basic biochem

• Element


  A substance that cannot be broken down into simpler chemical substances
• Atom


  Smallest particle of an element that still has the properties of that element
• Nucleus


  Center of an atom

  
• Subatomic particles in atomic nuclei

  • Protons
  • Neutrons

  
• Protons


  Positively charged, large in size, the number determines the identity of an element (atomic number)
• Neutrons


  Neutral charge, same size as protons, add mass to the nucleus

  
• Atomic number


  The number of protons in the nucleus of an atom

  
• Atomic mass


  The number of protons + the number of neutrons in the nucleus

  
• Electrons


  Negatively charged particles that orbit the nucleus in an electron cloud, very small

  
• In an atom, the number of protons=the number of electrons, atoms have no electric charge
• Electron energy levels and sublevels

  • 1st energy level holds up to 2 electrons (s sublevel)
  • 2nd energy level holds up to 8 electrons (s sublevel 2, p sublevel 6)
  • 3rd energy level holds up to 18 electrons (s sublevel 2, p sublevel 6, d sublevel 10)
  • 4th energy level holds up to 32 electrons (s sublevel 2, p sublevel 6, d sublevel 10, f sublevel 14)

  
• Isotopes


  Atoms of the same element that have a differing number of neutrons in their nuclei
• Compound


  Substance composed of two or more elements that have been combined chemically
• The properties of a compound are different than the properties of the elements that make it up
• Chemical reaction example


  • 2H2 + O2 → 2H2O
• Chemical bonds


  Hold compounds together
• Types of chemical bonds

  • Covalent bonds (atoms share electrons to form a compound)
  • Ionic bonds (electrons are transferred from one atom to another)
• Ionic bonds do not form molecules
• Chemical equation


  Must obey the Law of Conservation of Matter, so the number of atoms available before a reaction must equal the number of atoms available after the reaction
• Parts of a chemical reaction

  • Reactants (that join together chemically)
  • Products (what is formed in the reaction)
• Mixture


  Combination of substances where the individual components retain their own properties
• Types of mixtures


  • Homogeneous (uniformly mixed parts)
  • Heterogeneous (not uniformly mixed parts)
• Solution


  A mixture where one substance (the solute) is dissolved in another (the solvent)
• Water is the universal solvent
• Acid


  A substance that releases H+ ions when mixed with water, has a pH of 0-6
• Acid example


  • HCl → H+ + Cl-
• Base


  A substance that releases OH- ions when mixed with water, has a pH of 8-14
• Base example


  • NaOH → Na+ + OH-
• A pH of 7 is neutral, neither acid nor base
• pH scale


  Measures the concentration of H+ ions in solution, the greater the concentration the lower the pH
• The pH scale shows an exponential relationship, each number represents a factor of 10
• Acids and bases have the ability to neutralize each other, when an acid and a base of equal strength are mixed the result is a neutral solution
• Neutralization reaction example


  • HCl + NaOH → NaCl + H2O
• Indicators


  Chemicals that change color in the presence of other chemicals
• Common indicators


  • Litmus paper (blue turns red in acid, red turns blue in base)
  • Bromthymol blue (blue in base, yellow in acid)
  • Phenolphthalein (colorless in acid, pink in base)
• Water molecule


  Polar, covalently bonded but electrons not shared equally, positive hydrogen end and negative oxygen end
• The polarity of water is responsible for many of its unique properties
• Adhesion


  The tendency of water to stick to the walls of its container, responsible for capillary action
• Cohesion


  The tendency for water molecules to stick to each other, responsible for surface tension
• Cohesive forces cause water to be slow to gain and lose heat, and to expand when it freezes