Final answer:
ATP production in cellular respiration and photosynthesis is mediated by ATP synthase, which uses the energy from the flow of hydrogen ions across a concentration gradient in a process called chemiosmosis.
Step-by-step explanation:
The movement through the protein ATP synthase facilitates the production of ATP in both cellular respiration and photosynthesis. This process occurs as a result of an exergonic movement of hydrogen ions from areas of high concentration to low concentration. As hydrogen ions pass through ATP synthase, the energy released enables the enzyme to add a phosphate group to ADP, resulting in ATP formation. This flow of hydrogen ions is known as chemiosmosis, which occurs through a semi-permeable structure and is essential for generating the electrochemical gradient used in ATP synthesis. In cellular respiration, the electrochemical gradient is formed across the mitochondrial membrane, with hydrogen ions moving from the intermembrane space to the mitochondrial matrix. Similarly, in photosynthesis, the gradient is established across the thylakoid membrane in chloroplasts. The oxidative phosphorylation mechanism in cellular respiration is key to harvesting the potential energy stored within this gradient and is mirrored by the processes occurring during photosynthesis, which also rely on ATP synthase to produce ATP.