Cell Biology Laboratory Manual Table of Contents

  Techniques Manual Table of Contents

  Lab Safety Sheet

 

  Related Topics

Aseptic Technique

Sampling and Inoculation

Petri Dishes

Streaking for Isolation

Spread plates

Exoenzymes

Broth and Semi-solid Media

Staining Bacteria



  Return to START!

How to perform a Benedict's Test

Benedicts Test for Glucose
Procedure:
1. Using a clean 50 mL beaker, obtain 10 mL of a 1% (w/v) glucose solution.
2. Clearly label four clean 13x100 mm test tubes for your standards. Mix the appropriate amounts of glucose solution, distilled water, and Benedict's solution in the properly labeled test tubes as indicated by the following table. You will also need one test tube for the glucose solution made by each student in your group.

Tube No.
mL of glucose soln.
mL of water
mLof Benedict's soln.
1
0
5.0
1.0
2
0.5
4.5
1.0
3
1.0
4.0
1.0
4
2.0
3.0
1.0
5-?
2.0
3.0
1.0

 

3. Mix the contents of each tube by gently shaking the test tubes back and forth.
4. Place the tubes in a test tube rack and set the rack in the water bath. CAUTION! The water is very hot.
5. Incubate the tubes for 20 minutes.
6. Remove your test tubes and allow them to cool.
7. Transfer the contents to 15 mL centrifuge tubes and spin for two minutes Your instructor will tell you which program to use. If there are still suspended debris in any of the tubes, centrifuge for two more minutes.
**It is important that the solution be clear for the absorbance measurements. If there is solid matter suspended in the solution, the light being sent through the sample will be scattered and will cause error in the measurements.
8. Decant the supernatants into clean, labeled test tubes. Be careful that any sediment remains in the pellet at the bottom of the centifuge.
9. Determine the O.D. of each of the samples using a spectrophotometer set to read at 735 nm. Use distilled water to set the 100%T.
10. Prepare a graph of the standard solutions and determine the concentration of each unknown.