The site for the light reactions isa)Vacuolesb)Cisternaec)Stromad)GranaCorrect answer is option 'D'. Can you explain this answer?

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ACT Exam > ACT Questions > The site for the light reactions isa)Vacuoles...

The site for the light reactions is

a)
Vacuoles
b)
Cisternae
c)
Stroma
d)
Grana

Correct answer is option 'D'. Can you explain this answer?

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The site for the light reactions isa)Vacuolesb)Cisternaec)Stromad)Gran...

In plant cells, the chloroplasts are responsible for trapping light energy essential for photosynthesis. The grana, in the plastid, is the site of light reactions.

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The site for the light reactions isa)Vacuolesb)Cisternaec)Stromad)Gran...

The site for the light reactions is Grana.

The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts, specifically in structures called grana. Grana are stacks of pancake-shaped structures within the chloroplasts that contain the photosynthetic pigments and electron transport chains necessary for the light reactions to take place.

Explanation:
The light reactions are the initial phase of photosynthesis, where light energy is converted into chemical energy in the form of ATP and NADPH. These reactions occur in the thylakoid membranes, which are located within the chloroplasts of plant cells.

Thylakoid Membranes:
The thylakoid membranes are flattened sacs that are interconnected to form stacks called grana. These structures provide a large surface area for the absorption of light and the organization of the photosystems and electron transport chains. The thylakoid membranes are embedded with photosynthetic pigments, such as chlorophyll, which are responsible for capturing light energy and initiating the light reactions.

Grana:
Grana are the sites where the photosystems are located. Photosystems are large protein complexes that contain chlorophyll and other pigments. They capture light energy and transfer it to reaction centers, where the energy is used to drive the electron transport chain. The grana provide a structural framework for the organization of these photosystems and facilitate the efficient flow of electrons during the light reactions.

Other Possible Options:
a) Vacuoles: Vacuoles are storage organelles in plant cells and play a role in various cellular processes, but they are not directly involved in the light reactions of photosynthesis.

b) Cisternae: Cisternae are flattened, membrane-bound sacs found in various organelles, such as the Golgi apparatus and endoplasmic reticulum. However, they are not specifically associated with the light reactions of photosynthesis.

c) Stroma: The stroma is the fluid-filled space surrounding the thylakoid membranes within the chloroplasts. It is involved in the dark reactions (Calvin cycle) of photosynthesis, which occur after the light reactions. However, the light reactions primarily occur within the thylakoid membranes, specifically in the grana.

In conclusion, the correct answer is option D) Grana, as they are the specific sites within the chloroplasts where the light reactions of photosynthesis take place.

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