Refer to the table below. The table contains data collected by Melvin Calvin and his colleagues during experiments designed to trace the pathway of carbon in photosynthesis.Carbon dioxide labeled with carbon-14 was incubated with algal cells under different conditions outlined in the table before the cells were harvested and their contents analyzed for the amount of carbon-14 label in various compounds.Quantities of radioactivity in three compounds are listed in the table.Which statement correctly explains why the amount of carbon-14 present in 3PG increased after 30 seconds of dark?
A) Enough ATP and NADPH were synthesized during the period of light to allow synthesis of 3PG.
B) The enzyme rubisco is able to function for a short period in the dark following exposure to light.
C) The Calvin cycle can continue to run indefinitely in the dark after a period of illumination.
D) The Calvin cycle enzymes function better in the dark than in the light, which explains why the reactions they catalyze are called light-independent reactions.
E) The increase reflects a lag time that occurs once Calvin cycle enzymes are activated by light.

Question

Refer to the table below.  The table contains data collected by Melvin Calvin and his colleagues during experiments designed to trace the pathway of carbon in photosynthesis.Carbon dioxide labeled with carbon-14 was incubated with algal cells under different conditions outlined in the table before the cells were harvested and their contents analyzed for the amount of carbon-14 label in various compounds.Quantities of radioactivity in three compounds are listed in the table.Which statement correctly explains why the amount of carbon-14 present in 3PG increased after 30 seconds of dark?
A) Enough ATP and NADPH were synthesized during the period of light to allow synthesis of 3PG. 
B) The enzyme rubisco is able to function for a short period in the dark following exposure to light. 
C) The Calvin cycle can continue to run indefinitely in the dark after a period of illumination. 
D) The Calvin cycle enzymes function better in the dark than in the light, which explains why the reactions they catalyze are called light-independent reactions. 
E) The increase reflects a lag time that occurs once Calvin cycle enzymes are activated by light.

Quizplus · Accepted Answer

The increase in 3PG after 30 seconds of dark is likely due to the temporary ability of the enzyme rubisco to continue fixing carbon dioxide even in the absence of light. Rubisco has a slow turnover rate and can remain active for a short period in the dark following exposure to light.

Refer to the Table Below