Plants use the energy of sunlight to convert carbon dioxide into starch for animals and plants as food sources. Chloroplast is the place where plants carry out photosynthesis, so chloroplast can be said to be the medium through which sunlight transmits life. (1) Principle Plants are different from animals. They have no digestive system, so they have to rely on other ways to absorb nutrients. Is the so-called autotroph. For green plants, in sunny days, they will use the energy of sunlight for photosynthesis to obtain nutrients necessary for growth and development. The key participant in this process is the internal chloroplast. Under the action of sunlight, chloroplasts convert carbon dioxide entering leaves through stomata and water absorbed by roots into glucose, and at the same time release oxygen: 12H2O+6CO2 = (light) C6H 12O6 (glucose)+6o2+6o2 light is considered as a catalyst and does not participate in the reaction. (2) Note: The water on both sides of the middle number in the above formula cannot be offset, although the formula is very special in chemistry. The reason is that the water on the left is absorbed by plants to make oxygen and provide electrons and hydrogen ions. The oxygen atom of the water molecule on the right comes from carbon dioxide. In order to express the initial process of this raw material product more clearly, people are more accustomed to writing water molecules on the left and right sides of the equal sign, or adding an asterisk to the upper right corner of the water molecule. (3) Photoreaction and dark reaction Photosynthesis can be divided into two steps: photoreaction and dark reaction. (4) Photoreaction site: grana lamellae in chloroplasts. Influencing factors: light intensity, two absorption peaks of chlorophyll a and chlorophyll b in plant photosynthesis. Absorption peak process: there are two sets of photosynthesis systems on chloroplast membrane: photosynthesis system ⅰ and photosynthesis system ⅱ. However, the electron transfer starts from the second photosynthetic system). Under illumination, photons with wavelength of 680nm and 700nm are absorbed respectively. As energy, electrons obtained from the photolysis path of water molecules are constantly transferred (only a few chlorophyll a in a special state can be transferred) and finally transferred to coenzyme NADP. However, due to different concentrations, hydrogen ions obtained by water photolysis move from thylakoid to matrix through the protein complex on thylakoid membrane, and the potential energy between them decreases, which is used to synthesize ATP for dark reaction. At this time, the hydrogen ions with reduced potential energy are taken away by the hydrogen carrier NADP. One NADP molecule can carry two hydrogen ions. This NADPH+H ion acts as a reducing agent in the dark reaction. Significance: 1: photolyses water to produce oxygen. 2. Convert light energy into chemical energy, generate ATP, and provide energy for dark reaction. 3.NADPH+H ion is synthesized from hydrogen ion, which is the product of water photolysis, and provides reducing agent for dark reaction. (5) Dark reaction is essentially a series of enzymatic reaction sites: chloroplast matrix influencing factors: temperature, carbon dioxide concentration process: different plants have different dark reaction processes and different leaf anatomical structures. This is the result of plants adapting to the environment. Dark reactions can be divided into three types: C3, C4 and cam. These three types are divided according to the different processes of carbon dioxide fixation.