The carriers that move energy from the light-dependent reactions to the Calvin cycle reactions can be thought of as “full” because they bring energy. After the energy is released, the “empty” energy carriers return to the light-dependent reactions to obtain more energy. You should be familiar with the energy carrier molecules used during cellular respiration: NADH and FADH2. Photosynthesis uses a different energy carrier, NADPH, but it functions in a comparable way. The lower energy form, NADP+, picks up a high energy electron and a proton and is converted to NADPH. When NADPH gives up its electron, it is converted back to NADP+.
Producers are at the bottom or beginning of the food chain because they produce their own food. producers do not eat other organisms unless there are exceptions. consumers eat other consumers and also eat producers.
