorous muscle exercise. o Glucagon stimulates o No effect glycogenolysis Table Content 41 Glycogenesis Definition: - It is the synthesis of glycogen from glucose. Site: - Cytoplasm of liver and muscle cells. Sources of glucose units: - For liver glycogen: it includes. 1- Blood glucose. 2- Other hexoses: galactose & fructose. 3- Non-carbohydrate sources by gluconeogenesis e.g lactate & glycerol. - For muscle glycogen: - 1-Blood glucose only. Steps: - 1- Formation of UDP - glucose (UDP-G) as follow; Hexokinase in muscles Glucokinase in liver Phosphoglucomutase Glucose Glucose-6-P Glucose-1-P UDP-glucose UTP Phosphorylase PPi Uridine diphosphate glucose (UDP) 2- Formation of glycogen from UDP - G units needs: a) Glycogen primer which is formed of ✓ Few molecules of glucose linked by α1-4 linkage. or ✓ A protein called glycogenin where UDP - glucose residues are added to the hydroxyl group of its tyrosine residue. b) Glycogen synthase enzyme. ✓ The key regulatory enzyme of glycogenesis. Table Content 42 ✓ It catalyzes the formation of α 1-4 glucosidic bond between C1 of the activated glucose of UDP-G and C4 of a terminal glucose residue of a glycogen primer. Glycogen synthase UDP-G + Elongated glycogen primer Glycogen primer + UDP ✓ It elongates the primer up to 11 glucose units. c) Branching enzyme: - It transfers about 6 glucose units of the elongated chain to a neighboring chain forming α1-6 glucosidic bond forming a branch point in the molecule which is elongated by glycogen synthase. Table Content 43 Glycogenolysis Definition: - It is the process of degradation of glycogen into glucose units (in liver) or glucose-6-p (in muscles). Site: - Cytoplasm of liver and muscle cells. Steps: - Glycogenolysis needs the following 1- Phosphorylase enzyme: - o The key regulatory enzyme of glycogenolysis. o It acts on branches containing more than 4 glucose units. o It breaks down α l - 4 glycosidic bonds by phosphorylysis (i.e breakdown by addition of phosphate) giving glucose-1- P. 2- Glucan transferase enzyme: - o It acts on the branch containing 4 glucose units where it transfers 3 glucose units to another branch leaving the last one which is linked by α 1 - 6 linkage. 3- Debranching enzyme: - o It removes the last glucose units that is attached by α 1 - 6 linkage by hydrolysis (i.e breaking down by addition of water) giving glucose. o Note: - G-1-P is converted to G-6-P by phosphoglucomutase. Table Content 44 Fate of glucose -6- phosphate: - ✓ In liver: - The liver contains glucose - 6 - phosphatase so it converts g - 6 - p into glucose that is released to the blood. ✓ In muscle: - It contains no glucose - 6 - phosphatase, so muscle glycogenolysis ends with G-6-P which can’t leave the muscle. Table Content 45 Regulation of glycogenesis and glycogenolysis There is a coordinated regulation of glycogenesis and glycogenolysis i.e conditions stimulating glycogenesis inhibit glycogenolysis and vice versa. The key regulatory enzymes include: - 1- Glycogen synthase: - present in 2 forms. a. Active dephosphorylated form (glycogen synthase a). b. Inactive phosphorylated form (glycogen synthase b). 2- Phosphorylase: - present in 2 forms a. Active phosphorylated form (phosphorylase a). b. Inactive dephosphorylated form (phosphorylase b). During fasting: - 1. The blood glucose tends to decrease causing release of epinephrine in muscle and liver and glucagon in liver only. 2. These hormones bind to beta receptors in the cell membrane activating adenylate cyclase. 3. Active adenylate cyclase catalyzes formation of cAMP from ATP. 4. cAMP activates cAMP dependent protein kinase. 5. The active cAMP dependent protein kinase causes: a. Phosphorylation and inactivation of glycogen synthase inhibiting glycogenesis. b. Phosphorylation and activation of phosphorylase kinase that phosphorylates and activates phosphorylase enzymes producing glycogenolysis. Table Content 46 After meals: - ✓ Blood glucose level tends to be increased; this stimulates insulin secretion which decreases blood glucose by stimulation of glycogenesis and inhibition of glycogenolysis. ✓ This occurs by: - 1- Stimulation of phosphodiestrase enzyme which breaks down cAMP into 5AMP → no stimulation of protein kinase 2- Stimulation of phosphatase enzyme which removes the phosphate group from enzymes. Table Content 47 Regulation of glycogenesis Regulation of glycogenolysis Table Content 48 Gluconeogenesis Definition: - Is the synthesis of glucose or glycogen from non- carbohydrate sources. These sources include - Lactic acid - Pyruvic acid - Glycerol - Amino acids - Propionic acid. Site: - Organ site: 90% in the liver and 10% in the kidney. Cellular site: Cytoplasm and mitochondria. Importance of Gluconeogenesis: - 1) It provides blood with glucose during fasting more than 18 hours when glycogen stores are depleted. Glucose is required; 1. It is the only source of energy for nervous tissue, RBCs and skeletal muscles during exercise. 2. It is the precursor of milk sugar (lactose) in mammary gland. 2) Gluconeogenesis help to clear the blood from waste products as lactic acid produced in sk. muscles and RBCs. Steps: - Gluconeogenesis is mainly the reversal of glycolysis except for the 3 irreversible kinases which are overcome by the following enzymes. Enzyme of glycolysis Enzyme of gluconeogenesis 1- Pyruvate kinase - Pyruvate carboxylase (mitochondrial). - Phosphoenol pyruvate carboxykinase 2- Phosphofructokinase-1 - Fructose 1.6 biphosphatase 3- Hexokinase & glucokinase - Glucose-6-phosphatase Table Content 49 Table Content 50 1- Conversion of pyruvate to phosphoenol pyruvate: - o Pyruvate carboxylase enzyme is present in the mitochondria so pyruvate must be transported by special pyruvate transporter to enter the mitochondria. o While phosphoenol pyruvate carboxykinase is present in the cytoplasm. The conversion occurs as follow. Pyruvate carboxylase Malate dehydrogenase Pyruvate Oxaloacetate Malate CO2, ATP, Mn2+, Biotin Mitochondria Cytosol Phosphoenol pyruvate Malate carboxykinase dehydrogenase Phosphoenol pyruvate Oxaloacetate Malate H2O+CO2+GDP GTP NADH+ H+ NAD 2- Conversion of fructose 1,6 biphosphate into fructose-6- phosphate; Fructose 1,6 biphosphatase Fructose 1,6 biphosphate Fructose-6-phosphate H2O Pi 3- Conversion of glucose-6-phosphate into glucose; Glucose-6-phosphatase Glucose-6-phosphate Glucose H2O Pi Table Content 51 Gluconeogenic substances 1) Gluconeogenic amino acids. 2) Lactate. 3) Propionate: - This occurs only in ruminants. Propionic acid is converted into succinyl CoA. 4) Glycerol: - Glycerol is derived from lipids of adipose tissue during fasting. It is converted as follow. Glycerol-3-P CH2-OH Glycerol kinase CH2-OH Dehydrogenase CH2-OH CH-OH CH-OH C=O + CH2-OH ATP ADP CH2-O-P NAD NADH+ H CH2-O-P Glycerol Glycerol-3-P Dihydroxy acetone-P Then dihydroxy acetone phosphate binds the common pathway. Energy cost of gluconeogenesis: - For conversion of 2 molecules of pyruvate to glucose, 6 ATP molecules and 2 NADH+ H+ are consumed. 1) ATP 2 Pyruvate 2 oxaloacetates (2 ATP) 2 Oxaloacetate 2 phosphoenol pyruvate (2 GTP) 2 3 Phosphoglycerate 2 1.3 biphosphoglycerate (2 ATP) 2) NADH+H+ 2 1.3 Biphosphoglycerate 2 glyceraldhde-3-P (2 NADH+H+) Table Content 52 Regulation of gluconeogenesis: - ✓ Gluconeogenesis and glycolysis occur in coordinated manner i.e when one pathway is active the other should be inhibited. ✓ The key regulatory enzymes of gluconeogenesis include. 1. Pyruvate carboxylase. 2. Phosphoenol pyruvate carboxykinase. 3. Fructose 1,6 biphosphatase. 4. Glucose - 6 - phosphatase. ✓ These enzymes are regulated as follow. 1) Changes in the rate of enzyme synthesis: - o Glucocorticoids e.g cortisol stimulates gluconeogenesis By 1. Inducing synthesis of the key enzymes. 2. Provide gluconeogenic amino acids by increasing protein catabolism. o Insulin: It inhibits gluconeogenesis by repressing the synthesis of the key enzymes. 2) Covalent modification: - o Glucagon and epinephrine stimulate gluconeogenesis by phosphorylation of pyruvate kinase (inactive) this inhibit glycolysis and stimulate gluconeogenesis. 3) Allosteric regulation: - o Acetyl CoA: - ✓ Is an allosteric activator of the enzyme pyruvate carboxylase. ✓ It is derived from FA oxidation thus; FA oxidation stimulates gluconeogenesis by providing. a. Acetyl CoA which activates pyruvate carboxylase. Table Content 53 b. ATP needed by pyruvate carboxylase and phosphoenol pyruvate carboxykinase. o Fructose 2,6 biphosphate:- mentioned in glycolysis. Metabolism of other hexoses A-Fructose metabolism Sources of fructose: - Sucrase 1- Sucrose glucose + fructose 2- Diet (honey, fruits and vegetables) Importance of fructose: - 1- 15% of the total body energy is derived from fructose 2- The only source of energy for spermatozoa A-Fructose metabolism in the liver, kidney and intestine: o These tissues contain fructokinase enzyme which converts fructose into fructose- 1-P. o Fructose-1-P is then, hydrolyzed by aldolase B enzyme to give dihydroxyacetone phosphate and glyceraldehyde. Fructose ATP Fructokinase ADP Fructose-1-P Aldolase-B Dihydroxyacetone-P Glyceraldehyde Triokinase Glyceraldhyde-3-P Table Content 54 Aldolase-A Fructose 1,6 biphosphate Gluconeogenesis Glucose Glyceralhyde by triokinase gives glyceraldhyde-3-P. Glyceraldhyde-3-P is then 1. Enters glycolysis to give energy. 2. Combine with dihydroxyacetone phosphate to give glucose. B-Fructose metabolism in muscles and adipose tissues: - These tissues contain no fructokinase but contain hexokinase. Fructose ATP Hexokinase ADP Fructose-6-P ATP Phosphofructokinase-1 ADP Fructose 1,6 biphosphate Glycolysis 2 Pyruvate + energy C-In the testis, lens, peripheral nerves and renal glomeruli: - Glucose is converted into fructose as follow. Sorbitol Aldolase reductase dehydrogenase Glucose Sorbitol Fructose NADPH+H+ NADP+ NAD+ NADH+H+ N.B- In diabetes mellitus: - Excess glucose is converted into sorbitol in the lens causing cataract. Table Content 55 Galactose metabolism Sources of galactose: - Dietary milk: - Lactose Glucose + Galactose Importance of galactose: - Galactose enters in the structure of - Lactose - Glycolipids - Glycoproteins - Proteoglycans 1- Conversion of galactose to glucose in the liver: - Galactose ATP mg2+ Galactokinase ADP Glucose Galactose-1-P UDP-glucose Galactose-1-P uridyl transferase Glucose-6-Phosphatase UDP-galactose Glucose-1-P Glucose-6-P UDP-galactose 4- epimerase Phosphoglucomutase G. Synthase G. Phosphorylase UDP-glucose Glycogen Glucose-1-P Pi 2- Conversion of glucose into galactose in mammary gland: - This occurs for the formation of lactose. Hexokinase Phosphoglucomutase Glucose Glucose-6-P Glucose-1-P 2+ ATP mg ADP UTP UDP-glucose Table Content 56 pyrophosphorylase PPi UDP-glucose UDP-galactose 4-epimerase Lactose synthase UDP-Galactose Lactose + Glucose Blood Glucose Normal blood glucose: - - Fasting blood glucose (FBG) = 70 - 110 mg/dl. - 2 hours post prandial i.e after meal (2 hrs PP) = up to 140 mg/dl. Sources of blood glucose: - 1- Dietary carbohydrates as glucose, galactose and fructose (Galactose and fructose are converted into glucose in the liver) 2- Gluconeogenic substances e,g amino acids, lactate, glycerol..etc. 3- Liver glycogen by glycogenolysis. Table Content 57 Variations in blood glucose Hypoglycemia Definition: - Is a condition in which plasma glucose is decreased below 60 mg/dl. Symptoms: - o There is faintness, dizziness or lethargy, which may progress to coma. o If untreated → death occurs as a result of permanent cerebral damage. Causes: - There are 2 types of hypoglycemia 1) Stimulative hypoglycemia: - there must be a stimulus for hypoglycemia, the stimulus may be 1. Drugs: - Insulin overdoses or poisons e.g chloroform. 2. Inborn errors of metabolism: - Galactosemia and Hereditary fructose intolerance. 3. Postgastrectomy: - This causes rapid absorption of glucose with excessive insulin secretion → hypoglycemia. 4. Excess intake of alcohol. 5. Essential reactive hypoglycemia: - it means exaggeration of the normal insulin response to carbohydrate ingestion. 6. Idiopathic hypoglycemia. 2) Fasting hypoglycemia: - There is failure to maintain normal blood glucose especially during fasting due to Table Content 58 1. Starvation and malnutrition: - d.t. exhaustion of liver glycogen. 2. Inborn errors of metabolism: - these include - Dicarboxylic aciduria give neonatal or - Maple syrup urine disease - Tyrosinemia childhood hypoglycemia 3. Pancreatic disease: - As insulinoma, hyperinsulinism of childhood, pancreatitis and pancreatic tumors leading to enhanced glucose utilization caused by overproduction of insulin. 4. Defective glucose production due to: - a. Endocrine disease: - adrenocortical insufficiency, hypothyroidism and growth hormone deficiency. b. Liver disease: - sever liver cirrhosis, hepatic tumors. c. Renal disease: - defective gluconeogenesis. Table Content 59 Glucosuria Definition: - It is the presence of glucose in urine in amounts detectable by ordinary methods. Glucosuria occurs when the venous blood glucose concentration exceeds the renal threshold for glucose (180 mg/dl). Causes: - 1- Diabetes mellitus: - due to hyperglycemia caused by lack of insulin. 2- Renal glucosuria: - it is due to low renal threshold i.e decreased renal threshold below 180 mg/dl so glucose appear in urine even at low blood glucose concentration. Caused by 1. Inherited defects in the kidney. 2. Nephritis and nephrosis. 3. Drugs e.g phlorizin which inhibits glucose reabsorption by the renal tubules.