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
• \