Chemistry of Carbohydrates PDF

# Carbohydrates Chemistry ## MRH-DEN-MED ### **Part Two** **ADENIYI T.T.** **Dept Of Medical Biochemistry** **OAU** ## Carbohydrates - Carbohydrates, or saccharides (saccharo is Greek for-sugar) are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis. - Carbo...

# Carbohydrates Chemistry ## MRH-DEN-MED ### **Part Two** **ADENIYI T.T.** **Dept Of Medical Biochemistry** **OAU** ## Carbohydrates - Carbohydrates, or saccharides (saccharo is Greek for-sugar) are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis. - Carbohydrates include not only sugar, but also the starches that we find in foods, such as bread, pasta, and rice. - The term -carbohydrate comes from the observation that when you heat sugars, you get carbon and water (hence, hydrate of carbon). They contain the elements C, H and O ## Functions of Carbohydrates - Carbohydrates are compounds of tremendous biological importance: - they provide energy through oxidation - they supply carbon for the synthesis of cell components - they serve as a form of stored chemical energy - they form part of the structures of some cells and tissues. Eg. Cellulose in plants, exoskeleton of insects - Component of cell membranes and receptors - Excess COH is converted to fat in the body - Constituents of DNA and RNA - COH along with lipids, proteins, nucleic acids are known as biomolecules because they are closely associated with living organisms. ## Monosaccharides - ($CH_2O)_n$ - where n=3-7 - NB: Disaccharides or Oligosaccharides can be distributed into Penta saccharides. ## Classification: 1. **Monosaccharides (simple sugars):** - They can not be hydrolyzed into simpler units. E.g. glucose, galactose, ribose, Mannose. 2. **Disaccharides:** Two monosaccharides combined together with elimination of a water molecule eg sucrose, maltose etc 3. **Trisaccharides (3 units) ...etc. (Raffinose)** 4. **Oligosaccharides (oligo = few):** contain from two to ten monosaccharide units joined in glycosidic bonds. 5. **Polysaccharides (poly = many):** Also known as glycans. They are composed of more than ten monosaccharide units e.g. starch, glycogen, * **Homopolysaccharides -** have only one type of sugar eg starch * **Heteropolysaccharides -** have different types of sugar eg hyaluronic acid ## Classification of Monosaccharides 1. **According to the number of carbon atoms:** - Trioses, contain 3 carbon atoms. - Tetroses, contain 4 carbon atoms. - Pentoses, contain 5 carbon atoms. - Hexoses, contain 6 carbon atoms. - Heptoses, contain 7 carbon atoms. 2. **According to the characteristic carbonyl group (aldehyde or ketone group):** - **Aldo sugars: aldoses:** - Contain aldehyde group e.g. glucose, ribose, erythrose and glyceraldehydes. - **Keto sugars: ketoses:** - Contain ketone group e.g. fructose, ribulose and dihydroxy acetone. ### **Trioses:** - **Aldose:** - $HCO$ - $H-C-OH$ - $CH_2OH$ - **D- glyceraldehyde** - **Ketose:** - $CLOH$ - $C=O$ - $CH_2OH$ - **Dihydroxyacetone** ### Tetroses: - **Aldose:** - $HCO$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **D - erythrose** - **Ketose:** - $CH_2OH$ - $C=O$ - $CH_2OH$ - **D-erythrulose** ### **Pentoses:** - **Aldose:** - **D-Ribose:** - $HCO$ - $H-C-OH$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **D-Deoxyribose:** differs from ribose in carbon 2. - $HCO$ - $H-C-OH$ - $H-C-H$ - $H-C-OH$ - $CH_2OH$ - **Ketose:** - **D-Ribulose:** - $CH_2OH$ - $C-O$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **D-Xylulose:** differs from ribulose in carbon 3. - $CH_2OH$ - $C-O$ - $H-C-OH$ - $H-C-H$ - $CH_2OH$ ### **Hexoses:** - **Aldose:** - **D-Glucose:** - $HCO$ - $H-C-OH$ - $HO-C-H$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **D-Mannose:** - $HCO$ - $HO-C-H$ - $H-C-OH$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **D-Galactose:** - $HCO$ - $H-C-OH$ - $HO-C-H$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ - **Ketose:** - **D-Fructose:** - $CH_2OH$ - $C=O$ - $HO-C-H$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ ### **Heptoses:** - **D- sedoheptulose-a ketose sugar** - $CH_2OH$ - $C=O$ - $HO-C-H$ - $H-C-OH$ - $H-C-OH$ - $H-C-OH$ - $CH_2OH$ ## **Physical Properties of Monosaccharides** - Most monosaccharides have a sweet taste (fructose is the sweetest; (73% sweeter than sucrose). - They are solids at room temperature. - They are extremely soluble in water. - Despite their high molecular weights, the presence of large numbers of OH groups make the monosaccharides much more water soluble than most molecules of similar MW. - Glucose can dissolve in minute amounts of water to make a syrup (1g/1 ml H2O). ## Relative Sweetness of Sugars | Sugar | Relative Sweetness | Type | | :------- | :------------------ | :--------------- | | Lactose | 0.16 | Disaccharide | | Galactose | 0.22 | Monosaccharide | | Maltose | 0.32 | Disaccharide | | Xylose | 0.40 | Monosaccharide | | Glucose | 0.74 | Monosaccharide | | Sucrose | 1.00 | Disaccharide | | Invert sugar| 1.30 | Mixture of glucose and fructose| | Fructose | 1.73 | Monosaccharide | ## Van't Hoff's 2nd rule - When a molecule has more than one chiral carbon, each carbon can possibly be arranged in either the right-hand or left-hand form, thus if there are n chiral carbons, there are 2^n possible stereoisomers. - Maximum number of possible stereoisomers = 2^n **Can you tell no. of possible stereoisomers of CHOLESTEROL?** - The no of chiral carbon in Cholesterol is 8 ie the no of possible stereoisomers in Cholesterol will be 2^8 = 256 possible stereoisomers. ## D AND L ISOMERS (ENANTIOMERS) - **Enantiomers:** They are the mirror image of each others. The 2 mirror image forms of chiral molecule. - **D-Glyceraldehyde:** - $CHO$ - $H-C-OH$ - $CH_2OH$ - **L-Glyceraldehyde:** - $CHO$ - $HO-C-H$ - $CH_2OH$ - Carbohydrates are designated as D- or L- according to the stereochemistry of the highest numbered chiral carbon of the Fischer projection. (penultimate carbon) - If the hydroxyl group of the highest numbered chiral carbon is pointing to the right, the sugar is designated D (Dextro: Latin for on the right side). If the hydroxyl group pointing to the left, the sugar is designated as L (Levo: Latin on the left side). Most naturally occurring carbohydrates are the D-configuration. ## Stereoisomers - These forms are stereoisomers of each other. Have the same structures but different spatial arrangement - Glyceraldehyde is a chiral molecule-it cannot be superimposed on its mirror image. The two Mirror-image forms of glyceraldehyde are enantiomers of each other. - Chirality and Handedness - Chiral molecules have the same relationship to each other that your left and right hands have when reflected in a mirror. ## Stereochemistry of Carbohydrates - **Two Forms of Glyceraldehyde**: reference cpds - Glyceraldehyde, the simplest carbohydrate, exists in two isomeric forms that are mirror images of each other. - **Chiral Carbons** - Chiral objects cannot be superimposed on their mirror images-e.g., hands, gloves, and shoes. - Achiral objects can be superimposed on the mirror images-eg., drinking glasses, spheres, and cubes. - Any carbon atom which is connected to four different groups will be chiral and will have two nonsuperimposable mirror images; it is a chiral carbon or a center of chirality: - If any of the two groups on the carbon are the same, the carbon atom cannot be chiral. - Many organic compounds, including carbohydrates, contain more than one chiral carbon. ## Isomerism - **Optical Isomer**: Same molecular formula but different spatial arrangement - **Enantiomer**: Mirror Image, Non-superimposable - **Epimer**: Only One Chiral Carbon Difference - **Anomer**: Same molecular formula but different configuation - **Aldose-Ketose Isomer**: Same molecular formula but different functional groups ## What's so Great About Chiral Molecules? - Molecules which are enantiomers of each other have exactly the same physical properties (melting point, boiling point, index of refraction, etc.) but not their: - interaction with polarized light. - Polarized light vibrates only in one plane; it results from passing lights through polarizing filter ## Optical Activity - A levorotatory(-) substance rotates polarized light to the left [e.g., glucose; (-)-glucose]. - A dextrorotatory(+) substance rotates polarized light to the right [e.g.,d-glucose; (+)-glucose). - Molecules which rotate the plane of polarized light are optically active. They contain chiral carbon(s). - Many biologically important molecules are chiral and optically active. Often, living systems contain only one of the possible stereochemical forms of a compound, or they are found in separate system. - D-lactic acid is found in living muscles; D-lactic acid is present in sour milk. - In some cases, one form of a molecule is beneficial, and the enantiomer is a poison - Humans can metabolize D-monosaccharides but not L-isomers; only L amino acids are used in protein synthesis ## Aldotetroses - Glyceraldehyde is the simplest carbohydrate (C3; aldotriose; 2,3-dihydroxypropanal). The next carbohydrate are aldotetroses (C4; 2,3,4-trihydroxybutanal) ## Aldopentoses and Aldohexoses - Aldopentoses: C5; three chiral carbons, eight stereoisomers - Aldohexoses: C6; four chiral carbons, sixteen stereoisomers ## Cyclic Forms of Carbohydrates: Pyranose Forms <start_of_image> CH2OH - C1- OH and CH2OH are cis - It is also known as **β-D-Glucopyranose** CH2OH - C1- OH and CH2OH are trans - It is also known as **α-D-Glucopyranose** ## Mutarotation and the Anomeric Effect - The hem or hemiketal carbon of the cyclic form of carbohydrates is the anomeric carbon, ie. 1st carbon in aldoses and 2nd carbon in Ketoses. - Carbohydrate isomers that differ only in the stereochemistry of the anomeric carbon are called anomers. - **Mutarotation:** The a- and ẞ-anomers are in equilibrium, and interconvert through the open form. The pure anomers can be isolated by crystallization. When the pure anomers are dissolved in water they undergo mutarotation, the process by which they return to an equilibrium mixture of the anomer. ## Epimers - Two monosaccharides differ only in the configuration around one specific carbon atom, other than the penultimate carbon. - **D-glucose and D-mannose are epimers with respect to carbon atom 2** - **D-glucose and D-galactose are epimers with respect to carbon atom 4** - **Galactose is the 4th epimer of glucose**. - **Galactose and Mannose are diastereo-isomers** ## Aldose-Ketose Isomerism - Two monosaccharides have the same molecular formulae but differ in their functionl groups. - one has an aldehyde group (aldose e.g. Glucose) - the other has a ketone group (Ketose e.g. Fructose). ## Importance ### Pentoses - D-ribose is a structural element of ribonucleic acid (RNA) and coenzymes e.g. ATP, NAD, NADP and others. D-ribose-phosphate and D-ribulose-5-phosphate are formed from glucose in the body (HMS). - 2-deoxy D-ribose enters in the structure of DNA. - D-xylose: constituent of lyxoflavin in human myocardium. Lot of experiments are ongoing to establish it as a potent myocardial infarction marker. - Ribulose: intermediate of HMP shunt pathway. - Arabinose: in body glycoproteins. - Xylulose: intermediate of uronic acid pathway ### 2-Hexoses - **D-glucose (grape sugar, Dextrose as D-glucose is dextrorotatory):** - It is the sugar carried by the blood (normal plasma level 70-100 mg/dL) and the principal one used by the tissues. - It is found in fruit juices - obtained by hydrolysis of starch, cane sugar, maltose and lactose. - **D-Fructose:** - Anomeric carbon is C2, functional group isomer of glu. (honey sugar-lavulose as D-fructose is Invorotatory). - It is found in fruit juices. (fruit augar) - Obtained from sucrose by hydrolysis. - It is present in the semen in furanose form (D-fructofuranose) - **D-galactose:** - It is a constituent of galactolipids and glycoprotein in cell membranes and extracellular matrix. ## Reactions of Monosaccharides ### Iodocompounds - Glucose when heated with conc. Hydroiodic acid loses all its oxygen and converted to Iodohexane. - This suggests that glucose has no branched chain. - Glucose conc.HI- Iodohexane ### Sugar Ester Formation: - The - OH groups of monosaccharides can form esters with acids (phosphate, sulfate, acetate, benzoate, etc). - Phosphate-esters: - Glucose-1-phosphate - Glucose-6-phosphate - These are of great biological importance especially in glucose metabolism - Sulfate esters: - Galactose-3-sulfate ## Enediol Formation: Sugar as Reducing Agent - The monosaccharides and most of the disaccharides are rather strong reducing agents, particularly at high pH. - At alkaline pH free aldehyde or keto group tautomerizes to form highly reactive ENEDIOL group. As such glu is converted to fru and mannose. This reaction is called Lobry de Bruyn-Van Ekenstein transformation. Enediol has strong reducing property. So sugars are powerful reducing agents in alkaline medium. - $HCOH$ - $COH$ - $R$ - **1,2 enediol form** ## Enediols Contd. - In the presence of oxidizing agents like cupric ions, sugars form a mixture of carboxylic acids by breaking at the double bonds. ## Benedict's Reaction - Benedict's Reagent (Blue) $\rightarrow$ Copper(I) Oxide (Red/Orange) - Sugar + enediol + CuSO4 $\rightarrow$ Sugar + acid + Cu+2 + Cu(OH)2 (Yellow) $\rightarrow$ Cu2O + H2O (red) - Benedict's reagent contains sodium carbonate, copper sulphate and sodium citrate. - With enediol, cupric ions are reduced, corresponding sugar is oxidized. - Any sugar with free aldehyde or ketone group will reduce the Benedict reagent. - Benedict reagent is very commonly used to detect glu in urine. It is a standard lab test employed to diagnose diabetes mellitus. - Ammoniac silver nitrate solution may be reduced to metallic silver, producing a mirror-TOLLEN's Test. - Picric acid in alkaline medium is reduced to picramic acid. Color changes from yellowish orange to mahogany red. In acid solution sugar reduces less vigorously. ## Action of Strong Acid on Monosaccharides - With conc. Mineral acids like H2SO4 the monosaccharides get decomposed. - Pentoses yield cyclic aldehyde 'furfural'. - Hexoses are decomposed to 'hydroxymethyl furfural which decomposes further to produce laevulinic acid, CO,CO2The furfural producta can condense with certain organic phenols to form compounds having characteristic color. It forms the basis of certain tests used for detection of sugars. E.g. Barfood's test - Molisch's Test: With alpha-naphthol (in alcoholic solution) it gives purple ring. - A nennitive reaction but not specific. It is used as Group test of carbohydrate. - Seliwanoff's test: With resorcinol, a cherry red colour is produced. It is characteristic of D-fructose. - Other tests are anthrone test, Bial-orcinol test. ## Oxidation of Sugar 1. Under mild condition, oxidation of an aldoses with Br2-water converts the aldehyde group to a carboxyllic group ie. Aldonic acid D-gluconic acid, mannonic acid, galactonic acid. 2. Under strong conditions, like oxidation of aldoses with conc.HNOS under proper conditions convert both aldehyde and primary alcohol group to-COOH group, forming dibasic sugar acids, the Saccharic acid or aldaric acid. D-Glucosaccharic acid or D-Glucaric acid D-Galactose forma D-Mucic acid, D-Mannose, mannaric acid Mucic acid forma insoluble crystals and is the basis for a test for galactose. 3. When only the primary alcohol group of an aldose is oxidized to -COOH group, without oxidation of aldehyde group, a uronic acid is formed. - D-Glucuronic acid, D-Galacturonic acid, D-mannuronic acid - Due to presence of free -CHO group they exert reducing action. ## Osazone Formation - Used to differentiate simple sugar in biological fluids by their varied form of osazone and rate of osazone formation. ### Preparation - They are obtained by adding a mixture of phenylhydrazine hydrochloride and sodium acetate to the sugar solution and heating in boiling water bath for 30 to 45 mins. The solution is allowed to cool slowly by itself.crystala are formed. A coverslip preparation is made on a clean alide and seen under microscope. - Free carbonyl group of sugars react with phenylhydrazine to form phenylhydrazone. - With excess phenylhydrazine, the adjacent C-atom of carbonyl group react with phenylhydrazine to form yellow compounds called osazone. ## Reduction to Form Alcohols - When treated with reducing agents such as Na-amaigam, H2 reduces sugars. (catalytic hydrogenation) H O - R - H - H - R - OH - Aidose yields corresponding alcohol, ketose forms two alcohols e.g. glu forms sorbitol, mannose forma mannitol, fructose forma sorbitol and mannitol, galactose forms ducitol, ribose forma ribital - Sorbitol, mannitol and ducitol are used to identify bacteria colonies. - Mannitol is used to reduce intercranial tension by forced diuresis. The osmotic effect of sorbitol and ducitolcause changes in tissues when they accumulate abnormally e.g cataract of eye lens ## Other Sugar Derivatives of Biomedical Importance - **Phytic Acid** - The hexaphosphoric, ester of inositol. - Forma insoluble salts with Ca, Mg, Fo" & Cu"Prevent their absorption from diet in the small intestine. So it is better to avoid maize and legumes in diet of annemic patient with iron rich diet or haematinic drugs. - **Deoxysugars:** Biologically important ones are - 2-Deoxyribofuranose - Present in DNA - L-Fucose - 6-deoxy-L-galactose - Important component of some cell membrane glycoproteins & blood group antigens, ## Aminosugars - Formed from the corresponding monosaccharide by replacing the -OH group at C2 with an amino (NH2) group. - Non reducing, and do not form osazones - Are important constituents of GAGs & some types of glycolipids eg gangliosides. - Are conjugated with acetic acid &/or sulfate to form different derivatives. E.g. N-acetyl glucosamine - Glucosamine (2-amino-D-glucose) - Galactosamine - Mannosamine - Glucosamine - 2,6-bisulfate (heparin) - N-acetyl-glucosamine (hyaluronic acid) - N-acetyl-galactosamine (chondroitin sulfate) ## Aminosugars Acids - Are formed of 6-C aminosugars linked to 3-C acid. - Examples: - **Neuraminic acid:** (Mannosamine + Pyruvic acid) - **N-acetylneuraminic acid NANA(Sialic acid):** Enters in the structure of many glycolipida & glycoproteins. - **Forms an important structure of cell membrane & has many important functions:** e.g. important for cell recognition & interaction. - **Muramic acid:** (glucosamine + lactic acid) ## Glycosides - Formed by a reaction between the anomeric carbon (in the form of hemiacetal or hemiketal) with alcohols or phenols. - Are named according to the reacting sugar. - And glycosidit linkage is named according to the type of parent sugar eg glucosidic, galactosidic or fructosidic linkages. - Monosaccharide units may condense in the form of di-, oligo- & polysaccharides where the second sugar reacts as an alcohol & condenses with the anomeric carbon by removal of H2O. - A sugar may also condense with a non-sugar radical (aglycon) - **Nucleoside:** (pentose sugar + nitrogenous base) ## Biomedically Important Glycosides - **Cardiac glycosides:** obtained from digitalis - They all contain steroids as aglycone. - Digitalis glycosides include digitoxin, gitoxin, gitalin and digoxin - **Quabain:** It gains interest as class 1C antiarrhythmic drug that inhibit active transport of sodium in myocardium in vivo. It prevents paroxysmal atrial fibrillation. - **Philoridzin:** Obtained from the root and bark of apple tree. It blocks transport of sugar across mucosal cells of small intestine and renal tubular epithelium. Displaces Na+ from the binding site of carrier protein and prevents the binding of sugar molecule and produces glycosuria. - **Streptomycin, the well known antibiotic is also a Glycoside.** ## Disaccharides - 2 monosaccharides joined by a glycosidic linkage. - **A. Sucrose (a-D-glucosyl (1>2) B-D-frctoside) or (a-D-glucopyranosyl (1>2) B-D-fructofuranoside):** - Preasent in cane kugar and various fruits. - Contain glu and fru in 1>2 linkage. - Not a reducing sugar, do not form osazones - Hydrolysed sucrose has a reducing action (Test for sucrose). - Sucross (+66.50) when hydrolysed produces Imol of glu (+52.5) and 1mol of fru (-920). Product of hydrolysis changes dextro to levoratatory - That is, plane of rotation is inverted. It is called invert sugar. - The enzyme that hydrolyses sucrose is called sucrase or invertase. - Honey contains invert sugar. Invert sugar is sweeter than sucrose. - **B. Lactose: (D-galactosyl B(1>4)-glucose)** - Contains galactose and glu in B(1>4) linkage. - A reducing sugar, tits milk sugar. - Lactose may be alpha or bete depending on Ci of glu. It forms osazones. - **Lactose:** - CH2OH - CH2OH - OH - OH - OH - **C. Maltose** - Contains 2 glu residues in a(1>4) linkage. - A reducing sugar. Forms osazones. - **Maltose** - CH2OH - CH2OH - CH2OH - OH - OH - **D. Isomaltose** - Contain 2 glu in a-(1>6) linkage. - A reducing sugar. - Product of partial hydrolysis of glycogen and atarch. - It is hydrolysed into 2 glu units by oligo-1,6-glucosidase (intestinal enzyme) - **Cellobiose:** 2 glu in B(1>4) linkage - **Trehalose:** 2 glu in a-(1>1) linkage (in yeast, fungi) ## Polysaccharides - Polymerised product of many monosaccharide units. 1. **Starch** - It is the reserved carbohydrate of plant kingdom. - It is made up of: - a-amylose- (10-20%), soluble, glcose unita in n1>4 glycosidic bonds to form unbranched chain. - amylopectin-glucose unita, highly branched at a1>6 linkages. Insoluble. Absorba water to form paste-like gel. - Starch forms blue coloured complex with iodine. Colour disappear on heating, reappears on cooling (Test for starch). - Starch is non-reducing. (free sugar groups are negligible). 2. **Glycogen** - It is the reserved carbohydrate in animals. - It is composed of glucose units in al>4 glycosidic bonds, also a1>6 at branching points. - Innor core of glycogen contain a primer protein ie glycogenin. - Glycogen is more branched and more compact than amylopectin. 3. **Cellulose** - Supporting tissues of plants (99% in coton, 50% in wool). - Most abundant organic material in nature. - Made up of glu units in B1>4 linkages, no branches. B1>4 bonds are hydrolysed by cellobiase. - Animals and humans can not digest cellulose(no cellobiase). - Herbivorous animals have large caecum that contains bacteria which can hydrolyse cellulose. - Termites also digest cellulose with the help of intestinal bacteria - Cellulose has several commercial applications 4. **Dextrans** - Highly branched homopolymers of glu with 1>6, 1>4 and 1>3 linkages. - Produced by microorganisms. They are used as plasma volume expanderin intravenous infusion for treatment of hypovolemic shock. - **Note:** Dextran is different from Dextrin. 5. **Inulin:** - Long chain homoglycan composed of D-fructose units with repeating B1>2 linkages. - Reserve COH in dahlia, onions, garlic etc. - Clinically used to find renal clearance value and glomerular filtration rates. 6. **Chitin** - Present in exoskeletons of insects and crustacean. - Composed of units of N-acetyl glucosamine with B1>4 linkages. ## Heteroglycans 1. **Agar:** - Prepared from sea weeds. Contains gal, glu, and other sugars. - Used as supporting agent to culture bacteria colonies. - Agarose is made up of gal combine with 3,6-anhydrogalactose units, used as matrix for electrophoresis. 2. **Mucopolysaccharides- or glucosamine glycans (GAG):** - Contain uronic acid and amino sugars. - Mucopolysaccharides + proteins form mucoproteins e.g. hyaluronic acid, heparin, chondroitin sulfate, dermatan sulfate, keratan sulfate etc. ## Glycoproteins and Mucoproteins - If COH chains are attached to a polypeptide it forms proteoglycan generally - If COH content is less than 10% i.e. glycoproteins - If COH contemt is more than 10% ie mucoprotein - They are seen in almost all tissues and cell membranes. Their functions include their roles as enzymes, hormones, transport proteins, structural proteins and receptors. ### Bacteria Cell Wall - Major constituents are heteropolysaccharides consisting of repeating units of N-acetyl muraminic acid (NAM) and GluNac - Synthesis of this complex polysaccharides is inhibited by penicillin. (This is responsible for bactericidal action of penicillin) ## Hyaluronic Acid - Present in connective tissues, tendons, synovial fluid, vitreous humor. Serves as lubricant in joint carvities ## Heparin - An anticoagulant used in blood sampling. - Used in vivo in thromboembolic conditions to prevent intraventricular coagulation. - Commercial preparations of heparin is from lung tissues. ## Chondroitin Sulfate - Present in ground substances of connective tissues in cartilage, bone, tendons, cornea and skin.