Final answer:
ATP is produced during light-dependent reactions of photosynthesis and the electron transport chain of cellular respiration. It is utilized to drive light-independent reactions in photosynthesis and various cellular processes as the main energy currency.
Step-by-step explanation:
ATP is made during the light-dependent reactions of photosynthesis and during the third stage of cellular respiration known as oxidative phosphorylation. In the context of the light-dependent reactions, ATP is produced through a process known as photophosphorylation, which utlizes energy from sunlight. The generated ATP is then utilized to power the light-independent reactions of photosynthesis, where carbon molecules are fixed and sugars are synthesized.
In the third stage of cellular respiration, ATP is produced through oxidative phosphorylation during the electron transport chain. Here, through a series of redox reactions involving electron carriers like NADH and FADH2, a proton gradient is established across the mitochondrial membrane. The flow of protons back into the mitochondrial matrix via ATP synthase drives the synthesis of ATP from ADP and inorganic phosphate.
The ATP molecules serve as the energy currency of the cell, used in various cellular processes. The energy stored in ATP can be released through the hydrolysis of ATP, where it is converted back to ADP and inorganic phosphate, making energy available for the cell to do work.