The electron transport chain is found in both mechanisms of cellular respiration and photosynthesis. Cellular respiration uses a series of redox reactions to transfer electrons and protons across a membrane to form an electrochemical gradient whereas photosynthesis harvests the light as its energy source to form its electrochemical gradient. This proton electrochemical gradient is used to power ATP synthesis via ATP synthase. The simplified overall reactions of photosynthesis and cellular respiration exhibit reciprocity to each other in that the starting material of cellular respiration begins with H¬2O and the breakdown of glucose and ends with CO¬¬2 and H2O to create ATP. Photosynthesis initially utilizes energy from light combined with inorganic …show more content…
These reduced molecules are then oxidized by the electron transport chain to donate their electron through a series of enzymatic steps via electron carriers found in electron carrier complexes. Through proton pumping from the electron carrier complexes, the electrons are passed through electron carriers that have a low affinity for electrons down to carriers which have a high affinity for electrons. Each carrier complex “pumps” protons against their concentration gradient into the inter-membrane space from the mitochondrial matrix; or in chloroplasts, out of the stroma into the thylakoid space, with each pass of an electron. The order of the electron transport through these complexes relies on the differences in the redox potential between the complexes …show more content…
Quinone is a mobile hydrophobic molecule embedded within the membrane that carriers 1-2 electrons at a time. The quinone then takes the electron and gives it to the second electron carrier complex, cytochrome b-c1 complex. The cytochrome b-c1 complex contains electron carriers’ cytochromes and iron-sulfur proteins. The cytochromes are made of heme groups and the iron-sulfur proteins are made of two to four iron and sulfur molecules bound to cysteine, both only carrying 1 electron at a time. This complex takes the provided electron and passes to cytochrome c, which then in turn gives the electron to the cytochrome oxidase complex. Finally, the cytochrome oxidase complex receives electrons one at a time and sends them to the final electron carrier, O2, four at a time creating H2O. Additionally during this process, four protons are pumped out from the complex across the membrane as well. The end result is the proton motive force that drives ATP synthesis through oxidative phosphorylation of ADP and inorganic