Chemistry of Carbohydrates PDF

# CHEMISTRY OF CARBOHYDRATES ## MCI COMPETENCY BI 3.1 ### SAQ 1. Define and classify carbohydrates with suitable examples. 2. Biologically important Disaccharides. 3. Homopolysaccharides 4. Heteropolysaccharides and GAGs (Most Imp) 5. Dietary Fibres and it's role in diet. 6. Glycemic index 7. Fun...

# CHEMISTRY OF CARBOHYDRATES ## MCI COMPETENCY BI 3.1 ### SAQ 1. Define and classify carbohydrates with suitable examples. 2. Biologically important Disaccharides. 3. Homopolysaccharides 4. Heteropolysaccharides and GAGs (Most Imp) 5. Dietary Fibres and it's role in diet. 6. Glycemic index 7. Functions of Dextran 8. Isomers of Monosaccharides. ### Important clinical cases. #### Mucopolysaccharidoses 1. **Hurler syndrome** 2. **Hunter Syndrome** ##### A 13 yr old child presented with distention of abdomen, edema feet and stunted growth On examination: - Short stature - Coarse facies - Short neck - Corneal clouding - Hepato splenomegaly - X-ray - skeletal abnormalities Laboratory test - ↑ Heparan sulfate & Dermatan sulfate - Decreased Iduronidase activity in WBC Diagnosis: Mucopolysaccharidoses - Hurler syndrome. ##### A child brought to the Hospital with distended abdomen and stunted growth On examination: - Short stature, coarse facial, short neck - No corneal clouding - Hepato splenomegaly - x-ray - skeletal abnormalities Laboratory test: - ↑HS 4↑ DS - Decreased activity of Iduronate sulfatase Diagnosis: Mucopolysaccharidoses - Hunter syndrome ## CARBOHYDRATES **Definition**: Polyhydroxy aldehydes or ketones or compounds which produce them on hydrolysis are known as carbohydrates **Old definition**: Hydrates of carbon & formula CnH2nOn but Lactic acid, acetic acid are not carbohydrates and deoxyribose is a carbohydrate but Not Fits In to CnHanOn. ## SAQ: Define and classify carbohydrates with suitable examples. ### Classification | Type | Definition | Example | |---|---|---| | Monosaccharides | Simple sugars, single unit | Glucose, fructose, galactose | | Disaccharides | Two sugar units, connected by glucoside bond | Sucrose, lactose, maltose | | Oligosaccharides | 3-10 sugar units | Stachyose, Raffinose | | Polysaccharides | More than 10 units | Starch, glycogen, cellulose | **On the basis of**: | No. of C-atoms | Functional Group | |---|---| | Triose 3C | Glyceraldehyde, Erythrose | DHA.. | | Tetrose 4C | Erythrose | Erythrulose | | Pentose 5C | Ribose | Ribulose | | Hexose 6C | Glucose | Fructose | | Heptose 7C | Glucoheptose | Sedoheptulose | ### Tests for Monosaccharides (Mnemonic - MBBS) 1. **Molisch test**: It is a group test for all carbohydrates. 2. **Benedict's test**: for reducing sugars: Bedside test for detection of sugar in urine. Semiquantitative test, gives idea about approximate amount of Beducing sugars in urine (useful in DM). Green 0.5gro%, Yellow- 1 gro%, orange-1.5gm%, Red-2gm, Brick Red >2gm. 3. **Barfoed's test**: for monosaccharides only. 4. **Seliwanoff's test**: for ketose sugar eg. fructose ## Disaccharides **Reducing** 1. **Lactose**: Glucose + Galactose α(1-4) glucosidic bond 2. **Maltose**: Glucose + Glucose α(1-4) glucosidic bond **Osazone** Carbohydrate derivatives formed when reducing sugars are reacted with phenyl hydrazine at boiling temp. - **Lactosazone** - powder puff-shaped Crystals. - **Maltosazone** - petal shaped & sun flower shaped crystall. **Non-reducing** 1. **Sucrose** [Glucose+ Fructose] α(1-β) glucosidic linkage C₁ and C₂ both are involved in the linkage formation, Not available for osazene formation. *Does Not form Osazone* **Difference between glucose, fructose and mannose** - Glucose :Differ around C₁ & C₂ - Fructose : This difference get marked when phenyhedrazine get attached at C₂ Needle shaped - Mannose : Broom shaped ## Polysaccharide **Homopolysaccharides** [composed of same sugar units] **Heteropolysaccharides** [constituent monosaccharide are different] ## HOMOPOLYSACCHARIDES > 10 Monosaccharides Constituent monosaccharides same Example: G-G-G-G-G-G-G-G-G-G 1. **Starch**: storage form of carbohydrate in plant Composed of Amylose + Amylopectin 1. Straight chain Polymer of D-glucose 20%. of starch Water soluble α(1-4) glycosidic linkage between glucose molecules. 2. Branched chain Polymer of D-glucose 80%. of starch Insoluble in water α(1-4) in straight chain & α(1-6) in branch point 2. **Glycogen**: Multibranched polysaccharide of glucose. Main storage form of glucose in liver and skeletal muscle in animals. Homopolysaccharide of glucose with α(1-4) glycosidic linkage in linear chain and α(1-6) at branching point. Branching makes molecule more globular, compact and less space consuming. 3. **Cellulose**: Polymer of glucose with β(1-4) grecosidic linkage can't digested by humane due to lack of enzyme Cellulose acts as a dietary Fibre Increased bulk of stool, relieves constipation Decreases absorption of glucose and cholesterol from intestine. Important in management of DM and obesity 4. **Dextrin**: Partias degradation product of starch. Hemopolynoe? 5. **Dextran**: It is a complex, branched, homopolymer of glucose. It is a plasma volume expander and used in the treatment of byporolumic shock (MW > 60000 Da) Also has antithrombotic activity (MW 40000 Da) It is used in eyedrops as a Lubricant It provides parenteral nutrition. 6. **Inulin**: -polymer of fructose used in assessment of glomerular filtration rate Better marker for measurement of GFR over Urea and creatinine. ↓ Filtered through glomerulus Neither reabsorbed, Nor secreted by the renal tubuler. 7. **Chitin**: - present in exoskeleton of insects, cell walls in fungi Polymer of N-acetylglucosamine [amine derivative of glucose] ## SAQ: Enumerate important homopolysaccharides. Write about their functions. ## HETEROPOLYSACCHARIDES Composed of More than 10 sugar wuits and constituent unite (monosaccharides) are different. 1. **Glycosaminoglycans (GAG)/Mucopolysaccharider** 2. **Agar**: Made up of Glucose & Galactose, wed as a bacterial ... media. 3. **Agarose**: - Made up of Galactose + anhydro galaciopyranose wed for protein and Nucleic acid electrophoresis. 4. **Pectin**: - Main content is galaturonic acid, used in food al gelling agent, Also It is a dietary Fibre. ## GLYCOSAMINOGLYCANS [GAG] Mucopolysaccharides Heteropolysaccharides composed of repeating units of disaccharide ↓ composed of Amino sugar +[ Uronic acid Glucosamine D-Glucuronic acid Galactosamine L-Iduronic acid GAGS contains Negatively charged groupe [coo, Sou, Acetyl] ↓ Repulsion from each other Slippery achon [Hyaluronic acid, Mucous J Shock absorbent in [Synovial pluid, vitreous humor, extracellular matrix] **Examples**: - **Hyaluronic acid** - **Chondroitin sulfate** MCQ *Dermatan Sulfate-N-Acetyl Galactosamine + L-Iduronic acid - **Heparin** - **Heparan sulfate** MCQ Keratan sulfate - **No uronic acid** - **N-Acetyl glucosamine + Galactose** ## GAGS | GAGS | Composition | Present in | Functions | |---|---|---|---| | **1. Hyaluronic acid** | N-Acetyl glucosamine + D-glucuronic acid No sulfate group* *MCQ* | Synovias Huid vitreous humor | Lubricant Shock albsorbent cell migration Wound repais. | | **2. Chondroitin Sulfate** | N-Acetyl galactosamine + D-glucuronic acid | curtlage Bone Tendon | Shape and structure | | **3. Dermatan Sulfate** | N-Acetyl galactosamine + L-Iduronic acid | skin Valva | Shape & Structure | | **4. Heparin** | Glucosamine + glucuronic acid/ Iduronic acid | Lunge mast cells Blood skin endothelium | Anticoagulant* *MCQ* causer release of LPL from capillary endothelium | | **5. Heparan Sulpate** | Glucosamine + glucuronic acid/ Iduronic acid/ | Blood skin Kidney basement membrane | -Negative charge on MCQ Atachment of LPL TO ENL | | **6. Keratan Sulfate** | N-Acetyl glucosamine + Galactose mса | Comea cartilage | Transparency of Comea shape & structure | ## SAQ: Enumerate different glycosaminoglycans. Add a note on their role in our body. **Proteoglycan**: Mainly contains carbohydrates <اعه (GAGS) **Glycoproteins**: > 95% proteins <5% carbohydrates ## GLYCEMIC INDEX [GI] **Definition**: It is a Value used to measure how much specific foods increases your blood sugar level. It is a system of assigning a number to carbohydrates Containing foods according to how much food increases blood sugar. **Importance**: - To lose weight or to maintain a healthy weight - In the management of chronic diseases related to obelity such as DM & coronary artery diseases. **Examples** 1. **Low glycemic index foods**: green vegetables, Egge 2. **Medium glycemic index foods**: sweet corn, Bananas, oat 3. **High glycemic index foods**: white rice, potatoes, breade, sugary poode & drinks **GI of** - Glucose → 100 - Rice → 87 - Ice cream → 51 - kidney beane → 24 - Soyabeans → 16 ## SAQ:- Define glycemic index. Mention glycemic index of Some important foodstuffs. ## SAQ: Describe the importance of glycemic index. ## DIETARY FIBRES **BAQ:- Enumerate four important dietary fibres.** **SAQ: What is a role of dietary fibre in human health?** **Definition**: plant components that are NOT broken down by human digestive enzymes. **Names**: - Cellulose - Hemicellulose - Pectin - Lignin - Gums - Resistant starch - Oligosaccharides - Lactulose etc. **Sources**: Pruits, dark green vegetables, whole grains, Legumes, oats, rye, root tubers, almonde etc. **Mechanism of action** - Bulking (Absorb water) - Viscosity (Thicken the content of GIT) - fermentation **Important functions** 1. Increasse bulk of stool and relieves constipation 2. Helpful in weightloss 3. Decreases absorption of glucose from intedine and helps in reduction of blood sugar level in DM. 4. Decreases absorption of cholesterol from intestine and help to reduce cholesterol in patient with CAD, Atheroscleroes, DM etc. 5. Reduces the risk of colon cancer 6. Helpful in gastrointestinal disorders ## ISOMERS **Stereoisomers**: Compounds having samo moleculas formula but differ in orientation of groups in space. **Example**: D-Glucose and L-Glucose | | D-Glucose | L-Glucose | |---|---|---| | Formula | CHO H- C-OH HO-C-H H-C-OH CH2OH | CHO HO-C-H H-C-OH HO-C-H CH2OH | | Orientation | Orientation of -OH group to right/Left around the penultimate carbon atom | Orientation of -OH group to right/Left around the penultimate carbon atom | **Functonal Isomers**: compounds having same molecular formula but different funchonal groups. **Example**. Glucose [CHO], fructose [C=0] **Epimers** & Compounde having same molecular formula but differ around single c-atom, other than amomesic carbon. **mca** + Examples Glucose and Galaebse are epimers at 4th Glucose and Maunose are epimers at 2nd **Optical isomers**, optically active compounds that differ in their direction of rotation of plane polarized light to the right (+) or d porm to the left (-) or I form **Anomers**: Same molecular formula but differ in orientation of groups around anomeric C-atom. [Carbony Carbon 1st in glucose] - CH2OH - - - - - -CH2OH - - - - - - α-D glucose 04 is below the plane away from Oxygen - β-D Glucose P-on is above the plane towards oxygen atom