Chapter 8 Concept Questions

To synthesize one glucose molecule, the Calvin cycle uses ____ molecules of CO2, ______ molecules of ATP, and _____ molecules of NADPH.

6;18;12

How is photosynthesis similar in C4 plants and CAM plants?

c. in both cases, rubisco is not used to fix carbon initially.

Which of the following does not occur during the Calvin cycle?

c. release of oxygen

How did the use of an oxygen isotope help elucidate the chemistry of photosynthesis?

Oxygen produced during photosynthesis originates in water, not in carbon dioxide.

Which process is most directly driven by light energy?

d. removal of electrons from chlorophyll molecules.

Describe how photorespiration lowers photosynthetic output for plants.

Photorespiration decreases photosynthetic output by adding oxygen, instead of carbon dioxide, to the calvin cycle.

How are the large numbers of ATP and NADPH molecules used during the Calvin cycle consistent with the high value of glucose as an energy source?

The amount of energy and reducing power required to form a molecule determines the amount of potential energy that molecule stores. To reduce CO2 to glucose, a large amount of energy and reducing power are required in the form of large numbers of ATP and NADP+.

Predict what will happen to the rate of synthesis if a compound is added to the solution that makes membranes freely permeable to hydrogen ions.

The rate of ATP synthesis would slow and eventually stop. Because the added compound would not allow a proton gradient to build up across the membrane, ATP synthase would not be catalyze ATP production.

In the light reactions, what is the initial electron donor? At the end of the light reactions, where are the electrons?

Water is it initial electron donor; NADP+ accepts electrons at the end of the ETC, becoming reduced to NADPH.

What color of light is least effective in driving photosynthesis?

Green, because green light is mostly transmitted and reflected-not absorbed-by photosynthetic pigments.

How do the reactant molecules of photosynthesis reach the chloroplasts in leaves?

CO2 enters the leaves via stomata, and water enters the plant via roots and is carried to the leaves through veins.

The Calvin Cycle requires ATP and NADPH, products of the light reactions. If a classmate asserted that the light reactions don't depend on the Calvin cycle, could just keep on producing ATP and NADPH, how would you respond?

The light reactions could not keep producing NADPH and ATP w/out the NADP+, ADP, and phosphate that the Calvin cycle generates. The two cycles are interdependent.

Which of the following sequences correctly represents the flow of electrons during photosynthesis.

b. H2O ---> NADPH --> Calvin cycle

In mechanism, photophosphorylation is most similar to ______.

b. oxidative phosphorylation in cellular respiration.

The light reactions of photosynthesis supply the calvin cycle with _____.

d. ATP and NADPH

Which of the following statements is a correct distinction between autotrophs and heterotrophs?

d. autotrophs can nourish themselves beginning with CO2 and other nutrients that are inorganic.

Explain why a poison that inhibits an enzyme of the Calvin cycle will also inhibit the light reactions.

the light reactions require ADP and NADP+, which would not be formed in sufficient quantities from ATP and NADPH if the Calvin cycle stopped.