9. Photosynthesis

Calvin Cycle

8.3 Light-Independent Reactions of Photosynthesis

Convert light energy into chemical energy; Store chemical energy in the form of organic molecules.

Use light energy to produce ATP; Use chemical energy to produce ATP.

Store light energy; Use light energy to produce carbon.

Transfer heat captured from light to electrons; Use electrons to generate organic molecules.

The function of the light reactions is to ___________, while the function of the Calvin Cycle is to __________.

 No. Photosynthetic pigments are associated with the thylakoid membrane. 

 No. The thylakoids of the chloroplast are the sites of the light reactions. 

 No. Stomata, found on the leaf surface, allow for gas exchange with the external environment. 

The Calvin cycle occurs in the __________.

BioFlix: The Calvin Cycle (The C3 Cycle)

Which of the following processes occurs during the Calvin cycle?

 a two-carbon compound to form a three-carbon compound 

 No. Rubisco catalyzes the first step of the Calvin cycle&mdash;the incorporation of a molecule of carbon dioxide with the five-carbon sugar ribulose bisphosphate (RuBP).  

 a seven-carbon compound to form two four-carbon compounds 

 No. Rubisco catalyzes the first step of the Calvin cycle&mdash;the incorporation of a molecule of carbon dioxide with a five-carbon sugar.  

 a five-carbon compound to form a stable six-carbon compound that can be converted directly to glucose 

 No. Rubisco catalyzes the first step of the Calvin cycle&mdash;the incorporation of a molecule of carbon dioxide with a five-carbon sugar. 

 two two-carbon compounds to form a five-carbon compound 

 a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds 

Rubisco is involved with this reaction.

In the Calvin cycle, CO2 is combined with __________.

the enzyme responsible for splitting H2O to produce O2 in photosynthesis

 No. This occurs in conjunction with photosystem II. 

 the enzyme that forms a four-carbon compound in CAM photosynthesis 

No. The enzyme that catalyzes the first step of the Calvin cycle (in C3 plants) is RuBP carboxylase, or rubisco.

the first stable intermediate in C4 photosynthesis

the five-carbon sugar molecule that reacts with CO2 to begin the Calvin cycle

the enzyme in plants that captures CO2 to begin the Calvin cycle

The "ru-" in "rubisco" stands for ribulose.

Rubisco is __________.

Where in a plant cell does the Calvin cycle take place?

The enzyme rubisco combines RuBP with a carbon atom from:

Animation: The Calvin Cycle

Which of the following occurs during the Calvin cycle?
(A) carbon fixation
(B) reduction of NADP+
(C) release of oxygen
(D) generation of CO2

 Light energy is converted to chemical energy. 

 No. This is associated with the light reactions. 

 No. NADPH is already reduced, so this cannot be correct. 

 No. Although NADPH is oxidized during the Calvin cycle, is this a correct description of what happens to ATP? 

 Linear electron flow produces the materials required for the fixation of carbon from carbon dioxide. 

 No. Although the statement is true, it is not an accurate description of an event that occurs during the Calvin cycle. 

 ATP is hydrolyzed, and NADPH is oxidized. 

Consider which of these is associated with the Calvin cycle.

Which of the following occurs during the Calvin cycle?

 Excited electrons are conveyed from chlorophyll to an electron acceptor. 

Of the following, which occurs during the Calvin cycle?

Which of the following does not occur during the Calvin cycle?
a. carbon fixation
b. oxidation of NADPH
c. release of oxygen
d. regeneration of the CO2 acceptor

Nature's smallest factory: The Calvin cycle - Cathy Symington

 It helps produce ATP from the light reactions. 

 No. ATP is produced by other electron acceptors in the electron transport chain. 

 No. The electrons in the chlorophyll absorb the light energy. 

 No. It is not defined as part of the photosystem. 

No. The primary electron acceptor passes on electrons ultimately to NADP+.

 It forms NADPH to be used in the Calvin cycle. 

Consider the source of the electrons used to reduce carbon.

What is the role of NADP+ in photosynthesis?

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized “memory” that “reminds” it not to retry dead ends.

Propose an experiment that would test whether the coating of extracellular slime changed the speed at which the slime mold moved across the substrate.

 It is produced from glucose during glycolysis. 

 No. This is true, but there is a better response. 

 No. This is true, but there is a better response 

For every three molecules of CO2 reduced in the Calvin cycle, six molecules of G3P are formed but only one of these molecules exits the cycle to be used by the plant cell.

For every three molecules of CO2, six molecules of G3P are formed but five molecules must be recycled to regenerate three molecules of RuBP

 All of the listed responses are correct. 

Review the steps of the Calvin cycle. .

Glyceraldehyde-3-phosphate (G3P) is produced in the stroma of chloroplasts. Which of the following statements is most accurate regarding this compound?

 It is often too cold at night for these reactions to take place. 

 No. Although it is true that metabolic reactions are slower when the temperature is lower, this is not the best answer. 

 Carbon dioxide concentrations decrease at night. 

No. In the dark, stomata can open without danger of losing water and so adequate CO2 is available.

 Plants usually open their stomata at night. 

No. Because the Calvin cycle utilizes CO2, which enters through the stomata, having the stomata open would be beneficial, but nonetheless, the Calvin cycle usually does not occur at night.

 At night, no water is available for the Calvin cycle. 

 No. Although some water is required for the Calvin cycle, there is plenty of water available at night.  

 The Calvin cycle requires products only produced when the photosystems are illuminated. 

Think of the relationship between the light reactions and the Calvin cycle.

The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. Why?

Describe the three phases of the Calvin cycle and how the products of the light-capturing reactions participate in this process.

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