Carbohydrates Overview and Biomedical Importance
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Questions and Answers

Which term describes carbohydrates that yield only one type of monosaccharide upon hydrolysis?

  • Disaccharides
  • Monosaccharides
  • Homo-polysaccharides (correct)
  • Oligosaccharides
  • What class of carbohydrates is characterized by yielding more than ten monosaccharide units upon hydrolysis?

  • Oligosaccharides
  • Polysaccharides (correct)
  • Disaccharides
  • Monosaccharides
  • What type of monosaccharide is characterized by having a carbonyl group at C1?

  • Aldose (correct)
  • Hexose
  • Triose
  • Ketose
  • Which of the following correctly identifies a structure containing five carbon atoms in its backbone?

    <p>Pentose (C)</p> Signup and view all the answers

    Which carbohydrates are described as yielding two monosaccharide molecules upon hydrolysis?

    <p>Disaccharides (A)</p> Signup and view all the answers

    Which of the following statements correctly describes mutarotation?

    <p>It involves the equilibrium mixture of anomers A and B. (B)</p> Signup and view all the answers

    What is the specific rotation of β-D-Glucose?

    <p>+18.7° (C)</p> Signup and view all the answers

    Which monosaccharide is primarily known as the sweetest and is a ketohexose?

    <p>Fructose (A)</p> Signup and view all the answers

    Which of the following statements correctly identifies a precursor of glycerol?

    <p>D-glyceraldehyde and dihydroxyacetone (D)</p> Signup and view all the answers

    What is a common feature of the hexoses mentioned in the content?

    <p>They undergo mutarotation. (D)</p> Signup and view all the answers

    Which of the following statements regarding the structure of carbohydrates is accurate?

    <p>Carbohydrates can contain elements such as nitrogen, phosphorus, or sulfur. (C)</p> Signup and view all the answers

    What defines a reducing disaccharide?

    <p>It contains a free aldehyde group or a ketone group. (C)</p> Signup and view all the answers

    Which carbohydrate serves as a primary energy storage molecule in plants?

    <p>Starch (D)</p> Signup and view all the answers

    What is the primary role of carbohydrates in the context of cellular respiration?

    <p>To be converted into ATP for energy. (D)</p> Signup and view all the answers

    Which of the following carbohydrate derivatives is an example of a sugar acid?

    <p>Ascorbic acid (A)</p> Signup and view all the answers

    What is a common function of glycosaminoglycans (GAGS) in the body?

    <p>Act as structural components in connective tissues. (A)</p> Signup and view all the answers

    Which of the following polysaccharides is classified as a homopolysaccharide?

    <p>Cellulose (A)</p> Signup and view all the answers

    In what manner does the body utilize amino acids in the absence of carbohydrates?

    <p>Amino acids are transformed into glucose. (A)</p> Signup and view all the answers

    Which of the following is classified as an aldotriose?

    <p>D-Glyceraldehyde (A)</p> Signup and view all the answers

    What distinguishes D-Erythrulose from D-Fructose in their carbon configurations?

    <p>The position of the carbonyl group (B)</p> Signup and view all the answers

    Which compound is specifically categorized as an aldohexose?

    <p>D-Galactose (B)</p> Signup and view all the answers

    Which monosaccharide has four carbon atoms and contains a ketone group?

    <p>D-Ribulose (B)</p> Signup and view all the answers

    What is the characteristic feature of chirality in monosaccharides?

    <p>The presence of an asymmetric carbon atom (B)</p> Signup and view all the answers

    Which of the following pairs of monosaccharides share the same number of carbon atoms?

    <p>D-Glucose and D-Mannose (A)</p> Signup and view all the answers

    What structural feature differentiates aldopentoses from aldohexoses?

    <p>The total number of carbon atoms (D)</p> Signup and view all the answers

    Which statement about chiral and achiral molecules is false?

    <p>Ketoses with 3 carbon atoms are chiral. (B)</p> Signup and view all the answers

    What is the maximum number of stereoisomers for a hexose?

    <p>16 (C)</p> Signup and view all the answers

    Which of the following correctly matches the type of isomerism with its definition?

    <p>Epimerism - isomers differ at one chiral carbon. (A)</p> Signup and view all the answers

    Which of the following statements regarding optical isomerism is true?

    <p>Dextro and levorotatory refer to the direction of light rotation. (D)</p> Signup and view all the answers

    In the context of stereoisomers, which of the following statements is incorrect?

    <p>All stereoisomers have identical molecular formulas. (B)</p> Signup and view all the answers

    What is true about the stereoisomers of a pentose?

    <p>Pentoses can have 8 different stereoisomers. (D)</p> Signup and view all the answers

    What distinguishes D-glucose from L-glucose?

    <p>D-glucose and L-glucose are enantiomers and mirror images. (C)</p> Signup and view all the answers

    How many D stereoisomers does a tetrose have?

    <p>2 (A)</p> Signup and view all the answers

    What results when equal amounts of dextrorotatory and laevorotatory isomers are mixed?

    <p>The activities of each isomer cancel each other, resulting in no optical activity. (D)</p> Signup and view all the answers

    How do D-Mannose and D-Galactose differ in terms of their structure?

    <p>They differ in the positions of -OH groups at carbons 2 and 4. (D)</p> Signup and view all the answers

    Which of the following statements correctly describes isomers?

    <p>Isomers share the same chemical formula but have different structural arrangements. (B)</p> Signup and view all the answers

    What distinguishes α-D-glucopyranose from β-D-glucopyranose?

    <p>The -OH group on the anomeric carbon is positioned differently. (D)</p> Signup and view all the answers

    What is mutarotation in the context of sugar chemistry?

    <p>The spontaneous interconversion between α and β anomers in solution. (D)</p> Signup and view all the answers

    Which carbon is asymmetrical in the closed-chain structure of glucose?

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

    Why are D-Mannose and D-Glucose considered epimers?

    <p>They differ only at carbon 2. (C)</p> Signup and view all the answers

    Which statement about fructose is correct?

    <p>Fructose is a structural isomer of glucose and galactose. (A)</p> Signup and view all the answers

    Flashcards

    Monosaccharides

    Carbohydrates that can't be broken down into simpler sugars.

    Disaccharides

    Carbohydrates that yield two monosaccharide units on hydrolysis.

    Oligosaccharides

    Carbohydrates that yield 3 to 10 monosaccharide units on hydrolysis.

    Polysaccharides

    Carbohydrates that yield more than ten monosaccharide units on hydrolysis.

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    Classifying Monosaccharides

    Monosaccharides are classified based on the position of the carbonyl group and the number of carbon atoms.

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    What is the chemical definition of carbohydrates?

    Carbohydrates are organic compounds that typically have the formula (CH₂O)n, where n is a number greater than or equal to 3. They are polyhydroxy aldehydes or ketones, or substances that yield these compounds on hydrolysis.

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    What's the primary function of carbohydrates in the body?

    Carbohydrates serve as a primary source of energy for the body, providing fuel for cellular activities. They can be broken down into glucose, which is used in cellular respiration to produce ATP.

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    What are simple sugars called?

    Glucose, fructose, galactose, and ribose are examples of simple sugars called monosaccharides. They cannot be further broken down into smaller carbohydrate units.

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    What are sugars made of two monosaccharides called?

    Disaccharides are formed when two monosaccharides join together through a glycosidic linkage. Common examples include sucrose (glucose + fructose) and lactose (glucose + galactose).

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    What are complex carbohydrates called?

    Polysaccharides are complex carbohydrates composed of long chains of monosaccharides linked together by glycosidic bonds. They can be branched or unbranched. Examples include starch, glycogen, and cellulose.

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    What type of bond links monosaccharides together?

    A glycosidic linkage is a covalent bond formed between two monosaccharides by the removal of a water molecule. It is the type of bond that holds together disaccharides and polysaccharides.

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    What are the two main types of polysaccharides based on their composition?

    Starch, glycogen, and cellulose are examples of homopolysaccharides, meaning they are composed of only one type of monosaccharide. Heteropolysaccharides are made up of different types of monosaccharides.

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    What are complex molecules formed by the attachment of carbohydrates to other molecules called?

    Glycoconjugates are complex molecules formed by the covalent attachment of carbohydrates to other molecules like proteins or lipids. They play vital roles in cell recognition, signaling, and adhesion processes.

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    Triose

    The simplest type of sugar molecule, with three carbon atoms.

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    Tetrose

    A monosaccharide with four carbon atoms.

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    Pentose

    A monosaccharide with five carbon atoms.

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    Hexose

    A monosaccharide with six carbon atoms.

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    Aldose

    A monosaccharide with an aldehyde group (CHO) at one end.

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    Ketose

    A monosaccharide with a ketone group (C=O) at one end.

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    Asymmetric carbon

    A carbon atom that is bonded to four different atoms or groups of atoms.

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    Chirality

    The property of having a mirror image that cannot be superimposed on the original molecule.

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    Mutarotation

    A phenomenon where the specific rotation of an aqueous solution of a pure α or β anomer changes over time until it reaches a constant value, representing an equilibrium mixture of the anomers.

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    Reducing Sugar

    A type of sugar that can exist as both α and β anomers, which interconvert in solution.

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    Anomeric Carbon

    A chiral carbon atom that is bonded to at least one oxygen atom and has four different atoms or groups attached to it.

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    Ketohexose

    A monosaccharide with a carbonyl group (C=O) at the second carbon atom.

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    Aldohexose

    A monosaccharide with an aldehyde group (CHO) at the first carbon atom.

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    Chiral Carbohydrates

    Carbohydrates that have 3 or more carbon atoms and contain an aldehyde group, or have 4 or more carbon atoms and contain a ketone group.

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    Stereoisomers: How Many?

    The maximum number of possible stereoisomers for a molecule is determined by the formula 2^n, where n represents the number of chiral carbon atoms.

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    Enantiomers

    Stereoisomers that are non-superimposable mirror images of each other.

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    Epimers

    Stereoisomers that differ in the configuration of only one chiral center.

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    Anomers

    The two cyclic forms of a sugar that differ in the configuration of the anomeric carbon.

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    Optical Activity

    The rotation of plane-polarized light by a chiral molecule. Dextrorotatory molecules rotate light to the right, while levorotatory molecules rotate light to the left.

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    Dextrorotatory

    The ability of a molecule to rotate plane-polarized light to the right (clockwise). Designated with a plus sign (+).

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    Levorotatory

    The ability of a molecule to rotate plane-polarized light to the left (counterclockwise). Designated with a minus sign (-).

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    Racemic Mixture

    A mixture containing equal amounts of enantiomers (D and L isomers) resulting in zero optical activity.

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    Anomers (Alpha and Beta)

    Two forms of a cyclic sugar that differ in the orientation of the hydroxyl group attached to the anomeric carbon.

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    Stereoisomers

    A type of isomerism where the difference in structure is due to the arrangement of atoms around a chiral center.

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    Study Notes

    Carbohydrate Overview

    • Carbohydrates are compounds with the formula (CH₂O)ₙ, often called "hydrates of carbon."
    • Many, but not all, carbohydrates fit this empirical formula. Some may also contain nitrogen, phosphorus, or sulfur.
    • Carbohydrates are classified as polyhydroxy aldehydes or ketones, their derivatives, and their polymers.

    Biomedical Importance of Carbohydrates

    • Carbohydrates play a crucial role in numerous biological functions, including their nomenclature, classification, structures, glycosidic linkages, and cyclization.
    • Monosaccharides, their derivatives (e.g., sugar phosphates, deoxy sugars, sugar alcohols, sugar acids, ascorbic acid), and their diverse linkages (e.g., reducing and non-reducing disaccharides) are important.
    • Polysaccharides (homopolysaccharides and heteropolysaccharides) and glycoconjugates (proteoglycans, glycoproteins, and peptidoglycans) have vital roles.
    • Digestion and absorption of carbohydrates and associated clinical correlations are also key topics.

    Definition of Carbohydrates

    • Carbohydrates are polyhydroxy aldehydes or ketones, or derivatives, or polymers of these compounds.
    • Some carbohydrates don't precisely follow the (CH₂O)ₙ formula, like lactic acid.

    Carbohydrate Functions

    • Carbohydrates are the body's primary energy source, converted to ATP during cellular respiration.
    • They also serve as energy storage molecules (glycogen in animals, starch in plants).
    • Carbohydrates are structural components (e.g., cellulose in plants, chitin in insects).
    • They're also involved in forming part of various molecules, including connective tissue, bone, cartilage, skin, membranes, nerve tissue, and blood group substances, and nucleic acids (ribose and deoxyribose).
    • Carbohydrates are also components of vitamins, antibiotics, and drugs.

    Classification of Carbohydrates

    • Classification is principally based on the number of sugar units produced upon hydrolysis.
    • The major categories are monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
      • Monosaccharides cannot be further hydrolyzed, yielding only one sugar molecule.
      • Disaccharides are composed of two monosaccharides linked together.
      • Oligosaccharides have 3-10 monosaccharides, while polysaccharides have more than 10.
    • Polysaccharides are further divided in Homo and Hetero-polysaccharides.

    Monosaccharides

    • Simple sugars that cannot be hydrolyzed further.
      • Classified by the position of the carbonyl group (aldose or ketose) and the number of carbons (triose, tetrose, pentose, hexose, etc.).
      • Many, have stereoisomers ("D" and "L") that are mirror images.
    • Important examples include, D-ribose, D-deoxyribose, D-glucose, D-fructose, and dihydroxyacetone.

    Stereoisomers

    • Different arrangements of atoms in a molecule with the same chemical formula, but different configurations (shapes).
      • "D" and "L" isomers are mirror images (enantiomers).
      • Optical isomers have different optical activity (rotating plane-polarized light).
      • Epimers differ only in the configuration around one carbon.
      • Anomers are cyclic monosaccharides, differing in configuration around the anomeric carbon (the new chiral center).

    Mutarotation

    • The spontaneous interconversion of a and β anomers of a sugar in solution, leading to a stable equilibrium mixture.

    Important Monosaccharides (specific examples)

    • Glyceraldehyde and dihydroxyacetone are trioses.
    • Erythrose is a tetrose, Ribose a pentose, and D-glucose, D-fructose, and D-galactose are hexoses
    • Other important pentoses are D-ribose and 2-deoxy-D-ribose (component of RNA and DNA, respectively).
      • Other types of sugars could be important
    • Carbohydrates are involved in various biological processes, from energy production to forming structural components of cells.

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