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Module 5 Intro

1. Module 5 Intro

1.20. Page 2

Lesson 4

Module 5—Photosynthesis and Cellular Respiration

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You have already investigated factors affecting photosynthesis in Module 1: Lesson 1 of Biology 20. At the beginning of this course, you used a virtual lab to study photosynthesis under a variety of conditions. Your assignment asked you to make conclusions about the effect of light intensity, carbon dioxide, temperature, and light wavelength on the production of oxygen. You may want to review your Lesson 1 Assignment and the Photosynthesis Gizmo.

 

In Module 1 you also looked at biogeochemical cycles. Photosynthesis is critical in the cycling of oxygen and carbon dioxide. You now have a better idea of how oxygen and carbon are cycled by light-dependent and light-independent reactions.

 

The following two diagrams from Lessons 2 and 3 of Module 5 review the stages of photosynthesis.

 

 

In the Calvin-Benson cycle, RuBP combines with atmospheric carbon dioxide. Two, three-carbon molecules are formed. This is shown by a linear chemical equation. ATP and NADPH (from the light-dependent reactions) are oxidized so that the two C3 molecules can combine to form PGAL. This is shown by a curved arrow above PGAL. ATP and NADPH become ADP + P and NADP+. Some PGAL leaves the Calvin-Benson cycle to create glucose. This is shown by an arrow pointing out of the cycle to a glucose molecule. The rest of the PGAL molecules stay in the cycle so they can be broken down by the energy from ATP to replace RuBP molecules. This is shown by a curved arrow pointing from PGAL back to RuBP. The phrase “ATP energy breaks chemical bonds in PGAL” is written in the arrow. ATP is shown to break down and form ADP + P.

 

By looking at the process of photosynthesis as a series of reactions, you can now see exactly where the factors affecting photosynthesis have their effect. Answer the following Self-Check questions.

 

Self-Check

 

SC 1. Complete this Self-Check activity.