Metabolism Autotrophs such as plants can construct the complex organic molecules in cells such as polysaccharides and proteins from simple molecules like carbon dioxide and water. Heterotrophs, on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from inorganic oxidation reactions. Photosynthesis is the synthesis of carbohydrates from sunlight and carbon dioxide (CO). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced
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