Heterotrophs obtain energy by consuming organic matter produced by others. They cannot photosynthesize or fix carbon themselves, so they rely on eating or absorbing pre-formed organic compounds found in other organisms or dead organic matter. The energy in these compounds is released primarily through cellular respiration, yielding ATP that powers cellular processes. Key points
- What they eat: Heterotrophs ingest or absorb complex organic molecules such as carbohydrates, proteins, and fats from other organisms or detritus.
- How energy is released: Through cellular respiration (aerobic or anaerobic), which breaks down organic molecules and transfers energy to ATP. In aerobic respiration, oxygen is the final electron acceptor and water is produced; in anaerobic pathways, other acceptors (like nitrate, sulfate, or carbon dioxide) are used.
- Primary energy source: The energy ultimately traces back to the sun, because autotrophs convert solar energy into chemical energy stored in organic molecules, which heterotrophs then consume. Even when energy flows through ecosystems via detritus or parasitism, the initial energy input is sunlight captured by autotrophs.
