ATP and the Endosymbiotic Theory

Several compartments known as organelles can be found within the cytosol of eukaryotic cells. Organelles are bound by a plasma membrane and contain specific information related to different cellular functions (Hardin et al., 2012). Some of the most important organelles in eukaryotic cells are the mitochondrion. These double membrane power-houses are about the same size as a bacterial cell and contain their own (circular) DNA. The main function of the mitochondrion is to produce ATP, or adenosine triphosphate, which is a form of energy utilized within the cell.

ATP is produced through a process called glycolysis, when ADP (adenosine diphosphate) and a phosphate group are combined and the carbon-carbon bonds within glucose are broken apart (Hardin et al., 2012). Glucose is probably the most important oxidizable substrate because it is the main sugar found in the blood of vertebrates and in the vascular systems of most plants. Glycolysis itself is a ten-step reaction which converts every one glucose molecule into two molecules of pyruvate – a three carbon compound (van Maris et al., 2006). In order for this to occur, electrons from glucose must be placed on an electron carrier. The most common electron carrier is nicotinamide adenine dinucleotide, or NAD+. Every time NAD+ accepts two electrons, it is able to pick up a hydrogen atom and become NADH. Following several glycolysis reactions when enough ATP has been produced, glucose will have been metabolized into pyruvate. If oxygen is present, then pyruvate is transported to the mitochondria so that aerobic respiration may take place, which is what makes the mitochondria so vital to the cell (Hardin et al., 2012). The aerobic respiration process typically takes place on the cristae whi...

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