Question

Photorespiration___________

A) uses light to produce ATP instead of sugar.
B) is preferrable when conditions are hot and dry.
C) takes place in the bundle sheath cells. produces CO2 instead of sugar.
D) produces a 4-carbon sugar instead of the 3-carbon PGA molecule of th Calvin Cycle.

Answer 1

Photorespiration produces CO₂ instead of sugar, consuming energy without generating ATP or sugars, and occurs when Rubisco reacts with O₂ due to conditions like high temperatures causing closed stomata.

The correct answer is option D) produces a 4-carbon sugar instead of the 3-carbon PGA molecule of th Calvin Cycle.

Step-by-step explanation:

Photorespiration is a process in plants where the enzyme Rubisco adds O₂ to RuBP instead of CO2, leading to the production of a 3-carbon compound (3-PGA) and a 2-carbon compound (phosphoglycolate), which is not a sugar and is even toxic to cells. This process is energetically costly and does not produce ATP or sugars like the Calvin Cycle does. Instead, photorespiration consumes energy and releases CO₂, effectively reducing the efficiency of photosynthesis, especially under stress conditions such as high temperatures when stomata are closed to conserve water. The correct answer to the student's question is that photorespiration produces CO₂ instead of sugar.

The correct answer is option D) produces a 4-carbon sugar instead of the 3-carbon PGA molecule of th Calvin Cycle.