We noticed some difficulties in data collection for the photosynthesis lab:

• Several groups used the DPIP/phosphate buffer for the background instead of just the phosphate buffer. This was a mistake in following the instructions, and we think it indicates a misunderstanding of what running a background reference is for. Please review this concept and ask any questions you have.
• Other groups that seemed to have followed the protocols correctly only saw a decrease in UL absorbance between 0 minutes and 5 minutes, and the rest of the time the UL absorbance was basically constant. While we’re not sure of the reason for this, we suspect that perhaps the cuvettes were too close to the light, so the high intensity resulted in high photosynthesis, thus reducing all the DPIP very quickly (within the first 5 minutes).

Several groups did get data that seems useful. If your group’s data is suspect, clearly indicate that in your lab notebook along with some best guesses as to why. You may borrow data from a group that did obtain useful results, but make sure to credit that group clearly in your lab notebook.

We also took some data after lab ended. Here are the results we obtained, which you can use (if so, credit the data in your lab notebook to “instructors’ data”). We’ll discuss this data in class together when we get some time.

Instructors’ data: