bio 181 unit 1

basic chemistry, macromolecules

matter

• anything that occupies space and has mass

• comprised of atoms, the fundamental units of life

atom

• consists of a nucleus with neutrons and protons, surrounded by electrons

• atomic number: number of protons

the “big four” elements

• carbon, oxygen, hydrogen, nitrogen

• make up the bulk of living cells

• human body comprised of 65% O, 18% C, 10% H, and 7% other elements

electron

• negative charge

• more or less than the usual number creates an ion (cation +, anion -)

• metals donate e-, nonmetals accept e-

• valence electrons: outermost shell; responsible for bonding

isotope

• atom with a different number of neutrons than its number of protons

• some isotopes are radioactive

• adding neutrons to an atom’s nucleus can make it unstable, causing it to fall apart (decay) and release energy

  • half life

atomic bonding

• ionic bond: involves the transfer of one or more electrons from one atom to another

  • metal and nonmetal

• covalent bond: when two atoms share electrons

  • nonmetal with nonmetal

  • can be polar or nonpolar

polarity

• polar: electrons are distributed unequally about an atom

  • caused by a difference in electronegativity between atoms

  • positive (s+) and negative (s-) regions

• nonpolar: electrons are distributed equally about an atom

water properties

• cohesion: natural attraction of water molecules to each other through hydrogen bonding; sticking together

• frozen water floats because it is less dense than liquid water

  • hydrogen bonds hold molecules apart as water freezes

  • ice insulates the water below it, helping aquatic organisms survive

• water is a great solvent due to its polarity

• water has a high specific heat (amount of energy needed to raise the temp of a substance by 1’C)

  • absorbs large amounts of heat well; evaporation