Purpose:
Cellular respiration is a series of metabolic reactions that take place in the mitochondria and produce chemical energy in the form of ATP by the breakdown of food molecules.There are three processes involved in cellular respiration; glycolysis, the Krebs cycle and the electron transport chain. During this processes, glucose is oxidized by a series of redox reactions and its electrons and hydrogen ions are donated to two electron carriers called NAD+ and FAD. The electron carriers transport the electrons and hydrogen ions to the electron transport chain and hydrogen ions and electrons are passed to the last electron acceptor, which is oxygen. In this laboratory, the rate of cellular respiration in lima beans cells was measured. The quantitative data was measured by a spectrophotometer. For this, succinate and a solution called DPIP were used. During the Krebs cycle, succinate is oxidized and its electrons are donated to the electron carrier FAD. Due to the redox reaction, succinate becomes fumarate and FDA becomes FADH2. DPIP is a blue solution in its oxidized state and it acted as FDA during the experiment. This solution changes from blue to colorless when it’s being reduced. It was hypothesized that the faster reaction rate happens in in solutions containing more substrate during the reaction. If more succinate is added to a solution, then the reaction rate will increase and the color change of DPIP from blue to colorless will be faster. Materials and Methods: The spectrophotometer was turned on 15 minutes before the experiment. …show more content…
Then, it was set up at 600 nm and at 0% transmittance. Next, four cuvettes tubes were obtained and the control group and each of them were label, so the identification is more easy. Then, Blank Tube was prepared by adding 4.6 ml of phosphate buffer, 0.3 ml of mitochondrial suspension, and 0.1 ml of succinate with the aid of pipette pump. The blank solution was then covered with parafilm and shook to mix the reactants. Next, the spectrophotometer was calibrated. For this, the Blank Tube was placed inside the sample holder and the machine was set to 100% transmittance and then the cuvette was removed. After, each of the remaining cuvettes was prepared. In Tube 1, the following was added; 4.4 ml of phosphate buffer, 0.3 ml of DPIP, and 0.3 ml of mitochondrial suspension. In Tube 2, 4.3 ml of phosphate buffer were added along with 0.3 ml of DPIP and 0.3 ml of mitochondrial suspension. Lastly in Tube 3, 4.2 ml of phosphate buffer were poured along with 0.3 ml of DPIP and 0.3 ml of mitochondrial suspension. Each of the tubes was well covered with parafilm and shook to mix the reactants. After that, the succinate was added to Tube 2 and it was inserted to sample holder of the machine and its percent transmittance was measured and recorded. This same process was done to the remaining cuvettes tubes. Succinate was not added to Tube 1 because it was the control group. The percent transmittance of each solution was measured for 30 minutes with a intervals of 5 min. The machine was calibrated with the blank solution, each time the percent transmittance of a solutions was measured. Results: After the addition of different amounts of succinate to the three cuvette tubes, their percent transmittance was measured for 30 min with intervals of 5 min. Tube 1, at the beginning of the experiment