Carbohydrates: Monosaccharides, Oligosaccharides, Polysaccharides
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Questions and Answers

Which of the following accurately describes a property of carbohydrates?

  • They can only exist in a linear form.
  • They are exclusively energy storage molecules.
  • They commonly contain nitrogen as part of their structure.
  • They can have structural roles in both plants and animals. (correct)

    • What distinguishes oligosaccharides from polysaccharides?

  • Oligosaccharides contain many more than 20 monosaccharide units.
  • Oligosaccharides cannot form branched structures.
  • Polysaccharides are linked via ether bonds while oligosaccharides are not.
  • Oligosaccharides are made of fewer than 20 monosaccharide units. (correct)

    • Which statement about the Fischer projection of monosaccharides is correct?

  • Carbon atoms at intersections are explicitly shown.
  • Chiral centers are represented by vertical lines only.
  • The most highly oxidized carbon is always at the top. (correct)
  • The longest C-chain is always horizontal.

    • Which of the following statements about monosaccharides is accurate?

    <p>Most natural sugars are in the D configuration.</p> Signup and view all the answers

    Which classification of carbohydrates includes sugars that may vary from linear to complex branching forms?

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

    What is the primary role of carbohydrates during metabolism?

    <p>Energy generation and storage</p> Signup and view all the answers

    What role do carbohydrates play in pharmaceuticals?

    <p>They are often used as inactive ingredients or excipients.</p> Signup and view all the answers

    Which of the following best describes the difference between aldoses and ketoses?

    <p>Aldoses have a carbonyl group at the end of the carbon chain, while ketoses have it in the middle.</p> Signup and view all the answers

    Which of the following is true regarding the classification of monosaccharides based on carbon atom count?

    <p>Pentoses contain five carbon atoms.</p> Signup and view all the answers

    How do carbohydrates function in terms of osmosis?

    <p>They contribute to osmotic pressure both inside and outside cells.</p> Signup and view all the answers

    What role do selectins play in the body during inflammation?

    <p>They facilitate cell recognition and adhesion.</p> Signup and view all the answers

    Which statement accurately describes the role of integrins?

    <p>They act as receptors conveying information across plasma membranes.</p> Signup and view all the answers

    What is the primary function of Eptifibatide in clinical settings?

    <p>To block integrin-mediated platelet aggregation.</p> Signup and view all the answers

    How does Helicobacter pylori contribute to gastric conditions?

    <p>It adheres to the gastric surface via receptor interactions.</p> Signup and view all the answers

    What is the relationship between selectins and integrins in leukocyte movement?

    <p>Selectins modulate the initial rolling while integrins mediate firm adhesion.</p> Signup and view all the answers

    Which characteristic is unique to integrins compared to selectins?

    <p>Integrins act as receptors that convey information across membranes.</p> Signup and view all the answers

    What type of role do carbohydrates play in living organisms?

    <p>They serve as structural components and energy sources.</p> Signup and view all the answers

    Which of the following best describes the interaction of H. pylori with gastric epithelium?

    <p>It relies on the recognition of sugars by lectins.</p> Signup and view all the answers

    What is required for a sugar to exhibit reducing properties?

    <p>An acyclic form with a free anomeric OH</p> Signup and view all the answers

    Which method for glucose measurement utilizes peroxidase?

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

    Which of the following statements regarding lactose is true?

    <p>Lactose intolerance is due to the lack of lactase</p> Signup and view all the answers

    What type of sugar results from the linking of anomeric OHs?

    <p>Non-reducing sugar</p> Signup and view all the answers

    In the context of glucose metabolism, which method is noted for its clinical use?

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

    What happens to copper in the Fehling's reaction when glucose is present?

    <p>Copper is reduced from +2 to +1</p> Signup and view all the answers

    What is a characteristic property of non-reducing sugars?

    <p>They cannot undergo mutarotation</p> Signup and view all the answers

    Which enzyme is responsible for the breakdown of lactose?

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

    What is a potential health consequence of consuming excessive non-reducing sugars?

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

    What role does self-monitoring of glucose levels play in diabetes management?

    <p>It helps adjust treatment and diet.</p> Signup and view all the answers

    Which configuration do most natural sugars exhibit?

    <p>D relative configuration</p> Signup and view all the answers

    How many stereoisomers can a sugar with 4 chiral carbons have?

    <p>16 stereoisomers</p> Signup and view all the answers

    What term describes two sugars that differ only at one chiral carbon?

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

    What is the new chiral center created during the cyclization of monosaccharides called?

    <p>Anomeric carbon</p> Signup and view all the answers

    Which of the following refers to the interconversion of anomers of glucose?

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

    Which structural representation of D-glucopyranose has the lowest steric hindrance?

    <p>Equatorial-equatorial conformation</p> Signup and view all the answers

    What happens to the stability of α-D-glucopyranose compared to β-D-glucopyranose?

    <p>β-D-glucopyranose is more stable due to equatorial positions</p> Signup and view all the answers

    How do α and β anomers differ in their configurations?

    <p>They differ only at one specific stereocenter</p> Signup and view all the answers

    How does the process of mutarotation occur?

    <p>Via an acyclic intermediate form</p> Signup and view all the answers

    What characterizes D-fructose in terms of its structure?

    <p>It is a ketohexose</p> Signup and view all the answers

    What does cyclization of ketohexoses usually create?

    <p>Furanose or pyranose forms</p> Signup and view all the answers

    Which configuration leads to a higher number of stereoisomers?

    <p>An arrangement with 5 chiral centers</p> Signup and view all the answers

    In the context of monosaccharides, which functional group is critical for their unique properties?

    <p>Both alcohol and carbonyl groups</p> Signup and view all the answers

    What is the primary structural characteristic of cyclodextrins?

    <p>Cyclic oligomers of D-glucose linked α1→4</p> Signup and view all the answers

    Which characteristic is true for amylose?

    <p>It is a linear polymer with α1→4 linkages.</p> Signup and view all the answers

    What is the role of starch in pharmaceutical formulations?

    <p>It acts as a binder, diluent, and disintegrant.</p> Signup and view all the answers

    What is the fundamental unit that peptidoglycans provide to bacteria?

    <p>Strength and rigidity</p> Signup and view all the answers

    Which of the following describes the structure of cellulose?

    <p>Linear polymer with β1→4 linkages</p> Signup and view all the answers

    How do β-lactam antibiotics, such as penicillins, exert their effect on bacteria?

    <p>By inactivating bacterial transpeptidase.</p> Signup and view all the answers

    What type of linkages are found in glycogen?

    <p>α1→4 and α1→6</p> Signup and view all the answers

    Which method can modify the properties of cellulose?

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

    What type of linkage does chitin utilize in its structure?

    <p>β1→4 linkages</p> Signup and view all the answers

    What characteristic distinguishes the internal structure of cyclodextrins?

    <p>Hydrophilic exterior and hydrophobic interior</p> Signup and view all the answers

    Why is cellulose unsuitable for use as an energy source in animals?

    <p>Animals lack enzymes to digest β1→4 linkages.</p> Signup and view all the answers

    Which component is NOT part of the structure of peptidoglycan in Gram-positive bacteria?

    <p>L-tyrosine</p> Signup and view all the answers

    What structural modification enhances the lipophilicity of polysaccharides?

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

    Study Notes

    Carbohydrates

    • Carbohydrates are polyhydroxyaldehydes or polyhydroxyketones with the general formula (CH2O)n.
    • They can be linear or cyclic and include oligomers and polymers.
    • They are also called saccharides (Greek: sakcharon = sugar), and most common ones have the name ending in "-ose".
    • Carbohydrates are classified into monosaccharides, oligosaccharides, and polysaccharides.

    Monosaccharides

    • Monosaccharides are single units of polyhydroxyaldehydes or ketones.
    • Examples include glucose, fructose, erythrose.
    • They are the simplest form of carbohydrates.

    Oligosaccharides

    • Oligosaccharides are formed by linking a few monosaccharide units via ether bonds.
    • Sucrose, a disaccharide containing one unit of D-glucose and one unit of D-fructose, is an example.

    Polysaccharides

    • Polysaccharides are formed by linking more than 20 monosaccharide units.
    • Some can have over 100,000 units.
    • They can be linear, like amylose, or branched, like amylopectin and glycogen.

    Roles of Carbohydrates

    • Energy generation and storage: Oxidation of carbohydrates is the primary energy generating process in metabolism.
    • Structural role: Cellulose in plants, cell walls of bacteria, and exoskeleton of insects are examples of structural roles.
    • Inactive ingredients: Carbohydrates act as excipients in tablets, capsules, and other pharmaceutical formulations.
    • Osmolites: They contribute to osmotic pressure inside and outside cells.
    • Recognition elements: They play a role in immunity, immune response, cell identity, and recognition.

    Monosaccharides: Types and Nomenclature

    • Two main types: polyhydroxyaldehydes (aldoses) and polyhydroxyketones (ketoses).
    • The number of carbon atoms in the molecule is also stated, such as trioses, tetroses, pentoses, and hexoses.

    Monosaccharides: Chirality

    • The smallest monosaccharide is glyceraldehyde with two stereoisomers: D and L configurations. Most natural sugars have the D configuration.
    • Dihydroxyacetone, a ketotriose, does not have stereoisomers.

    Monosaccharides: Fischer Projection

    • A conventional 2D representation of the 3D molecular structure that shows the configuration of all chiral centers within a molecule.
    • The longest carbon chain is written vertically with the most oxidized carbon on top.
    • Horizontal lines represent bonds projecting forward, while vertical lines represent bonds projecting to the rear.
    • Carbon atoms at the intersection of horizontal and vertical lines are not shown.
    • Carbon atoms are numbered sequentially from the top.
    • The relative configuration is determined by the position of the hydroxyl group on the most distant chiral carbon from the carbonyl group.
    • On the right: D configuration.
    • On the left: L configuration.

    Carbohydrates: An Overview

    • Carbohydrates are essential biomolecules in living organisms, serving diverse roles.
    • They are classified based on their structure, with monosaccharides, disaccharides, and polysaccharides representing the primary groups.
    • Monosaccharides are simple sugars, disaccharides are composed of two monosaccharide units, and polysaccharides are complex polymers of monosaccharides.

    Monosaccharide Structure and Isomers

    • D versus L configuration: Most natural sugars exhibit the D configuration, determined by the orientation of the hydroxyl group on their penultimate chiral carbon.
    • Enantiomers: Each chiral carbon in a monosaccharide can have two possible configurations, creating enantiomers.
    • Epimers: Two sugars differing only in the configuration of one chiral carbon are considered epimers.
    • Anomers: Cyclic forms of monosaccharides have two stereoisomers, α and β, which differ in the stereochemistry at the hemiacetalic carbon.
    • Mutarotation: The interconversion between α and β anomers through the acyclic form is termed mutarotation, leading to an equilibrium mixture.
    • Conformation: The pyranose ring of monosaccharides adopts a non-planar, chair conformation, with two possible chair forms: equatorial-equatorial and axial-axial. The equatorial-equatorial conformation is more stable due to reduced steric hindrance.

    Reducing Properties of Monosaccharides

    • Monosaccharides can exhibit reducing properties, where they reduce copper ions from +2 to +1.
    • This property is essential for diagnostic tests like the Fehling’s reaction and Clinitab® test for measuring urine glucose levels.
    • The reducing nature is linked to the presence of a free anomeric hydroxyl group.

    Disaccharides and Glycosidic Bonds

    • Disaccharides consist of two monosaccharide units joined by a glycosidic bond.
    • The glycosidic bond can involve the anomeric hydroxyl group of one monosaccharide and a hydroxyl group on the other monosaccharide.
    • The type of glycosidic linkage affects the properties of the disaccharide.

    Polysaccharides: Structure and Function

    • Polysaccharides are complex polymers of monosaccharides, serving structural and energy storage functions.
    • Starch: A storage polysaccharide in plants, composed of amylose (linear) and amylopectin (branched) chains of D-glucose linked by α1→4 glycosidic bonds.
    • Glycogen: A storage polysaccharide in animals, structurally similar to amylopectin but more highly branched.
    • Cellulose: A structural polysaccharide in plants, composed of D-glucose units linked by β1→4 glycosidic bonds, forming rigid fibers.
    • Chitin: A structural polysaccharide found in the exoskeletons of invertebrates, composed of N-acetylglucosamine units linked by β1→4 glycosidic bonds.

    Glycoconjugates: Peptidoglycans

    • Peptidoglycans are structural components of bacterial cell walls, providing strength and rigidity.
    • They are composed of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) residues linked by β1→4 glycosidic bonds, with peptide cross-links for additional strength.

    Bacterial Peptidoglycan Synthesis and Inhibition

    • Bacterial peptidoglycan synthesis involves a multi-step pathway, with the final cross-linking step targeted by penicillins.
    • Penicillins are a class of β-lactam antibiotics that inhibit bacterial transpeptidases, enzymes responsible for peptidoglycan cross-linking. Inhibition of peptidoglycan synthesis weakens the bacterial cell wall, leading to cell lysis under osmotic pressure.

    Lectin/Oligosaccharide Recognition in Inflammation

    • Lectins are proteins that bind to specific carbohydrate structures, playing roles in cell recognition and adhesion.
    • Selectins are lectins involved in leukocyte rolling and migration during inflammation.
    • Integrins are another type of lectin that act as receptors, conveying information across cell membranes. They play a crucial role in diverse cellular processes, including inflammation, blood coagulation, and cell-matrix interactions.

    Oligosaccharides in Cell Adhesion and Recognition

    • Oligosaccharides are short chains of monosaccharides that are involved in cell adhesion and recognition processes.
    • They can be attached to proteins (glycoproteins) or lipids (glycolipids), forming glycoconjugates.
    • The specific sugar moieties on glycoconjugates can serve as recognition sites for various cellular interactions, including cell-cell adhesion, signaling, and pathogen binding.

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    Carbohydrates Lecture Notes PDF

    Description

    Explore the fascinating world of carbohydrates, including their classifications into monosaccharides, oligosaccharides, and polysaccharides. This quiz will test your understanding of their structures and functions. Discover key examples like glucose, sucrose, and amylose as you learn more about these essential biomolecules.

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