Energy and Metabolism

Scientists use the term bioenergetics to discuss the concept of energy flow (Figure) through living systems, such as cells. Cellular processes such as building and breaking down complex molecules occur through stepwise chemical reactions. Some of these chemical reactions are spontaneous and release energy; whereas, others require energy to proceed. Just as living things must continually consume food to replenish what they have used, cells must continually produce more energy to replenish that which the many energy-requiring chemical reactions that constantly take place use. All of the chemical reactions that transpire inside cells, including those that use and release energy, are the cell’s metabolism.

This diagram shows energy from the sun being transferred to producers, such as plants, as well as releasing heat. The producers in turn transfer the energy to consumers and decomposers, which release heat. Animals also transfer energy to decomposers.
Most life forms on earth obtain their energy from the sun. Plants use photosynthesis to capture sunlight, and herbivores eat those plants to obtain energy. Carnivores eat the herbivores, and decomposers digest plant and animal matter.
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