Question

Chemical reaction that takes place during the dark reaction of photosynthesis is called
A. Photolysis
B. Hydrolysis
C. Binding of carbon dioxide with RuBP
D. Nitrogen fixation

Answer 1

Hint: The mechanism of photosynthesis has two phases. These two phases are the light reaction and the dark reaction. The light reaction is also known as the light-dependent process. Moreover, the dark reaction is also known as the light-independent process.

Complete answer: The word photolysis is made up of two words, Photo meaning light and Lysis meaning breaking. Therefore, photolysis refers to the breakdown of the water molecules in the presence of sunlight. As this step is dependent upon the sunlight, hence, it cannot occur during the dark reaction of photosynthesis.
-The word photolysis is made up of two words, Hydro meaning water, and Lysis meaning breaking. Therefore, hydrolysis refers to the breakdown of the water molecules in the presence of sunlight. Water is the source of protons and electrons. The protons are used in the formation of the NADPH and the electrons are used for the production of the ATP. As this step is dependent upon the sunlight, hence, it cannot occur during the dark reaction of photosynthesis.
-RuBP refers to the Ribulose Biphosphate. It is converted into 3-phosphoglyceric acid by binding with the carbon dioxide with the help of the RUBISCO enzyme during the dark reaction. This process is known as carboxylation. Therefore, the dark reaction is the carbon dioxide fixation process.
-The process of nitrogen fixation is not related to photosynthesis. Nitrogen fixation refers to the conversion of the free nitrogen into nitrogenous compounds. It occurs by atmospheric nitrogen fixation, industrial nitrogen fixation, and biological nitrogen fixation.
Thus, based on the above information we can conclude that the chemical reaction that takes place during the dark reaction of photosynthesis is called the binding of carbon dioxide with RuBP.
Hence, the correct answer is option (C).

Note: The dark reaction takes place in the stroma portion of the chloroplast. This process was first observed by Melvin Calvin. It is a biochemical process due to which it is slow. The dark reaction depends upon the products of the light reaction i.e., the ATP and the NADPH. Therefore, it indirectly depends upon the light.