Аннотация:An agent-based mathematical model reproducing the dynamics of redox transformations of the components of the photosynthetic electron transport chain with explicit simulation of mobile electron carriers diffusion in the complex interior of the intrachloroplast space is considered. The geometry of granal and stromal thylakoids is set analytically on the basis of modern ideas about the spatial organization of thylakoid membranes. The model considers a grana, consisting of several (from 2 to several dozen) cylindrical thylakoids, and stromal lamellae connected with it. It is assumed that the grana, which consists of stacked cylindrical thylakoids, "pierces" the stromal lamellae, and spiral structures are formed in the contact area. The dimensions and shape of the compartments are specified as numerical parameters of the model. The model is discrete in time and space. The space inside the chloroplast is divided into rhombic dodecahedral cells with a volume of 2 cubic nm, toroidal (periodic) boundary conditions are used. The model considers redox reactions occurring with the participation of agents - transmembrane protein complexes (photosystems 1 and 2 and the cytochrome b6f complex) and mobile electron carriers - plastoquinone, plastocyanin and ferredoxin. One cell of the model is used to represent the plastoquinone molecule; protein molecules occupy several adjacent cells, their shape is set according to X-ray diffraction analysis or cryoelectron microscopy, and the rotation angle is determined randomly when the model is run. All agents in the model are considered as mobile; for transmembrane protein complexes, lateral diffusion in the membrane plane is available; for mobile carriers, three-dimensional diffusion within the corresponding compartment (the lipid layer of the membrane for plastoquinone, the thylakoid lumen for plastocyanin, and the stroma for ferredoxin) is available. In one step of the model (2 us), the agent can move one cell in any direction; for each type of agents, the probability of displacement in one step of the model is set. For mobile carriers, the displacement probability was chosen in such a way that the diffusion coefficients observed in the model corresponded to the experimentally measured ones. Each of the agents can be in one of several redox states. The way the transitions between the states of agents occur is determined by the program specified for each type of agents, so one can easily change the level of detail of the processes occurring in each of the agents, regardless of other agents. One or several cells near the surface of the transmembrane complexes are set as active sites, the hit of mobile electron carriers into which leads to the launch of a program that analyzes this interaction. A maximally simplified system was considered, in which all processes of electron transport between transmembrane complexes are modeled as irreversible diffusion-controlled reactions. If, at the current step of the model, a molecule of an agent, a reaction partner, is in the interaction site, and the redox states of two agents allow the exchange of electrons between them, then a corresponding change in the states of these agents occurs. In addition, spontaneous reactions can occur in complexes, which correspond to light-induced charge separation in photosystems and electron transfer between the carriers included in the complex. With the help of the developed model, the influence of the geometric parameters of the grana on the transient redox processes occurring under the illumination of dark-adapted leaves was studied. Despite its simplicity, such a model made it possible to reproduce the main features of the curves observed in experiments using a small number of adjustable parameters. The model is implemented as a program in the Python programming language.