Prominently displayed in the back of my science classroom at Bucharest Christian Academy is an oversized poster showing biochemical pathways—the enzyme-mediated processes that occur in all cells, in organisms ranging from bacteria to humans. The poster presents an incredible amount of information, outlining processes such as electron transport in the mitochondria (in eukaryotes), and the synthesis and degradation of amino acids, carbohydrates, lipids, and nucleotides. The poster is a little overwhelming to my middle school and high school students, but that is part of my purpose for having it. Even the most simple living cells are incredible machines, and I want them to have a glimpse of what that means.
For the web site of the week, I have chosen a similar metabolic pathways poster from the ExPASy Proteomics Server. By clicking on individual tiles on the poster, you can zoom in to see details of various processes, with the names of the enzymes that control molecular transformations in blue.
From discussions with biochemists, my understanding is that the simplest cell that could perform the basic functions of life (such as respiration, digestion, reproduction—processes that define life) could do without some of the processes diagrammed on this poster. However, this primitive cell would still have to include about 60% of the processes depicted on these types of posters. This defines the magnitude of what needs to be explained in any naturalistic explanation for the origin of life.
Grace and Peace
I did find one article (I’m sure there are many) on the internet that puts a lower limit on the number of proteins in the most primitive cell at 300. Note that on the metabolic processes poster I have here, only the blue names, the enzymes, are proteins. The other substances are all substances that are produced or modified by those enzymes.