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Department of Biochemistry Faculty of Medicine – Umm Alqura University Basics of Biochemistry First Year – MBBS & Dentistry program 1446 H- 2024/2025 g  Learning Objectives By the end of this lecture, students will be able to: Illustrat...

Department of Biochemistry Faculty of Medicine – Umm Alqura University Basics of Biochemistry First Year – MBBS & Dentistry program 1446 H- 2024/2025 g  Learning Objectives By the end of this lecture, students will be able to: Illustrate the chemical structure, physical criteria, and classification of carbohydrates. Describe the medical significance of carbohydrates in both structure and cellular function of body tissues Mention the clinical significance of disaccharides digestion and absorption 2 Biochemistry Department, college of Medicine, UQU 8/17/2024  Lecture Outlines Food and healthy diet (nutritional pyramid). The medical importance of carbohydrates Types of Carbohydrates Types and nomenclature of monosaccharides and disaccharides isomerization of sugars (Stereoisomers, Epimers) Glycosides, Amino sugars, Deoxy sugars Glycosidic bond and condensation reaction. Disaccharide hydrolysis Clinical correlations of disaccharides digestion and absorption. 3 Biochemistry Department, college of Medicine, UQU 8/17/2024 Food and Healthy Diet (Balanced Diet) ▪ A balanced diet means eating a variety of food in the right amounts and in the healthiest proportions. ▪ Each food has different nutrients, and each nutrient has its own function in our body. ▪ Energy intake and nutrient needs are different depending on our age and gender. ▪ Eating too much or not enough are both bad for our health. Nutrients – Energy Producing CB: Caloric Breakdown 4 Biochemistry Department, college of Medicine, UQU 8/17/2024  CARBOHYDRATES Carbohydrates are: ▪ Organic biomolecules abundantly present in the nature. ▪ Composed of the elements C, H and O. ▪ General formula: Cn(H2O)n or (CH2O)n ▪ At least number of carbon atom (n) = 3. ▪ Found in the cells of plants and animals. ▪ Produced by photosynthesis in plants. ▪ Also called saccharides “sugars”. 5 Biochemistry Department, college of Medicine, UQU 8/17/2024 Importance of carbohydrates ▪ Carbohydrates are widely distributed both in plants and in animal tissues. ▪ They are the most abundant biomolecules on Earth. ▪ Major source of energy from the diet. ▪ Structural & protective elements in cell walls of bacteria, plants and in connective tissues. ▪ Recognition and communication between cells. ▪ Precursors for other biomolecules (purines, pyrimidines). ▪ Components of other molecules (nucleosides, nucleotides, coenzymes, glycolipids ,glycoproteins). 6 Biochemistry Department, college of Medicine, UQU 8/17/2024 Types of Carbohydrates ▪ Monosaccharides are the simplest carbohydrates (i.e., on hydrolysis, they can not give a simpler form). ▪ Disaccharides consist of two monosaccharides. ▪ Polysaccharides contain many monosaccharides. 7 Biochemistry Department, college of Medicine, UQU 8/17/2024 Monosaccharides ▪ The simplest units of carbohydrate ▪ i.e., they can not be hydrolyzed to simpler form. Classification of Monosaccharides ▪ Aldoses are monosaccharides with an aldehyde group and many hydroxyl (-OH) groups. ▪ Ketoses are monosaccharides with a ketone group and many hydroxyl (-OH) groups. 8 Biochemistry Department, college of Medicine, UQU 8/17/2024  Nomenclature of Monosaccharides 9 Biochemistry Department, college of Medicine, UQU 8/17/2024  Aldoses and Ketoses 10 Biochemistry Department, college of Medicine, UQU 8/17/2024  Stereoisomerism of Monosaccharides ▪ Stereoisomers: are compounds with the same formula but different in spatial arrangements due to the presence of asymmetric carbons. ▪ Asymmetric (Chiral) carbon: a carbon atom attached to 4 different groups. Any substance containing 4 asymmetric 3 asymmetric asymmetric carbon atoms carbon atoms carbon atom shows 2 properties, A) optical activity and ▪ Monosaccharides are chiral compounds (have stereoisomers) thus occur in B) optical optically active isomers, except dihydroxyacetone. isomerism. 11 Biochemistry Department, college of Medicine, UQU 8/17/2024 Stereoisomerism of Monosaccharides ▪ Stereoisomers that are mirror images are called Enantiomers (D &L). ▪ Stereoisomers that are not mirror images are called Diastereoisomers. ▪ Epimers are diastereoisomers different in only one asymmetric carbon. Enantiomers Diastereomers Epimers O O O O O O H H H H H H C C C C C C HO C* H H C* OH HO C* H H C* OH H C* OH HO C* H H C* OH HO C* H HO C* H HO C* H HO C* H HO C* H HO C* H H C* OH H C* OH HO C* H H C* OH H C* OH HO C* H H C* OH H C* OH H C* OH H C* OH H C* OH CH2OH CH2OH CH2OH CH2OH CH2OH CH2OH L-glucose D-glucose D-mannose D-galactose D-glucose D-mannose 12 Biochemistry Department, college of Medicine, UQU 8/17/2024 D and L Monosaccharides The —OH on the chiral atom farthest from the carbonyl group is used to assign the D or L configuration. By convention, the letter L is assigned to the structure with the —OH on the left. The letter D is assigned to the structure with —OH on the right. The D form is usually the isomer found in nature. D-glucose is the form used in injection. 13 Biochemistry Department, college of Medicine, UQU 8/17/2024  Structure of Monosaccharides Cyclic Structure) Carbon (1) in the cyclic structure is the “new” chiral carbon (Anomeric carbon) Fischer Projection ( and  Anomers for D-Glucose & Fructose) The new –OH on C1 is drawn down for the  anomer, and up for the  anomer. Glucose Anomers Fructose Anomers 14 Biochemistry Department, college of Medicine, UQU 8/17/2024 D-Glucose “blood sugar” An aldohexose with the formula of C6H12O6. The naturally occurring form of glucose found in fruits, corn syrup and honey. It is also known as dextrose, grape sugar, and blood sugar It is broken down in cells to produce energy → the principal fuel for the brain. In the liver and other tissues, glucose is converted to all carbohydrates in the body e.g. glycogen, galactose, ribose and fructose. 15 Biochemistry Department, college of Medicine, UQU 8/17/2024  glucose Blood Glucose Level ▪ Glucose known as blood sugar in the body. ▪ Glucose is the principal fuel for the brain. ▪ In the body, glucose has a normal blood level of 70-110 mg/dL It’s normal concentration in the blood (normal blood glucose) is (70-110 mg/dL). Blood glucose above normal range= Hyperglycemia. Blood glucose below normal range= Hypoglycemia. In a glucose tolerance test, blood glucose is measured for several hours after ingesting glucose. 16 Biochemistry Department, college of Medicine, UQU 8/17/2024  D-Fructose "fruit sugar" Is a ketohexose with formula of C6H12O6. Is the sweetest carbohydrate. Is found in fruit, juices and honey. Converts to glucose in the body. Fructose is combined with glucose to give sucrose, or table sugar. CH2OH C O HO C H H C OH H C OH CH2OH D-Fructose 17 Biochemistry Department, college of Medicine, UQU 8/17/2024  18 Biochemistry Department, college of Medicine, UQU 8/17/2024 D-Galactose “In Milk Sugar" Is found combined with glucose in the disaccharide lactose, which is present in milk and other dairy products. Is an epimer of glucose at C4. Is important in cellular membranes. D-Galactose Epimer 19 Biochemistry Department, college of Medicine, UQU 8/17/2024 Galactosemia It is the inability to transform galactose to glucose. Galactosemia is a rare genetic disorder It's caused by a deficiency of enzymes needed to break down galactose sugars. Accumulation of galactose can lead to serious health issues, especially in infants. Treatment involves eliminating galactose-containing foods like milk and dairy. 20 Biochemistry Department, college of Medicine, UQU 8/17/2024 Reduction of Monosaccharides ▪ The reduction of the carbonyl group produces sugar alcohols, or alditols. ▪ D-Glucose is reduced to D-glucitol also called Sorbitol. 21 Biochemistry Department, college of Medicine, UQU 8/17/2024 CARBOHYDRATES DERIVATIVES Derivative Group Example Sugar acids Sugar contain COOH group Gluconic acid, glucuronic (oxidation) Structure of polysaccharides Deoxy sugars Removal of O from C2 Deoxy ribose: Structure of nucleic acids Amino sugars (NH2) replaces OH at 2nd carbon N-acetyle-glucosamine Structure of polysaccharides Sugar alcohol Addition of OH to CHO or CO groups Sorbitol (alcohol of glucose) artificial (reduction) sweetener 22 Biochemistry Department, college of Medicine, UQU 8/17/2024  DISACCHARIDES Disaccharides are: ▪ Formed from two monosaccharides ▪ Joined by a glycosidic bond ▪ A condensation reaction: ▪ glucose + glucose → maltose ▪ glucose + galactose → lactose ▪ glucose + fructose → sucrose 23 Biochemistry Department, college of Medicine, UQU 8/17/2024 Glycosidic bond. ▪ Disaccharide is formed when the anomeric carbon (C-1) on one monosaccharide reacts with hydroxyl group of another monosaccharide to form a glycosidic bond. ▪ Linkages may be α or β. ▪ 1-4 linkage: The anomeric carbon is bonded through an oxygen to C4 of second sugar (Maltose). ▪ 1-2 linkage: The anomeric carbons of the two sugars are bonded through an oxygen (Sucrose). ▪ The free anomeric carbon is called reducing end. ▪ According to the position of the linkage between the sugar units, disaccharides are classified into non-reducing such as sucrose and reducing such as maltose and lactose. -D-Glucose -D-Glucose 24 Biochemistry Department, college of Medicine, UQU 8/17/2024 Glycosidic bond and condensation reaction C C C O C O C C C C C C C C OH OH H2O 25 Biochemistry Department, college of Medicine, UQU 8/17/2024  Condensation reaction C C C O C O C C 1 4 C C C C O C C A disaccharide 1,4 glycosidic bond 26 Biochemistry Department, college of Medicine, UQU 8/17/2024 Maltose (Malt Sugar) it Is formed of 2 molecules of -D-glucose molecules joined by an -1,4-glycosidic bond.  - D-Maltose 27 Biochemistry Department, college of Medicine, UQU 8/17/2024  Maltose (Malt Sugar) Sources: a) Malt. b) Maltose Is produced during the digestion of starch by the amylase enzyme. Properties: Maltose contains a free carbonyl (aldehyde) group, so having the following properties: a) It is a reducing agent (can reduce Benedict's reagent). b) It can be present in α and β forms. c) It can show mutarotation. 28 Biochemistry Department, college of Medicine, UQU 8/17/2024  Lactose (Milk Sugar) Structure: It Is formed of 2 molecules of -glucose and -galactose linked by a -1,4-glycosidic bond.  - D-Lactose 29 Biochemistry Department, college of Medicine, UQU 8/17/2024  Lactose (Milk Sugar) Sources: It is the sugar present in milk. In human milk, its concentration is 7.4 g/dl. It may appear In urine in late pregnancy and during lactation. Properties: lactose contains a free carbonyl group, so having the following properties: a) It is reducing sugar (can reduce Benedict's reagent). b) It can be presented in α and β forms. c) It can show mutarotation. d) Lactose Is digested by an intestinal enzyme called: lactase into galactose and glucose. 30 Biochemistry Department, college of Medicine, UQU 8/17/2024  Sucrose (Table Sugar) ▪ Structure: it is formed of 2 molecules of α-glucose and β-fructose molecules joined by ,-1,2-glycosidic bond. α, -1,2-glycosidic bond 31 Biochemistry Department, college of Medicine, UQU 8/17/2024  Sucrose (Table Sugar) Sources: cane and beet sugar. It is also present in pineapple and carrot. Properties: sucrose contains no free carbonyl group (because both the anomeric carbons; carbon 1 of α-glucose and carbon 2 of β-fructose are involved in glycosidic bond) so fructose has the following properties: a) It is not a reducing sugar (cannot reduce Benedict's reagent). b) It cannot be present in α and β forms. c) It cannot show mutarotation. d) Sucrose is dextrorotatory. On hydrolysis by invertase (sucrase) enzyme, it gives a mixture of equal number of glucose and fructose molecules. This mixture is called invert sugar and it is levorotatory. 32 Biochemistry Department, college of Medicine, UQU 8/17/2024 Disaccharide Synthesis 33 Biochemistry Department, college of Medicine, UQU 8/17/2024  Disaccharide Hydrolysis Disaccharide hydrolyzed to its corresponding of monosaccharides. Maltose + H2O Glucose + Glucose Lactose + H2O Glucose + Galactose Sucrose + H2O Glucose + Fructose 34 Biochemistry Department, college of Medicine, UQU 8/17/2024 Disaccharides Comparison Maltose Lactose Sucrose Composition - Glucose + -  -Galactose + - α-D-glucose + β-D- Glucose Glucose fructose Bond 1,4-glycosidic bond  1,4-glycosidic bond ,-1,2-glycosidic Reduction Reducing sugar Reducing sugar Non-reducing sugar property Anomeric C Free Free No free anomeric C Mutarotation , anomers , anomers No  or  anomers Hydrolysis by Maltase Lactase Sucrase Source Enzymatic hydrolysis of Milk Cane sugar, beet sugar, starch and malt by Table sugar amylase 35 Biochemistry Department, college of Medicine, UQU 8/17/2024 Disaccharidase deficiencies are caused by the decreased hydrolysis of the disaccharides by the disaccharidase enzymes* (lactase; maltase; sucrase). Lactose intolerance is the inability to digest lactose, It is caused by a shortage of lactase in the body, an enzyme produced by the small intestine that is needed to digest lactose. This leads to milk fermentation by intestinal bacteria, diarrhea and abdominal distension (Lactose intolerance). While lactose intolerance is not dangerous, its symptoms can be distressing. 36 Biochemistry Department, college of Medicine, UQU 8/17/2024 Thank you