CBSE Class 10 Answered

ATP - Adenosine triphosphate

ADP - Adenosine diphosphate

NADP - Nicotinamide adenine dinucleotide phosphate.

NADPH - The reduced form of NADP.

In the Light Dependent Processes i.e Light Reactions, the light strikes chlorophyll a in such a way as to excite electrons to a higher energy state. In a series of reactions the energy is converted, along an electron transport process into ATP and NADPH. Water is split in the process, releasing oxygen as a by-product of the reaction. The ATP and NADPH are used to make C-C bonds in the Light Independent Process (Dark Reactions).

Thus in photosynthesis, these 4 molecules are needed to carry out the various energy conversions.