Aerobic Cellular Respiration in Isolated Mitochondria of Lima Bean Lab Report

Aerobic Cellular Respiration in Isolated Mitochondria of Lima Bean Seeds - Lab Report Example During aerobic respiration, oxygen in the air is used as the final electron receptor which subsequently gets reduced to water. Energy is generated during this process in the form of a high energy molecule, adenosine triphosphate (ATP). This is a complex process involving a series of reactions that use many chemicals and enzymes. Glucose is the most preferred source for cellular respiration and as reported by Rich (2003), it release high energy (29-30 ATP molecules per glucose molecule) during aerobic respiration. Aerobic respiration consists of 3 major steps as glycolysis, Krebs cycle (Citric acid cycle) and electron transport chain. During glycolysis, pyruvate is produced by glucose which is converted to a 2C molecule, acetyl-CoA. Acetyl-CoA combines with the 4C oxaloacetate (last product of the previous Krebs cycle) to produce citrate which is a very high energy source. During the Krebs cycle, citrate is consumed in an 8-step process to release this energy (electrons). Here, the co enzymes FAD (flavin adenine dinucleotide) and NAD+ (nicotinamide adenine dinucleotide) gets reduced to produce a small quantity of carbon dioxide and ATP. Therefore, hydrogen electrons coming from glucose will reduce FAD and NAD+ to FADH2 and NADH + H+ respectively. These electrons then enter the electron transport chain to get oxidized and produce ATP. ... This reaction is catalyzed by the enzyme succinic dehydrogenase using FAD as co-enzyme. In this reaction, 2 hydrogen atoms are removed from succinate and transfer to FAD thereby reducing it to FADH2. DPIP (2, 6-dichloro-phenol-indophenol) blue dye can act as a hydrogen molecule acceptor instead of FAD during this reaction. When DPIP receive hydrogen from succinate, blue color get decolorized. Thus the DPIP color change from blue to colorless is an indication of the level of enzyme activity in the mitochondria which can be measured and recorded with a spectrophotometer. The Krebs cycle is influenced by competitive and noncompetitive inhibitors. Competitive inhibitors compete with the substrate to bind to the active site of the enzyme and this can be overcome by providing more quantity of substrate molecules. Conversely, noncompetitive inhibitors such as metal ions (copper, Cu2+ and mercury, Hg2+) will deactivate the enzyme thereby making it impossible to return back to the reaction. T herefore, the reaction cannot be reactivated by incorporation of more substrate. In the succinate-to-fumarate reaction of the Krebs cycle, Malonate act as a competitive inhibitor on succinate molecule. Molecule shape of malonate is similar to succinate molecule and thus it obstructs the conversion reaction of succinate to fumarate by binding to active site of the enzyme succinate dehydrogenase. However, as described in Zeevalk, Derr-Yellin and Nicklas (1995) it will not react further and result in the termination of the reaction. Therefore FAD will not reduce to FADH2 and fumarate will not be produced, thus arresting the Krebs cycle. As malonate is a competitive inhibitor, the reaction can be