Fractionation of carbon isotopes in oxygenic photosynthesis characterization of food chains. Oxygenic photosynthesis is a metabolic pathway facilitated by autotrophs, including plants, algae, and cyanobacteria. This pathway converts inorganic carbon dioxide from the atmosphere or aquatic environment into carbohydrates, using water and energy from light, then releases molecular oxygen as a product. Organic carbon contains less of the stable isotope Carbon-13, or C, relative to the initial inorganic carbon from the atmosphere or water because photosynthetic carbon fixation involves several fractionating reactions with kinetic isotope effects. These reactions undergo a kinetic isotope effect because they are limited by overcoming an activation energy barrier. The lighter isotope has
Carbon dioxide clathrate Celsius (bottom and top respectively). On the vertical ones are given the pressure (left) and the estimated depth in the Martian regolith (right). The horizontal dashed line at zero depth represents the average Martian surface conditions. The two bent dashed lines show two theoretical Martian geotherms after Stewart & Nimmo (2002) at 30° and 70° latitude. Carbon dioxide clathrate Carbon dioxide hydrate is a snow-like crystalline substance composed of water ice and carbon dioxide. It normally is a Type I gas clathrate. However, there has been some experimental evidence for the development of a metastable Type II phase at A