Carbohydrate Chemistry Lecture Notes (PT 2024-2025) PDF

Biochemistry I ‫جامعة سفنكس‬ ‫كلية عالج طبيعي‬ Chemistry of Carbohydrates Objectives List different classes of carbohydrates Define...

Biochemistry I ‫جامعة سفنكس‬ ‫كلية عالج طبيعي‬ Chemistry of Carbohydrates Objectives List different classes of carbohydrates Define chemistry and functions of monosaccharides and some of their derivatives Study some of the chemical properties of sugars Understand the concept of isomerism Define chemistry and functions of disaccharides. Define and classify polysaccharides. Discuss structure and functions of medically important homo- and Prof. Abdelraheim Meki hetero-polysaccharides. Dr. Eman Magdy Radwan  Definition of Carbohydrates: Carbohydrates (carbon-hydrates) are aldehyde (-CHO) or ketone (-C=O) derivatives of polyhydric alcohols (alcohols that have more than one -OH group) or are compounds which yield these derivatives on hydrolysis. CHO CHO CH2OH CHO CH2OHCHO H C O C H C =HO C OH OH HO C H C =HO HO C H H C HO OHC H H C OH HO C HH C OH H C OH HO C H C OHH C H HO OH CHO H C H H C OH HO C H C OHH C H HO OH CHO H C H CH2OH CH2OHCH OH CH2OH CH OH CH2OH 2 2 Note L-Mannose D-Glucose D-Fructose L-Glucose D-Mannose L-Fructose e.g. Lactase Lactose Importance of carbohydrates: 1. Carbohydrates form 60% of human diet, and are the main source of energy. 2. Carbohydrates are a part of important structural components of human cells, e.g. nucleic acids. 3. Major antigens are carbohydrates in nature, e.g. blood group substance. 4. They have a biological role as a part of enzymes, coenzymes, hormones and their receptors. 5. Glycoproteins and glycolipids are components of cell membranes and receptors. 6. Hyaluronic acid is a polysaccharide important for joint lubrication. 7. Carbohydrates metabolism is closely related to diabetes mellitus. Classification of carbohydrates: According to the number of sugar units in the molecule: Monosaccharides (simple sugars): They contain one sugar unit, the simplest form of sugars, and cannot be further hydrolyzed. They represent the end products of carbohydrate digestion in the human body. For example, glucose and fructose. Disaccharides: They are sugars which yield two molecules of the same or different molecules of monosaccharide on hydrolysis. For example, lactose and maltose. Oligosaccharides: They contain 3 - 10 monosaccharide units per molecule and give monosaccharides on acid hydrolysis. Most are not digested by human enzymes. For example, rhaffinose. Polysaccharides: They contain more than 10 monosaccharide units per molecule and give monosaccharides on acid hydrolysis. For example, starch and glycogen. Monosaccharides (Simple sugars): They are classified according to the number of carbon atoms into Bioses (2Cs), Trioses (3Cs), Tetroses (4Cs), Pentoses (5Cs) and Hexoses (6Cs). Each of these groups is further subdivided according to the type of functional active chemical group into: Aldoses (sugars containing aldehyde group at C1) Ketoses (sugars containing ketone group at C2). Aldoses of physiological importance Ketoses of physiological importance  Medical significance of some monosaccharides: Ribose: Ribose is the most important pentose because it enters in the structure of DNA, RNA, important nucleotides as ATP and coenzymes Glucose: It is called grape sugar, blood sugar or dextrose. It is a fermentable and reducing sugar. It is found in fruit juice and is produced by hydrolysis of starch, dextrins, glycogen, sucrose, maltose and lactose. All monosaccharides are converted into glucose to be utilized in the body as the major body and blood sugar. It appears in urine (glucosuria) in diabetes mellitus.  Mannose: It is a subunit in glycoproteins and glycolipids. It is a subunit in glycoproteins and sialic acid. It is obtained by hydrolysis of plant mannosans and gums. Galactose: It is a subunit of the milk sugar (lactose) and a component of glycolipids, glycoprotein and mucopolysaccharides. It accumulates in blood and appears in urine in a disease called galactosemia.  Fructose: It is the main sugar in bee's honey and fruits and is the sweetest sugar known. It is converted into glucose in the body and failure of its metabolism leads to accumulation in cells and blood (hereditary fructose intolerance). It is a reducing and fermentable sugar. It is called the semen sugar. CH2OH C=O HO C H H H C OH HO H C OH HO CH2OH D-Fructose L- Optical activity It is the ability of the sugar to rotate the plane polarized light. The sugar that rotates the light to the right is called dextrorotatory (d or +) such as glucose, galactose and starch and that rotating light to the left is called levorotatory (l or -) such as fructose and invert sugar. It is due to the presence of asymmetric carbon atom. Asymmetric carbon atom is the carbon atom attached to which 4 different groups or atoms. Racemic mixture is a mixture of equal amounts of dextrorotatory and levorotatory isomers of a compound (dl mixture). This mixture is optically inactive because they equalize the effect of one another. Isomerism Isomers are substances which have the same molecular formula but differ in distribution of their atoms into groups or distribution of these groups and atoms in the space around carbon atoms. There are 2 types of isomerism: Structural isomerism. Stereoisomerism. Structural isomerism: They are isomers that have different structures due to different ways of arrangement of atoms and groups forming the molecule. OH CH2O-P=O CH2OH OH CH2OH O O O H H 1. Positional isomerism: These are isomers that have H H H H H H H OH H OH H OH H OH the same carbon skeleton but differ in the position of OH OH OH OH OH O-P=O the substituent groups, e.g. phosphoglucose. H OH H OH H OH OH -D-Glucose Glucose-6-phosphate Glucose-1-phosphate 2. Functional group isomerism: isomers that have CHO CH2OH CHO CH CHO the same carbon skeleton and the same position of H C OH HO CC = HO HO CC H HO C H HOC C OH H H HO CH C H the substituent groups but have different functional H C OH HO HC C H OH H HO C C O H C OH HO HC C H OH H HO C C O groups (aldo-/keto-pairs): e.g. erythrose/erythrulose, CH2OH CH CH 2OH 2OH CH2CH O ribose/ribulose and glucose/fructose. D-Glucose D-Fructose L-Glucose L-Fr D-Mann Stereoisomerism: They are molecules having the same structure but differ in position of their different groups and atoms in the space; i.e. in spatial configuration. 1. D and L-isomerism (enantiomers): They differ in distribution of -H and -OH groups around the asymmetric subterminal carbon atom (the one before the last carbon). Metabolizable sugars in human body are D-forms only. Examples: D-glucose and L- glucose or D-mannose and L-mannose. Glyceraldehyde is called the reference sugar because it contains one asymmetric carbon atom. CHO CHO CHO CHO CHO CHO HO H H OH H C OH HO C H HO H H OH C C CH2OH CH2OH C C D-Glyceraldehyde L-Glyceraldehyde OH group on sub-terminal OH group on sub-terminal CH2OH CH2OH CH2OH CH2OH carbon is written on right side. carbon is written on left side. CHO CHO CHO CHO 2. Epimers: They differ in distribution of -H and -OH groups around a single asymmetric carbon atom other than the anomeric carbon atom CHO CHO CHO CHO CHO CHO 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 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 H C OH CH2OH CH2OH CH2OH CH2OH CH2OH CH2OH Ribose Arabinose Xylose Glucose Mannose Galactose 3. Anomers: They are stereoisomers which differ in distribution of -H and -OH groups around the asymmetric carbon atom C1 in aldoses or C2 in ketoses after cyclization of the molecule (anomeric carbon), e.g. - and -glucose are anomers. CH2OH CH2OH O O OH H H H H H OH H OH H OH H OH OH H OH H OH -D-Glucose -D-Glucose Cyclic structure of monosaccharides Sugars exist in solutions mostly in a cyclic form and a very small fraction is transiently present in the open chain form Steps of the cyclic form construction: H OH HO H C C CH2OH Fisher's projection formula H C OH H CH2OH O H H C OH H O OH HO C H H H HO C H OH H OH H H C OH H C OH H OH OH OH H C O H C O H OH H OH CH2OH CH2OH -D-glucopyranose -D-glucopyranose Haworth's projection formula  Some chemical properties of monosacharides I. Reducing properties The presence of a free aldehyde or ketone group in the carbohydrates is responsible for its reducing ability. Monosaccharides are reducing sugars that reduce cupric hydroxide in Fehling’s or Benedict reagents. Some disaccharides are reducing sugars as maltose and lactose, others are non reducing as sucrose. Polysaccharides are non-reducing. Cupric hydroxide (Cu(OH)2) + Reducing sugar (R-CHO) → Aldonic acid (R-COOH) + Cuprous oxide (Cu2O) a red precipitate II. Fermentation of sugars: Some micro-organisms (bacteria) and yeast can ferment certain sugars by several biochemical steps into ethyl alcohol and carbon dioxide and cannot ferment others. Glucose, mannose and fructose are fermentable monosaccharides, whereas, galactose is weakly fermented. Sucrose and maltose are fermentable disaccharides. Polysaccharides are non-fermentable.  Sugar derivatives of medical importance: 1. Amino sugars (sugar amines): (hydroxyl group at C2 is replaced by an amino group). CH2OH O H H H H OH H Glucosamine: It enters in the structure of OH H 2 NH2 OH OH mucopolysaccharides, e.g. hyaluronic acid and heparin. -D-glucoamine N-ace CH2OH O OH H OH H Galactosamine (Chondrosamine): It enters in the structure of H OH H 2 OH H the sulfated mucopolysaccharides (chondroitin sulfate) and H NH2 - D-galactosamine N- glycolipids. CH2OH H O H H OH NH2 Mannosamine: It enters in the structure of antibiotics, e.g., OH 2 OH H H erythromycin where it is required for their activity. -D-Mannosamine 2- Deoxysugars: These are sugars in which OH group is replaced by H. This may occur at: 1. At C2: to give deoxy sugar, e.g., deoxyribose that enters in structure of DNA. 2. At C6: to give methyl pentoses (Methylose) e.g., L-galactose gives L-fucose and, L-Mannose gives L-rhamnose. L-rhamnose and L-fucose enter in the structure of glycoproteins, e.g., blood group substance. CHO CHO CHO CHO CHO CHO CHO CHO CHO CHO HO C HHO C HO H C HHO C H H C OHH C OH H C OH H C OHH C OH H C H H C OHH C OH H C OHH C OHH C OHH C OH H C OH H C OHH C OH H C OH H C OHH C OH H C OHH C OH HO C HHO C HO H C HHO C H H C OH H C OH HO C HHO C HO H C HHO C HHO C HHO C H HO C HHO C H CH2OH CH2OH CH2OH CH2OH CH 3 CH3 CH2OH CH2OHCH CH3 3 Ribose Deoxyribose L-galactose L-galactose L-fucose L-fucose L-Mannose L-Mannose L-Rhamnose L-Rhamnose 3. Sugar acids (products of oxidation of sugars) The product of oxidation depends on the nature of oxidizing reagent (Weak, moderate and strong reagent): 1. Oxidation by mild or weak oxidizing reagent: Bromine water oxidizes the first carbon to give aldonic acids. CHO COOH H C OH H C OH Examples are: HO C H bromine water, O2 HO C H Gluconic acid is an intermediate in carbohydrate H H C C OH OH H H C C OH OH metabolism and used as Ca+2 gluconate for intravenous CH2OH CH2OH supplementation of calcium. D-Glucose D-Gluconic acid O C Ascorbic acid (Vitamin C) is synthesized from gulose HO HO C C O (glucose derivative) in plants and animals except human, H C HO C H O primates and guinea pig. CH 2OH NH-C-CH 3 H L-ascorbic acid O COOH H OH H OH Sialic acid is a carbohydrate-derived acid that enters in CH2OH H H OH H the synthesis of glycolipids and glycoproteins. OH H Sialic acid 2. Oxidation by moderate oxidizing reagents: H2O2 & diluted HNO3 oxidize the last carbon (-CH2OH) to give uronic acid. Examples include: Glucuronic acid: Glucose gives glucuronic acid. It is synthesized in the liver. L-iduronic acid is the 5-epimer of D-glucuronic acid and it enters in structure of mucopolysaccharides. CHO CHO CH2OH COOH H O O O H C OH H C OH H H H H H OH H H COOH Di. Nitric acid HO C H H2O2 HO C H OH H OH H OH H OH OH H2O2 OH OH OH H H C OH Dil. Nitric acid H C OH H OH H OH H OH H C OH H C OH -D-Glucose -D-Glucuronic acid -L-Iduronic acid CH2OH COOH D-Glucose D-Glucuronic acid CHO CHO H C OH H C OH Galacturonic acid: Galactose gives galacturonic HO C H H2O2 HO C H acid that enters in plant gums and pectin HO H C C H OH Dil. Nitric acid HO H C C H OH structure. CH2OH COOH D-Galactose 21 D-Galacuronic acid 3. Oxidation by strong oxidizing reagents: Concentrated HNO3 oxidizes the first and last carbon to give aldaric acid. This reaction is important to differentiate between glucose and galactose since glucaric acid is water soluble, whereas, mucic acid is insoluble in water and precipitates in the form of insoluble crystals of specific shape. CHO COOH CHO COOH H C OH H C OH H C OH H C OH HO C H O2 HO C H HO C H O2 HO C H HO C H Conc. Nitric acid HO C H H C OH Conc. Nitric acid H C OH H C OH H C OH H C OH H C OH CH2OH COOH CH2OH COOH D-Galactose D-Galactaric acid D-Glucose D-Glucaric acid Mucic acid  CHO CH 2OH 4. Sugar alcohols (products of reduction of sugars) H C OH H2 H C OH H C OH H C OH Ribose reduction gives ribitol that is a part of the H C CH 2OH OH Na amalgum, H 2SO 4 H C CH 2OH OH structure of vitamin B2 (Riboflavin). Ribose Ribitol CHO CH2OH H C OH H C OH Glucose reduction gives sorbitol that enters in several HO H C C H OH H2 Na amalgum, H2SO 4 HO H C C H OH medical industries. H C CH2OH OH H C CH2OH OH Glucose Sorbitol CHO CH 2OH Mannose reduction gives mannitol, which is injected HO HO C C H H H2 HO HO C C H H H C OH H C OH intravenously to reduce intracranial hypertension as in H C OH Na amalgum, H 2SO 4 H C CH 2OH OH CH 2OH cases of meningitis, cerebral hemorrhage or thrombosis. Mannose Mannitol CHO CH2OH H C OH H C OH HO C H Galactose gives dulcitol on reduction. H2 HO C H HO C H Na amalgum, H 2SO 4 HO C H H C OH H C OH CH2OH CH2OH Galactose Dulcitol Inositol Inositol is a hexahydric sugar alcohol (6 OH groups), It is present in high concentrations in bran (outer coat of cereals) where it combines with 6 molecules of phosphoric acid to give phytic acid. Phytic acid forms insoluble iron, calcium and magnesium salts (phytate) which hinders the absorption of Ca2+, Mg2+ and iron in the intestine. It is present in high concentrations in heart and muscles tissues, so it is called muscle sugar It is considered a member of vitamin B complex because it is essential for synthesis of phospholipids, phosphatidylinositol. OH OH H 5 6 H H H 4 1 OH H OH 3 2 OH H OH Inositol  Disaccharides a) Maltose: It is a reducing disaccharide that consists of 2 glucose units linked by alpha () 1,4-glucosidic linkage. It is produced during digestion of starch by amylase enzyme. It is hydrolyzed in human intestine by maltase enzyme. b) Lactose (Milk sugar) It is a reducing disaccharide that consists of glucose and galactose linked by beta() 1,4-glucosidic linkage. It is digestible in human intestine by lactase enzyme. It is the most suitable sugar for baby feeding as a sweetener for milk : It is the least sweet sugar so that the baby can nurse a large amount of mother’s milk without getting his appetite lost. Because it has a -glycosidic linkage so it is non-fermentable (it does not form gases and does not cause colic to the infant). It has a laxative effect, prevents constipation and is non-irritant to the stomach. Unabsorbed sugar is used as food for large intestinal bacteria that form a number of vitamins that benefit the baby. It is easily digested. It helps in the absorption of the calcium of milk. c) Sucrose (Cane or Table sugar): It is formed of -glucose linked to -fructose by --1,2- linkage. It is hydrolyzed by sucrase enzyme. The 2 active carbons (C1 of glucose and C2 of fructose) are in the linkage, therefore it is a non-reducing sugar. d) Cellobiose: It is formed of 2 -glucose units linked by -1,4-glucosidic linkage. CH2OH CH2OH O O H OH It is a reducing disaccharide. H H 1 O 4 H OH H OH H H OH H It is the building unit of cellulose. H OH H OH -Glucose -Glucose It is non-fermentable and indigestible. Cellobiose  Polysaccharides Homopolysaccharides Heteropolysaccharides They are polysaccharides They yield only one type that on hydrolysis of monosaccharides on produce several types of hydrolysis sugars.  Homopolysaccharides named according to the type of monosaccharide Hexosans Pentosans N-acetyl Glucosans Fructosans Galactosans Glucosans Starch, Glycogen, Inulin Agar Agar Chitin Dextrins, Dextran & Cellulose  Polysaccharides Glucosans: a) Starch It is the stored form of carbohydrate in plants (storage polysaccharide). It doesn’t exist in animals. It is present in cereals such as wheat and rice, also in tubers such as potatoes and sweet potatoes. Starch granules are formed of: The core amylose (20%): A straight chain compound formed of a large number of -glucose units linked by -1,4-glucosidic bond. The shell amylopectin (80%): Branched chains formed of a large number of - glucose units linked by -1,4-glucosidic linkage along the branch and by -1,6- glucosidic linkage at the branching point that occur periodically every 25-30 glucose units.  CH2OH 6CH OH CH2OH CH2OH CH2OH 2 O 5 O H O H O H H O H H H H H H H H H H H OH H 1 4 OH H 1 OH H OH H OH H O O O O OH OH 2 3 CH2OH CH2OH H OH H OH H OH H OH H OH O O H H H H H H 1 amylose H 1 4 OH OH O O H OH H OH n CH2OH CH2OH Amylose H O H H O H amylopectin H H OH H OH H 1 O OH O H OH H OH CH2OH CH2OH 6 CH2 CH2OH CH2OH CH2OH CH2OH H O H H O H H 5 O H H O H H O H O O H H H H H H H H H H 1 4 H H 1 OH H OH H 4 OH H OH OH OH H 1 4 OH O O O O OH OH O 3 2 O H OH H OH H OH H OH H OH H OH H OH CH CH2OH CH2OH 62 O O Starch is digestible because human amylases hydrolyze -glucosidic linkage. It O H H H H H H H H H 1 1 4 1 4 OH H 1 4 OH OH O O O O can be hydrolyzed into dextrins H OH n that are further hydrolyzed into maltose and H OH H OH Amylopectin isomaltose. b) Glycogen: It is the stored form of carbohydrate in animal, particularly in muscles and liver. Its structure is similar to amylopectin a branched tree with -1,4-glucosidic linkage along the branch and -1,6-glucosidic linkage at the branching point. However, the glycogen tree is shorter and more branched (a branch point every 8-10 glucose units) than amylopectin. Glycogen is hydrolyzed by amylases into dextrins, maltose and isomaltose. C H2OH C H2OH H O O glycogen H H H H H OH H OH H 1 O OH O H OH H OH C H2OH C H2OH 6 C H2 C H2OH C H2OH H O H H O H H 5 O H H O H H O H H H H H H OH H OH H OH H 1 4 OH H OH H 4 O O O O OH OH 3 2 H OH H OH H OH H OH H OH c) Cellulose: It is a structural polysaccharide. It forms the skeleton of plant cells and does not enter in animals cell structures. It is a straight chain molecule formed of a large number of -glucose units linked by - 1,4-glucosidic linkage. It gives cellobiose on hydrolysis with HCl. It is indigestible in humans because of the lack of enzymes that hydrolyze -glycosidic linkage. Cellulose is very essential in food for: Prevention of constipation by increasing the bulk of stools. It adsorbs toxins present in foods and prevents its absorption into the body. It has anticancer actions. CH2OH 6CH OH 2 CH2OH CH2OH CH2OH O 5 O O H O H O OH H H H H H H H H OH H 1 O 4 OH H 1 O OH H O OH H O OH H OH H H H H 2 H 3 H OH H OH H OH H OH H OH cellulose  Comparison between Starch, Glycogen and Cellulose Starch Glycogen Cellulose Nature: Stored form of carbohydrate in plants. Stored form of carbohydrates in Structural form of carbohydrate in plant animals. cells. Source: Cereals, e.g., wheat, rice, and tubers, e.g., potatoes. Muscles and liver Linen and cotton Nature of the chains: Amylose is helical straight chain (-glucose units Branched chain similar to amylopectin Straight chain (large number of - linked by -1,4-glucosidic bonds). Amylopectin is but its trees are shorter and have more glucose units linked by -1,4- glucosidic branched chain (-glucose units linked by -1,4- branches than amylopectin tree. bonds). and -1,6-glucosidic bonds). Reaction with iodine: Amylose gives blue color and amylopectin gives red Gives red color. No color. color. Digestibility: Is hydrolyzed by HCl or Digestible by amylase into Digestible by amylase into dextrins and Non-digestible but HCl hydrolysis gives dextrins and maltose. maltose. cellobiose.  Fructosan Inulin: is formed of fructose only and is present in onions. It is not metabolized in human body, therefore, it is used in evaluation of kidney function (inulin clearance test). Galactosans Agar Agar: is present in seaweed. It is used for growth of bacteria and mammalian cells in culture.  Heteropolysaccharides Nitrogenous Non Nitrogenous Contain sugar-amines No sugar-amines e.g. Pectin Acidic Nitrogenous Neutral Nitrogenous Mucopolysaccharides/ Glycosamineglycans/ Proteoglycans Glycoproteins Sulfated: Sulfur Free: Heparin Hyalouronic acid Chondroitin Sulfate  Neutral Nitrogenous Heteropolysaccharides: Glycoproteins: They do not contain uronic acids or sulfate groups. They are formed of a large protein core to which chains of carbohydrate are attached. Glycoproteins include: 1. Mucins of saliva and epithelium lining of gastrointestinal, urinary and respiratory tracts (act as lubricant and protective). 2. Cell membranes and as a part of collagen of connective tissue (structural function). 3. Blood group substances: A and B antigens. 4. Mineral transporting protein (e.g. transferrin), immunoglobulins (e.g. IgG, IgM) and some hormones, (e.g LH, FSH).  Acidic Nitrogenous Heteropolysaccharides: Proteoglycans consist of very small core protein molecule to which a huge carbohydrate tree is attached. The carbohydrate moiety is an unbranched polysaccharide made up of repeating disaccharides. They are also called mucopolysaccharides or glycosaminoglycans (GAGs). Functions: GAGs are components of the ground substance of connective tissue. GAGs constitute 5% of cell membrane structure, presenting on the outer surface of the membrane (extracellular matrix). GAGs are highly viscous to the solution, so it is ideal for a lubricating fluid in the joints.  Structure of GAGs Amino sugar (Hexosamine) Uronic acid: N-acetyl-glucosamine or + L-glucuronic acid or N-acetyl galactosamine L-iduronic acid Unbranched repeated CH2OH COOH H disaccharide unit H O H H O H H COOH O OH H Di. Nitric acid H OH H H OH H OH OH OH H2O2 OH OH OH H GAGs H OH H OH H OH -D-Glucose -D-Glucuronic acid -L-Iduronic acid Attachment of glycosaminoglycans to proteins. The sugars are linked to a serine or threonine residue of the protein. A and B represent the sugars of the repeating disaccharide. I. Sulfur free Mucopolysaccharides: Hyalouronic acid It is formed of -N-acetyl glucosamine linked to -glucuronic acid. It is formed of 400 - 4000 repeating disaccharide units. It is present in connective tissue matrix, vitreous humor of the eye and in the synovial fluid in joints for lubrication. II. Sulfur containing Mucopolysaccharides: a. Chondroitin sulfate Chondroitin sulfate A is formed of sulfated -N-acetyl galactosamine and - glucuronic acid. It is present in cornea of the eye, tendons, ligaments, bones, cartilage and connective tissue matrix. b. Heparin: It is formed of a long repeat of sulfated -glucosamine and sulfated -L- iduronic acid. It is an anticoagulant produced by mast cells that prevents intravascular clotting. It is used in cases of increased coagulability, e.g., cardiac ischemia or deep venous thrombosis.  Comparison between glycoproteins & proteoglycans Glycoproteins Proteoglycans Distribution: Blood group substance, Skeletal and supporting pituitary hormones, and mucin tissues, e.g., cartilage, bone in body fluids and secretions. and in cell membrane. Carbohydrate part: Oligosaccharide units. Mucopolysaccharides. Type of sugars: No uronic acids, Uronic acids, N-acetyl-hexosamines; Glucosamine, N-acetyl-glucosamine, Galactosamine, and xylose. N-acetyl-galactosamine, Sialic acid, and fucose. Sulfate: No sulfate. Rich in sulfate. Size of monosaccharide units: Less than 25 monosaccharide More than 50 units. monosaccharide units. Repeating structures: Little or no. Many. Shape of carbohydrate chains: Branched. Linear.  Sources: 1. Harper’s Illustrated Biochemistry (31 ed., 2018 McGraw-Hill Education / Medical). 2. Lippincott Illustrated Reviews: Biochemistry, 8th Edition, Wolters Kluwer, 2017. Revise your knowledge: 1. α-D-glucose and β-D-glucose are: (A) Enantiomers (B) Epimers (C) Anomers (D) Keto-aldo pairs 2. Compounds with the same structural formula but different spatial configuration are: (A) Structural isomers (B) Functional isomers (C) Stereoisomers (D) Positional isomers 3. ……… is called the semen sugar. (A) Fructose (B) Glucose (C) Mannose (D) Galactose 4. Concentrated HNO3 oxidizes the ……………..to give aldaric acids (A) First carbon of sugar (B) Second carbon (C) Last carbon (D) A and C 5. In some sugars, OH group is replaced by H at C2 to give: (A) Methyl pentoses (B) Deoxy sugars (C ) Sugar acids (D) Sugar alcohols Glycoproteins are formed of a large protein core attached to chains of carbohydrate (A) True (B) False Lactose is a non-reducing sugar (A) True (B) False Heparin is one of the sulfur containing mucopolysaccharides (A) True (B) False Inulin is one of the heteropolysaccharides (A) True (B) False The monosaccharide units are linked by α-1-4 glycosidic linkage in maltose (A) True (B) False Lactose is digestible in human intestine by lactase enzyme. (A) True (B) False The pentose that enters in the structure of DNA is arabinose (A) True (B) False Glucosamine is a sugar acid (A) True (B) False 14. Cellulose prevents the constipation by increasing the bulk of stools. (A) True (B) False 15. Glycoproteins do not contain uronic acids or sulfate groups. (A) True (B) False 16. GAGs are highly viscous to the solution, so it is ideal for a lubricating fluid in the joints. (A) True (B) False 17. Starch is digestible because human sucrase hydrolyze -glucosidic linkage (A) True (B) False 18. Because lactose has a -glycosidic linkage so it is non-fermentable, so, it does not form gases and does not cause colic to the infant. (A) True (B) False 19. Hyaluronic acid is formed of -N-acetyl glucosamine linked to sulfated -L-iduronic acid. (A) True (B) False