Biochemistry: Chapter 2
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Questions and Answers

Which class of molecules is characterized by having both hydrophilic and hydrophobic properties?

  • Amphipathic compounds (correct)
  • Hydrophobic compounds
  • Ionic compounds
  • Aromatic hydrocarbons
  • What is primarily responsible for NaCl's high solubility in water?

  • The ionic nature of NaCl
  • Formation of hydration shells (correct)
  • High density of water molecules
  • Presence of hydrogen bonds
  • Which of the following statements about hydrophilic substances is true?

  • They are always ionic compounds.
  • They have higher boiling points than hydrocarbons.
  • They tend to be water-soluble. (correct)
  • They cannot form hydrogen bonds.
  • How does the high dielectric constant of water affect ionic compounds?

    <p>It reduces charge-charge interactions among ions.</p> Signup and view all the answers

    What term describes substances that do not dissolve well in water?

    <p>Hydrophobic substances</p> Signup and view all the answers

    Osmosis refers to the movement of water across a semi-permeable membrane influenced by what factor?

    <p>Differences in osmotic pressure</p> Signup and view all the answers

    Which type of compound is primarily formed when water hydrates cations and anions in solution?

    <p>Ionic compounds</p> Signup and view all the answers

    Which of the following properties is altered by solutes in a solvent?

    <p>Boiling point</p> Signup and view all the answers

    What happens to the electrostatic interactions of ions when dissolved in water?

    <p>They are weakened due to hydration.</p> Signup and view all the answers

    Why do nonpolar and nonionic compounds remain undissolved in water?

    <p>They do not interact with water molecules.</p> Signup and view all the answers

    What percentage of total human body weight is constituted by water?

    <p>45%-75%</p> Signup and view all the answers

    Why do polar molecules dissolve readily in water?

    <p>They replace water-water interactions with water-solute interactions.</p> Signup and view all the answers

    What is the lifetime of a hydrogen bond in water?

    <p>1-20 picoseconds</p> Signup and view all the answers

    Which of the following bonds has the highest dissociation energy?

    <p>Covalent O-H bond</p> Signup and view all the answers

    Which statement accurately describes nonpolar molecules in water?

    <p>They interfere with water-water interactions and cluster together.</p> Signup and view all the answers

    Which types of compounds typically form hydrogen bonds with water?

    <p>Alcohols, aldehydes, and ketones</p> Signup and view all the answers

    What structural arrangement allows water molecules to form hydrogen bonds?

    <p>Almost tetrahedral arrangement</p> Signup and view all the answers

    How does water act as a solvent for biological processes?

    <p>By solubilizing large numbers of ions and molecules</p> Signup and view all the answers

    What is a characteristic of hydrogen bonds?

    <p>They are relatively weak with a low bond dissociation energy.</p> Signup and view all the answers

    In what way do nonpolar molecules behave in aqueous solutions?

    <p>They tend to cluster together.</p> Signup and view all the answers

    Study Notes

    Water

    • Water constitutes a significant portion of the human body, ranging from 45% to 75% of total body weight.
    • It is distributed both inside cells (intracellular) and outside cells (extracellular).
    • Water plays a crucial role in various metabolic processes, including absorption, transport, digestion, and excretion of substances.

    Hydrogen Bonds

    • Hydrogen bonds are formed between water molecules due to their polarity.
    • These bonds provide the forces that keep water in a liquid state at room temperature.
    • Hydrogen bonds are relatively weak compared to covalent bonds.
    • The lifetime of a single hydrogen bond is fleeting, lasting only a few picoseconds.
    • Each water molecule can form hydrogen bonds with up to four neighboring water molecules.

    Water as a Solvent

    • Water's polarity and ability to form hydrogen bonds make it an excellent solvent.
    • Substances that form hydrogen bonds with water, such as alcohols, aldehydes, ketones, and compounds containing N-H bonds, readily dissolve in water.
    • Water can also dissolve ionic compounds, such as NaCl, by hydrating and stabilizing the ions, reducing electrostatic interactions between them.
    • The high dielectric constant of water further contributes to the solubility of ionic compounds by decreasing the attraction between oppositely charged ions.
    • Substances that dissolve in water are considered "hydrophilic," whereas those that don't are called "hydrophobic."

    Amphipathic Compounds

    • Amphipathic molecules possess both hydrophilic and hydrophobic regions.
    • Examples of amphipathic compounds include fatty acids, detergents, and phospholipids.

    Micelles and Liposomes

    • Amphipathic molecules can form structures like micelles and liposomes in aqueous solutions.
    • Micelles have a hydrophobic core with hydrophilic heads facing outwards.
    • Liposomes are spherical vesicles with a bilayer membrane of phospholipids, encapsulating a hydrophilic interior.

    Solutes and Physical Properties

    • Solutes can alter a solvent's physical properties, including:
      • Vapor pressure
      • Boiling point
      • Melting point
      • Osmotic pressure

    Osmosis

    • Osmosis is the movement of water across a semipermeable membrane driven by differences in osmotic pressure.

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    Water and Solubility PDF

    Description

    Test your knowledge on the properties of water, including its significance in the human body, the role of hydrogen bonds, and its effectiveness as a solvent. This quiz will help you understand the essential functions of water and how it interacts with various substances.

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