General Chemistry Study Guide: Intermolecular Forces, Solution Chemistry, Acids & Bases, and Biochemistry Fundamentals

Chapter 7: Attractive Forces & Lipids

Intermolecular Attractions & Strength

Intermolecular forces are the forces of attraction between molecules, which determine many physical properties of substances, such as boiling and melting points.

• London Dispersion Forces: Weakest, present in all molecules, especially nonpolar ones.

• Dipole-Dipole Interactions: Occur between polar molecules.

• Hydrogen Bonding: Strongest type, occurs when H is bonded to N, O, or F.

Example: Water exhibits hydrogen bonding, leading to its high boiling point compared to other group 16 hydrides.

Gases & Liquid-Gas Laws

Gas laws describe the relationships between pressure, volume, temperature, and amount of gas.

• Boyle's Law: $P_1V_1 = P_2V_2$ (at constant T and n)

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant P and n)

• Ideal Gas Law: $PV = nRT$

Example: Calculating the volume of a gas at different temperatures using Charles's Law.

Phase Changes & Diagrams

Phase changes are transitions between solid, liquid, and gas states. Phase diagrams show the conditions under which these phases exist.

• Melting, Freezing, Vaporization, Condensation, Sublimation, Deposition

• Triple Point: All three phases coexist.

Lipid Characteristics

Lipids are a diverse group of hydrophobic biomolecules, including fats, oils, and steroids.

• Types: Fatty acids, triglycerides, phospholipids, steroids.

• Solubility: Generally insoluble in water, soluble in nonpolar solvents.

Membrane Lipids & the Bilayer

Phospholipids form the basic structure of cell membranes, creating a bilayer that separates the cell from its environment.

• Hydrophilic heads face outward; hydrophobic tails face inward.

Chapter 8: Solution Chemistry

Factors Affecting Solubility

Solubility depends on the nature of solute and solvent, temperature, and pressure (for gases).

• "Like dissolves like": Polar solutes dissolve in polar solvents; nonpolar in nonpolar.

• Temperature: Solubility of solids increases with temperature; gases decrease.

Electrolytes & Nonelectrolytes

Electrolytes dissociate into ions in solution and conduct electricity; nonelectrolytes do not.

• Strong electrolytes: Completely dissociate (e.g., NaCl).

• Weak electrolytes: Partially dissociate (e.g., acetic acid).

• Nonelectrolytes: Do not dissociate (e.g., sugar).

Solution Calculations

Concentration expresses the amount of solute in a given amount of solution.

• Molarity (M): $M = \frac{\text{moles of solute}}{\text{liters of solution}}$

• Percent by mass/volume: $\% = \frac{\text{part}}{\text{whole}} \times 100$

Diffusion & Cellular Transport

Diffusion is the movement of particles from high to low concentration. In biology, this includes osmosis (water movement) and facilitated diffusion (via proteins).

• Osmosis: Water moves across a semipermeable membrane toward higher solute concentration.

• Active transport: Movement against a concentration gradient, requiring energy.

Chapter 9: Acids, Bases, Equilibrium & Buffers

Acids & Bases (Brønsted-Lowry)

Acids donate protons (H+); bases accept protons.

• Strong acids/bases: Completely ionize in water.

• Weak acids/bases: Partially ionize.

Ionization & Neutralization

Ionization is the process of forming ions in solution. Neutralization is the reaction of an acid with a base to form water and a salt.

• General equation: $\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}$

Chemical Equilibrium

At equilibrium, the rates of the forward and reverse reactions are equal.

• Equilibrium constant: $K = \frac{[\text{products}]}{[\text{reactants}]}$ (at equilibrium)

Le Châtelier's Principle

If a system at equilibrium is disturbed, it will shift to counteract the disturbance.

• Changes in concentration, temperature, or pressure can shift equilibrium position.

pH, pOH, and Buffer Systems

pH measures the acidity of a solution; buffers resist changes in pH.

• pH: $\text{pH} = -\log[H^+]$

• pOH: $\text{pOH} = -\log[OH^-]$

• Relationship: $\text{pH} + \text{pOH} = 14$ (at 25°C)

• Buffer: Solution of weak acid and its conjugate base (or vice versa).

• Henderson-Hasselbalch Equation: $\text{pH} = \text{p}K_a + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)$

Chapter 10: Amino Acids, Proteins & Enzymes

Amino Acids: Structure & Properties

Amino acids are the building blocks of proteins, each containing an amino group, carboxyl group, hydrogen, and unique side chain (R group).

• Classification: Polar, nonpolar, acidic, basic, aromatic, etc.

Protein Structure & Terminology

Proteins have four levels of structure:

• Primary: Sequence of amino acids.

• Secondary: Local folding (α-helix, β-sheet).

• Tertiary: 3D folding of a single polypeptide.

• Quaternary: Association of multiple polypeptides.

Enzymes: Function & Mechanism

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Active site: Region where substrate binds.

• Specificity: Enzymes are specific to substrates.

• Factors affecting activity: pH, temperature, inhibitors.

Enzyme Inhibition

Enzyme activity can be regulated by inhibitors.

• Competitive inhibitors: Bind to active site.

• Noncompetitive inhibitors: Bind elsewhere, changing enzyme shape.