Organic molecules (found in living systems) connect to form rings through their use of carbon atoms as inter-linkers (each C atom makes 4 bonds). Carbon chains that are 5 carbons long link up to form pentagonal structures whereas carbon chains that are 6 carbons long link up to form hexagonal structures, and since glucose is 6 carbons long, this is very common since glucose is made through photosynthesis and so there is lots of it about. Glucose gets used as a chemical feed into other biochemical metabolic transformations - changing the molecular structure in terms of number of carbons and changing the other functional groups bonded to each carbon; creating alcohols, lipids, amino acids, nucleotides, pheromones and hormones. This is where organic chemistry ('organic' meaning 'of life', involving molecules that link carbon, oxygen and hydrogen together) meets biochemistry (the chemistry of biological processes), which adds atoms of elements such as Nitrogen, Phosphorus, Sulphur, Potassium, Sodium and Chlorine. Since carbon forms the basis of chemical energy exchange for life, when animals either eat plants or eat animals that have previously eaten plants, the carbon stores that were initially made in photosynthesis are passed from one species into the other where, depending on the efficiency of digestion, they become integral to the organic chemistry of the cells in the recipient species. Similarly when plants donate some of their glucose to symbiotic mycorrhizal fungi in the soil, the fungi return the favour by donating minerals and water into the plant roots. Through respiration (releaseing energy contained within glucose) and through death and microbial decomposition, carbon dioxide is released back into the atmosphere. In pre industrial carbon cycling, the overall flux of carbon between atmosphere and living organisms was in balance meaning that there was a stable amount of carbon contained in the atmosphere for 100's of millions of years, with equal rates of carbon fixing (via plant photosynthesis) and carbon release via respiration. Since industrialisation began with the ever increasing and relentless burning of fossil fuels, a new loop has been added to our planet's carbon cycle, rapidly releasing geological fossil carbon (which had been removed from the atmosphere indefinitely) into the atmosphere. This has led to a rapid increase in carbon dioxide levels in the atmosphere, causing an increase in greenhouse gasses, trapping more heat in the atmosphere and warming the planet, causing feedback releasing other more potent greenhouse gasses such as methane from melting permafrost. The long eons of stability in carbon flux, during which life on our planet thrived, has been brought to an untimely end, and we now see a carbon cycle that is out of balance, risking eventual extinction of life. However there is a solution to this problem. The easiest way to re-balance the carbon cycle would be to stop the extraction of and burning of fossil fuels and to simultaneously increase the rate of afforestation, thereby increasing the rate by which photosynthesis removes carbon dioxide from the atmosphere. The easiest way to increase the ammount of land to regrow forests would be to reduce the frequency with which we eat livestock and poultry. This is because most of the land used in rearing livestock and poultry is used to grow the food that these animals eat, and if humans fed themselves instead on a more healthy balance of vegetables, fruit, microbes such as fungi, bacteria and algae, as well as reared insects, the land currently used to provide livestock and poultry feed could be returned to forest. The easiest way to stop burning fossil fuels would be to simply substitute them for the already existing but yet to be produced at scale biologically fermented and digested fuels from microbial decomposition of wastes such as bioethanol, biodiesel, biokerosine, biomethane from agricultural waste, food waste, sewerage and cultivated coastal seaweed feedstocks. Every fossil fuel product has a biological substitute which, when produced at scale, could simply be substituted in the global move away from fossil fuel dependence, towards a sustainable civilisation that returns the carbon cycle into balance once more.