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General Biology: Water and the Chemistry of Life

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Termini in questo insieme (25)

  • What defines the atomic number of an element?
    Atomic number is the number of protons in the nucleus of an atom.
  • What are isotopes?
    Isotopes are forms of an element with the same number of protons but different numbers of neutrons.
  • What is the difference between Carbon-12 and Carbon-14?
    Carbon-12 has 6 neutrons and is stable; Carbon-14 has 8 neutrons and is radioactive.
  • Why are isotopes important in science?
    Isotopes help track compounds, determine structure by NMR, and are used in medical imaging like MRI.
  • Which elements make up over 99% of atoms in the human body?
    Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P), and Sulfur (S).
  • What determines how elements bond?
    The number and arrangement of valence electrons in the outermost electron shell.
  • What is a covalent bond?
    A bond where valence electrons are shared between two atoms.
  • How do polar and nonpolar covalent bonds differ?
    Polar bonds have unequal sharing of electrons due to differences in electronegativity; nonpolar bonds share electrons equally.
  • What is electronegativity?
    An atom's affinity for electrons, increasing from left to right and bottom to top on the periodic table.
  • What is an ionic bond?
    An attraction between oppositely charged ions formed by the transfer of electrons.
  • Define cation and anion.
    A cation is a positively charged ion (loses electrons); an anion is negatively charged (gains electrons).
  • What is the difference between molecules and compounds?
    Molecules are atoms held together by covalent bonds; compounds are molecules with atoms of different elements.
  • Why is water called the 'universal solvent'?
    Because its polarity allows it to dissolve many polar and ionic substances.
  • What is a hydrogen bond?
    A weak electrostatic attraction between a hydrogen atom with a partial positive charge and an electronegative atom like O or N.
  • List some unique properties of water due to hydrogen bonding.
    High cohesion, surface tension, adhesion, high specific heat, and high heat of vaporization.
  • What is cohesion in water?
    Attraction between water molecules due to hydrogen bonding, leading to high surface tension.
  • What is adhesion in water?
    Attraction between water molecules and other substances, enabling capillary action.
  • What is specific heat?
    The amount of energy required to raise the temperature of 1 gram of a substance by 1°C.
  • How does water dissociate spontaneously?
    Water dissociates into H3O+ (hydronium) and OH- (hydroxide) ions: 2 H2O ⇋ H3O+ + OH-.
  • Define acids and bases according to Brønsted theory.
    Acids donate protons (H+); bases accept protons or donate hydroxide ions (OH-).
  • What is pH and how is it calculated?
    pH measures proton concentration: \(pH = -\log[H^+]\).
  • What is the role of buffers in biological systems?
    Buffers minimize pH changes by absorbing or releasing protons, maintaining homeostasis.
  • How does the carbonic acid buffer system regulate blood pH?
    It shifts equilibrium between H2CO3, HCO3-, and CO2 to counteract pH changes.
  • Why does water have a high heat of vaporization?
    Because hydrogen bonds require significant energy to break during evaporation.
  • What is the relative strength order of chemical bonds?
    Covalent > Ionic > Hydrogen bonds > van der Waals interactions.