How do prokaryotes obtain energy?

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Prokaryotes are composed of cells that do not contain a nucleus or membrane-bound organelles. Prokaryotes can be either autotrophic or heterotrophic. Each process is explained below.

1. Autotrophic prokaryotes make their own food. Autotrophic prokaryotes obtain energy through either photosynthesis or chemosynthesis. Each process is briefly explained below.

  • Although prokaryotes do not contain organelles such as the chloroplast, they may contain chlorophyll that is housed within vesicles. Photosynthetic prokaryotes use this chlorophyll to make their own food via photosynthesis. During photosynthesis, sunlight energy is captured by the chlorophyll in order to convert carbon dioxide gas and water into a sugar known as glucose and oxygen gas.  
  • Chemosynthetic prokaryotes use chemosynthesis to obtain energy. During chemosynthesis, organic compounds are synthesized using the energy from the oxidation of inorganic compounds. Prokaryotes that lie along the hydrothermal vents at the base of the seafloor use the hydrogen sulfide that is produced from the hydrothermal vents to produce energy via chemosynthesis.

2. Some prokaryotes are heterotrophic. These prokaryotes must consume organic compounds in order to obtain energy. Prokaryotes do not have mitochondria to convert the organic compounds into ATP via cellular respiration. Instead, prokaryotes utilize enzymes that are attached to their cell membranes to produce ATP.

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