Which structural adaptation of chloroplasts is specifically designed to maximize their function in photosynthesis?

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Question restatement: Which structural adaptation of chloroplasts is specifically designed to maximize their function in photosynthesis?
Option 1: The stroma and thylakoid space are maintained at identical pH levels to ensure chemical equilibrium. While pH differences across compartments are important for photosynthesis (the lumen becomes acidic during electron transport, while the stroma is more neutral to alkaline), the statement about identical pH across stroma and thylakoid space is incorrect. It overlooks the purposeful pH gradient that drives ATP synthesis and the separation of light-dependent versus light-independent processes.
Option 2: The thylakoid membranes are organized into stacked grana connected by unstacked stroma lamellae, creating specialized compartments for light-dependent and light-independent reactions. This description accurately captures a core chloroplast adaptation: grana increase surface area for photosystems I and II and the electron transport chain, while the stroma lamellae connect grana and facilitate metabolite exchange, effectively separating and optimizing the light-dependent reactions from the Calvin cycle in the stroma.
Option 3: Chloroplasts have a single, uniform membrane to allow unrestricted movement of all molecules. This is incorrect: chloroplasts have a double membrane system (outer and inner envelope) plus internal membranes (thylakoid), and the idea of a single uniform membrane contradicts the classic organelle structure that supports selective transport and compartmentalization essential for photosynthesis.
Option 4: Chloroplasts contain no DNA to prevent competition with nuclear control of photosynthesis. This is false: chloroplasts contain their own circular DNA and ribosomes, which encode a subset of photosynthetic proteins and enable local synthesis of some components, not to mention the broader genetic autonomy that supports organelle function.
Summary: Among the options, only Option 2 aligns with the well-established structural adaptation that maximizes photosynthetic efficiency by organizing thylakoids into grana and connecting lamellae, thereby optimizing light reactions and substrate exchange within the chloroplast.

Bio 93 Section CDE 2025 Midterm 1- Section E

Which structural adaptation of chloroplasts is specifically designed to maximize their function in photosynthesis?

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