The structure of a chloroplast, specifically its membranes and thylakoids, makes its function, the chemical reactions of photosynthesis, more efficient because it provides a large surface area for the reactions to occur on and a way to organize the reactions in a sequence that allows the products of one reaction to be used immediately in the next reaction.
The membranes of a chloroplast are made up of two layers of phospholipid molecules, which form a lipid bilayer. This structure provides a large surface area for the chemical reactions of photosynthesis to occur on. The thylakoids, which are stacks of membrane-bound compartments, increase the surface area even further.
In addition, the structure of the thylakoids allows the reactions of photosynthesis to be organized in a sequence that allows the products of one reaction to be used immediately in the next reaction. The thylakoids are arranged in stacks called grana, which are interconnected by strands of thylakoid membrane called stroma lamellae. The thylakoid membranes within a granum are organized into discrete units called photosystems, which are the sites of the light-dependent reactions of photosynthesis. The thylakoid membranes within the stroma lamellae are the site of the light-independent reactions of photosynthesis. This organization allows the products of the light-dependent reactions, which are carried out in the thylakoid membranes of the grana, to be used immediately in the light-independent reactions, which take place in the thylakoid membranes of the stroma lamellae.
Overall, the structure of a chloroplast, with its membranes and thylakoids, provides a large surface area for the reactions of photosynthesis to occur on and a way to organize the reactions in a sequence that allows the products of one reaction to be used immediately in the next reaction. This makes the function of the chloroplast, photosynthesis, more efficient.