Why Are Chloroplasts Green?


Chloroplasts, the parts of plant cells responsible for photosynthesis, are green because they contain the pigment chlorophyll, which absorbs the red and blue wavelengths of light and reflects back the green wavelengths. Chlorophyll absorbs particular colors of light to provide the right amount of energy for photosynthesis to take place. Photosynthesis is the process by which plants use the energy from the sun to convert carbon dioxide from the air into carbohydrates for food.

Chloroplasts are found in cells located in the leaves of plants. The chlorophyll in the chloroplasts gives the leaves their distinct green coloring. Chloroplasts develop fully when they are exposed to light.

Each chloroplast has a double layer of membranes that protects its structures. Stroma, a thick, enzyme-rich fluid, fills the area enclosed by the membranes. Layered structures called grana, which contain chlorophyll, are located throughout the stroma.

When a chloroplast is exposed to light, photosynthesis starts. The light is absorbed by the chlorophyll and converted to chemical energy in the grana. Then enzymes in the stroma begin a series of reactions which use the chemical energy to convert carbon dioxide molecules into carbohydrate molecules. The plant uses the carbohydrates for growth and respiration. Extra carbohydrates are stored for later use.