Unit 3: Carbohydrates
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Questions and Answers

What is a primary reason carbohydrates are named so?

  • They contain no chiral centers.
  • They are derived from simple sugars.
  • They are produced exclusively by animals.
  • They have a general formula of Cn(H2O)n. (correct)

    • What role do carbohydrates play in cell membranes?

  • They provide thermal insulation.
  • They serve as an energy source.
  • They act as structural components in cell walls. (correct)
  • They facilitate DNA replication.

    • Which statement about monosaccharides is true?

  • Dihydroxyacetone is the only monosaccharide without chiral centers. (correct)
  • They are always used for energy storage.
  • They all contain a chiral carbon atom.
  • Monosaccharides cannot exist in optically active forms.

    • What determines the interaction of carbohydrates with other biomolecules?

    <p>The arrangement of groups around their chiral carbons.</p> Signup and view all the answers

    What is the function of the TAS1R2 and TAS1R3 proteins?

    <p>They encode sweet-taste receptors.</p> Signup and view all the answers

    What is a characteristic of sugar stereoisomers?

    <p>They can be both D-series and L-series.</p> Signup and view all the answers

    Which type of carbohydrates serves as building blocks for larger polymers?

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

    What is one of the biological functions of glycoconjugates?

    <p>They are responsible for cell-cell signaling.</p> Signup and view all the answers

    Which of the following correctly describes an aldose?

    <p>It contains an aldehyde functionality.</p> Signup and view all the answers

    What type of sugar is sucrose?

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

    Which sugar is considered a five-carbon standard sugar?

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

    What defines an epimer?

    <p>Sugars that differ only in the configuration around one carbon atom.</p> Signup and view all the answers

    Which statement about the cyclic structures of monosaccharides is true?

    <p>The carbonyl carbon becomes the anomeric carbon.</p> Signup and view all the answers

    What type of carbohydrate is formed following the oxidation of aldoses?

    <p>Uronic acids</p> Signup and view all the answers

    What is the purpose of glucose oxidase in colorimetric glucose analysis?

    <p>It catalyzes the conversion of glucose to glucono-δ-lactone.</p> Signup and view all the answers

    How do intramolecular cyclic structures affect the reactivity of monosaccharides?

    <p>The anomeric carbon can act as a reducing agent.</p> Signup and view all the answers

    Which of the following is a characteristic of polysaccharides?

    <p>They are sugar polymers with ten or more monosaccharide units.</p> Signup and view all the answers

    What is the relationship between glucose and fructose?

    <p>Fructose is the ketose form of glucose.</p> Signup and view all the answers

    What are glycosaminoglycans primarily composed of?

    <p>Repeating disaccharide units</p> Signup and view all the answers

    Which component of the extracellular matrix provides strength and elasticity?

    <p>Collagen fibers</p> Signup and view all the answers

    What role do proteoglycans play in cellular function?

    <p>Regulate cell growth and interact with receptors</p> Signup and view all the answers

    Which of the following is a characteristic of glycoproteins?

    <p>They are primarily found in the plasma membrane and ECM.</p> Signup and view all the answers

    What is a primary function of glycolipids in cellular membranes?

    <p>Contribute to membrane structure</p> Signup and view all the answers

    What is the role of glycosphingolipids primarily found in neurons?

    <p>Play a role in signal transduction</p> Signup and view all the answers

    Which type of glycan is crucial for determining blood groups in vertebrates?

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

    What principle underlines the function of molecular interactions in biological systems?

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

    What bond type is involved in the formation of disaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which of the following best describes glycogen?

    <p>A branched homopolysaccharide of glucose</p> Signup and view all the answers

    What type of polysaccharide is characterized by having no defined molecular weight?

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

    Which enzyme is active in the small intestine after the pH is neutralized?

    <p>Pancreatic α-amylase</p> Signup and view all the answers

    What is the structure of amylopectin?

    <p>Long branched chains of monomers with α(1→4) and α(1→6) bonds</p> Signup and view all the answers

    How does salivary α-amylase affect starch and glycogen?

    <p>Acts on random α(1→4) bonds</p> Signup and view all the answers

    What can lead to lactose intolerance in the adult population?

    <p>Deficiency of digestive enzymes</p> Signup and view all the answers

    Which statement accurately describes the glycosidic bonds in polysaccharides?

    <p>They determine the properties and functions of the polymer</p> Signup and view all the answers

    What is maltose formed from?

    <p>Two glucose molecules linked by a 1,4 glycosidic bond</p> Signup and view all the answers

    Study Notes

    Carbohydrates Overview

    • Named due to the general formula Cn(H2O)n.
    • Synthesized from CO2 and H2O through photosynthesis in plants.
    • Molecular weights range from glyceraldehyde (90 g/mol) to amylopectin (200,000,000 g/mol).
    • Sugar stereoisomers occur due to chiral centers, influencing interactions with enzymes.
    • Enzymes acting on sugars are stereospecific, demonstrating a preference for certain isomers.
    • Carbohydrates can form glycoproteins and proteoglycans via covalent links with proteins.

    Functions and Properties of Carbohydrates

    • Serve as energy sources and storage.
    • Act as structural components in cell walls and exoskeletons.
    • Function as informational molecules for cell-cell signaling.

    Monosaccharides and Their Characteristics

    • Monosaccharides are simple sugars with one polyhydroxy aldehyde or ketone unit (e.g., D-glucose).
    • Dihydroxyacetone is the only monosaccharide without chiral centers.
    • Exist in optically active forms; most common type is D-series.
    • Sweet taste perception is linked to TAS1R2 and TAS1R3 receptors.

    Types of Carbohydrates

    • Disaccharides consist of two monosaccharides (e.g., sucrose = glucose + fructose).
    • Oligosaccharides are short chains of monosaccharides linked by glycosidic bonds.
    • Polysaccharides consist of 10+ monosaccharide units (examples include cellulose and glycogen).

    Aldoses vs. Ketoses

    • Aldoses contain an aldehyde group.
    • Ketoses contain a ketone group.

    Structural Variants of Sugars

    • Ribose and glucose are standard five- and six-carbon sugars, respectively.
    • Galactose is an epimer of glucose, differing at one carbon atom.
    • Fructose is the ketose form of glucose.
    • Monosaccharides can cyclize, forming new chiral centers (anomeric carbons).

    Variants of Hexoses

    • Hexose derivatives include phosphate esters and oxidized forms (aldonic and uronic acids).
    • These derivatives can form lactones, which are stable intramolecular esters.

    Glycosidic Bonds and Polysaccharides

    • Disaccharides form through glycosidic bonds between anomeric and hydroxyl carbons (e.g., maltose from two glucose units).
    • Polysaccharides can be homopolysaccharides or heteropolysaccharides and vary in branching and linear forms.

    Storage Forms of Energy

    • Glycogen and starch are primary storage forms of carbohydrates.
    • Glycogen: branched structure of glucose with (α1→4) chains and (α1→6) branch points.
    • Starch consists of amylose (unbranched) and amylopectin (branched).

    Digestion of Carbohydrates

    • Glycosidases in saliva and intestines hydrolyze glycosidic bonds, with specificity to structure.
    • Salivary α-amylase and pancreatic α-amylase are crucial for starch digestion.
    • Intestinal disaccharidases convert disaccharides to monosaccharides for absorption.

    Absorption and Metabolism

    • Monosaccharides are absorbed in the small intestine via active and facilitated transport.
    • Disaccharidase deficiencies can lead to digestive disorders such as lactose intolerance.

    Glycosaminoglycans and Extracellular Matrix

    • Glycosaminoglycans are linear polymers made of repeating disaccharide units (e.g., hyaluronan).
    • They play essential roles in the extracellular matrix, providing structure, strength, and elasticity.

    Glycoconjugates

    • Biologically active molecules consisting of carbohydrates bound to proteins or lipids.
    • Include proteoglycans, glycoproteins, glycolipids, and glycosphingolipids.
    • Proteoglycans are involved in cell signaling and are integral to the extracellular matrix.

    Molecular Complementarity

    • Fundamental to the function of glycosylated molecules, affecting interactions and recognition between biomolecules.

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    Description

    Explore the essential details of carbohydrates in this quiz. Learn about the structures, names, and biological functions of mono-, di-, and polysaccharides, as well as glycoconjugates. Test your knowledge on their properties and significance in biology.

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