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General Biology: Chemical Basis of Life

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Termini in questo insieme (30)

  • What four types of atoms make up 96% of matter in organisms?
    Hydrogen, carbon, nitrogen, and oxygen.
  • What is the atomic number of an element?
    The number of protons in the nucleus of an atom, written as a subscript to the left of its symbol.
  • What is the mass number of an atom?
    The sum of protons and neutrons in the atom's nucleus.

  • What are isotopes? Radioactive isotopes?

    • Atoms of the same element with different numbers of neutrons, resulting in different masses.

    • Unstable isotopes that decay over time

  • What is an electron shell?
    A grouping of orbitals around the nucleus where electrons move; shells are numbered by their distance from the nucleus.
  • What is a valence shell and valence electrons?
    The outermost electron shell of an atom; electrons in this shell are called valence electrons.
  • Why are atoms most stable when their valence shells are full?
    Because full valence shells minimize reactivity; atoms fill shells by forming chemical bonds.
  • What is a covalent bond?
    A chemical bond formed when two atoms share unpaired valence electrons.
  • Difference between nonpolar and polar covalent bonds?
    Nonpolar bonds share electrons equally; polar bonds share electrons unequally due to differences in electronegativity.
  • What is electronegativity?
    The strength with which an atom pulls electrons toward itself, influenced by proton number and valence shell distance.
  • What partial charges result from polar covalent bonds in water?
    Oxygen has a partial negative charge and hydrogen atoms have partial positive charges.
  • What is an ionic bond?
    A bond formed by the transfer of electrons from one atom to another, creating charged ions.
  • Why is water an excellent solvent?
    Because it is polar and forms hydrogen bonds, allowing it to dissolve many ionic and polar substances.
  • What are hydrophilic and hydrophobic molecules?
    Hydrophilic molecules interact well with water; hydrophobic molecules do not dissolve in water.
  • What causes water's cohesion and surface tension?
    Hydrogen bonds between water molecules cause cohesion, leading to high surface tension.
  • Why does ice float on water?
    Because water expands when it freezes, forming a less dense crystal structure.
  • What is specific heat and why is water's specific heat high?
    Specific heat is energy needed to raise temperature; water's is high due to many hydrogen bonds requiring energy to break.
  • What is pH and what does it measure?
    pH is the logarithmic measure of hydrogen ion concentration in a solution, indicating acidity or basicity.
  • What is a buffer and its role in biological systems?
    A buffer is a substance that minimizes pH changes by reversibly binding or releasing H+ ions.
  • What is the first law of thermodynamics?
    Energy cannot be created or destroyed, only transferred or transformed.
  • What determines if a chemical reaction is spontaneous?
    Reactions are spontaneous if products have lower potential energy and higher entropy than reactants.
  • What was the significance of Stanley Miller's experiment?
    It demonstrated that complex organic molecules could form from simple molecules under early Earth conditions.
  • Why is carbon essential to life?
    Carbon forms four covalent bonds, allowing diverse and complex organic molecules.
  • What are functional groups in organic molecules?
    Specific groups of atoms (e.g., amino, carboxyl, hydroxyl) that determine chemical behavior of molecules.
  • What is polymerization?
    The process of linking monomers together to form polymers via condensation reactions.
  • What is hydrolysis?

    A reaction that breaks polymers into monomers by adding water.

  • What is chemical evolution, and how did it lead to life?

    • Formation of increasingly complex carbon-containing substances

    • Led to a molecule that could replicate itself

    • Switch from chemical → biological evolution

    • Natural selection took over

    • Descendants became metabolically active and acquired a membrane

    • → Characteristics of life fulfilled

  • What 4 atom types make up 96% of matter in organisms?

    Hydrogen, carbon, nitrogen, and oxygen

  • What is the mass of one proton or neutron? Mass of one electron?

    • One dalton (Da)

    • So small, practically nothing

  • Atomic Mass vs. Atomic weight

    • Atomic mass: The mass of one atom of an element, based on the average of its isotopes.

    • Atomic weight: The average atomic mass of an element found in nature