AP Lab 4

Completing the Research Notebook for AP Biology Lab #4.....Plant Pigments and Photosynthesis

Resource: Lab Four, Plant Pigments and Photosynthesis

Page 45 in AP Biology Lab Manual


Pre-lab: Complete the following parts in your research notebook prior to conducting the laboratory.


Part 1: Title

Develop a title in the form of a question after you have completed the pre-lab.


Part 2: Objectives (What are the objectives for this laboratory?)


Part 3: Pre-lab Questions

Exercise 4A

1. p 45 Read the background

Paper chromatography. Make a bulleted list of ideas that explain this phenomenon

- technique for separating and identifying pigments

-a solvent moves up paper by capillary action


2. Chemically, why do pigments differ in how they separate by chromatography?

Name the pigment and explain its chemistry (4 pigments)

Exercise 4B

1. p 48 Compare energy of short wavelengths to that of long wavelengths. Give specific examples.

2. What really happens when light is absorbed by leaf pigments?

3. What will be used in place of the electron receptor of the light reaction:

abbreviation_______ name________________________

4. p 48 last paragraph: Explain how this experiment works. Be thorough and specific.

4. Explain how a spectrophotometer works. You may use http://en.wikipedia.org/wiki/Spectrophotometer for this.

Note: you can measure absorbance or transmittance of light. We will measure transmittance of light.

6. Copy the table 4.3 which is the design matrix for each cuvette (tube).


Part 4: Method

Exercise A

(Note: you will be following a different method than the lab manual, but the technique is the same. The following

procedure is used in the lab kit for this lab for Carolina Biological)

A chlorophyl sample will be placed on an 8cm square piece of chromatography paper 1.5 cm from the bottom. Care

will be taken not to touch the paper where chromatography will be occurring. The paper will be bent into a cylinder

and stapled so that the edges are not touching. The bottom edge of the paper will be submerged in

chromatography solvent in a glass jar, and the cap will be placed on the jar.

Exercise B

A spectrophotometer will be turned on and set to wavelength of 605 nm. Five cuvettes will be set up with solutions

as explained in a table in the lab protocol. Everything will be added to the cuvettes EXCEPT THE CHLOROPLAST

suspension. When the team is ready to begin the timed experiment, the spectrophotometer will be set to 0%

without the blank, and then to 100% with the blank. One by one, chloroplast suspension will be added to the

cuvettes and an immediate initial transmittance reading will be taken from the spectrophotometer. Transmittance

data will be collected at 5 min, 10 min and 15 min.

Hypothesis: If light intensity is related to photosynthetic rate, then___________________________________

Hint: notice that you will have one unboiled in the dark and the light

If temperature is related to photosynthetic rate, then _______________________________________________

Hint: notice that you will have one boiled in light and one unboiled in light.


Part 5: Data Tables

Exercise 4.a

Table 4.1 Chromatography of Plant Pigments

Table 4.4 Transmittance (%)


Post Lab:

Part 6: Questions

Page 47

1. copy table 4.2 and calculate the Rf values

2. Topics for Discussion questions and answers # 1,2 and 3

Page 52 # 1-8


 Part 7: Graph (see page 51)

Plot points and graph

a. label independent variable

b. label dependent variable


Part 8: Theme Correlation

Energy transfer Explain how energy is transferred throughout the photosynthetic process.

Inquiry: what was an experimental variable in this study, and how was the experiment controlled to test this variable?


Part 9: Conclusion Topics.

1. Explain the evidence that you have that chromatography worked. How did it work?

2. Explain the effect of boiling on the rate of photosynthesis. Cite good data to support your discussion.

3. Explain the effect of light and dark on the rate of photosynthesis. Cite good data to support your discussion.

4. Why did we use DPIP? Evidence????