Overview of
Photosynthesis: 3 of 3

In the light reactions, one molecule of the pigment chlorophyll absorbs one photon and loses one electron. The free electrons generate activity that drives four key reactions: (1) the joining of ADP and phosphate to create ATP, (2) the reduction of NADP+ to form NADPH, (3) the splitting of water, and (4) the release of oxygen.

In the light-independent (or dark) Calvin cycle, the newly formed ATP and NADPH molecules convert carbon dioxide and water into metabolism-driving sugar molecules.

Show/Hide Video Description
Starting off illustrating the same Chloroplast cell, cylinder-like Light reactions, and the circular Calvin cycle from the previous lesson, this video goes further to show the ADP, Phosphate, and NADP+ reacting with electrons within the Light reactions and forming the ATP and NADPH. An H2O molecule is then shown entering the Light Reaction, with O2 being released. In the next stage, the energy, electrons, and carbon from the ATP, NADPH, and CO2 are shown entering the Calvin cycle, in order to produce the outcome of sugar molecules.