Which organelle in plant cells contains chlorophyll?

The chloroplast is the correct answer because it is the organelle responsible for photosynthesis in plant cells. Chlorophyll, which is the green pigment essential for capturing light energy, is embedded in the thylakoid membranes of the chloroplasts. This pigment allows plants to absorb sunlight, which is then used to convert carbon dioxide and water into glucose and oxygen during the photosynthetic process. This transformation of light energy into chemical energy is vital for the growth and energy needs of the plant, as well as for the overall ecosystem, since it produces oxygen as a byproduct.

In contrast, mitochondria are involved in cellular respiration, converting glucose into usable energy, but they do not contain chlorophyll. The nucleus serves as the control center of the cell, housing genetic material, and is not involved in photosynthesis. The endoplasmic reticulum is involved in protein and lipid synthesis but, like the others mentioned, does not have any role in the absorption of light or photosynthesis. Thus, the unique function of chloroplasts and their chlorophyll content is what makes them essential in plant biology.