Which organelle is primarily responsible for photosynthesis?

The chloroplast is the organelle primarily responsible for photosynthesis, a process in which light energy is converted into chemical energy in the form of glucose. Chloroplasts contain chlorophyll, the green pigment that captures sunlight, and this is where the light-dependent and light-independent reactions of photosynthesis occur. The thylakoid membranes within chloroplasts are essential for the light reactions, while the stroma is where the Calvin cycle takes place, ultimately leading to the synthesis of sugars from carbon dioxide and water.

In the context of this question, the other organelles play different roles in cellular function. Ribosomes are involved in protein synthesis, mitochondria are the powerhouses of the cell that generate energy through cellular respiration, and the nucleus contains the genetic material and regulates gene expression. Understanding the specific functions of these organelles highlights why chloroplasts are distinctively positioned as the site for photosynthesis in plant cells.