🧪 Buffers – Mechanism, pKa Matching & Physiology Examples

Buffers are essential for maintaining pH stability, and the DAT loves testing their chemistry and physiology. You’ll see buffers in:

  • Acid-base chemistry questions

  • The Henderson-Hasselbalch equation

  • Biology concepts like blood buffering and enzymes

Let’s explore how buffers resist pH change, when they work best, and how to solve DAT-style questions.

🔍 What Is a Buffer?

A buffer is a solution made of:

  • A weak acid and its conjugate base

  • Or a weak base and its conjugate acid

It resists pH changes when small amounts of strong acid or base are added.

🧠 Buffer = biochemical shock absorber.

🧪 Henderson-Hasselbalch Equation

Concept Details
Henderson-Hasselbalch Equation pH = pKa + log([A⁻]/[HA])
Buffering Capacity Maximal when pH ≈ pKa
Effective Range pKa ± 1
Ratio Meaning Equal concentrations → log(1) = 0 → pH = pKa

🩸 Physiological Buffer Examples on the DAT

Buffer System Location Components pKa
Bicarbonate Blood plasma H₂CO₃ / HCO₃⁻ ~6.1
Phosphate Intracellular fluid H₂PO₄⁻ / HPO₄²⁻ ~7.2
Protein Buffers Hemoglobin in RBCs Amino acid side chains Variable

✅ DAT questions may ask about which buffer is most important in a given organ system or what happens if CO₂ levels change.

📈 DAT-Style Practice Question

Q: Which of the following is the best buffer for a solution at pH 5.0?
A) pKa = 3.0
B) pKa = 4.0
C) pKa = 5.0
D) pKa = 7.0

🎯 DAT Strategy Tips

✅ Buffers work best when pKa ≈ target pH
✅ Use HH equation for ratio and range calculations
✅ Know bicarbonate = most tested buffer system
✅ Match buffer systems to physiology (blood, cells, enzymes)

Need more visuals? Visit kingofthecurve.org/studyscience

🚀 Call-to-Action

Want to keep your DAT prep stable under pressure?

Download the KOTC App to access:

  • Buffer practice questions

  • HH equation tutorials

  • pKa flashcards and curve coin drills

  • Visual guides for all general chemistry topics

🧪 Stay balanced—prep smarter with KOTC.


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