Water, the Solvent of Life - Vocabulary Flashcards

Vocabulary flashcards covering key concepts from water properties, solution chemistry, acid-base theory, and foundational origin-of-life topics in the lecture notes.

Hydrogen bond

A directional electrostatic attraction between the oxygen atom of one water molecule and a hydrogen atom covalently bonded to another electronegative atom, giving water its unique properties.

Dielectric constant

A dimensionless property that reflects a solvent’s ability to screen electric charges; water at 25°C has ε ≈ 78.5, aiding ionic interactions in solution.

Hydration/solvation

The process by which water surrounds and stabilizes solute ions or molecules through interactions like hydrogen bonding.

Hydrophilic

Describes compounds that dissolve easily in water; typically polar or charged.

Hydrophobic

Describes nonpolar compounds that tend to avoid water and have low solubility in water.

Amphipathic

Molecules that contain both polar/charged and nonpolar regions, leading to dual solubility behaviors.

Micelle

Thermodynamically stable aggregates of amphipathic molecules in water, with nonpolar tails inward and polar heads outward.

Bilayer

A membrane structure formed by amphipathic molecules with polar heads facing water and nonpolar tails shielded inside.

Hydrophobic effect

Tendency of nonpolar regions to cluster together in water, promoting ordered water structure around solutes and driving micelle/bilayer formation.

Van der Waals interactions

Weak interatomic attractions/repulsions arising from transient dipoles; include London dispersion forces.

London dispersion forces

A type of van der Waals interaction due to instantaneous dipoles, present in all molecules. Strength increases with molecular size.

van der Waals radius

A measure of the effective size of an atom for nonbonding interactions; used to estimate distances between atoms in close contact.

Clathrate (water cage)

An ordered water structure that forms a cage around a nonpolar solute, reducing solute–solvent disruption.

Osmotic pressure

The minimum pressure needed to prevent solvent flow across a semipermeable membrane; described by Π = i c R T.

Osmolarity

Product of the van’t Hoff factor and the solute’s molar concentration (i · c).

Isotonic

Solution with osmolarity equal to that of a cell’s cytosol, causing no net water movement.

Hypertonic

Solution with higher osmolarity than the cytosol, causing water to move out of the cell.

Hypotonic

Solution with lower osmolarity than the cytosol, causing water to move into the cell.

Ion product of water (Kw)

The product [H+][OH−] of water; at 25°C, Kw = 1.0 × 10−14.

pH

A measure of acidity; pH = −log[H+]. Neutral pH is 7.0 at 25°C.

pOH

The negative log of the hydroxide concentration; pH + pOH = 14 at 25°C.

pKa

The negative logarithm of an acid’s Ka; lower pKa means a stronger acid.

Ka

Acid dissociation constant; a measure of an acid’s strength in solution.

Conjugate acid-base pair

Two species that differ by one proton (H+), existing on opposite sides of a reaction.

Brønsted–Lowry acid

A substance that donates a proton (H+).

Brønsted–Lowry base

A substance that accepts a proton (H+).

Amphoteric

A substance that can act as both an acid and a base.

Monoprotic/Diprotic/Triprotic acids

Acids that donate one, two, or three protons, respectively (e.g., HCl, H2SO4, H3PO4).

Keq (equilibrium constant)

Ratio of product activities to reactant activities at equilibrium for a given reaction.

Ionization of water

H2O ⇌ H+ + OH−; in aqueous solution, hydronium ions (H3O+) form when H+ is solvated.

Proton hopping

A mechanism by which protons are rapidly transferred through a network of hydrogen bonds (e.g., via H3O+).

Endosymbiotic theory

Hypothesis that organelles like mitochondria originated as engulfed prokaryotes living inside larger cells.

Miller–Urey experiment

Classic experiment simulating early Earth conditions that produced amino acids from simple gases.

Hydrothermal vents

Undersea environments with high temperatures and minerals, proposed as possible sites for origin of life.

Domains of life

Three domains: Bacteria, Archaea, and Eukarya, representing major phylogenetic lineages.

Chirality (R/S and D/L)

Property of asymmetry in molecules; R/S are stereochemical descriptors, D/L denote enantiomers in relation to glyceraldehyde.

Enantiomers vs. diastereomers

Enantiomers are non-superimposable mirror images; diastereomers are non-mirror stereoisomers with different properties.

Gibbs free energy (∆G)

∆G = ∆H − T∆S; negative ∆G indicates spontaneous processes.

Enthalpy/Entropy (∆H, ∆S)

∆H is heat content change; ∆S is disorder/entropy; their balance determines spontaneity.

Equilibrium constant vs. pH relationships

Keq describes equilibrium; pH is the negative log of hydrogen ion concentration, related to acid-base equilibria.