Photosynthesis occurs on the inner thylakoid membrane in the chloroplast of plants. Photosystem I and photosystem II are embedded in the thylakoid membrane, which is called the photosynthesis unit. It is composed of light-harvesting pigments composed of 200-300 antenna pigments. It is composed of body (absorbing light energy) and reaction center (consisting of 1 chlorophyll a, 1 electron donor and 1 electron acceptor), etc. (Photosystem II also contains an oxygen-evolving complex).
The strongest absorption wavelength of chlorophyll a in the reaction center of photosystem I is 700 nm, the electron donor is plastocyanin, and the electron acceptor is ferredoxin; the strongest absorption wavelength of chlorophyll a in the reaction center of photosystem II is 680 nm, The electron donor is water and the electron acceptor is plastoquinone (Figure 2-1). The chlorophyll molecule that obtains light energy transitions from the ground state to the excited state, and the excitation energy has three possible destinations (Figure 2-2). ①Energy is transferred to the reaction center through the antenna pigment, causing charge separation, electron transfer and photophosphorylation in the reaction center, promoting the photochemical reaction, and forming the assimilation force (ATP and NADPH) for fixing and reducing carbon dioxide. ② Dissipate directly in the form of heat. ③ release photons and generate fluorescence.
In photosynthesis, only chlorophyll a directly participates in the light reaction of photosynthesis, its absorption wavelength peaks are 432nm and 660nm, and chlorophyll b absorption wavelength peaks are 458nm and 642nm (Figure 2-1). Because chlorophyll b transmits 100% of the absorbed energy to chlorophyll a, and other pigments also absorb light of different wavelengths in sunlight, and then pass it to chlorophyll a, but the energy transfer efficiency is not too high. Therefore, the light waves that mainly promote photosynthesis are blue light near 432 nm and red light near 660 nm.
Figure 2-1 shows that chlorophyll a and chlorophyll b each have two absorption bands, the blue band and the red band, respectively. The central wavelengths of the absorption bands are 432 nm, 458 nm and 660 nm, 642 nm, respectively. It can be seen from Figure 2-1 that in photosynthesis, green light with the strongest energy in sunlight has little effect and is reflected and transmitted, which is very unfavorable for plants to make full use of solar energy.
From the above results, it can be inferred that only part of the light of the sun’s panchromatic spectrum is absorbed by plants. According to the theory of quantum mechanics, when sunlight irradiates plants, only those photons whose frequency is equal to the natural frequency of certain energy levels of chlorophyll a molecule can be absorbed, so that the chlorophyll a molecule produces electronic transitions for photosynthesis.
Photosynthesis process
Photosynthesis occurs on the inner thylakoid membrane in the chloroplast of plants. Photosystem I and photosystem II are embedded in the thylakoid membrane, which is called the photosynthesis unit. It is composed of light-harvesting pigments composed of 200-300 antenna pigments. It is composed of body (absorbing light energy) and reaction center (consisting of 1 chlorophyll a, 1 electron donor and 1 electron acceptor), etc. (Photosystem II also contains an oxygen-evolving complex).
The strongest absorption wavelength of chlorophyll a in the reaction center of photosystem I is 700 nm, the electron donor is plastocyanin, and the electron acceptor is ferredoxin; the strongest absorption wavelength of chlorophyll a in the reaction center of photosystem II is 680 nm, The electron donor is water and the electron acceptor is plastoquinone (Figure 2-1). The chlorophyll molecule that obtains light energy transitions from the ground state to the excited state, and the excitation energy has three possible destinations (Figure 2-2). ①Energy is transferred to the reaction center through the antenna pigment, causing charge separation, electron transfer and photophosphorylation in the reaction center, promoting the photochemical reaction, and forming the assimilation force (ATP and NADPH) for fixing and reducing carbon dioxide. ② Dissipate directly in the form of heat. ③ release photons and generate fluorescence.
In photosynthesis, only chlorophyll a directly participates in the light reaction of photosynthesis, its absorption wavelength peaks are 432nm and 660nm, and chlorophyll b absorption wavelength peaks are 458nm and 642nm (Figure 2-1). Because chlorophyll b transmits 100% of the absorbed energy to chlorophyll a, and other pigments also absorb light of different wavelengths in sunlight, and then pass it to chlorophyll a, but the energy transfer efficiency is not too high. Therefore, the light waves that mainly promote photosynthesis are blue light near 432 nm and red light near 660 nm.
Figure 2-1 shows that chlorophyll a and chlorophyll b each have two absorption bands, the blue band and the red band, respectively. The central wavelengths of the absorption bands are 432 nm, 458 nm and 660 nm, 642 nm, respectively. It can be seen from Figure 2-1 that in photosynthesis, green light with the strongest energy in sunlight has little effect and is reflected and transmitted, which is very unfavorable for plants to make full use of solar energy.
From the above results, it can be inferred that only part of the light of the sun’s panchromatic spectrum is absorbed by plants. According to the theory of quantum mechanics, when sunlight irradiates plants, only those photons whose frequency is equal to the natural frequency of certain energy levels of chlorophyll a molecule can be absorbed, so that the chlorophyll a molecule produces electronic transitions for photosynthesis.