Chemical Basis of Life - Organic Compounds
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Questions and Answers

What is the main element that consists in living matter?

Carbon

Which organic molecules consist only of carbon and hydrogen?

  • Nucleic Acids
  • Carbohydrates
  • Proteins
  • Lipids (correct)

    • Monosaccharides are reducing sugars.

    True

    Cellulose is made up of long chains of __________ molecules linked together by beta-1,4 glycosidic bonds.

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

    Match the following organic compounds with their descriptions:

    <p>Starch = Mixture of amylose and amylopectin; stored in plants Glycogen = Composed of long chains of glucose linked by alpha-1,4 glycosidic bonds with frequent branches Cellulose = Most abundant organic compound on Earth used as a structural component in plant cell walls Chitin = Polysaccharide composed of N-acetylglucosamine monomers with nitrogen atoms</p> Signup and view all the answers

    What is the primary sugar monomer found in cellulose?

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

    Hemicellulose contains a diverse array of sugar units, including pentoses and hexoses.

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

    What is the primary component of pectin?

    <p>Galacturonic acid</p> Signup and view all the answers

    Chitin is a major component of cell walls and exoskeletons in ___________ and some algae.

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

    Match the following carbohydrates with their respective tests:

    <p>Molisch's test = Presence of carbohydrates Benedict's test = Presence of reducing sugars Fehling's test = Presence of reducing sugars Seliwanoff's test = Presence of ketoses Barfoed's test = Presence of monosaccharides Iodine test for starch = Presence of starch</p> Signup and view all the answers

    Study Notes

    Carbon Atom

    • Atomic number: 6
    • Electron configuration: 2, 4
    • Carbon atom has 4 valence electrons
    • Can form 4 covalent bonds with C, H, O, and N atoms
    • Forms molecules with straight chains, branched chains, and ring/cyclic structures

    Organic Compounds

    • Chemical compounds that consist of carbon
    • Examples: hydrocarbons (molecules consisting only of carbon and hydrogen)
    • Carbon and hydrogen atoms have similar electronegativity, making simple hydrocarbons nonpolar
    • Functional groups can attach to hydrocarbons, making them polar

    Biological Macromolecules

    • Simple molecules combine to form large molecules (macromolecules)
    • Often polymers
    • Monomer: repeating unit that serves as the building block for polymer synthesis
    • Polymer: giant molecule consisting of many similar repeating subunits linked by covalent bonds
    • Examples: carbohydrates, proteins, nucleic acids

    Synthesis and Breakdown of Polymers

    • Monomers connect through dehydration reactions, releasing water molecules
    • Each monomer contributes part of the water molecule released during the reaction
    • Every time a bond forms between monomers, a water molecule is removed
    • Hydrolysis: reverse reaction, adding water to break bonds and disassemble macromolecules

    Carbohydrates

    • Macromolecules containing C, H, and O
    • Molar ratio of H:O is 2:1
    • Empirical formula: Cx(H2O)y
    • Classified into 3 categories: monosaccharides, disaccharides, and polysaccharides

    Monosaccharides

    • Simplest carbohydrates
    • Contain carbonyl group (C=O) and multiple hydroxyl groups (-OH)
    • Formula: (CH2O)n
    • All monosaccharides are reducing sugars
    • Classified by:
      1. Number of carbon atoms (trioses, tetroses, pentoses, hexoses, heptoses)
      2. Placement of carbonyl group (aldose or ketose sugar)
      3. Chiral handedness (L-sugars or D-sugars)

    Hexoses

    • Monosaccharides with 6 carbon atoms
    • Examples: glucose, galactose, fructose
    • Glucose is a major nutrient for cells
    • Ring structure forms in aqueous solutions

    Functions of Monosaccharides

    • Primary source of energy for living organisms
    • Substrate for biosynthesis
    • Involved in cell-cell recognition and signaling

    Disaccharides

    • Composed of two sugar molecules
    • Examples: sucrose, lactose
    • Can be hydrolyzed into subunits
    • All are reducing sugars (except sucrose)

    Polysaccharides

    • Composed of many sugar molecules
    • Examples: starch, glycogen, cellulose
    • Classified into:
      1. Starch: mixture of amylose and amylopectin
      2. Glycogen: similar to starch, but more branched
      3. Cellulose: complex carbohydrate, provides structural support in plant cell walls
    • Functions:
      • Energy storage
      • Structural support
      • Cellular communication

    Derivatives of Carbohydrates

    • Chitin: complex carbohydrate in exoskeletons of arthropods
    • Hemicellulose: mixture of sugar monomers, serves as a structural component in plant cell walls
    • Pectin: complex polysaccharide found in plant cell walls, particularly in fruits

    Identification Tests for Carbohydrates

    • Molisch's test
    • Benedict's test
    • Fehling's test
    • Seliwanoff's test
    • Barfoed's test
    • Iodine test for starch

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    Description

    Learn about the importance of carbon atoms in living matter, their electron configuration, and how they form covalent bonds with other atoms to create various molecules.

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