Chemistry Review

• Element: A substance that cannot be broken down into other kinds of substances by ordinary chemical means
• Atom: The smallest unit of an element that retains all of the element’s properties
• Proton: mass = about 1 unit, electric charge = +1 unit
• Neutron: mass = about 1 unit, electric charge = 0
• Electron: mass = about 0 units, electric charge = -1 unit
• The number of protons in an atom determines the element
• Isotopes: Atoms with the same number of protons (the same element), but different numbers of neutrons
• Valence Shell: The outermost shell that contains one or more electrons
• Covalent Bond: A chemical bond in which two atoms share one pair of valence electrons
• Molecule: Two or more atoms held together by chemical bonding
• Compound: Molecules with two or more elements
• Emergent Properties: The properties of a compound are not simply a combination of the properties of its elements
• Polar Molecule: A molecule with an uneven distribution of electric charge
• Hydrogen Bond: Weak attraction between polar molecules
• Ion: Atom (or molecule) with a net electric charge
• Ionic Bond: A chemical bond resulting from the attraction between oppositely charged ions
• Crystal: A regular three-dimensional lattice of atoms
• Homogeneous Mixture/Solution: Components cannot be distinguished with a light microscope
• Heterogeneous Mixture: Components can be distinguished visually
• Chemical Reaction: The making and breaking of chemical bonds
• Enzyme: Makes a chemical reaction take place more easily (a catalyst)
• Molecules always have kinetic energy, they are moving
• Temperature is just a measure of the average kinetic energy of molecules
• Diffusion: The net movement of a substance from an area of high concentration to an area of low concentration
• Osmosis: The diffusion of water across a semi-permeable membrane
• Four Classes of Biologically Important Macromolecules:

  • Lipids (e.g., fat, oil, wax): non-polar, high in chemical energy
  • Carbohydrates (e.g., sugars, starch, cellulose): polar, high in chemical energy
  • Nucleic Acids (e.g., DNA, RNA)
  • Proteins (e.g., enzymes, hormones, structural proteins)
• Monosaccharides: single sugar unit (e.g., glucose, fructose, galactose)

  • Disaccharides: two sugar units (e.g., sucrose, lactose, maltose)
  • Polysaccharides: many sugar units (e.g., starch, cellulose, glycogen)
• Proteins:

  • Folded chain of amino acids (unfolded: polypeptide)
  • Some parts polar, other parts non-polar
  • Primary structure: the sequence of amino acids
  • Secondary structure: repeated coils or folds of the primary structure
  • Tertiary structure: irregular folding of the primary and secondary structure
  • Quaternary structure (not always present): two or more tertiary structures integrated into a functional unit
  • Hydrophobic (water fearing) vs. hydrophilic (water loving)
• What is acidity?

  The concentration of hydrogen ions.
• What is acid?

  A substance that in water increases the concentration of hydrogen ions.
• What is a base?

  A substance that in water increases the concentration of hydroxide ions.
• Acidity of Water:

  • high pH = low concentration of hydrogen ions
  • low pH = high concentration of hydrogen ions
• What is the movement of a substance from a high concentration to a low concentration?

  Diffusion