Photosynthesis – class 11 revision notes

Last updated on February 5th, 2022 at 04:48 am

Z-scheme

Summary of the light-dependent stage of photosynthesis with electron movement can be shown in a diagram called the Z-scheme (Figure 3).

The higher up the diagram, the higher the energy level.

If you follow one electron from a water molecule, you can see how it:

(1) is taken up by PSII

(2) has its energy raised as the chlorophyll in PSII absorbs light energy

(3) loses some of this energy as it passes along the electron carrier chain

(4) is taken up by PSI

(5) has its energy raised again as the chlorophyll in PSI absorbs light energy

(6) becomes part of a reduced NADP molecule

At the end of this process, two new substances have been made. These are ATP and reduced NADP. Both of them will be used now in the next stage of photosynthesis, the light-independent stage.