Britannica Sources used in this answer

How do green plants use sunlight to make carbohydrates?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

biology; microscope — Biology A researcher using a microscope to examine a specimen in the laboratory.

Green plants produce carbohydrates through a two-stage process known as photosynthesis, which occurs within specialized cell organelles called chloroplasts.12

The Light Reactions

The process begins with the light-harvesting reactions, which occur in the thylakoids of the chloroplast. Pigment complexes, primarily chlorophylls and carotenoids, absorb sunlight and transfer this energy to reaction centers. This energy drives a series of electron transfers that convert light into chemical energy in the form of ATP and NADPH. During this stage, water is oxidized, releasing oxygen as a byproduct.132

The Dark Reactions

The second stage, or carbon-assimilating reactions, takes place in the stroma and does not require direct sunlight. Using the ATP and NADPH generated in the light reactions, plants perform carbon fixation through the Calvin-Benson cycle. In this cycle, carbon dioxide is converted into simple sugars, such as glucose, which serve as the plant's primary energy-rich organic products.3142