Plant Pigments and Photosynthesis

Pre-Lab Questions

1. Describe how the functional units for beta carotene, xanthophyll, chlorophyll A, and chlorophyll B are different. Be sure to identify the subunits that adhere to paper during chromatography.

2. Describe a technique for measuring photosynthetic rate.

3. Many deciduous trees have leaves which turn yellow in the fall. What do you suppose is happening in the leaves at the cellular and molecular level?

4. We have seen that chloroplasts are the organelles in plant cells that provide energy to the cell. The equivalent organelle in eukaryotic (animal) cells is the mitochondria. Both are also unusual in that they have double membranes and contain their own set of DNA. Can you think of any explanations for this observation?

5. Using your data from Part A - D, determine the most appropriate method to graph the information, and provide the graph(s) in the space below. Include a brief statement describing why you selected the graphing method you did. Be sure to clearly indicate the x and y axes, the units used, and the graph title(s). You may also use a graphing software program, if authorized by your instructor.

6. Identify the controls used in this experiment. Which control is positive, and which control is negative? How do you know? Did you receive the results you would expect from such a control?

7. What was the purpose of the sodium bicarbonate?

8. What was the purpose of the soap?

9. Describe why the leaves rise. Alternatively, describe why the leave sink.

10. How does darkness affect photosynthesis. Be specific and be sure to discuss biological processes and molecules involved.

11. Predict what might happen if the solutions and leaf disks were boiled prior to the photosynthesis. Alternatively, what might happen if the solutions and leaf disks were subjected to very cold temperatures?

12. Will the leaf disks float faster or slower if the experiment is adjusted to decrease the photosynthetic rate?