Biochemistry: pH, Ka, pKa, and Henderson-Hasselbalch — Vocabulary

Vocabulary flashcards covering key terms related to pH, acids/bases, Ka, pKa, and Henderson-Hasselbalch from the lecture notes.

pH

A measure of solution acidity, defined by pH = -log[H+].

Hydrogen ion concentration ([H+])

Concentration of protons in solution; higher [H+] means lower pH (more acidic).

Strong acid

A substance that completely dissociates in water, producing maximum [H+].

Weak acid

A substance that partially dissociates in water, existing in equilibrium with its conjugate base.

Acid dissociation constant (Ka)

Ka = [H+][A-]/[HA]; a measure of how readily an acid dissociates; larger Ka indicates a stronger acid.

pKa

pKa = -log(Ka); lower pKa means stronger acid; used for comparing acids on a manageable scale.

Conjugate base

The unprotonated form of an acid after dissociation; often negatively charged in biochemistry.

Acid

A substance that donates a proton (H+); in solution, can exist with its conjugate base in equilibrium.

Protonated species

The acid form that has accepted a proton (H+).

Unprotonated species

The conjugate base form after losing a proton; the unprotonated form.

Henderson-Hasselbalch equation

pH = pKa + log([A-]/[HA]); used to calculate pH of solutions containing a weak acid and its conjugate base.

Relation between Ka and pKa

pKa = -log(Ka); smaller pKa and larger Ka indicate a stronger acid.