So this is my attempt to describe a highly simplified carbon cycle, which seems in need of review after some general observations and conversation (though I think pyrrhosrepublic might have had an overly optimistic estimate of interest).  Unfortunately, general science education is frequently blown off, maybe because people take these vital life processes for granted.  There are more important or interesting things to worry about than processes that will continue to work without our knowledge.  Yet nearly everything is directly dependent on these processes, not just our bodily functions, but also our jobs, our resources, and even the warm glowing warming glow of the internet.  As we rapidly approach energy and climate concerns, these processes can no longer be taken for granted.  

The picture above illustrates the major biological processes that cycle carbon from atmospheric to organic forms.  It becomes easy to see that by digging up and burning fossil fuels, we are disrupting the cycle.  Up through the present, nearly all of our energy, which our technological innovations and economy are completely dependent upon, came from sunlight energy that has been concentrated over hundreds of millions of years.  And it all started with photosynthesis, which is probably my all-time favorite sequence of chemical reactions…      

The second law of thermodynamics states that, though matter and energy are conserved, energy dissipates or degrades.  That is, energy flow is one way, with the universe tending toward disorder.  To create complex structures, such as a highly ordered cell, we must continually apply energy just to overcome entropy.

Through photosynthesis, plants use the sun’s energy to bind low-energy carbon dioxide molecules into high-energy organic molecules, such as carbohydrates.  This is the only way carbon enters the life cycle.  Animals then eat those energy molecules, and both plants and animals (and other kingdoms) break them down through respiration to access that energy stored in their bonds, re-releasing carbon dioxide.  Decomposing microbes utilize the energy stored in dead tissues, and the cycle goes on.  However, in certain environments, dead organisms are buried and compressed over geologic time scales to produce fossil fuels.  Previously, the cycle was in balance, with photosynthesis and respiration being relatively equal.  But now respiration plus combustion are outpacing photosynthesis, leading to a buildup of greenhouse CO2 in the atmosphere and an approaching shortage of fossil energy. 

This shows the very generalized reactions of photosynthesis and respiration.  In the chloroplast, photons strike a chlorophyll molecule, splitting water to release an excited electron (thus water, not carbon dioxide, is converted to oxygen).  The excited electron loses energy that is stored in ATP, the cell’s energy currency molecule, and NADPH.  Those energized molecules are required in the Calvin cycle, or light independent reactions, of photosynthesis.  They are used to bind up carbon dioxide molecules into energy-rich sugars.

Respiration is the reverse reaction to complete the cycle.  Energy-rich sugars are consumed (or produced in the case of autotrophs) by the organism where they are broken down through glycolysis and the Krebs cycle.  The oxidation of these molecules releases excited electrons in the form of NADH.  With bonds broken, the molecule leaves in the form of CO2 waste (thus organic molecules, not oxygen, are converted to carbon dioxide).  Those high energy electrons then enter the electron transport chain in the mitochondrial membrane.  As the electrons lose energy, it is stored in the form of ATP. The low energy electron is accepted by oxygen and leaves as water (thus oxygen is converted to water, not carbon dioxide).  ATP is then used to carry out all other cell functions to battle entropy.

Of course, the carbon cycle isn’t completely organic, and the drawing below includes the geologic processes involved.

It’s important to note that while technology can solve many problems, advances in technology, human innovation, and GDP are necessarily dependent upon increases in energy consumption.  Most problems can be solved with an unlimited energy supply.  For example, if our issue is water shortages, with unlimited energy we can desalinize and transport ocean water.  But how can technology solve an energy shortage when technology, by definition, requires increasing energy inputs?  We were fortunate to find a storage of energy on our planet, but we are currently consuming energy equivalent to hundreds of millions of years of sunlight.  That storage is running low, and there is no alternative that can provide that level of consumption need.  So what’s the solution?

Well, I think it’s all fascinating, anyway.

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