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

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

What do you eat?

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

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

Atomic Structure Protons Electrons Neutrons

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?

The Ultimate Graphic Organizer

Lewis Dot Structures Anyone?

The top 18 Lewis Dot Structures

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

Ionic and Covalent Bonding

Which Bond – When? it’s all about Electronegativity Definition – the “grabbiness” of an atom for an electron; the more grabby, the greater the EN value ex, F = 4.0; Na = 0.9; C = 2.5; H = 2.1; O = 3.5 Use EN difference to determine bond type Ionic bonds – EN difference ≥ 1.5 Covalent Bonds - EN Difference < 1.5

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

Practice – Which Bond Type? Chemical Bond EN difference I, PC, NPC H-F |2.1 – 3.98|= 1.88 I C-H |2.55 – 2.1|= 0.45 NPC Cl-O K-Cl O-H C-O S-O Br-Br

Molecular Polarity

Molecular Polarity examples CH4 CH3Cl HCl NH3 H2O

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

Intermolecular Forces Bond type Dissociation energy (kcal),[2][3] Covalent 400 Hydrogen bonds 12–16 Dipole–dipole 0.5–2 Dispersion Forces <1

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

Intermolecular Forces - Dispersion Electrons momentarily gang up on one side of the molecule 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. e.g. bromine is a liquid, whereas iodine is a solid at STP

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.” http://www.flatworldknowledge.com/node/421745#web-421745

Intermolecular Forces – Dipole Interactions attraction between polar molecules defines the behavior of many biological compounds

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. “ http://www.friedli.com/herbs/phytochem/proteins.html

Hydrogen Bonds

Intermolecular Forces Hydrogen Bonding

Hydrophilic - Hydrophobic

Water – remember your chemistry? 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

Amazing Water Properties Surface Tension Capillary Action Density Differences Solubility

Water Properties – Surface Tension

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

Water Properties - Density

Water Properties - Solubility Life’s necessity

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