Carbohydrates PDF - Biochemistry LEC

BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 Classification of Carbohydrates Introduction to Carbohydrates...

BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 Classification of Carbohydrates Introduction to Carbohydrates Classifications and Categories Chemical Formulas and Structures Carbohydrates are classified based on the Carbohydrates are polyhydroxyaldehydes number of carbon atoms, functional groups, or polyhydroxyketones. polymerization, optical rotation, anomers, They are compounds that yield these sugar units, glycosidic linkage, and components upon hydrolysis. reducing properties. Categories include monosaccharides, Characteristics and General Information disaccharides, and polysaccharides. Carbohydrates are often referred to as the Monosaccharides 'hydrate of carbon'. They consist of carbon, hydrogen, oxygen, Basic carbohydrate units that cannot be and sometimes nitrogen. further hydrolyzed under mild conditions. General formula: Cn(H2O)m. Have a sweet taste, are soluble in water, Commonly known as saccharides, sugars, and typically end with the suffix '-ose'. and starches. Examples include glucose, maltose, and Abundant in the plant world. ribulose. Functions of Carbohydrates Classification Based on Functional Groups Main energy source, with glucose being Aldoses contain aldehyde groups, while crucial for energy production and protein ketoses contain ketone groups. retention. Glyceraldehyde is the simplest aldose, and Act as a storehouse of chemical energy in dihydroxyacetone is the simplest ketose. the forms of glycogen (in animals) and Aldoses and ketoses are constitutional starch (in plants). isomers with the formula C3H6O3. Essential components of supportive structures in plants, crustacean shells, and Classification Based on Number of Carbon Atoms animal connective tissues. Carbohydrates are categorized into trioses, Play a role in nucleic acids and can be tetroses, pentoses, and hexoses based on found in coenzymes and hormones like the number of carbon atoms they contain. Acetyl Coenzyme A. Examples include glyceraldehyde and dihydroxyacetone (trioses), ribose and BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 arabinose (pentoses), and glucose and Additional Concepts fructose (hexoses). Glycemic Index and Carbohydrate Sources Structural Representations Glycemic index categorizes foods based on Fischer and Haworth Projections their impact on blood sugar levels. Good carbohydrates have a low glycemic Fischer Projection: Represents the open- index and are high in fiber, while bad chain form and D/L conformation of carbohydrates have a high glycemic index carbohydrates. and are often processed or refined. Haworth Projection: Depicts the cyclic chain Carbohydrates are macronutrients form and α/β conformation of essential for proper bodily functions, carbohydrates. sourced from both healthy (animal and Optical rotation and anomers are key plant sources) and unhealthy sources aspects represented in these projections. (processed foods, artificial sugars). Optical Rotation and Chirality Centers Functional Groups and Seatwork Carbohydrates have one or more chirality Identify functional groups and the number centers, affecting their optical rotation. of carbons in different carbohydrate Dextrorotatory (D) substances rotate light structures. clockwise, while levorotatory (L) substances Engage in exercises to differentiate rotate light anti-clockwise. between aldehyde and ketone functional Glyceraldehyde, the simplest aldose, has groups, as well as classify sugars based on one chirality center with two possible their carbon content. enantiomers. Classification and Optical Rotation Multiple Chirality Centers Chirality Center and D/L Classification Some sugars, like glucose, have multiple chiral centers, influencing their structural The configuration of the chirality center representations. farthest from the carbonyl group Glucose, for example, has four chirality determines if a monosaccharide is D or L. centers. Dextrorotatory (D) substances rotate light clockwise, while levorotatory (L) substances rotate light anti-clockwise. BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 The prefix D is used when the -OH group is Mutarotation and Glucose on the right side of the carbon chain, and L when it's on the left. Mutarotation leads to a change in optical Naturally occurring sugars are typically D rotation due to equilibrium shifts between sugars. anomers. Glucose, known as dextrose, is the most Haworth Projection and Cyclic Forms abundant monosaccharide and can be given intravenously to patients. Haworth Projection is an improvement over Normal blood glucose levels range the cyclic Fischer projection. between 3.5-7.8 mmol/l. When an aldehyde reacts with an alcohol, a hemiacetal is formed. Other Monosaccharides The C atom in the hemiacetal becomes a new chirality center called the anomer Fructose, also called levulose, is highly carbon. soluble and sweet, found in fruits and honey. Cyclic forms of monosaccharides can exist Galactose is an isomer of glucose, present in alpha and beta anomers. in milk sugar and some glycoproteins. Ribose is crucial for DNA and RNA structure, Fischer to Haworth Projection while D-ribose is important in ATP production. To cyclize D-glucose, the appropriate Xylose, an aldopentose, is used as a alcohol must be chosen to form a six- diabetic sweetener and diagnostic agent. membered ring. D-glucose can exist in alpha and beta Disaccharides and Glycosidic Bonds forms in Haworth projections. Ketohexoses like fructose form five- Disaccharides Composition membered rings with two anomers. Disaccharides consist of two Anomers and Mutarotation monosaccharides linked by a glycosidic bond. Anomers Classification Hydrolysis of disaccharides yields two monosaccharides. An alpha anomer has the OH group at the Examples include lactose (glucose + bottom of the anomeric carbon, while a galactose) and sucrose (glucose + beta anomer has it at the top. fructose). Mutarotation involves the conversion of alpha to beta anomers and vice versa. BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 Glycosidic Bond Formation Disaccharides and Monosaccharides Formation involves removing H and OH Disaccharides: Sucrose, Maltose, Lactose groups to form a water molecule. Monosaccharides: Glucose, Fructose A new bond is drawn from the anomeric Linking of two monosaccharides forms carbon to the carbon of the other residue. disaccharides The bond joining two monosaccharides is Formation of ring structures in called a glycosidic linkage. monosaccharides Types of Glycosidic Bonds Common Disaccharides Alpha (α) glycosidic bonds point down, Sucrose while beta (β) glycosidic bonds point up. Known as table sugar or cane sugar Glycosidic Bond Formation Composed of Glucose + Fructose Principal sources include sugar cane, sugar Steps of Glycosidic Bond Formation beets, sorghum, pineapple, and carrot root Considered the sweetest disaccharide with An H atom is removed from the hydroxyl high caloric content group (OH) bonded to the anomeric carbon Artificial sweeteners developed to reduce of the left-most residue, while an OH is caloric intake removed from any carbon in the right-most residue, forming a water molecule. Maltose A new bond is drawn from the oxygen (O) remaining on the anomeric carbon in the Also known as malt sugar left-most residue to the carbon from which Formed by Glucose + Glucose the OH was removed in the right-most Found in barley and used in brewing beer residue, oriented in the same direction as Produced by hydrolysis of starch, common the removed OH bond. in syrups Classification of Glycosidic Bonds Lactose α-glycosidic bond: Points down Found in milk, hence called milk sugar β-glycosidic bond: Points up Fermented by bacteria to form lactic acid Used in high calcium diets and infant foods Increases calorie intake without adding much sweetness BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 Lactose intolerance leads to digestive Cellulose issues due to the lack of lactase enzyme Sourced from wood, cotton, and paper Other Disaccharides Acts as a structural component in plants, insoluble in water Cellobiose: Obtained from cellulose-rich Not digestible by humans due to the lack of materials, used in bacteriology enzymes to break beta-glycosidic bonds Trehalose: Found in fungi, plants, and Used in foods as a bulking agent and in insects industries like textile for making rayon Lactulose: Beneficial for constipation and liver diseases Sugar Metabolism Chitobiose: Present in bacteria, insect exoskeletons, and marine animals Energy Production by Oral Bacteria Polysaccharides Oral bacteria like mutans ferment dietary sucrose for energy. Overview of Polysaccharides Sucrose metabolism in dental plaque leads to acid liberation. Long chains of sugar molecules, either Acids from sucrose metabolism linear or branched demineralize dental tissues, contributing to Classified into homopolysaccharides (one caries. type of monosaccharide) and heteropolysaccharides (multiple types) Chemical Reactions of Sugars Examples include Starch, Glycogen, and Hyaluronic acid Reduction reactions convert simple sugars to alditols. Starch Aldoses and ketoses can be reduced to alcohols using different agents. Functions as an energy storage in plants Naming convention for sugar alcohols Found in plant seeds and tubers involves adding -itol to the root name. Comprises amylose and amylopectin, insoluble in water Alcohol Sugars Amylose is a linear polymer, while amylopectin is highly branched Alcohol sugars are used as thickeners and Used as a thickening agent in food and sweeteners in the food industry. cosmetic products They provide sweetness with fewer calories and do not cause tooth decay. BIOCHEM LEC Bulan, Stephanie M. Semester 1 | BSPSYA | SY. 2024-2025 Examples include mannitol, sorbitol, and Reducing vs. Non-Reducing Sugars xylitol. Reducing sugars react with mild oxidizing Sweeteners agents and have open-chain forms. Ketoses can be exceptions and undergo Types of Sweeteners enediol reactions to become aldoses. Disaccharides like maltose and lactose can Natural sweeteners are derived from also be reducing sugars. carbohydrates or other compounds. Artificial sweeteners are synthesized in laboratories. Sucrose serves as the reference standard for sweetness. Artificial Sweeteners Examples like Acesulfame K and Aspartame are several times sweeter than sucrose. Aspartame can be harmful to individuals with phenylketonuria. Saccharin, the first artificial sugar, has a bitter aftertaste. Oxidation and Classification of Sugars Oxidation Reactions Aldehyde carbonyl groups in sugars can be oxidized to carboxylic acids. Aldoses are oxidizable, while ketones are not. Classification based on reducing properties distinguishes between reducing and non- reducing sugars.