Question

Cyclic phosphorylation produces
A. NADPH
B. ATP \[+\] NADPH
C. ATP
D. ATP \[+\] NADPH \[+\] \[~{{O}_{2}}\]

Answer 1

Hint: Cyclic phosphorylation is a process that is performed by plant cells to yield carbohydrates required for growth. It is a two-step process that occurs in the presence of light. Under the process of photosynthesis, the cyclic phosphorylation process utilizes water, carbon dioxide, and sunlight. Generally, phosphorylation means the addition of phosphorus to any organic compound.

Complete answer: Cyclic phosphorylation is an important metabolic process that is performed by plants to produce carbohydrates. The process occurs during photosynthesis in presence of sunlight. It is a two-step process. The first step comprises a light reaction. This step occurs in the grana of the chloroplast. The chloroplast is an organelle that converts light energy into chemical energy in the form of ATP (Adenosine triphosphate) and NADPH (Nicotinamide adenine dinucleotide phosphate). The key characteristic of this step is the addition of phosphate in presence of light due to which is called phosphorylation. As this process involves the utilization of light energy, it is called photophosphorylation.
The other step occurs in the dark. The energy produced in the light reaction is utilized to convert carbon dioxide into carbohydrates. This process occurs in the stroma of the chloroplast. The photophosphorylation is of two types that are cyclic and non-cyclic. Let us understand the cyclic photophosphorylation. The process helps in energy production and not the formation of biological molecules. In this process, the conversion of ADP (Adenosine Di-phosphate) to ATP takes place. The pathway neither produces NADPH nor \[~{{O}_{2}}\].
Therefore, the correct answer is option C.

Note: The cyclic photophosphorylation occurs in the thylakoid membrane. The electron in a pigment complex called photosystem begins a cyclic electron flow. Then, it further passes from the primary acceptor to ferredoxin and then at last to cytochrome b6f. The electron transfers to plastocyanin before returning to chlorophyll. A concentration gradient is produced throughout this electron transport chain that is used to power ATP synthase.