Conjugate base
MCAT glossary · Chemical & Physical Foundations of Biological Systems
Definition
The species that remains after an acid donates a proton.
Conjugate base in plain English
In chemistry, an acid is a molecule that likes to give away a proton (a hydrogen ion, written H^+). The conjugate base is simply what's LEFT OVER after the acid hands off that proton. Think of it like a person who gives away one coin: the 'person minus one coin' is the conjugate base. For example, when hydrochloric acid (HCl) donates its H^+, the leftover chloride (Cl^-) is its conjugate base — same molecule, just one proton lighter.
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