A Level Biology Practice Exam

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What is a granum in the context of plant cells?

A type of cell membrane
A stack of thylakoids in chloroplasts
A structure involved in protein synthesis
A waste storage structure

The correct answer is: A stack of thylakoids in chloroplasts

A granum refers specifically to a stack of thylakoids found within the chloroplasts of plant cells. Thylakoids are membrane-bound structures that play a crucial role in the photosynthetic process, where they facilitate the capture of light energy and the production of ATP and NADPH. These stacks resemble coins and are interconnected by stroma thylakoids, which form a network essential for the efficient functioning of photosynthesis. The structure of a granum is vital for maximizing the surface area available for the light-dependent reactions of photosynthesis, thereby allowing plants to absorb more light energy. This efficient arrangement contributes significantly to the overall productivity of photosynthesis in plants, making the granum an essential component of their ability to convert light energy into chemical energy. Understanding granums and their role highlights the intricate design of chloroplasts and the specialized functions of various cellular components in plant biology.