Lesson Plans

Biology 5th Edition ©1999

by Campbell, Reece, Mitchell

Week 6: Photosynthesis

Chapter 10: Photosynthesis

College Board Performance Objectives:

• Explain how photosynthesis converts light energy into chemical energy.
• Describe how the chemical products of the light-trapping reactions couple to the synthesis of carbohydrates.
• Explain the kinds of photosynthetic adaptations that have evolved in response to different environmental conditions.
• Explain what interactions exist between photosynthesis and cellular respiration.

College Board Lab Objectives:

• Conduct chromatography to separate two or more compounds that are initially present in a mixture and calculate their R_f values.
• Design a lab that tests the relationship between light wavelength or light intensity or temperature and photosynthetic rate.
• Explain why the rate of photosynthesis varies under different environmental conditions.

Suggested Laboratory Experiments:

Resources:

• Chapter 10: Photosynthesis, pp. 168–187
• Instructor's Guide, pp. 125–144
• Student Study Guide, pp. 67–75
• Test Bank, pp. 108–124
• Lab Manual, pp. 135–160
• CD-ROM: Chapter 10 includes narrated presentations, activities, and links to the Internet.

Pacing Guide:

• Chapter 10: Photosynthesis and extended activity—3 days
• AP* Lab 4, Plant Pigments and Photosynthesis—2 days
• Grind chloroplast in acetone, and grind another batch in water. Shine a light on the two solutions while in the dark. Ask students why the flask with the chloroplasts that were ground in acetone glow after the light is turned off. Use this demonstration and discussion as a springboard to the details of photosynthesis.
• Block Scheduling
  Photosynthesis can be accomplished in two blocks and the lab will take one block.

Key Words:

Suggested Exercises:
Critical thinking questions and end-of-chapter activities are included in these exercises.

1. Challenge Questions, p. 187 #1
2. Science, Technology, and Society, p. 187 #1
3. Lab Topic 6, pp. 135–150, could be done as a large group or as an extended activity by some students. In Exercise 6.2, the effectiveness of wavelengths of light can be demonstrated with light being filtered and testing for starch with iodine. Determining the absorption spectrum for leaf pigments in Exercise 6.4 is a good class demonstration that sparks discussion on quantitative data about pigments and light absorption. Exercise 6.5 is a good demonstration that allows the collection of data based on oxygen production and allows for a good comparison to the rates studies done with DPIP in the AP* lab. Demonstrations coupled with lab activities provide a diverse background for the study of photosynthesis.

Troubleshooting Tips/Error Traps:

• Photosynthesis, similar to respiration, is a concept that needs to be taught at least two or three times for understanding. It is best to teach photosynthesis by going through a simple outline of photosynthesis events and the basic location of each event. Get to the final products of glucose and oxygen. Then return to each component of photosynthesis (light reaction, electron transport, and associated chemiosmosis and the Calvin Cycle) and deal with the details. There are so many abstract concepts that visualizations and student participation is very important. There must a balance between the understanding of details and overall generalities of photosynthesis. Be sure that students can explain why it is important to the photosystems that NADP⁺ must be reduced and why electrons must be replaced. Photosynthesis is understandable and students should see the similarities of each of the processes to respiration. The structure and factions of the chloroplast should be compared and contrasted to the structure and function of the mitochondria.
• The photosynthesis lab helps students to have quantitative analysis of pigments and the light reaction of photosynthesis. Emphasize that DPIP is substituting for NADP⁺ in the light reaction. It is best to do the pigment part of the lab on a separate day from the study of the light reaction of photosynthesis with DPIP. The colorimeters are inexpensive and allow for excellent data collection. Since the colorimeters are so inexpensive, you can have more equipment and smaller groups for more hands-on time or you can buy other needed computer and CBL equipment to do other labs with sensors. The money saved by purchasing colorimeters instead of spectrophotometers is a significant budget strategy to help make the lab more economical and to help generate money for other lab equipment. Also, the colorimeters are small and easy to store.