Module 7: Introduction to Carbohydrates PDF

9/29/24 Learning Objectives MODULE 7: At the end of this module, you should be able to:...

9/29/24 Learning Objectives MODULE 7: At the end of this module, you should be able to: Know the major sources and the major functions of carbohydrates in Introduction to Carbohydrates the human body Be able to differentiate classifications of carbohydrates Be familiar with the functional groups present in carbohydrates molecules C-NMC2LEC First Semester, AY 2024-2025 University of the Assumption University of the Assumption 1 2 Occurrence and Functions of Carbohydrates CARBOHYDRATES Carbohydrates -consists of polyhydroxyaldehydes or polyhydroxyketones and their derivatives Øare the most abundant class of bioorganic molecules on planet Earth. Functional Groups present: Vital Functions of Carbohydrates: Øconstitute about 75% by mass of dry plant materials 1. –OH (hydroxyl group) 1. Storehouses of chemical energy e.g. glucose, starch, Photosynthesis glycogen ØGreen (chlorophyll-containing) plants produce carbohydrates via this process 2. carbonyl group ØIn this process, carbon dioxide from the air and water from the soil are the 2. Supportive structural components in plants and some reactants, and sunlight absorbed by chlorophyll as the energy source. animals e.g. cellulose and chitin 3. Essential components of the genetic material e.g. D- ribose, 2-deoxy-D-ribose 4. Ligands and receptors in cellular communication e.g. lectins University of the Assumption University of the Assumption 3 4 Two main uses of carbohydrates in Plants Two main uses of carbohydrates in Plants 1. Cellulose 1. Starch Øcarbohydrates serve as structural elements Ø a carbohydrate commonly found in nature and one of the primary sources of food Øa central component in plant cell walls energy for human beings Øprovides rigidity and structure of the cell Øregularly eaten in the form of wheat, rice, potatoes, and other staple foods cultivated throughout the world Øyour body needs to break starches down into sugars to use them for energy University of the Assumption University of the Assumption 5 6 1  9/29/24 Functions of carbohydrates in the Human Body 1. Carbohydrate oxidation provides energy. SIMPLE SUGARS 2. Carbohydrate storage, in the form of glycogen, provide short-term energy reserve. 3. Carbohydrates supply carbon atoms for the synthesis of other biochemical substances (proteins, lipids and nucleic acids). 4. Carbohydrates form part of the structural framework of DNA and RNA. COMPLEX 5. Carbohydrates linked to lipids as a structural components of cell membrane. CARBOHYDRATES 6. Carbohydrates linked to proteins- function in a variety of cell-cell and cell-molecule recognition processes. University of the Assumption University of the Assumption 7 8 CLASSIFICATION OF CARBOHYDRATES 1. MONOSACCHARIDES Ø cannot be hydrolyzed to simpler components Ø general formula, Cn H2n On , where n varies from 3 to 8 Ø e.g. glucose, fructose, galactose 2. DISACCHARIDES Ø consist of two monosaccharide units joined by a glycosidic bond, Ø e.g. sucrose, lactose, maltose 3. OLIGOSACCHARIDES Ø consist of 3-10 monosaccharide units, e.g. raffinose, stachynose 4. POLYSACCHARIDES Ø consist of many monosaccharide units, e.g. glycogen, starch, cellulose University of the Assumption University of the Assumption 9 10 MONOSACCHARIDES Classes: 1. based on carbonyl group present 2. based on number of C atoms Ø Aldoses- contain the aldehyde group, e.g. Ø triose- contains 3 C glucose, galactose Ø tetrose- contains 4 C Ø Ketoses- contain the keto group, e.g. Ø pentose- contain 5 C fructose University of the Assumption University of the Assumption 11 12 2  9/29/24 L and D Sugars Monosaccharides may be in the L or D form. The D form is most common. L and D sugars are enantiomers (mirror images) of each other. If the -OH group on the bottom chiral center is on the right, the sugar is a D sugar. If the -OH on the bottom chiral center points to the left, the sugar is an L sugar. University of the Assumption University of the Assumption 13 14 Fischer and Haworth Projections Structure of Monosaccharides (Fischer to Haworth) Monosaccharides may be drawn in either the Fischer (straight line) or Haworth projection (cyclic). University of the Assumption University of the Assumption 15 16 DISACCHARIDES Like monosaccharides, disaccharides are crystalline, water-soluble substances. Sucrose (table sugar) & Lactose (milk sugar) Hydrolysis of a disaccharide produces two monosaccharide units University of the Assumption University of the Assumption 17 18 3  9/29/24 OLIGOSACCHARIDE POLYSACCHARIDE “oligo” comes from the Greek The number of oligos, which means small or polysaccharide varies from few. few hundred units to over OL-ee-go-SACK-uh-ride 50,000 units. “Free” oligosaccharide are Undergo hydrolysis given seldom appropriate conditions to produces monosaccharides Fun Fact! Complete hydrolysis of oligosaccharide produces The paper on which our biochemistry book is printed is several monosaccharides mainly cellulose. University of the Assumption University of the Assumption 19 20 Learning Objectives MODULE 7.2: At the end of this module, you should be able to: Discuss the important monosaccharides namely glucose, fructose, and Classifications of galactose. Discuss the important disaccharides namely sucrose, maltose, and Carbohydrates lactose. Discuss the important polysaccharides namely starch, dextrin, glycogen, cellulose, pectin, agar-agar. Illustrate how carbohydrate is synthesized through dehydration C-NMC2LEC First Semester, AY 2023-2024 reaction. University of the Assumption University of the Assumption 21 22 Classification of Carbohydrates Classification of Carbohydrates Carbohydrates are classified according to the number of sugar 1. Monosaccharides molecule or saccharide groups contained in their molecules. simple sugars containing 1 sugar molecule or saccharide group 1. Monosaccharides 2. Oligosaccharides § Trioses (C3H6O3) - glycerose, dihydroxyacetone A. Disaccharides § Tetroses (C4H8O4) - threose, erythrose, erythrulose B. Trisaccharides § Pentoses (C5H10O5) - arabinose, ribose, xylose § Hexoses (C6H12O6) - glucose, galactose, mannose 3. Polysaccharides § Heptoses (C7H14O7) - mannoheptułose University of the Assumption University of the Assumption 23 24 4  9/29/24 Classification of Carbohydrates Classification of Carbohydrates 1. Monosaccharides 2. Oligosaccharides are classified by the: sugars which upon hydrolysis yields only small number of § location of the saccharide sugar molecules usually from 3 to 10 carbonyl group (as aldose or ketose) A. Disaccharides (C12H22O11) – are anhydrides of monosaccharides. § number of carbon Anhydride: compound produced by the removal of water molecule atoms in the carbon skeleton § reducing disaccharides (lactose, maltose, cellobiose) § non-reducing disaccharide (sucrose) University of the Assumption University of the Assumption 25 26 Classification of Carbohydrates Classification of Carbohydrates 2. Oligosaccharides 3. Polysaccharides B. Trisaccharides (C18H32O16) – derived from 3 hexoses by the sugars which yield a number of molecules of monosaccharides upon elimination of 2 molecules of water hydrolysis § Ex: Raffinose (glucose + fructose + galactose) are polymers (substances having large molecules consisting of repeated units) with units that are anhydride of a monosaccharide A. Starch group (starch, glycogen, insulin, dextrin) a. Pentosans (C5H8O4) – anhydride of pentoses (e.g. gum arabic) b. Hexosans (C6H10O5) – anhydride of hexoses, about 1,800 – 3000 units (e.g. glucosans, fructosans, galactans) University of the Assumption University of the Assumption 27 28 Classification of Carbohydrates The Monosaccharides (C6H12O6) 3. Polysaccharides B. Mixed polysaccharide – compound which give various products upon hydrolysis. In some cases, it gives even non-sugar derivatives. University of the Assumption University of the Assumption 29 30 5  9/29/24 The Monosaccharides (C6H12O6) The Monosaccharides (C6H12O6) 1. Glucose 1. Glucose known as dextrose, grape sugar, corn sugar its composition includes: an aldehyde group, 4 found in ripe fruits, young vegetables, honey, molasses, and blood secondary alcohols, 1 primary alcohol in blood it is present normally in about 80-120 mg/dL administered to patients in the concentration of 5-50% sterile solutions in case the patient is not when the blood limit exceeds the normal, glucose is converted to glycogen able to take nourishment by mouth excess glucose is secreted in the urine and the condition is known found in corn syrup which is used to feed infants as glycosuria used in making smooth candies it is the most important monosaccharide, physiologically optical rotation is +52.50 University of the Assumption University of the Assumption 31 32 The Monosaccharides (C6H12O6) The Monosaccharides (C6H12O6) 2. Fructose 2. Fructose also called levulose and fruit sugar the only sugar component of insulin, a the sweetest sugar polysaccharide which is an anhydride of found in ripe fruits, young vegetables, honey, maple syrup and fructose found in tubers of Jerusalem artichoke molasses and in the bulbs of onions when formed with glucose on hydrolysis of cane sugar, it is called it is a keto hexose and also enhancing invert sugar monosaccharide it is absorbed more slowly in the small intestine than glucose its composition includes: a ketone group, 3 secondary alcohols, 2 primary alcohol optical rotation is -92o University of the Assumption University of the Assumption 33 34 The Monosaccharides (C6H12O6) 3. Galactose less sweet than glucose not found free in nature formed on hydrolysis of lactose and agar-agar a constituent of cerebrosides: a compound lipid in brain and nerve tissue this sugar is not found in the circulation optical rotation is +50.5° University of the Assumption 35 36 6  9/29/24 The Disaccharides (C12H22O11) The Disaccharides (C12H22O11) sucrose, maltose, and lactose 1. Sucrose anhydride of hexoses glucose + fructose linkage is made from aldehyde group of one monosaccharide with the also known as cane sugar or beet sugar, table sugar hydroxyl or ketone group of another monosaccharide (hexose) found in sugar cane, sugar maple, beets, vegetables, and fruits if both aldehyde and ketone group are involved in the linkage as in used in sweetening foods, candies, and cakes sucrose (glucose and fructose) the reducing power is lost a non-reducing sugar; also referred to as invert sugar 50-75% of invert sugar is used in treating varicose veins maltose and lactose have reducing power since the linkage is in aldehyde and hydroxyl group next only to fructose in sweetness optical rotation is +66.5° University of the Assumption University of the Assumption 37 38 The Disaccharides (C12H22O11) 2. Maltose glucose + glucose found in nature, present temporarily in sprouting grains formed from the hydrolysis of starch in the grains by means of diastase found in brown crust of bread formed by the linkage of 2 molecules of glucose (aldehyde-OH) a reducing disaccharide has a slight laxative property optical rotation is +136° University of the Assumption 39 40 The Disaccharides (C12H22O11) The Disaccharides (C12H22O11) 3. Lactose 3. Lactose glucose + galactose least fermentable of the sugars hence it is the ideal constituent of known as milk sugar milk because brewer's yeast does not contain lactose which is the the least soluble and the least sweet enzyme that hydrolyze lactose However, lactose in milk undergoes lactic acid fermentation when synthesized in the mammary glands from glucose and galactose milk sours or when treated with certain wild yeast cultures in the 6.8% in human; 4.88% in cow, 2.5% in reindeer making of yogurt essential food for infant to furnish galactose which is needed in the optical rotation is +55.5° formation of galactolipids or cerebrosides in the brain and nerve tissue digested more slowly than sucrose and maltose University of the Assumption University of the Assumption 41 42 7  9/29/24 The Disaccharides (C12H22O11) University of the Assumption 43 44 The Disaccharides (C12H22O11) The Polysaccharides the most abundant and important are starch, dextrin, glycogen, and cellulose which are anhydrides of glucose often called hexosans and glucosans Pentoses rarely occur as such in nature. They are usually found as polysaccharide pentosans and are obtained by hydrolysis with dilute acids. Examples: (c) Dehydration reaction in the synthesis of lactose § Arabinose: aldose obtained from gum arabic, cherry gum & beet pulp § Xylose – an aldose formed from straw, corn cobs § Ribose – constituent of nucleic acid University of the Assumption University of the Assumption 45 46 The Polysaccharides The Polysaccharides 1. Starch 1. Starch the principal plant-storage form of carbohydrate as well as the composed of a large number of glucose units united as in maltose to principal carbohydrates in the diet beyond the infant stage form long-chained starch molecules. It is composed of amylose found in cereals, roots, tubers, mature vegetables, and unripe fruits (unbranched chains of glucose) and amylodextrin (branched chains its grain is enclosed by a layer of amylopectin, one of the of glucose) components of starch which is ruptured on heating or through the contain phosphorus, while wheat starch contains nitrogen assistance of certain ferments Starch on hydrolysis, forms dextrin of various complexities, with a more digestible when cooked than when uncooked because of the molecule of maltose splitting off at each stage in the hydrolysis, until rupture of this outer layer and the splitting up of the starch grains into finally all of the starch has been hydrolyzed into maltose. This is in smaller colloidal particles turn hydrolyzed into glucose (e.g. ripening of fruits; maturing of vegetables) University of the Assumption University of the Assumption 47 48 8  9/29/24 The Polysaccharides 2. Dextrin the polysaccharide with the smallest number of glucose units are of various complexities: A. Amylodextrin – gives purple color with iodine B. Erythrodextrin – gives red color with iodine C. Achrodextrin – colorless with iodine found in small amounts in germinating grains formed upon hydrolysis of starch through the assistance of strong heat, enzymes, or dilute acids and heat University of the Assumption 49 50 The Polysaccharides The Polysaccharides 2. Dextrin 3. Glycogen used in place of glue on stamps and envelopes because of their manufactured in the body from glucose in the blood gummy consistency storage form of carbohydrate in animals as starch is in plants have a slightly sweet taste, which is noticeable in the crust of bread found in all muscles and in the liver, in oysters, and scallops and toast, where the heat of the oven or toaster hydrolyses the starch glycogen in the liver is used up rapidly in emotional reactions like fear into dextrins and anger, and in excessive exercise its molecule is believed to be much like starch molecule, only slightly smaller. Upon hydrolysis, glucose is formed. This glucose helps maintain the normal glucose content of the blood and furnishes energy on oxidation in the tissue. University of the Assumption University of the Assumption 51 52 The Polysaccharides The Polysaccharides 4. Cellulose 4. Cellulose found in the cell walls and woody fibers of all plants outside the body cellulose, may be hydrolyzed into glucose by boiling made up of as many as 1,800 to 3,000 glucose units with dilute acids because of absence of enzymes for the hydrolysis of cellulose in the Uses of cellulose: digestive tract, it passes unaltered into the large intestines. It § in the manufacture of cellulose nitrate or nitrocellulose called gum stimulates peristalsis and so aids in the elimination of wastes. cotton Herbivorous animals like horses, carabaos, cows, goats, and sheep § in the manufacture of celluloid, collodion, artificial leather, have ferments in their intestines which are capable of hydrolyzing photographic film, and quick drying lacquers cellulose into monosaccharides. Hence herbivorous animals are able § in the manufacture of synthetic fiber called rayon to obtain calorific food value from cellulose. University of the Assumption University of the Assumption 53 54 9  9/29/24 The Polysaccharides 5. Pectin yields the pentose sugar arabinose upon hydrolysis are mixtures of pentosans and salts of complex acids, apparently formed on oxidation of carbohydrates found in the peelings of many sour fruits and in vegetables, like citrus fruits, apples, carrots, santol, and many others it forms a jelly in combination with sugar and acid. It is used in making jams and jellies it is also used to control diarrhea and in the treatment of slow healing wounds and sores University of the Assumption 55 56 The Polysaccharides The Polysaccharides 5. Pectin 6. Agar-agar sterilized pectin solutions are used as a substitute for plasma in the contains galactans and is the most common mucilage which is a transfusion treatment for shock normal component of certain plants § Mucilages are odorless and tasteless absorb water very readily, forming colloidal dispersions that set to form rigid gels extracted from sea weeds commercially on esterification with sulfuric acid, it forms the sulfuric ester called agar which is used in making slants for the growth of bacterial colonies. University of the Assumption University of the Assumption 57 58 The Polysaccharides University of the Assumption 59 60 10  9/29/24 ------------------------------------------ End of Module 7 ------------------------------------------------------------ Readings and References: Stoker, H. Stephen. Biochemistry. Cengage Learning Asia Pte Ltd, 2016 Hart, Harold, et al. Organic Chemistry: A Brief Course. Cengage Learning Asia Pte Ltd, 2012 Stoker, H. Stephen Exploring General, Organic and Biochemistry. Cengage Learning Asia Pte Ltd, 2013 University of the Assumption 61 62 11