1. AP BIOLOGY Chapter 2: Chemistry

2. 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.

4. Chemical Elements and Compounds  Organisms are made of matter Matter Element Atom Compound Organic compound Molecule Organic macromolecule

5. Life requires about 25 elements  92 naturally occurring  CHNOPS = 96% of dry weight  CHOPKINS CaFe, Mg NaCl = >99% 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 <0.01% of body mass

6. 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

7. 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

8. 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

9. Bonds  Covalent  Polar covalent  Nonpolar covalent  Ionic  Hydrogen  Van der Waals Interactions

10. 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.

12. 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.

14. 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