Monosaccharides and Their Configurations
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Questions and Answers

What determines the D or L configuration of a monosaccharide?

The –OH group of the highest chiral carbon

What is a triose?

  • A monosaccharide with five carbon atoms
  • A monosaccharide with three carbon atoms (correct)
  • A monosaccharide with six carbon atoms
  • A monosaccharide with four carbon atoms

    • Which of the following are types of monosaccharides based on the number of carbon atoms?

  • Triose
  • Pentose
  • Hexose
  • All of the above (correct)

    • An aldose contains a ketone functional group.

    <p>False</p> Signup and view all the answers

    What is the difference between D-glucose and D-galactose?

    <p>They differ in the placement of the -OH group on carbon 4.</p> Signup and view all the answers

    What are cyclic monosaccharides formed from?

    <p>The reaction between a carbonyl group and a hydroxyl group</p> Signup and view all the answers

    Which cyclic sugar form has a six-atom ring?

    <p>Pyranose</p> Signup and view all the answers

    What is an anomeric carbon atom?

    <p>The hemiacetal carbon atom in a cyclic monosaccharide.</p> Signup and view all the answers

    Haworth projection formulas accurately represent the stereochemistry of sugars.

    <p>True</p> Signup and view all the answers

    What is the biochemical importance of D-Ribose?

    <p>Structural elements of nucleic acids and coenzymes.</p> Signup and view all the answers

    Are all carbohydrates sweet?

    <p>No</p> Signup and view all the answers

    Give at least one medical use for carbohydrates.

    <p>Carbohydrates can be used in medical applications such as intravenous glucose solutions.</p> Signup and view all the answers

    What are carbohydrates primarily classified on?

    <p>Molecular size</p> Signup and view all the answers

    The human diet should ideally be about two-thirds carbohydrate by mass.

    <p>True</p> Signup and view all the answers

    What process do green plants use to produce carbohydrates?

    <p>Photosynthesis</p> Signup and view all the answers

    What is a chiral center?

    <p>A carbon atom bonded to four different groups.</p> Signup and view all the answers

    What does the term 'enantiomers' refer to?

    <p>Stereoisomers that are nonsuperimposable mirror images</p> Signup and view all the answers

    Achiral molecules possess handedness.

    <p>False</p> Signup and view all the answers

    Which phrase correctly describes an optically active compound?

    <p>It rotates the plane of polarized light.</p> Signup and view all the answers

    What is the role of insulin in the body?

    <p>Insulin helps cells absorb blood sugar for energy or storage.</p> Signup and view all the answers

    What happens when blood sugar levels drop too low?

    <p>Alpha cells in the pancreas release glucagon.</p> Signup and view all the answers

    What can result from high glucose levels in cells?

    <p>Insulin resistance</p> Signup and view all the answers

    Why should carbohydrates be eaten before exercise?

    <p>To top up energy stores in muscles and the liver, improving performance.</p> Signup and view all the answers

    What happens to performance when all carbohydrates are used?

    <p>Performance decreases, and the body starts to use protein as its energy source.</p> Signup and view all the answers

    Eating carbohydrates is unnecessary for high endurance sports.

    <p>False</p> Signup and view all the answers

    What are the two structural polysaccharides mentioned?

    <p>Cellulose and Chitin</p> Signup and view all the answers

    What is the structural component of plant cell walls?

    <p>Cellulose</p> Signup and view all the answers

    Chitin is the most abundant naturally occurring polysaccharide.

    <p>False</p> Signup and view all the answers

    What are glycosaminoglycans (GAGs) also known as?

    <p>Mucopolysaccharides</p> Signup and view all the answers

    What is the role of proteoglycans?

    <p>They provide mechanical support and cushioning to joints.</p> Signup and view all the answers

    Which of the following is associated with the inflammatory response after tissue injury?

    <p>Heparin</p> Signup and view all the answers

    The 2nd most abundant naturally occurring polysaccharide, next to __________.

    <p>cellulose</p> Signup and view all the answers

    Hyaluronic acid is a small polysaccharide with 15–90 disaccharide residues.

    <p>False</p> Signup and view all the answers

    What is the medical condition characterized by an inability to metabolize galactose?

    <p>Galactosemia</p> Signup and view all the answers

    Match the following GAGs with their descriptions:

    <p>Chondroitin Sulfate = Structural polysaccharide of ligaments, cartilage, and tendons Dermatan Sulfate = Structural polysaccharide in skin Keratan Sulfate = Found primarily in the cornea of the eye Heparan Sulfate = Component of cell-surface proteoglycans</p> Signup and view all the answers

    Which type of diabetes is generally diagnosed in children and teenagers?

    <p>Type 1</p> Signup and view all the answers

    Match the following terms related to stereoisomerism and carbohydrates:

    <p>Enantiomers = Nonsuperimposable mirror image Diastereomers = Not mirror images of one another Chiral molecule = Has a non-superimposable mirror image Achiral molecule = Superimposable mirror image Epimers = Stereoisomers that differ at one specific chiral center Carbohydrate = Most abundant class of bioorganic molecules on Earth Starch = Energy reserve in plants Cellulose = Structural component in plants Photosynthesis = Process of converting light energy into chemical energy</p> Signup and view all the answers

    Diastereomers are _____ of each other.

    <p>not mirror images</p> Signup and view all the answers

    What is the structure being illustrated? (1) a-D-altrose, (2) b-D-altose, (3) a-L-altrose, (4) b-L-altrose.

    <p>a-D-altrose</p> Signup and view all the answers

    Which of the following monosaccharide structural relationships is CORRECT?

    <p>1 and 2 are enantiomers, while 2 and 3 are diastereomers</p> Signup and view all the answers

    What form must all carbohydrates be in for cells to use them as an energy source?

    <p>Glucose</p> Signup and view all the answers

    Polysaccharides are saccharide units that contain 3 to 10 units.

    <p>False</p> Signup and view all the answers

    What is the primary source of energy for cells?

    <p>D-Glucose</p> Signup and view all the answers

    The process that forms glycosides from cyclic monosaccharides involves a reaction with _____ in acid solution.

    <p>alcohols</p> Signup and view all the answers

    D-Fructose is the sweetest tasting sugar.

    <p>True</p> Signup and view all the answers

    What metabolic condition leads to the presence of D-Glucose in urine?

    <p>Diabetes mellitus</p> Signup and view all the answers

    Match the following disaccharides with their common names:

    <p>Maltose = Malt sugar Cellobiose = Intermediate in the hydrolysis of cellulose Lactose = Milk sugar Sucrose = Table sugar</p> Signup and view all the answers

    What is the structure of the glycosidic linkage in Maltose?

    <p>α(1-4)</p> Signup and view all the answers

    Which of the following is a common reaction of monosaccharides?

    <p>Oxidation to acidic sugars</p> Signup and view all the answers

    What are the three common natural amino sugars?

    <p>D-glucosamine, D-galactosamine, N-acetyl derivatives</p> Signup and view all the answers

    Which type of polysaccharide serves as an energy storage polysaccharide in animals?

    <p>Glycogen</p> Signup and view all the answers

    Polysaccharides are typically sweet and soluble in water.

    <p>False</p> Signup and view all the answers

    Study Notes

    Carbohydrates Overview

    • Carbohydrates are the most abundant bioorganic molecules on Earth.
    • They constitute about 75% of dry plant materials, produced through photosynthesis (reactants: carbon dioxide, water; energy source: sunlight).
    • Major carbohydrate sources for humans and animals come from dietary plant materials, ideally two-thirds of the average diet by mass.

    Classification of Carbohydrates

    • Carbohydrates are classified based on molecular size into:
      • Monosaccharides: Single sugar units (e.g., glucose and fructose).
      • Disaccharides: Two sugar units linked (e.g., sucrose).
      • Oligosaccharides: Short chains of sugar units.
      • Polysaccharides: Long chains of sugar units (e.g., starch, cellulose).

    Molecular Structure and Chirality

    • Carbohydrates can be polyhydroxy aldehydes or polyhydroxy ketones.
    • Chirality refers to "handedness" in molecules; chiral molecules have non-superimposable mirror images.
    • The presence of a chiral center (a carbon atom bonded to four different groups) determines chirality.
    • Chiral molecules exhibit different biological responses; the body may respond differently to left-handed versus right-handed forms.

    Importance of Chiral Molecules

    • Right-handed and left-handed forms can elicit different responses in biological systems.
    • Example: Human body reacts 20 times more effectively to the right-handed form of epinephrine compared to its left-handed counterpart.

    Stereoisomerism

    • Stereoisomers share the same molecular formula but differ spatially:
      • Enantiomers: Non-superimposable mirror images (e.g., right and left-handed forms).
      • Diastereomers: Stereoisomers that are not mirror images (e.g., cis-trans isomers).

    Designating Handedness Using Fischer Projections

    • Enantiomers can rotate polarized light (dextrorotatory = clockwise, levorotatory = counterclockwise).
    • D,L system helps determine configuration based on the highest-numbered chiral center's hydroxyl group:
      • If -OH is right, it is a D-isomer.
      • If -OH is left, it is an L-isomer.
    • Fischer projections visually represent spatial arrangement around chiral centers.

    Summary

    • Understanding carbohydrates involves reviewing molecular structures, classifications, and the importance of chirality in their biological functions.
    • Applications of carbohydrates extend to their roles in energy storage, structural roles in plants, and their implications in health, notably in carbohydrate-related diseases.### Structures and Classification of Monosaccharides
    • Monosaccharides typically contain 3 to 7 carbon atoms.
    • Three-carbon monosaccharides are called trioses (e.g., glyceraldehyde).
    • Four-carbon monosaccharides are tetroses (e.g., erythrose).
    • Five-carbon monosaccharides are pentoses (e.g., ribose, arabinose).
    • Six-carbon monosaccharides are hexoses (e.g., glucose, fructose).
    • Aldoses contain an aldehyde functional group; ketoses contain a ketone functional group.
    • Classification can be based on both the number of carbon atoms and functional groups (e.g., aldohexose, ketopentose).
    • "Sugar" refers to both monosaccharides and certain disaccharides, often associated with sweetness.

    Optical Isomers and Chiral Centers

    • The number of possible optical isomers is determined by the number of chiral centers in the monosaccharide.
    • Each chiral carbon can result in varying configurations, affecting the sugar's stereoisomers.
    • Aldohexose (6C) can produce 16 optical isomers; aldohexose has 4 chiral centers.
    • Ketoses have fewer optical isomers due to fewer chiral centers.

    Epimers

    • Epimers are forms of carbohydrates that differ at only one chiral center (e.g., D-glucose and D-galactose differ at carbon 4).
    • Unlike enantiomers, epimers are not mirror images of each other.

    Cyclic Monosaccharides: Haworth Projection

    • Monosaccharides can exist in cyclic forms, represented by Haworth projection formulas.
    • Cyclic structures result from the reaction of carbonyl groups with hydroxyl groups.
    • Pyranoses (six-atom rings) and furanoses (five-atom rings) are the two cyclic forms.
    • The formation of cyclic monosaccharides usually leads to two stereoisomers known as anomers (alpha and beta forms).
    • The anomeric carbon is the hemiacetal carbon; its configuration defines the type of anomer.

    Biochemically Important Monosaccharides

    • D-Ribose: Essential component of nucleic acids and ATP; involved in various metabolic pathways.
    • D-Ribulose: An intermediate in the pentose phosphate pathway.
    • D-Arabinose: Present in various plant gums; constituent of glycoproteins.
    • D-Glucose: Known as the "sugar" of the body; normal concentration is 70-100 mg/dL; key energy source.
    • D-Fructose: Found in fruit juices; used by the liver and considered the sweetest sugar.
    • D-Galactose: Derived from lactose; crucial for brain function and appears in glycolipids.
    • D-Mannose: Found in plant mannans; a constituent of glycoproteins used for prevention of certain diseases.### Urinary Tract Infections (UTIs)
    • UTIs are common infections affecting the urinary system, often treated with antibiotics.
    • Understanding carbohydrate metabolism can help manage genetic disorders like carbohydrate-deficient glycoprotein syndrome.

    Reactions of Monosaccharides

    • Five major reactions include oxidation to acidic sugars, reduction to sugar alcohols, glycoside formation, phosphate ester formation, and amino sugar formation.

    Oxidation to Acidic Sugars

    • Involves redox reactions of monosaccharides, transforming them into acidic forms:
      • Aldonic Acid: Acid group at terminal carbon.
      • Alduronic Acid: Acid group at the terminal carbon opposite the aldehyde.
      • Aldaric Acid: Acid groups at both ends of the molecule.

    Reduction to Sugar Alcohols

    • Carbonyl group can be reduced to a hydroxyl group.
    • The product is a sugar alcohol (e.g., D-glucose reduced to D-glucitol or D-sorbitol) used in cosmetics and as a sweetener.

    Glycoside Formation

    • Hemiacetal forms of monosaccharides react with alcohols to create acetals, termed glycosides.
    • Glycosides can exist in alpha and beta forms, defined by the orientation of the -OH group.

    Phosphate Ester Formation

    • Hydroxyl groups of monosaccharides may react with oxyacids to form phosphates.
    • Forming glucose 1-phosphate and glucose 6-phosphate is important for carbohydrate metabolism.

    Amino Sugar Formation

    • A hydroxyl group replaced by an amino group leads to amino sugar formation (common examples: glucosamine and galactosamine).
    • Amino sugars are crucial in constructing polysaccharides like chitin and hyaluronic acid.

    Disaccharides

    • Formed from the glycosidic linkage between two monosaccharides functioning as a hemiacetal and an alcohol.
    • Glycosidic linkages consist of carbon–oxygen–carbon bonds.

    Features of Disaccharides

    • Maltose: Comprised of two D-glucose units, linked by α(1-4) linkage.
    • Cellobiose: Comprised of β(1-4) glucose and galactose units.
    • Lactose: Composed of D-galactose and D-glucose with β(1-4) linkage.
    • Sucrose: Comprising glucose and fructose via α,β(1-2) linkage.

    Oligosaccharides

    • Contain 3 to 10 monosaccharides linked via glycosidic bonds.
    • Example trisaccharide: Raffinose (α-D-galactose, α-D-glucose, β-D-fructose).
    • Example tetrasaccharide: Stachyose (two α-D-galactose, one α-D-glucose, one β-D-fructose).

    Importance of Oligosaccharides

    • Blood types (O, A, B, AB) are defined by specific oligosaccharides on red blood cells.

    Polysaccharides

    • Polymers of numerous monosaccharide units, often non-sweet and limited in solubility.
    • Used as thickeners in cooking due to the hydrophilic nature of -OH groups.

    Types of Polysaccharides

    • Storage Polysaccharides:

      • Starch: Energy storage in plants, includes amylose (linear) and amylopectin (branched).
      • Glycogen: More branched than amylopectin, serves as energy storage in animals.

    • Structural Polysaccharides:

      • Cellulose: Main component of plant cell walls, indigestible by humans.
      • Chitin: Structural element in exoskeletons of arthropods, similar structure to cellulose.

    • Acidic Polysaccharides:

      • Composed of disaccharide repeating units with amino sugars and negative charges (e.g., hyaluronic acid and heparin).

    Glycosaminoglycans (GAGs)

    • Also known as mucopolysaccharides, consist of repeating disaccharide units.
    • Often contain one amino sugar, playing essential roles in biological processes such as joint lubrication and cellular hydration.

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    Description

    Explore the crucial concepts surrounding monosaccharides, including their D or L configurations, types such as trioses, and the structural differences between D-glucose and D-galactose. This quiz will test your understanding of the formation and classification of these important carbohydrates.

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