Biology Ch. 2

  • Atoms are composed of protons neutrons and electrons
  • APE MAN (Atomic Number, Element, Atomic Mass)   * Electrons: negatively charged particles located in orbitals   * Neutral atoms have the same number of electrons and protons
  • Ions: charged particle electrons change
  • Atomic Number: equal to the number of protons
  • Element: can’t be broken down into another substance by ordinary means
  • Atomic Mass: sum of protons and neutrons
  • Cations (cat eyes)
  • Anion (ant)
  • Isotopes: atoms of a single element that possess different numbers of neutrons
  • Radioactive isotopes are unstable
  • Nucleus is center of an atom ( DNA inside nucleus)

Electron Arrangement

  • energy levels

  KLM (k is inner) K-2 L-8 M-8

  • If an atom has a full outer shell it is non reactive

Redox

  • LEO says GER

Oxidation: lose electron

Reduction: gain electron

  • valence electrons: outer most shell
  • Inert: atoms outer most level is full
  • Octet rule: must have 8

CHON

  • carbon hydrogen oxygen nitrogen make up 96.3 % of body
  • Molecule: group of 2 or more atoms held together in a stable association
  • Compounds: molecule containing more than one element

all compounds are molecules but not all molecules are compounds

Bonds

  • Ionic bonds: formed by the attraction of oppositely charged ions
  • Loses an electron to have a positive charge
  • Gains an electron to have a negative charge

electrical attraction of water molecules can disrupt forces holding ions together

  • Covalent Bonds: form when atoms share 2 or more valence electrons
  • Strength of a covalent bond depends on number of bonds present

Electronegativity: atoms affinity for electrons

  • Nonpolar Covalent Bonds: if electron sharing is equal
  • Polar Covalent Bonds: if electron sharing is unequal

Water Molecule Diagram with negative O and positive H

  • Chemical Reactions require reactants and products; formation and breaking of bonds
  • Photosynthesis Reaction: 6H2O+ 6CO2~ C6H12O6+6O2
  • Aerobic requires oxygen
  • The extent of chemical reactions is influenced by… temperature concentration and catalysts
  • as temp increases, molecule movement increases, reaction rate increases
  • catalysts: a substance that speeds up a chemical reaction (related to enzymes)

Many reactions are reversible

  • Water is life sustaining
  • most outstanding chemical property of water is the ability to form hydrogen bonds
  • Order of Increasing Strength ( H-BOND, IONIC, COVALENT )
  • Hydrogen bonds are stronger in numbers
  • Cohesion: attraction to one another
  • Adhesion: attraction to other polar molecules
  • Properties of Water

     1. High Specific Heat: theres a large amt of energy required to change the temp.   2. High Heat of Vaporization: evaporation of water from a surface causes cooling   3. Solid water is less dense than liquid water ex. ice floating   4. Water is a good solvent: water can dissolve polar molecules and ions   5. Water organizes nonpolar molecules: hydrophobic/hydrophilic   6. Water can form ions: OH- H+

           1. Water freezes from the top down      2. solute: solid      3. solvent: liquid

Acids and Bases

  • aka pH
  • Acid- any substance that dissociates in water to increase the H+ concentration
  • Base- substance that combines with the H+ dissolved in water to lower the H+ concentration \

The lower the H+ the more basic (higher pH)

  • Buffer: substance that resists changes in pH, keeps pH in a certain range
  • Acts by   * releasing H+ when base is added   * absorbing H+ when acid is added
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