Question

Light reaction during photosynthesis takes place in
A. The outer surface of the chloroplast envelope
B. Stroma
C. Thylakoid membrane
D. The inner surface of the chloroplast envelope

Answer 1

Hint: Chlorophyll is the green pigment that helps organisms to absorb sunlight during the process of photosynthesis. In plants, it is seen in chloroplasts, that are double membrane-bound cell organelles that help for photosynthesis.

Complete Answer:
- Photochemical phase is the first phase in photosynthesis in plants. It is also called a light reaction because this process is completely light-driven. ATP and NADPH are formed in these sets of reactions.
- The light reaction takes place in the grana of the chloroplasts. Grana is the structure that appears like a pile of coins. It consists of several flattened sac-like structures called thylakoids. The light reaction takes place in the membrane system present in thylakoids and the stromal lamellae.
- Stromal lamellae are the thylakoids that connect different grana. Oxygen release associated with the photochemical phase of the light reaction. It involves two pigment systems in which chlorophyll a is the reaction centre of both systems. Oxygen is released in the process called Non-cyclic photophosphorylation.
- Photochemical reaction, which is also called light reaction, takes place only in organisms having chlorophyll a. Chlorophyll a is found in all Oxygen releasing photosynthetic forms of animals. Chlorophyll molecules are of different types. Some of them are chlorophyll a 673, chlorophyll-a 683, etc. Chlorophyll a is the chief pigment associated with photosynthesis.

Hence the correct option is C.

Note: Many types of chlorophyll are known. They are chlorophyll a, chlorophyll b, chlorophyll c and chlorophyll d. Among these, chlorophyll a is widely distributed in all autotrophic plants. Chlorophyll contains a porphyrin ring that has a magnesium atom at the centre. A long hydrocarbon chain will be connected to it called phytol tail.