Saturday Science: Earth, A Biography: Another Building Block

This is actually a footnote to an earlier post on this topic. It seems that researchers may have discovered the forerunners of the means by which living cells turn raw materials into energy:

Our cells turn oxygen organic compounds, especially sugars, into energy and CO2 through a process known as cellular respiration. You may have been told in school that mitochondria, the specialized organelles which handle cellular respiration, ‘burn' food to release energy, and that's a pretty functional illustration of the process. The whole picture is, however, much larger that.

Energy-producing mechanisms in our body are often referred to as cycles - one of the most common ones is the citric acid / Krebs cycle. These are usually very complicated processes, and as such, are very difficult to wrap your head around and study them in the lab. Which is a pain if you're the kind of scientist who's trying to understand how these cycles came to be, where they first started from, and how they evolved. However, new research could offer these researchers the lucky break they need.

The processes they've discovered are, by living organism standards, pretty rudimentary:

However, the team, which also included members from the Scripps Research Institute in California and two undergrads at Furman, found two compounds which could maintain a Krebs-like cycle in experiments mimicking conditions on early Earth. Christened the HKG- and malonate-cycles, the team says these processes are likely very similar to the pre-life versions of the reactions that keep us alive today.

They're hugely less efficient than the Krebs cycle, but that was to be expected, given the lack of supportive enzymes. More importantly, however, they're based on a similar chemical blueprint - both cycles turn a molecule called glyoxylate into CO2 and other molecules in the presence of an electron-capturing agent. They're so similar, the authors' hypothesis is that biology picked them up as it was and simply tweaked and improved upon them, leading to the reactionary cycles we see today.

Given that evolution spends a lot of time adapting existing structures and processes, these two processes could very well be the beginning of metabolism --- add a few enzymes here and there as you go along, and eventually, you wind up with the Krebs cycle.

As it stands, these early processes could very well have made life possible.