1. Why chemistry, why again?
Because every topic we study in biology leads back to and requires an understanding of chemistry.
Why chemistry, why again?

2. You are what you eat! Energy and Building blocks for
You are made up of biomolecules!
Your biomolecules are built from food you eat
Your body breaks them down and rearranges them to give you:
Energy and
Building blocks for
lipids
carbohydrates,
proteins,
Nucleic acids (DNA, RNA)

3. What do you eat?

4. a mixture of biomolecules
Lipids – (fats, oils, cholesterol)
Carbohydrates (sugar and starch)
Protein
Vitamins
Minerals (Ca, PO4-2, Se, Fe, Ni, Zn, etc)
H2O
and
Energy (stored in chemical bonds)

5. Let’s review the basics - atoms
element
Carbohydrate
Lipids
Protein
Nucleic acids C  H O N P * S
**
* phospholipids
** some proteins

6. Atomic Structure
Protons
Electrons
Neutrons

7. Valence Electrons Anyone?
What are they?
How do I figure out how many an atom has?
How do I figure out how many an ion has?

8. The Ultimate Graphic Organizer

9. Molecular
Forces
Intramolecular
Forces
Intermolecular
Forces
Ionic Bonds
Covalent
Bonds
Dispersion
Forces
Dipole
Forces
Hydrogen
Bonds

10. Ionic and Covalent Bonding

11. Covalent Bond Polarity
Nonpolar Covalent bonds – equal sharing
0.0 < Electronegativity difference ≤ 0.4
Polar Covalent Bond – unequal sharing
0.4 < Electronegativity difference < 1.5
Line becomes arrow from positive to negative
Insulin

12. Molecular Polarity
When atoms don’t share equally, covalent bonds become polar (one end is more positive than the other end). But that doesn’t mean that the molecules are polar. Polar bonds can cancel each other out in a molecule.

13. Molecular Polarity examples
CH4
CO2
NH3
H2O

14. Molecular
Forces
Intramolecular
Forces
Inter molecular
Forces
Ionic Bonds
Covalent
Bonds
Dispersion
Forces
Hydrogen
Bonds
Dipole
Forces

15. Forces Comparisons Bond type Relative Strength Covalent 400x
Hydrogen bonds
10x
Dispersion Forces
<1x

16. Dispersion Weakest intermolecular force
Caused by the motion of electrons
More electrons per molecule, more attraction between molecules; i.e. halogens

17. Intermolecular Forces - Dispersion
Dispersion forces influence boiling point in nonpolar covalently bonded compounds. The greater the number of electrons in the molecule, the stronger the dispersion forces and hence the more energy requested to cause a change of phase (liquid to gas). Dispersion forces are the primary intermolecular attraction forces in nonpolar molecules.
Electrons momentarily gang up on one side of the molecule
e.g. bromine is a liquid, whereas iodine is a solid at STP

18. Intermolecular Forces - Dispersion
“Dispersion forces. Dispersion forces arise when a normally nonpolar atom becomes momentarily polar due to an uneven distribution of electrons, leading to an instantaneous dipole that induces a shift of electrons in a neighboring nonpolar atom. Dispersion forces are weak but can be important when other types of interactions are either missing or minimal (part (d) of Figure 18.6, “Tertiary Protein Structure Interactions”). This is the case with fibroin, the major protein in silk, in which a high proportion of amino acids in the protein have nonpolar side chains. The term hydrophobic interaction is often misused as a synonym for dispersion forces. Hydrophobic interactions arise because water molecules engage in hydrogen bonding with other water molecules (or groups in proteins capable of hydrogen bonding). Because nonpolar groups cannot engage in hydrogen bonding, the protein folds in such a way that these groups are buried in the interior part of the protein structure, minimizing their contact with water.”

19. Intermolecular Forces – Hydrogen Bonds
Strongest of the intermolecular forces
Only molecules with hydrogen in them
BIG role in living organisms!!!
Helical protein structures are stabilized by intrachain hydrogen bonding between the carbonyl oxygen atom of one amino acid and the amide hydrogen atom four amino acids up the chain (located on the next turn of the helix). This figure represents a right-handed α-helix.
“Hydrogen bond patterns in beta-sheets. A four-stranded beta-sheet is drawn schematically which contains three antiparallel and one parallel strand. Hydrogen bonds are indicated with red lines (antiparallel strands) and blue lines (parallel strands) connecting the hydrogen and receptor oxygen. “

20. Hydrogen Bonds

21. Hydrophilic - Hydrophobic
Hydrogen bonds determine whether a molecule or a part of a molecule is hydrophobic or hydrophilic.

22. Water H2O What’s the H, what’s the O? Why the 2?
Hydrogen Bonding – a big deal!
solubility (water is the universal solvent)
cohesion
adhesion
heat retention

23. Amazing Water Properties
Solubility
Capillary Action
Heat of Vaporization
Heat of Fusion
Surface Tension
Density Differences

24. Water Properties - Solubility
Life’s necessity

25. Water Properties- Capillary Action
425 ft
Paper Towels and Redwood Trees

26. Heat of Vaporization

27. Heat of Fusion

28. Water Properties – Surface Tension

29. Water Properties - Density

30. All together now Molecular Forces Intramolecular Forces Intermolecular
Ionic Bonds
Covalent
Bonds
Dispersion
Forces
Dipole
Forces
Hydrogen
Bonds