Lab 2

Agenda

  1. Turn in Lab 1 by the staplers on the North bench.
    1. Needs names and group number
  2. ~10 min.: Q&A on Lab 1 material
  3. 20 min.: Quiz 1
  4. ~2 hrs.: Lab 2: pH & Buffers
  5. ~30 min.: Next lab reminders/questions/review

Lab 1 Q&A

Quiz 1

pH & Buffers

Lab 2

Lab Purpose

To allow students to experiment with the carbon dioxide and bicarbonate buffer system that regulates body pH and observe how changes in pH affect enzymatic function.

Lab objectives

  • Define what a buffer is and be able to explain how buffers large changes in pH when an acid or a base is added.
  • Be able to manipulate the bicarbonate reaction and understand the terminology of alkalosis and acidosis.
  • Use the pH meter to determine how the pH of a salt solution (strong acid) changes when it is titrated with a strong acid.
  • Use the pH meter to determine how the pH of a solution containing a weak anion changes when it is titrated with a strong acid.
  • Be able to use the Henderson-Hasselbach equation.

Lab Safety

  • Goggles!
  • Closed toed shoes
  • Gloves
  • Adequate coverage from neck to ankles
  • Put your hair up!
  • If you spill acid tell me so we can clean it up properly.

What are we doing?

  • We're experimenting with the bicarbonate buffer system.
  • Add differing amounts of acid to solutions that mimic this system.
  • Graph pH to make titration curve.
  • Two analytes: NaHCO3 and NaCl.

pH Meter Demo

Core Principles

What is pH?

Why is pH important?

CO_2+H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-

Carbonic

anhydrase

What is the law of mass action?

Henderson-Hasselbach Equation

pH = 6.1 + log(\frac{[HCO_3^-]}{[H_2CO_3]})
pH = 6.1 + log(\frac{[HCO_3^-]}{0.03 \frac{mmol}{L\times mmHg} \times PaCO_2})

Alkalosis or Acidosis?

  • Is the pH higher or lower than normal?
    • Normal = 7.35-7.45
    • If high then alkalosis
    • If low then acidosis
  • Metabolic or respiratory?
    • Is the bicarbonate abnormal?
    • Is the PaCO2 abnormal?
      • Could the lungs be trying to compensate?

Lab 3: Enzymes

  • Read:
    • Stanfield pgs. 65-72
    • Silverthorn 98-101
  • Bring:
    • Goggles
    • Calculator
    • Wear adequate clothing
Made with Slides.com