How The Process Of Photosynthesis And Cellular Respiration

All living organisms require energy in order to perform the principal functions and activities that are necessary for life. Cells obtain this energy through the processes of photosynthesis and cellular respiration. In photosynthesis, organisms harness light energy obtained from the sun to produce organic compounds. On the other hand, cellular respiration breaks down the organic compounds produced from photosynthesis to harvest the energy needed to carry out the energy-consuming activities of the cell. As complementary processes, photosynthesis and cellular respiration provide each other with the raw materials needed for each reaction to take place. Whereas water and carbon dioxide produce oxygen and glucose in photosynthesis, oxygen and glucose
Glycolysis, the Krebs cycle, and oxidative phosphorylation are the three stages that coordinate to carry out the energy harvesting function of respiration. Occurring in the cytosol, glycolysis initiates the catabolic process by breaking down glucose into two molecule of pyruvate, where most of the potential energy is stockpiled. Through the Krebs cycle, pyruvate is further oxidized in the mitochondrial matrix, where the breakdown of glucose to carbon dioxide is completed. In glycolysis and the Krebs cycle, some ATP synthesis occurs through substrate level phosphorylation . However, a majority of the ATP produced by respiration comes from the metabolic pathway of oxidative phosphorylation. During this final stage, the energy-carrying NADH and FADH2 created by the Krebs cycle serve as the source of electrons, which are transferred to an electron transport chain. In the final step of the electron transport chain, the electrons combine with oxygen, thereby reducing it to water. Meanwhile, hydrogen ions from the electron transport chain are pumped into the inter-membrane space from the mitochondrial matrix, creating a proton gradient that is capable of performing work. In a process called chemiosmosis, the synthesis of ATP is coupled with the diffusion of hydrogen ions back into the mitochondrial matrix through ATP
Photosynthesis, which occurs in the chloroplasts of plant cells, is divided into two stages: the light reactions and Calvin cycle. Located in the thylakoid membrane, chlorophyll absorbs solar energy and uses it to generate the light reactions of photosynthesis by exciting the electrons from two photosystems into a high-energy state. Furthermore, water is split, releasing oxygen as a by-product and providing a source of hydrogen ions and electrons for the following steps. Via an electron transport chain, these electrons are transferred to the final electron acceptor NADP+, forming NADPH. Meanwhile, the hydrogen ions are pumped into the thylakoid space, contributing to the proton motive force that is subsequently used in chemiosmosis. With the help of ATP synthase complexes, hydrogen ions diffuse back into the stroma from the thylakoid space and synthesize ATP in a process known as photophosphorylation. The ATP and NADPH are then discharged into the stroma where they power the second stage of photosynthesis. Unlike the Krebs cycle in cellular respiration, the Calvin cycle is an anabolic process that occurs in the stroma. It uses energy from ATP and electrons from NADPH to produce carbohydrates from carbon