Today’s Task: Improve and Redo Your Experiment

Questions to answer before you start over:  

1. Did the alcohol concentrations you chose in last weeks lab help to identify the point at which betacyanin begins to leak from the beetroot? Or did you use very high concentrations of alcohol (a chemical sledge hammer!) that caused betacyanin to pour out of the tissue? 

2. Have you chosen concentrations of alcohol too widely spaced apart to identify with precision the critical concentration of alcohol that starts leakage? 

3. Have you replicated all experimental groups and the control group at least three times? 

4. Have you constructed a data collection table following the format explained in the online laboratory manual? Note that the data collection table is not the final format for presenting your results, but an organized way for recording your data in the lab notebook.

Tools:

1. Use the mass balance equation to make up your alcohol dilutions.
2. Use the spectrophotometer and Beer's Law to convert betacyanin absorbance into uM concentrations.

Final format for your data:

1.      Construct a figure presenting your final results using the format shown below. Note that the figure must have axes that are clearly labeled including appropriate units. Also, the figure must have a descriptive title and a legend that indicates how many replicates of each data point were done and a sentence that describes the trends (if any) in the data.

Figure 1. Effect of alcohol treatments on betacyanin leakage from beetroot segments. Each data point represents the mean of three replicates. The results show that the critical concentration inducing leakage occurs between 14 and 16% ethanol.

  Analysis:

  What was the relationship between alcohol concentration and betacyanin leakage in your experiment? Was it linear? Nonlinear? Explain.

1. Did the results support your hypothesis?
2. Why does betacyanin normally stay in the beetroot? Why does ethanol cause betacyanin to leak from the beet tissue faster than water?

Lab Report:

1. Today's work will be presented as Lab Report 1. It will be due at the beginning of the period next week. No late reports will be accepted. Refer to the online laboratory manual for the format and helpful hints on how to do this assignment. To help you put your report together, note the grading sheet that will be used to assess your report.