AP Biology Summer Reading Chapter 2 Chapter 3 Chapter 4

Chemical Context of Life Matter- how would you define it??? Element/Compounds What’s the difference?

Chemical Context of Life The atom- composed of: Atomic number: Mass number: Isotopes: Radioactive isotopes: Atomic notation:

Chemical Context of Life Energy (definition from physics): Energy levels: How many energy levels are found on the periodic table: Valence electrons:

Chemical Bonding Covalent Double covalent Nonpolar covalent Ionic Hydrogen van der Waals

Covalent Bonding Sharing pair of valence electrons Number of electrons required to complete an atom’s valence shell determines how many bonds will form Ex: Hydrogen & oxygen bonding in water; methane

Polar/nonpolar covalent bonds Electronegativity attraction for electrons Nonpolar covalent •electrons shared equally •Ex: diatomic H and O Polar covalent •one atom more electronegative than the other (charged) •Ex: water

Polar/nonpolar bonds

Ionic bonding High electronegativity difference strips valence electrons away from another atom Electron transfer creates ions (charged atoms) Cation (positive ion); anion (negative ion) Ex: Salts (sodium chloride)

Hydrogen bonds Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)

van der Waals interactions Weak interactions between molecules or parts of molecules that are brought about by localized charge fluctuations Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

Water: Why is it important? Creates environment suitable for life Necessary for many biological and chemical processes

Water as a polar molecule: Polar- opposite ends, opposite charges Oxygen is more electronegative than hydrogen Partial charges result Gives water many distinct properties

Properties of Water: Cohesion- H+ bonds holding molecules together Adhesion- H+ bonds holding molecules to another substance Examples: water transportation in plants- flowing against the force of gravity (adhesion also)

Properties of Water: Surface tension- measurement of the difficulty to break or stretch the surface of a liquid Gives rain drops their tear- drop shape Result of Cohesion

Properties of Water: Water has a relatively high specific heat capacity Specific heat- amount of heat required to raise the temperature of 1g. of a substance 10C. Hydrogen bonds contribute to this property

Properties of Water: Heat of vaporization- quantity of heat required to convert 1g from liquid to gas states Why is this important?

Density Water is a dense substance: D= 1g/mL Due to hydrogen bonding At what temperature is water its most dense? What happens to the density as water approaches 00C?

Acid/Base & pH Dissociation of water into a hydrogen ion and a hydroxide ion Acid: increases the hydrogen concentration of a solution Base: reduces the hydrogen ion concentration of a solution pH: “power of hydrogen” Buffers: substances that minimize H+ and OH- concentrations (accepts or donates H+ ions)

The molar mass of table sugar is ??? (C12H22O11) How would you make a sugar water solution with a 1M concentration?

Organic chemistry Carbon: tetravalence Tetrahedron: shape determines function

Carbon based molecules Organic Chemistry: Carbon based molecules Tetravalence- carbon has four valance electrons (4 covalent bonds) High energy storage Diverse Molecules: hydrocarbons

same molecular formula, but different structure & properties Isomers: same molecular formula, but different structure & properties

Isomers: Structural-differing covalent bonding arrangement (straight vs. branched) Geometric-differing spatial arrangement Enantiomers-mirror images pharmacological industry

Functional Groups, I Attachments that replace one or more of the hydrogen bonded to the carbon skeleton of the hydrocarbon Each has a unique property from one organic compound to another

Functional Groups: Hydroxyl Group (-OH): oxygen bonded to hydrogen Alcohols Polar

Functional Groups: Carbonyl (C=O): carbon atom double bonded to oxygen Keytones and Aldehydes Polar

Functional Groups: Carboxyl Group (O=C-OH): oxygen double bonded to carbon bonded to a hydroxyl Polar Releases H+ ion- forms acids

Functional Groups: Amino Group (-NH2): nitrogen bonded to two hydrogen (Amino acids also contain carboxylic acids) amines acts as base

Functional Groups, II Sulfhydryl Group (C-SH) or (R- SH): carbon bonded to sulfur bonded to H Thiols Sulfur analogue of alcohols (sulfur takes the place of oxygen:

Functional Groups: Phosphate Group (-PO42-): phosphate ion one oxygen is bonded to a carbon skeleton polar

Biological thought: Vitalism (life force outside physical & chemical laws) Berzelius Mechanism (all natural phenomena are governed by physical & chemical laws) Miller