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Questions and Answers
What is primarily broken down by the body to produce glucose for energy?
What is primarily broken down by the body to produce glucose for energy?
Which polysaccharide is commonly known as an energy storage molecule in animals?
Which polysaccharide is commonly known as an energy storage molecule in animals?
What role do carbohydrates play in the formation of other biological molecules?
What role do carbohydrates play in the formation of other biological molecules?
Regarding carbohydrates, which statement is correct?
Regarding carbohydrates, which statement is correct?
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Which laboratory skill is among the learning objectives for understanding carbohydrates?
Which laboratory skill is among the learning objectives for understanding carbohydrates?
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In which context do carbohydrates mainly act as an energy source?
In which context do carbohydrates mainly act as an energy source?
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What type of molecule do plants convert light energy into for energy storage?
What type of molecule do plants convert light energy into for energy storage?
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Which of the following is NOT a carbohydrate?
Which of the following is NOT a carbohydrate?
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What does the reference plane for ring atoms generally involve?
What does the reference plane for ring atoms generally involve?
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In the designation of ring conformation, how are atoms above and below the reference plane notated?
In the designation of ring conformation, how are atoms above and below the reference plane notated?
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How many atoms are in the planar configuration of ribose in its envelope form?
How many atoms are in the planar configuration of ribose in its envelope form?
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What are the major and minor forms of the twisted cyclic ribose conformation?
What are the major and minor forms of the twisted cyclic ribose conformation?
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What representation suggests monosaccharides are flat, yet does not reflect their actual structure?
What representation suggests monosaccharides are flat, yet does not reflect their actual structure?
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Which configuration do pyranoses adopt to achieve low energy?
Which configuration do pyranoses adopt to achieve low energy?
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Which of the following forms is minor among the dominant forms of twisted cyclic ribose?
Which of the following forms is minor among the dominant forms of twisted cyclic ribose?
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What is one reason for the non-planarity of furanose and pyranose rings?
What is one reason for the non-planarity of furanose and pyranose rings?
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What product is formed from the reduction of a monosaccharide?
What product is formed from the reduction of a monosaccharide?
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Which reducing agent is specifically mentioned as capable of reducing the carbonyl group of monosaccharides?
Which reducing agent is specifically mentioned as capable of reducing the carbonyl group of monosaccharides?
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What is a unique characteristic of alditols compared to their aldose precursors?
What is a unique characteristic of alditols compared to their aldose precursors?
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Which alditol is produced from the reduction of glucose using sodium borohydride?
Which alditol is produced from the reduction of glucose using sodium borohydride?
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What technique is applied to determine glycosidic linkages in sugars?
What technique is applied to determine glycosidic linkages in sugars?
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Which of the following monosaccharides can produce more than one alditol upon reduction?
Which of the following monosaccharides can produce more than one alditol upon reduction?
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What product is obtained from exhaustive methylation of trehalose followed by hydrolysis?
What product is obtained from exhaustive methylation of trehalose followed by hydrolysis?
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Which of the following compounds is classified as a sugar alcohol?
Which of the following compounds is classified as a sugar alcohol?
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Which disaccharide is known as milk sugar and found in dairy products?
Which disaccharide is known as milk sugar and found in dairy products?
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What enzyme is responsible for the digestion of sucrose in the small intestine?
What enzyme is responsible for the digestion of sucrose in the small intestine?
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Which of the following statements about glycosidic linkages is correct?
Which of the following statements about glycosidic linkages is correct?
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What is the most common dietary disaccharide?
What is the most common dietary disaccharide?
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What are the primary functions of polysaccharides in nature?
What are the primary functions of polysaccharides in nature?
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Which disaccharide is commonly found in beer and resulting from the fermentation of malt?
Which disaccharide is commonly found in beer and resulting from the fermentation of malt?
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Which monosaccharides combine to form maltose?
Which monosaccharides combine to form maltose?
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Which type of glycosidic linkage is associated with high molecular weight polysaccharides?
Which type of glycosidic linkage is associated with high molecular weight polysaccharides?
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What is the primary structural difference between glycogen and starch?
What is the primary structural difference between glycogen and starch?
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What type of linkage connects glucose units in cellulose?
What type of linkage connects glucose units in cellulose?
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What characteristic of glycogen allows for rapid glucose release?
What characteristic of glycogen allows for rapid glucose release?
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How does the orientation of glucose units in cellulose contribute to its stability?
How does the orientation of glucose units in cellulose contribute to its stability?
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Which of the following best describes the physical form of glycogen within cells?
Which of the following best describes the physical form of glycogen within cells?
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What is the role of hydrogen bonds in the structure of cellulose?
What is the role of hydrogen bonds in the structure of cellulose?
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What is the approximate number of glucose units that may be contained in a single glycogen granule?
What is the approximate number of glucose units that may be contained in a single glycogen granule?
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Which polysaccharide serves as a major structural component of plant cell walls?
Which polysaccharide serves as a major structural component of plant cell walls?
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Which glycosaminoglycan is known for its high viscosity and serves as a lubricant in synovial fluid?
Which glycosaminoglycan is known for its high viscosity and serves as a lubricant in synovial fluid?
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Which of the following glycosaminoglycans has the highest net negative charge and acts as a natural anticoagulant?
Which of the following glycosaminoglycans has the highest net negative charge and acts as a natural anticoagulant?
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What is a primary function of proteoglycans in the extracellular matrix?
What is a primary function of proteoglycans in the extracellular matrix?
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What type of linkage connects the disaccharide units in hyaluronic acid?
What type of linkage connects the disaccharide units in hyaluronic acid?
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Which statement about dermatan sulfate is true?
Which statement about dermatan sulfate is true?
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Which glycosaminoglycan is primarily found in tendons and cartilage?
Which glycosaminoglycan is primarily found in tendons and cartilage?
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What is the molecular weight of glycosaminoglycans like hyaluronic acid commonly up to?
What is the molecular weight of glycosaminoglycans like hyaluronic acid commonly up to?
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Which function is NOT associated with proteoglycans?
Which function is NOT associated with proteoglycans?
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Study Notes
Carbohydrates Introduction
- Carbohydrates are the most abundant bioorganic molecules on Earth.
- They are one of three main nutrients, alongside proteins and fats.
- Many carbohydrates are polysaccharides (e.g., glycogen, starch, cellulose).
- Our bodies break down starch and glycogen into glucose for immediate energy or storage.
- Carbohydrates are metabolic precursors to other molecules like amino acids and fats.
Learning Objectives
- Relate carbohydrate structure, properties, and reactivity to their functions.
- Isolate glycogen from chicken liver.
- Interpret results of carbohydrate qualitative tests.
- Estimate glucose content in commercially available drinks.
Functions of Carbohydrates
- Energy storage: Plants convert light energy into monosaccharides and starch; animals use this for energy.
- Structural components: Cellulose, chitin, and bacterial cell walls.
- Nucleic acid components: Ribose and deoxyribose.
- Cell-cell recognition: Carbohydrates on cell surfaces play key roles.
- Biological membranes: Glycolipids are components.
Structure, Nomenclature, and Classification
- Carbohydrates are polyhydroxy aldehydes or ketones, or compounds that produce these upon hydrolysis.
- Monosaccharides (simple sugars) have the general formula Cn(H2O)n.
- Oligosaccharides are formed from a few monosaccharides.
- Polysaccharides are formed from many monosaccharides.
- Carbohydrates are classified by complexity:
- Monosaccharides (e.g., glucose, fructose, mannose, galactose).
- Disaccharides (e.g., sucrose, maltose, cellobiose).
- Oligosaccharides.
- Polysaccharides (e.g., starch, cellulose, glycogen).
Monosaccharides
- Cannot be hydrolyzed to simpler carbohydrates.
- General formula Cn(H2O)n (where n is 3-8).
- Can be aldoses (aldehyde group) or ketoses (ketone group).
- Classified by the number of carbon atoms (e.g., triose, tetrose, pentose, hexose, heptose).
- Hexoses are the most common.
Common Monosaccharides
- Glucose: Blood sugar, dextrose, grape sugar; the most abundant monosaccharide in our bodies. Provides energy (ATP) to cells.
- Fructose: Levulose, sweetest monosaccharide; energy source; naturally found in honey, fruits, and vegetables.
- Galactose: Energy source; component of glycolipids and glycoproteins; part of lactose (milk sugar).
- Mannose: Converted to glucose in the body; found in certain bacteria, fungi, and plants; used in treating carbohydrate-deficient glycoprotein syndrome.
Fischer Projection
- A common method for representing open-chain carbohydrates.
- The carbon chain is vertical; the lowest numbered carbon is at the top.
- Numbering follows the convention that the most oxidized end of the molecule has the lowest number.
Epimers
- Differ in the arrangement about one chiral carbon.
- Example: Glucose and mannose.
Haworth Projection
- A diagrammatic representation for the ring forms of sugars.
- Represents the placement of substituents in relation to the plane of the paper, showing how glucose can exist in a cyclic form.
- Important for understanding the stereochemistry of carbohydrates.
Conformational Structures
- Sugars exist in various conformations.
- The terms describing conformations are: chair, boat, skew-boat
- Haworth Diagrams are simplified representations reflecting the ring structures.
Oxidation of Monosaccharides
- Oxidation reactions with weak oxidizing agents (Benedict's, Barfoed's, Fehling's) convert monosaccharides into their corresponding acids (e.g., glucose to gluconic acid).
- Oxidation can be used to identify or quantify specific carbohydrates.
- Additional oxidation produces uronic acids from the hydroxymethyl groups.
Reduction of Monosaccharides
- Reduction of the carbonyl group of monosaccharides forms alditols (sugar alcohols).
- Example: Glucose to glucitol (sorbitol)
- Alditols cannot cyclize.
Exhaustive Methylation
- Methylation of all free hydroxyl groups allows identification of glycosidic linkages.
- Can be utilized to determine glycosidic linkages and the component monosaccharides.
- Example: Methylation of trehalose.
Formation of Derivatives
- Esterification: Phosphate groups transfer to carbohydrates, important for metabolism (e.g., glucose to glucose-6-phosphate).
- Glycoside Formation: A hydroxyl group (of the anomeric carbon) in a carbohydrate is replaced by an OR group (from an alcohol or another carbohydrate), making it a glycoside.
- Formation of amino sugars: Amino groups substitute for hydroxyl groups (e.g., glucose to glucosamine).
- Formation of sugar sulfates: Sugar sulfates are found in proteoglycans (e.g., chondroitin sulfates).
- Formation of N-acetylneuraminates: Often found as a terminal residue in oligosaccharides (e.g., sialic acid).
- Important for recognition, protection, and biological roles.
Disaccharides
- Formed by joining two monosaccharides via a glycosidic bond.
- Examples include maltose, lactose, and sucrose.
- Only monosaccharides can be absorbed from the digestive tract.
- Disaccharides are digested into their constituent monosaccharides for absorption into the bloodstream.
Polysaccharides
- Large, complex molecules composed of repeating monosaccharide units joined by glycosidic bonds.
- Classification:
- Homoglycans: contain only one type of monosaccharide (e.g., starch, glycogen).
- Heteroglycans: contain more than one type of monosaccharide (e.g., glycosaminoglycans).
Storage Polysaccharides: Starch
- Major source of carbohydrate in the human diet (about 50% of carbohydrate intake).
- Synthesized from glucose from photosynthesis in plants, stored in roots and seeds.
- Consists of two types: amylose (linear) and amylopectin (branched).
- Both consist of repeating glucose units in a-1,4 linkages; amylopectin has additional a-1,6 linkages.
Storage Polysaccharides: Glycogen
- Storage form of glucose in animals.
- Found in liver and muscle cells.
- Highly branched structure with more α(1→6) linkages, allowing for rapid glucose release.
Other Homoglycans: Cellulose
- Major structural component of plant cell walls.
- Consists of long, linear chains of glucose linked by β-1,4 linkages.
- Its structure enables intermolecular hydrogen bonding that makes it strong.
- Humans lack the enzyme needed to break down ß-1,4 linkages.
Other Homoglycans: Chitin
- Structural component of exoskeletons of insects and crustaceans, cell walls of fungi.
- Repeating units of N-acetyl-β-D-glucosamine connected by β-1,4 linkages.
- Structural component of exoskeletons and cell walls in various organisms.
Other Homoglycans: Alginic Acid and Dextran
- Alginic acid: structural polysaccharide of brown algae.
- Dextran: produced by lactic acid bacteria; used as a food additive or in chromatography.
Other Homoglycans: Pectic Acid
- Polygalacturonic acid
- Intercellular layers of plant tissues and functions.
Heteroglycans: Glycosaminoglycans
- Long linear polysaccharides consisting of repeating disaccharide units that contain an amino sugar and often negatively charged sulfate or carboxyl groups.
- Functions: lubricants, tensile strength, elastic properties to soft tissues, acts as shock absorber, and helps in disposing of unwanted cellular artifacts.
- Major components of mucins, connective tissues, and extracellular matrix, such as hyaluronic acid, chondroitin sulfates, keratin sulfates, dermatan sulfates, and heparin.
Other Heteroglycans
- Glycosaminoglycans and glycosamino glucuronoglycans are examples of heteroglycans
- These have a variety of functions.
Peptidoglycans
- Major components of bacterial cell walls.
- Consists of repeating disaccharide units alternating with short peptides.
- Crucial for bacterial structural integrity.
- Site for bacterial identification (e.g. gram-positive/gram-negative).
Lipopolysaccharides (LPS)
- Found in the outer membrane of Gram-negative bacteria
- Consist of lipid and carbohydrate components.
- Play important roles in the antigenic properties of gram-negative bacteria.
Glycoproteins
- Proteins with covalently attached oligosaccharides.
- Important for a variety of functions, from cell-surface recognition to protein function and structure.
- O-linked oligosaccharides are attached to hydroxyl groups of serine or threonine, N-linked glycosaminoglycans are attached to hydroxyl groups of asparagine, and N-linked are linked to amide nitrogen.
- Examples include blood group antigens and mucus production.
O-linked and N-linked oligosaccharides
- Types of glycosidic linkages between each oligosaccharide and protein.
- Key determinants for antigenicity.
- Important for cell recognition processes.
Exercises
- Questions, answers to test student understanding.
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Description
Explore the fundamental roles and properties of carbohydrates in living organisms. This quiz covers carbohydrate structure, functions, and practical applications, including glycogen isolation and glucose estimation in beverages. Understand how carbohydrates impact energy storage and structural components in biology.
