AP Bio Pre-lab #4 - Carl Schurz High School



AP Bio Pre-lab #4



Key Concepts I: Plant Pigment Chromatography

Paper chromatography is a technique used- 1 __________. The molecules migrate, or move up the paper, at different rates because of differences in solubility, molecular mass, and hydrogen bonding with the paper.

Analysis of Results I

If you did a number of chromatographic separations, each for a different length of time, the pigments would migrate a different distance on each run. However, the migration of each pigment relative to the migration of the solvent would not change. This migration of pigment relative to migration of solvent is expressed as a constant, Rf (Reference front). It can be calculated by using the formula:

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2. What is the Rf value for carotene calculated from the chromatogram below? SHOW YOUR WORK!!

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a. 1.09 b. 0.17 c. 0.96 d. 0.33 e. 0.50

Using DPIP As an Electron Acceptor

In this activity you will measure the rate of electron excitation when light hits chlorophyll. You will use DPIP compound, 3____________The thylakoid membranes of the chloroplasts are mechanically disrupted so that the natural electron transport chain no longer functions normally. When light strikes the chloroplasts, the DPIP is reduced by the excited electrons from chlorophyll, and it changes from its original 4 ______ color to 5 _______ as it accepts the electrons. You will use a spectrophotometer to measure the color change, which gives an indication of the rate of the light reactions of photosynthesis under various conditions.

The Spectrophotometer

The spectrophotometer is an instrument that can be adjusted to illuminate a sample with a specific wavelength of light. The spectrophotometer then measures the amount of light energy that is 6 _____________by the sample. In this laboratory, as DPIP goes from blue to colorless, the amount of light of wavelength 7 ___ nm transmitted through the sample will increase. Though you can note this color change visually, the spectrophotometer quantifies the change.

8. What is the role of DPIP in this experiment?

9. Which graph would be the most likely result of performing the photosynthesis experiment using fresh chloroplasts placed in light and DPIP?

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Lab Sheet-

10. Why does a green substance appear green?

11. Match the following-

Chlorophyll a dark to olive green

Chlorophyll b orange

Carotene primary photosynthetic pigment

Xanthophyll yellow

12. What is the reason for doing AP Lab #4a?

13. List the objectives for Activity #4b.

14. When NADP is reduced to HADPH and then transfers its energy-rich electrons to the Calvin Cycle, what is the eventual product?

15. Why is it important to keep the sides of the cuvettes clean?

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