Living organisms harness energy primarily through three main strategies: photosynthesis, chemosynthesis, and consumption of other organisms.
- Photosynthesis : Autotrophic organisms like plants, algae, and some bacteria capture sunlight and convert it into chemical energy. This process involves chlorophyll molecules absorbing light energy to produce ATP and NADPH, which then drive the synthesis of organic molecules (e.g., glucose). These molecules store energy in chemical bonds that can be used later by the organism or others in the ecosystem
- Chemosynthesis : Certain bacteria, especially those near hydrothermal vents, harness energy by oxidizing inorganic molecules such as hydrogen sulfide. This chemical energy is used to synthesize organic compounds, supporting life in environments without sunlight
- Consumption (Heterotrophy) : Heterotrophic organisms obtain energy by consuming autotrophs or other heterotrophs. They digest complex organic molecules, breaking them down into simpler compounds while releasing energy through cellular respiration. This energy is converted into ATP, the universal energy currency in cells, which powers biological functions like growth, movement, and reproduction
At the cellular level, energy conversion involves metabolic pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation. These pathways break down nutrients to produce ATP, which cells use to perform work. Excess energy is often stored in molecules like carbohydrates (e.g., glycogen), lipids, and sometimes proteins for later use
. In summary, living organisms harness energy by capturing it from sunlight or chemical sources or by consuming organic matter, then converting and storing it in chemical forms like ATP to fuel life processes
