All organisms require the input of energy in order to facilitate metabolic processes. All energy originates with the sun. This energy is converted into cellular energy by photosynthetic organisms. This energy can then be broken down further into the most basic form of cellular energy, adenosine triphosphate, ATP.
Cellular processes are highly regulated, and energy-producing reactions are often paired with energy-consuming reactions. This happens all the time in the cell, and photosynthesis will be a great example of this.
As always, energy is neither created nor destroyed in the processes of cellular respiration and photosynthesis. Most energy is “lost” in the form of heat due to the use of the energy for a variety of metabolic processes. This will come into play when food webs are discussed in Unit 8 - Ecology.
Energy is gained through eating. All organisms get their energy from plants, regardless of whether or not the organism consumes plants. Carnivores still obtain their energy from plants, it has just been transferred from a plant to the organism that they are eating.
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