1. Basic Chemistry for Biology

2. Subatomic Particles Proton Neutron Electron Nucleus Positive charge
Identifies the atom (atomic #)
Neutron
No charge
# can change (isotopes)
Electron
Electron cloud
Negative charge
# can change (ions)

3. Elements in Biology
Element: pure substance that consists of only one kind of atom
Six elements found in all living things: NCHOPS
Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorus, Sulfur
The four major biomolecules in living things:
Carbohydrates (CHO) – sugars/starches
Lipids (CHO) – fats, waxes, steroids
Proteins (NCHOS) – enzymes, structures
Nucleic acids (NCHOP) – DNA/RNA

4. Energy Levels within an Atom

5. Chemical Bonds Hold two elements together (compound)
Atoms want to fill their outer energy level when bonding
Element
Electrons
1st orbital
2nd orbital
Valence e-
Hydrogen 1
Carbon 6
Oxygen 8
Nitrogen 7

6. Chemical Bonds Chemical bond: force that holds atoms together
Atoms react to form chemical bonds – WHY?
Achieve stability (fill outer energy level – valence electrons)
Satisfy the octet rule (full, stable outer energy level)
Share electrons = covalent bond
Transfer electrons = ionic bond
About Hydrogen bonding….
It’s an attractive force BETWEEN molecules, NOT a real chemical bond. More on that later….

7. Ionic Bonds Transfer of electrons between a metal and a nonmetal
Charged atoms = ions
Positive (cation) or negative ions (anion)
Attraction between ions = ionic bond
Example:
Sodium loses electron positive charge
Chlorine  gains electron  negative charge
Solid crystals at room temp
Ex: NaCl = table salt

8. Covalent Bonds
Electrons are SHARED between atoms to fill each atom’s outer energy level
Weakest bond type (not counting H-bonds, of course)
Can be any physical state at room temp

9. Covalent Bonds Involving Carbon
Needs 4 electrons  makes 4 bonds

10. Methane Gas: CH4
Sharing 4 electrons =4 Covalent Bonds

11. Oxygen Gas: O2
Shares 2 sets (pairs) of electrons
Double Bond

12. Water: H2O

13. Hydrogen Bond Weak attractive force between neighboring molecules
A hydrogen of one molecule is “slightly +” and attracts the “slightly negative” side of another molecule (lone pairs of e-)

14. Hydrogen Bonding: Water

15. Van der Wals Weak attractive forces between molecules
It’s a force… NOT a chemical bond
Ex: Gecko’s feet and glass

16. Dissociation of Water Molecules
Usually shortened to
“H+ ion”

17. pH Scale Acid Neutral Base Forms H+ ions in water 1 to 6.9
Ex: Orange Juice, coffee
pH of 1  strongest
Neutral
pH = 7 (pure water)
# of H+ ions= # of OH- ions
Base
Forms OH- (hydroxide) in water
7.1 to 14
Ex: Ammonia, bleach
FYI: pH = potential of Hydrogen ions

18. Buffer Solution that prevents drastic changes in pH
Maintains homeostasis

19. Neutralization Reaction
HCl + NaOH  H2O + NaCl Acid + Base  Water + Salt