Two main energy pathways are recognised in living systems. These are photosynthesis and cellular respiration. Both have their respective but different electron transfer chains. During photosynthesis carbohydrates are synthesized from carbon dioxide and water in the presence of sunlight and the green pigment chlorophyll. This is an anabolic process. In this process radiant energy of the sun is converted into chemical energy and stored in the chemical bonds of carbohydrates.
Note: The sun is the ultimate source of energy for all activities of living matter.