A sequence to better understand the photosynthesis that takes place in the chloroplast. Photosynthesis is a metabolic process that is carried out in the leaves of chlorophyllous plants and consists of producing organic matter from light and mineral matter such as carbon dioxide and water. The leaf tissue is made up of chlorophyll cells organized into parenchymas: the palisade chlorophyll parenchyma and the lacunar chlorophyll parenchyma. The carbon dioxide present in the atmosphere penetrates the leaf through the stomata and then reaches all the chlorophyllous cells. It is also through the stomata that the release of gases resulting from photosynthetic activity such as dioxygen takes place. The chlorophyllous cell contains a large number of chloroplasts which are the organelles specialized in photosynthesis. A chloroplast is made up of 2 main compartments in which photosynthetic metabolism takes place: the thylakoids are membrane folds and the stroma corresponds to the matrix of the chloroplast. Photosynthesis that takes place in the chloroplast is subdivided into 2 major stages. In the first stage, light acts on the thylakoids by triggering the photolysis of water. This reaction is at the origin of the production of reduced coenzymes RH2 or NADH,H+ and energy in the form of ATP. All of these reactions constitute the light or photochemical phase of photosynthesis. The 2nd stage takes place in the stroma of the chloroplast and corresponds to the Calvin cycle which is responsible for the incorporation of carbon dioxide into organic molecules using the compounds produced in the light. All of the reactions that take place in the stroma correspond to the dark or non-photochemical phase of photosynthesis. The thylakoid membrane contains photosystems, in particular composed of photosynthetic pigments such as chlorophyll, xanthophylls or carotenoids. Chlorophyll is a photosynthetic pigment that has the property of absorbing light, in particular blue radiation with a wavelength of 440 nm and red radiation with a wavelength of 680 nm. Chlorophyll is at the origin of a photo-oxidation of the water molecules contained inside the thylakoids, which leads to the production of electrons and dioxygen, the latter being released outside the plant. In the chloroplast, there are coenzymes that are in the oxidized state (NADP+). By accepting the electrons from the photolysis of water, the coenzymes will undergo a reduction. On the other hand, the accumulation of H+ protons inside the thylakoid due to the photolysis of water is responsible for a proton gradient between the inside and the outside of the thylakoid: protons will then pass through the ATP synthases located in the thylakoid membrane, which is at the origin of the production of energy in the form of ATP. The production of reduced coenzymes and ATP by the thylakoids during the photochemical phase of photosynthesis will be used to reduce carbon dioxide in the stroma during the non-photochemical phase, constituting what is called the Calvin cycle. Carbon dioxide is first fixed by an enzyme (rubisco) on a molecule present in the stroma: ribulose diphosphate or RuDiP, thus giving rise to a first organic molecule: APG or phosphoglyceric acid. In a second step, the use of reduced coenzymes and ATP from the light phase of photosynthesis will allow the production of trioses-phosphates then hexoses-phosphates leading ultimately to the synthesis of starch.