CHAPTER 10

PHOTOSYNTHESIS


 OBJECTIVES

After reading this chapter and attending lecture, the student should be able to:

1.

Distinguish between autotrophic and heterotrophic nutrition.

2.

Describe the location and structure of the chloroplast.

3.

Explain how chloroplast structure relates to its function.

4.

Write a summary equation for photosynthesis.

5.

Explain the role of REDOX reactions in photosynthesis.

6.

Describe the wavelike and particlelike behaviors of light.

7.

Describe the absorption spectrum of the primary photosynthetic pigments.

8.

List the wavelengths of light that are most effective for photosynthesis.

9.

Explain what happens when chlorophyll absorbs photons of light energy.

10.

List the components of a photosystem and explain their function.

11.

Trace electron flow through photosystems II and I.

12.

Summarize the light dependent reactions with an equation and describe where they occur.

13.

Describe important differences between phosphorylation in mitochondria and in chloroplasts.

14.

Summarize the light independent reactions (carbon-fixing) of the Calvin cycle and describe changes that occur in the carbon skeleton of the intermediates.

15.

Describe the role of ATP and NADPH in the Calvin cycle.

16.

Describe what happens to the light independent reactions when the O2 concentration is much higher than CO2.

17.

Describe the major consequences of photorespiration.

18.

Describe two important photosynthetic adaptations that minimize photorespiration.

19.

Describe the fate of photosynthetic products.

KEY TERMS

autotrophic

accessory pigment

photoautotroph

electromagnetic radiation

chlorophyll

carotenoids

wavelength

photophosphorylation

electromagnetic spectrum

chloroplast

Calvin cycle

fluorescence

mesophyll

photosystem

stomata

stroma

thylakoid membrane

primary electron acceptor

CAM pathway

C4 pathway

photorespiration


LECTURE NOTES

I. Plants and other autotrophs are the producers of the biosphere

II. Chloroplasts are the sites of photosynthesis in plants

LEAF CROSS SECTION

III. Evidence that chloroplasts split water molecules enabled researchers to track atoms through photosynthesis: science as a process

A. The Splitting of Water

B. Photosynthesis as a Redox Process

IV. The light dependent reactions and the Calvin cycle cooperate in transforming light to the chemical energy of food: an overview

V. The light reactions transform solar energy to the chemical energy of ATP and NADPH: a closer look

A. The Nature of Sunlight

B. Photosynthetic Pigments: The Light Receptors

C. The Photoexcitation of Chlorophyll

D. Photosystems: Light-Harvesting Complexes of the Thylakoid Membrane

E. Noncyclic Electron Flow

Electron Flow in Photosystem I

Electron Flow in Photosystem II

Photophosphorylation

F. Cyclic Electron Flow

G. A Comparison of Chemiosmosis in Chloroplasts and Mitochondria

Summary of the Light Reactions:

VI. The Calvin cycle uses ATP and NADPH to convert CO2 to sugar: a closer look

Phase 3: Regeneration of Starting Material (RuBP).

VII. Alternative mechanisms of carbon fixation have evolved in hot, arid climates

A. Photorespiration

Certain species of plants, which live in hot arid climates, have evolved alternate modes of carbon fixation that minimize photorespiration. C4 and CAM are the two most important of these photosynthetic adaptations.

B. C4 Plants

The steps of C4 carbon fixation.

C. CAM Plants

VIII. Photosynthesis is the biosphere’s metabolic foundation: a review


REFERENCES

Atkins, P.W. Atoms, Electrons, and Change. New York, Oxford: W.H. Freeman and Company, 1991. Chapter 9, "Light and Life" is a witty, imaginative description of photosynthesis. Though written for a lay audience, it is probably best appreciated by someone already familiar with photosynthesis.

Campbell, N. Biology. 4th ed. Menlo Park, California: Benjamin/Cummings, 1996.

Lehninger, A.L., D.L. Nelson and M.M. Cox. Principles of Biochemistry. 2nd ed. New York: Worth, 1993.

Matthews, C.K. and K.E. van Holde. Biochemistry. 2nd ed. Redwood City, California: Benjamin/Cummings, 1996.