But getting from 6CO2 and 6H2O to C6H12O6 and 6O2 is not one simple step. It's a scenic route. Light reaction is the capture of light energy in the chloroplast of plant cells. The chloroplast is an organelle in the cell encased in a membrane. The inside of the chloroplast is composed of a network of stacked membranes called thylakoids and the 'juice' around these membranes called the stroma.
Light reaction takes place in association with the thylakoids .
But not just any light, it has to be red or blue to be most efficient. The electron can lose its excess energy in a couple of ways. When it reacts with other molecules photosynthesis happens. Light energy strikes PSII and kicks an electron out of chl a. They are what provide energy for the 'dark' reaction by giving their energy to sugar as it is made .