Biochemistry I: Carbohydrates
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Questions and Answers

What is a key function of D-Ribose in the body?

  • Structural component of RNA (correct)
  • Energy storage in adipose tissues
  • Source of calcium in bones
  • Precursor for glucose metabolism

    • Which monosaccharide is known as fruit sugar?

  • D-Galactose
  • D-Glucose
  • D-Fructose (correct)
  • D-Ribose

    • What is the normal blood glucose level range?

  • 120-140 mg/dl
  • 60-80 mg/dl
  • 70-100 mg/dl (correct)
  • 100-130 mg/dl

    • How can D-Galactose be primarily obtained?

    <p>Hydrolysis of lactose</p> Signup and view all the answers

    Which statement correctly describes 2-Deoxy D-Ribose?

    <p>It forms part of DNA structure.</p> Signup and view all the answers

    What is D-Fructose derived from commercially?

    <p>Sugar cane and sugar beets</p> Signup and view all the answers

    Which of the following describes the origin of D-Glucose?

    <p>Mainly produced during photosynthesis</p> Signup and view all the answers

    What is the role of D-Galactose in the human body?

    <p>Part of glycolipids and glycoproteins</p> Signup and view all the answers

    What type of isomerism occurs between glucose and fructose?

    <p>Structural Isomerism</p> Signup and view all the answers

    What characteristic defines stereoisomers?

    <p>Same molecular and structural formulae but differ in configuration</p> Signup and view all the answers

    Which carbon atom is designated as the anomeric carbon in glucose?

    <p>C-1</p> Signup and view all the answers

    Which type of isomerism involves D- and L- enantiomers?

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

    What is formed when a cyclic structure has an aldehyde functional group?

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

    Which of the following represents a form of structural isomerism?

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

    Which of the following statements accurately describes monosaccharides?

    <p>They consist of either one polyhydroxy aldehyde or ketone unit.</p> Signup and view all the answers

    What distinguishes anomerism from other types of stereoisomerism?

    <p>Differences in the configuration around the anomeric carbon</p> Signup and view all the answers

    What type of carbon atom is required for a molecule to be classified as a stereoisomer?

    <p>Chiral carbon atom</p> Signup and view all the answers

    Which of the following monosaccharides is classified as a hexose?

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

    What type of saccharide is formed when two monosaccharides join together?

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

    Which of the following is a correct pair of aldose and ketose monosaccharides based on their number of carbon atoms?

    <p>Tetrose: Erythrose and Erythrulose</p> Signup and view all the answers

    Identify the correct straight chain representation of glucose.

    <p>An aldehyde with six carbon atoms.</p> Signup and view all the answers

    What maximum number of monosaccharides can form oligosaccharides?

    <p>10</p> Signup and view all the answers

    How are monosaccharides primarily categorized based on their functional groups?

    <p>As aldoses and ketoses.</p> Signup and view all the answers

    Which of the following statements regarding carbon atom number in monosaccharides is true?

    <p>Monosaccharides can have a range of three to seven carbon atoms.</p> Signup and view all the answers

    Which of the following best describes the definition of biochemistry?

    <p>The study of the structure and function of biomolecules.</p> Signup and view all the answers

    Which biomolecules are classified as carbohydrates?

    <p>Sugars like glucose and fructose.</p> Signup and view all the answers

    What is the general formula for carbohydrates?

    <p>(CH2O)n</p> Signup and view all the answers

    Which type of carbohydrate consists of 1 unit?

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

    What is true about the ratio of hydrogen to oxygen in carbohydrates?

    <p>H:O is 2:1.</p> Signup and view all the answers

    Which of the following is an example of a heteropolysaccharide?

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

    Which type of saccharide contains more than 10 units?

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

    Which of these carbohydrates is classified as a polysaccharide?

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

    What are D- and L- isomers primarily defined by?

    <p>Their relationship as mirror images</p> Signup and view all the answers

    Which of the following describes a racemic mixture?

    <p>A mixture of equal amounts of D- and L-enantiomers</p> Signup and view all the answers

    What characteristic do epimers share?

    <p>They differ at exactly one carbon atom, other than the anomeric carbon</p> Signup and view all the answers

    What is created when glucose cyclizes in solution?

    <p>An additional asymmetric center</p> Signup and view all the answers

    Dextrorotatory substances are characterized by what property?

    <p>They rotate polarized light to the right</p> Signup and view all the answers

    Which of the following pairs represents epimers of glucose?

    <p>Galactose and Mannose</p> Signup and view all the answers

    What is the result of the cyclization of glucose regarding its structural forms?

    <p>Formation of anomers such as α- and β- glucopyranose</p> Signup and view all the answers

    The measurement of specific rotation in a polarimeter is dependent on what?

    <p>The concentration of the solution and the path length</p> Signup and view all the answers

    Study Notes

    Biochemistry I

    • Biochemistry is the study of the structure and function of biomolecules and their chemical reactions that occur in our body.
    • Biomolecules include carbohydrates, lipids, proteins, and nucleic acids.

    Carbohydrates

    • Carbohydrates are molecules composed of C, H, and O with H & O existing in the ratio of 2:1.
    • The general formula is (CH2O)n, hence the name carbohydrates.
    • Carbohydrates consist of sugars, which are polyhydroxy aldehydes (e.g., glucose, galactose, mannose) or polyhydroxy ketones (e.g., fructose).

    Classification of Carbohydrates

    • Monosaccharides are single sugar units.
    • Oligosaccharides contain 2-10 sugar units.
    • Polysaccharides contain more than 10 sugar units.
    • Homo-polysaccharides are composed of the same type of monosaccharide.
    • Hetero-polysaccharides are composed of different types of monosaccharides.
    • Examples include glucose, fructose, galactose, cellulose, chitin, starch, glycogen, glycoproteins, glycolipids, and various glycosaminoglycans (GAGs) such as hyaluronic acid, dermatan sulfate, heparin, chondroitin sulfate, and keratan sulfate.

    α- and β- Anomers of Glucose

    • Glucose exists as a closed-chain structure in solution.
    • Due to cyclization, an additional asymmetric center is created at C-1, called the anomeric carbon.
    • This leads to the formation of two isomers: α-glucopyranose and β-glucopyranose.

    Physiologically Important Monosaccharides

    • D-Ribose: An important structural component of ribonucleic acid (RNA) and other biomolecules like NAD and ATP.
    • 2-Deoxy-D-ribose: Participates in the structure of DNA.
    • D-Glucose: The most important and abundant monosaccharide.
    • Normal blood glucose level is 70-100 mg/dl.
    • The primary source of energy for living organisms.
    • Mainly made by plants and most algae during photosynthesis.
    • Present in fruit juices and obtained by hydrolysis of starch, sucrose, and maltose.
    • D-Fructose: Absorbed directly into the blood during digestion.
      • Found in honey, fruits, and berries.
      • Obtained by hydrolysis of sucrose and inulin.
      • Commercially derived from sugar cane and sugar beets.
      • Found in semen in the pyranose form.
    • D-Galactose: C-4 epimer of glucose.
      • Found in dairy products, avocados, and sugar beets.
      • Synthesized by the body, where it forms part of glycolipids and glycoproteins in various tissues.
      • A component of antigens present on blood cells.
      • Obtained by hydrolysis of lactose.

    Monosaccharides

    • Simple sugars consisting of a single polyhydroxy aldehyde (Glucose, Galactose) or ketone unit (Fructose).
    • Cannot be hydrolyzed into simpler units.

    Monosaccharides According to the Number of Carbon Atoms

    • Triose: Glyceraldehyde, Dihydroxyacetone
    • Tetrose: Erythrose, Erythrulose
    • Pentose: Ribose, Xylose, Ribulose, Xylulose
    • Hexose: Glucose, Galactose, Mannose, Fructose
    • Heptose: L-glycero-D-manno-heptose, Sedoheptulose

    Monosaccharide Combinations

    • Disaccharides: Formed by two monosaccharides (e.g., sucrose, lactose, maltose).
    • Oligosaccharides: Formed by 3-10 monosaccharides.
    • Polysaccharides: Formed by 11 or more monosaccharides.

    Structure of Monosaccharides

    • Glucose is a critical physiological and medicinal monosaccharide.
    • Represented in:
      • Straight-chain structure.
      • Ring/Cyclic structure (cyclic Fischer/Haworth projection).

    Isomerism of Monosaccharides

    • Isomers are compounds with the same molecular formula but different structures or configurations.
    • There are two main types:
      • Structural Isomerism: Different structures with the same molecular formulae. (e.g., Aldose-Ketose isomerism)
      • Stereoisomerism: Same molecular and structural formulae, but different configurations. (e.g., Enantiomerism, Epimerism, Anomerism)

    Types of Stereoisomerism

    • Enantiomerism (Optical isomerism): Mirror images of each other, denoted as D- and L-isomers.
    • Epimerism: Sugars differing from each other with respect to one carbon (excluding the anomeric carbon). (e.g., Galactose and mannose are epimers of glucose).
    • Anomerism: Two isomers (anomers) formed due to cyclization, which creates a new asymmetric center at C-1 (anomeric carbon). (e.g., α-glucopyranose and β-glucopyranose).

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    Description

    This quiz covers the fundamentals of carbohydrates within the field of Biochemistry. Explore the classification and structure of various types of carbohydrates, including monosaccharides, oligosaccharides, and polysaccharides. Understand their roles and significance in biochemical processes.

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