Buffer
MCAT glossary · Chemical & Physical Foundations of Biological Systems
Definition
A solution of a weak acid and its conjugate base that resists changes in pH.
Buffer in plain English
A buffer is a solution whose job is to keep acidity (pH) steady even when you add a splash of acid or base — like a thermostat that fights to hold a room at one temperature. It pulls this off by containing a pair that work as a team: a weak acid (which can hand out extra H⁺ if things get too basic) and its conjugate base (which soaks up H⁺ if things get too acidic). Because it can absorb or release H⁺ from either direction, the pH barely budges. Your blood uses a buffer to stay near pH 7.4, since even small swings would be dangerous.
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