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General Biology: Water and Its Properties

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이 집합의 용어 (24)

  • What type of bonds share electrons equally?
    Nonpolar covalent bonds share electrons equally, such as 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 or C-O bonds.
  • Why is water a polar molecule?
    Water is polar because it has polar covalent bonds and an asymmetrical shape, causing partial positive and negative regions.
  • What is electronegativity and how does it relate to water's polarity?
    Electronegativity is an atom's ability to attract electrons; oxygen is more electronegative than hydrogen, pulling electrons closer and creating polarity.
  • What are hydrogen bonds in water?
    Hydrogen bonds are weak attractions between the partially positive hydrogen of one water molecule and the partially negative oxygen or nitrogen of another.
  • How strong are hydrogen bonds compared to covalent bonds?
    Each hydrogen bond is about 5% as strong as a covalent bond, but many together create significant effects.
  • Name three emergent properties of water due to hydrogen bonding.
    Cohesion/adhesion, high specific heat and heat of vaporization, and ice floating due to lower density.
  • What is cohesion in water?
    Cohesion is the attraction between water molecules due to hydrogen bonding.
  • What is adhesion in water?
    Adhesion is the attraction between water molecules and other polar molecules.
  • Why does water have a high specific heat?
    Because hydrogen bonds absorb heat when breaking, water resists temperature changes, stabilizing environments.
  • Why does ice float on water?
    Ice forms a crystal structure stabilized by hydrogen bonds, making it less dense than liquid water.
  • What does it mean that water is a good solvent for polar solutes?
    Water dissolves polar molecules because its partial charges interact with and separate solute molecules or ions.
  • What is hydrophobic and give an example?
    Hydrophobic molecules are nonpolar and do not dissolve in water, e.g., oils and fats.
  • What is hydrophilic and give an example?
    Hydrophilic molecules are polar and interact well with water, e.g., salt and sugar.
  • Are electrons shared in hydrogen bonds?
    No, hydrogen bonds are noncovalent and do not involve sharing electrons.
  • How do hydrogen bonds contribute to DNA structure?
    Hydrogen bonds hold complementary base pairs together, stabilizing the DNA double helix.
  • What is pH a measure of?
    pH measures the concentration of hydrogen ions \([H^+]\) in a solution.
  • How is pH calculated?
    pH = -log10 \([H^+]\), a logarithmic scale of hydrogen ion concentration.
  • What does a pH of 7 indicate?
    A pH of 7 is neutral, meaning \([H^+] = [OH^-]\) in pure water.
  • How does pH change with hydrogen ion concentration?
    Each pH unit change represents a tenfold change in \([H^+]\) concentration.
  • What is the role of buffers in biological systems?
    Buffers resist changes in pH by accepting or donating hydrogen ions to maintain stable conditions.
  • What happens to hydrogen bonds when water evaporates?
    Hydrogen bonds break, allowing water molecules to escape as vapor, which cools surfaces (evaporative cooling).
  • Why is water's polarity important for membrane structure?
    Water's polarity drives the formation of hydrophobic and hydrophilic regions, essential for phospholipid bilayer formation.
  • What is the difference between polar and nonpolar molecules in water?
    Polar molecules dissolve in water (hydrophilic), while nonpolar molecules do not (hydrophobic).