Question

Which scientist is related to light reaction and what is the site?
A) Argon and Hill, Grana
B) Ruben and Kamen, Stroma
C) Willstatter, Stoll, Inner membrane of Chloroplast
D) Calvin and Benson, the outer membrane of the chloroplast

Answer 1

Hint: Chloroplast that aligns themselves along the walls of the mesophyll cells contains an internal membranous system consisting of grana, stroma lamellae and the stroma. The thylakoid stalks are interconnected in some regions of the stroma called stroma lamellae. The stroma does not contain chlorophyll.

Complete answer: Hill conducted an experiment on an isolated chloroplast. He isolated the chloroplast using Hill reagents which are some oxidants like ferrocyanide and benzoquinone. By placing them under the sunlight, he noticed that oxygen was evolving from the water. Hill concluded that if there was a hydrogen acceptor in the medium then it would have been reduced. Argon conducted the same Hill’s experiment with an isolated chloroplast and concluded that the Hydrogen acceptor present in NADP gets reduced to NADH2. He also concluded that in the presence of light and by utilizing inorganic phosphorus, the ADP molecule is converted to ATP. So, experimentally it is observed that the light reaction takes place in the grana.
Thus, the correct option is A.

Additional information: The dark reaction of the photosynthesis takes place in the stroma, but they are dependent on the products of the light reaction (ATP and NADPH). However, it should not be considered that dark reactions occur in darkness or they are not light-dependent.

Note: The membrane system is responsible for trapping the light energy. In the stroma, enzymatic reactions incorporate carbon dioxide into the plant leading to the synthesis of sugar, which in turn form starch. The set of reactions, since they are directly light-driven, are called light reactions.