AP BIOLOGY

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AP BIOLOGY

• Chapter 2 Chemistry

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Chemistry

• Study of matter and its forms and interactions
• Important to Biology
• Themes of hierarchy and form fits function , as
  well as, emergent properties are all because of
  chemistry to some degree.

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Chemical Elements and Compounds

• Organisms are made of matter
• Matter
• Element
• Atom
• Compound
• Organic compound
• Molecule
• Organic macromolecule

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Life requires about 25 elements

• 92 naturally occurring
• CHNOPS 96 of dry weight
• CHOPKINS CaFe, Mg NaCl gt99
• Carbon, hydrogen, oxygen, phosphorus, potassium,
  iodine, nitrogen, sulfur, calcium, iron,
  magnesium, sodium and chlorine..
• Trace elements are those required by an organism
  in quantities of lt0.01 of body mass

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Atomic structure

• Proton
• Positive, central/nucleus
• Mass 1 amu or Dalton
• Can not leave/add
• Atomic number
• Neutron
• Neutral, central/nucleus
• Mass 1 amu or Dalton
• Neutron proton atomic mass
• Atomic weight vs. mass number
• Electron
• Negative, found in orbitals
• Can leave, add, transfer, move
• Creates charge as well as many properties of
  element

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Ions

• Elements that have a charge as a result of the
  proton number and the electron number being
  unequal.
• Positive ions are called cations and have more
  protons than electrons
• Negative ions are called anions and have more
  electrons than protons

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Isotopes

• These are atoms of the same element with varying
  numbers of neutrons, thus different masses.
• Many elements have naturally occurring isotopes
  (decimals in atomic mass are from averaging
  these)
• C12 and C14 are examples.
• Radioactive isotopes spontaneously decay, giving
  off energy and particles.
• Can be biologically harmful
• Can also be medically/scientifically useful as
  tracers

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Bonds

• Covalent
• Polar covalent
• Nonpolar covalent
• Ionic
• Hydrogen
• Van der Waals Interactions

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Covalent bonds

• Created when electrons are shared by several
  atoms. Orbitals overlap. Bond is tight (short)
  and strong.
• Nonpolar covalent bonds contain equally shared
  electrons and create no charged regions
• Polar covalent bonds share electrons UNEVENLY and
  create areas of CHARGE within the molecule.

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Ionic bonds

• Are created between atoms when electrons are
  transferred and ions are created.
• Ions of opposite charge then attract.
• Relatively distant (long) and weaker.
• Ionic bonds can dissociate or separate and
  re-bond with something else more attractive.

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Hydrogen Bonds

• Exist between two molecules because of regions of
  charge within the molecules.
• Water forms many H-bonds.
• Polar covalent water has negative regions near
  the oxygen and positive regions near the hydrogen
  .
• Oxygen region from one water attract hydrogen
  regions from other waters.
• Water beads because of this.
• Very, very, very weak, but collectively HUGE

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