Which of the following is responsible for photosynthesis in plant cells?

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process occurs specifically in chloroplasts, which are specialized organelles found in the cells of green plants and some other photosynthetic organisms.

Chloroplasts contain chlorophyll, the green pigment that captures sunlight, and other substances necessary for the photosynthetic process. When light is absorbed by chlorophyll, it drives the chemical reactions that convert carbon dioxide and water into glucose and oxygen. This is essential for plant growth and provides energy for nearly all living organisms on Earth, as plants serve as primary producers in the food chain.

The other organelles listed have different functions; for example, mitochondria are involved in cellular respiration and energy production, the nucleus contains the genetic material and controls cell activities, and the endoplasmic reticulum is involved in the synthesis of proteins and lipids. Therefore, chloroplasts are uniquely responsible for the process of photosynthesis in plant cells, making them the correct answer.