1 / 12

Buffering Systems and Water as a Reactant

Buffering Systems and Water as a Reactant. CHEM 7784 Biochemistry Professor Bensley. Chapter 2.3 through 2.5 Buffering Systems and Water as a Reactant. How buffers work and why we need them How water participates in biochemical reactions. Today’s Objectives : to understand.

torn
Download Presentation

Buffering Systems and Water as a Reactant

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Buffering Systems and Water as a Reactant CHEM 7784 Biochemistry Professor Bensley

  2. Chapter 2.3 through 2.5Buffering Systems and Water as a Reactant • How buffers work and why we need them • How water participates in biochemical reactions Today’s Objectives: to understand

  3. Buffers are mixtures of weak acids and their anions

  4. Phosphate has three ionizable H+ and three pKas

  5. Henderson–Hasselbalch Equation:Derivation  HA H+ + A-  • Solve for [H+] • Take negative logarithm of both sides • Substitute pH for –log[H+] and pKa for –log Ka • Invert –log [HA]/[A-] (changes sign)

  6. Case where 10% acetate ion/ 90% acetic acid • pH = pKa + log10[0.1 ] ¯¯¯¯¯¯¯¯¯¯ [0.9] • pH = 4.76 + (-0.95) • pH = 3.81

  7. Case where 50% acetate ion/50% acetic acid • pH = pKa + log10[0.5 ] ¯¯¯¯¯¯¯¯¯¯ [0.5] • pH = 4.76 + 0 • pH = 4.76 = pKa

  8. Case where 90% acetate ion/ 10% acetic acid • pH = pKa + log10[0.9 ] ¯¯¯¯¯¯¯¯¯¯ [0.1] • pH = 4.76 + 0.95 • pH = 5.71

  9. Cases when buffering fails • pH = pKa + log10[0.99 ] ¯¯¯¯¯¯¯¯¯¯ [0.01] • pH = 4.76 + 2.00 • pH = 6.76 • pH = pKa + log10[0.01 ] ¯¯¯¯¯¯¯¯¯ [0.99] • pH = 4.76 - 2.00 • pH = 2.76 So why do we care so much about buffers in Biochemistry?

  10. Water as a reactant in biochemistry

  11. Chapter 2: Summary The goal of this chapter was to help you to better understand: • The nature of intermolecular forces • The properties and structure of liquid water • The behavior of weak acids and bases in water • The way water can participate in biochemical reactions

More Related