Question

What are the end products of light reactions?

Answer 1

Hint: The process of using the energy in sunlight to make food (glucose) is known as photosynthesis. It occurs in the chloroplast (organelle-specific to plant cells). The light reaction is also known as photolysis in which a water molecule breaks down to hydrogen, oxygen, and electrons.

Complete answer:
 Light energy absorbed by pigments in leaves gets converted to chemical energy during the first stage of photosynthesis that involves a series of chemical reactions known as the light-dependent reactions.
Steps:
Energy from the sunlight is absorbed by the pigment chlorophyll and is converted into chemical energy in the form of electron charge carrier molecules such as NADPH and ATP.
Light energy is utilized in both the Photosystems I and II, present inside thylakoid membranes of the chloroplasts.
Carbohydrate molecules are obtained from carbon dioxide through the use of chemical energy.
The light energy splits into the water and extracts electrons from PS II; then the electrons move from PSII to cytochrome and PSI.
The electrons are re-energized in the Photosystems I and the electrons of high energy reduce NADP+ into NADPH.
The transfers of electrons from PSII to PSI, and from PSI to NADPH, are energy-releasing steps since electrons in P680 and P700 are boosted to very high energy levels by the absorption of energy from light.
In cyclic photophosphorylation, electrons follow a circular path, and only ATP is produced.

Therefore, the end products are ATP and NADPH.

Note: The ATP and NADPH from the light-dependent reactions are used to make sugars in the Calvin cycle. It takes place in the stroma. The Calvin cycle adds carbon to a simple five-carbon molecule known as RuBP. The end product of Calvin cycle is glucose. 9 ATP are converted to 9 ADP. 6 NADPH are converted to 6 NADP+.