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Water and Molecular Bonds in General Biology

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  • What type of bond shares electrons equally between atoms?
    Nonpolar covalent bonds share electrons equally, such as in C-C or C-H bonds.
  • What makes a covalent bond polar?
    Polar covalent bonds share electrons unequally due to differences in electronegativity, e.g., O-H bonds.
  • Why is water (H2O) a polar molecule?
    Water is polar because oxygen is more electronegative than hydrogen, causing electrons to spend more time near oxygen, creating partial charges.
  • What is the shape and molecular geometry of a water molecule?
    Water has a bent molecular shape with a bond angle of about 104.4°, due to two lone pairs on oxygen.
  • How does electronegativity affect bond polarity?
    Greater difference in electronegativity between atoms leads to more polar bonds, with electrons pulled toward the more electronegative atom.
  • What is a hydrogen bond?
    A hydrogen bond is a weak attraction between a partially positive hydrogen atom and a partially negative atom like oxygen or nitrogen.
  • Are electrons shared in hydrogen bonds?
    No, hydrogen bonds are noncovalent and do not involve sharing electrons.
  • What role do hydrogen bonds play in water's properties?
    Hydrogen bonds cause water's unique properties like cohesion, high specific heat, and ice floating.
  • What is the difference between hydrophilic and hydrophobic molecules?
    Hydrophilic molecules are polar and interact well with water; hydrophobic molecules are nonpolar and do not dissolve in water.
  • Why does ice float on liquid water?
    Ice is less dense because stable hydrogen bonds form a crystal lattice that spaces molecules farther apart than in liquid water.
  • What is the significance of water's high specific heat?
    Water can absorb or release large amounts of heat with little temperature change, helping moderate climate and body temperature.
  • How does water dissolve ionic compounds like salt?
    Water molecules surround ions, with oxygen attracting cations and hydrogen attracting anions, separating them into solution.
  • What is the pH scale a measure of?
    The pH scale measures the concentration of hydrogen ions \([H^+]\) in a solution.
  • How is pH calculated?
    pH = \(-\log_{10}[H^+]\), a logarithmic scale where each unit change represents a tenfold change in \([H^+]\).
  • What defines an acid and a base in terms of hydrogen ions?
    Acids donate hydrogen ions (H+), lowering pH; bases accept hydrogen ions, raising pH.
  • What is the molecular shape and polarity of methane (CH4)?
    Methane has a tetrahedral shape and is nonpolar due to symmetrical distribution of C-H bonds.
  • How does molecular shape affect polarity?
    Asymmetrical shapes with polar bonds create polar molecules; symmetrical shapes can cancel bond polarities, making molecules nonpolar.
  • What is the difference between polar and nonpolar molecules in terms of solubility?
    Polar molecules are soluble in water (hydrophilic), while nonpolar molecules are insoluble (hydrophobic).
  • What is the role of hydrogen bonds in DNA structure?
    Hydrogen bonds hold complementary base pairs together, stabilizing the DNA double helix.
  • What is the effect of hydrogen bonding on protein structure?
    Hydrogen bonds help fold proteins into specific 3D shapes essential for their function.