Water: The Polarity for Biochemical Reactions

Vocabulary flashcards covering polarity, bonding types, solubility, and key water properties relevant to biochemical reactions.

Electronegativity

The tendency of an atom to attract electrons toward itself in a chemical bond.

Water

is the principal component of most cells.

Polarity

Unequal sharing of electrons in a bond, producing partial positive (δ+) and partial negative (δ−) ends.

Dipole

A bond or molecule with partial positive and negative ends due to polar bonds.

δ+ and δ−

Partial positive and partial negative symbols used to denote unequal electron distribution in polar bonds.

Polar covalent bond

A covalent bond in which electrons are shared unequally due to electronegativity differences.

Water polarity

Water has polar O–H bonds with oxygen more electronegative than hydrogen, giving a polar molecule.

Water structure

H2O: two hydrogens single-bonded to oxygen; bond angle about 104.5°.

Hydrogen bonding

A noncovalent attraction between a hydrogen atom bonded to an electronegative atom and a lone pair on another electronegative atom.

Ionic bonds

Bond in which positive and negative ions attract; strongest type among those discussed; common in salt crystals.

Covalent bonds

Bond formed by sharing electron pairs between atoms; strong bonds in biomolecules.

Van der Waals forces

Weak noncovalent forces including dipole-dipole, dipole-induced dipole, and London dispersion forces.

Ion–dipole interactions

Electrostatic interactions between ions in solution and polar molecules (e.g., water's dipole with ions).

Dipole–dipole interactions

Forces between molecules with permanent dipoles, aligning partial charges.

Dipole–induced dipole interactions

A permanent dipole can induce a temporary dipole in a nearby molecule, creating attraction.

London dispersion force

Induced dipole–induced dipole attraction arising from momentary distortions of electron clouds; present in all molecules, stronger for larger nonpolar molecules.

Hydrophilic

Ionic and polar substances that dissolve readily in water due to electrostatic attractions.

Hydrophobic

Tending not to dissolve in water; driven by nonpolar interactions.

Amphipathic

Molecule with one polar (water-soluble) end and one nonpolar (water-insoluble) end.

Solvent properties of water

Water readily dissolves ionic and polar substances due to ion–dipole and dipole–dipole interactions.

Water’s high heat capacity

Water can absorb and store heat, moderating temperature in organisms and the environment.