Question

A lab experiment to determine the rate of ATP production and its use in plants is conducted. In the lab, twenty circles cut from plant leaves are placed in a container of water with a light source, which allows photosynthesis to occur. When the rate of ATP production exceeds the ATP use, oxygen is given off by the plant cells, causing the leaf circles to float.

A graph titled Leaf Circles Floating versus Time shows Time (minutes) numbered 0 to 30 on the x axis and Number of Leave Circles Floating numbered 0 to 25 on the y axis. Point A is (6, 0). Point B is (14, 20). Point C is (16, 20). Point D is (26, 2).

Using the graph of data from this experiment, at which point was the light source most likely removed?

A
B
C
D

Answer 1

C

Explanation: After point C (16 min) the number of floating discs begins to fall (by 26 min only 2 float), indicating photosynthesis stopped and oxygen was lost. That drop corresponds to the light being removed at C.