Ap Bio Lab Report

Topics: Cellular respiration, Adenosine triphosphate, Oxygen Pages: 7 (2288 words) Published: January 1, 2013
Effect of temperature on the rate of respiration in the case of big cricket versus the small cricket Aammar Alam Paracha

Cellular respiration is the basic process by which organism make energy and increases the chances of the survival in the world. In this experiment, the amount of oxygen taken up by the organism( in this case crickets) is investigated, and how this uptake is affected by the temperature and the time of the lifecycle that an organism is in. The subjects are placed in different vials completely submerged in water that have different temperatures. This investigation used three trials at different temperatures. The amount of oxygen consumed was calculated by the amount of water that enters the pipette of the respirometer and the level it moves in a time of 20 minutes. It was found that at lower temperatures the crickets would respire more quickly than they would do at higher temperatures. We placed three different respirometers in different water chambers. They all had different temperatures. One respirometer had a big cricket another had a small cricket and the last one had glass beads which acted as our control. We noted the amount of water that moved in the respirometer after every 5 minutes for 20 minutes. Then the results were corrected for difference and then plotted on the graph for the three temperatures. The results show that consumption of oxygen is highest at 13 degree Celsius and lowest for temperature at 26 degree Celsius.

Cellular respiration is a process in which the food molecules are broken down to release the energy; and it has three main parts: glycolysis, the Krebs cycle, and the electron transport system. Glycolysis takes place in the cytosol of the cell. When it gets oxygen, then it splits one sugar compound into two pyruvates in ten steps that are catalyzed by an enzyme. These steps can be divided into two phases: an energy investment phase, in which the cell spends ATP for the fuel, and an energy payoff phase where ATP is produced by substrate-level phosphorylation and NAD+. Glycolysis, the initiative process occurs in the cytosol. Glucose is split into two compounds of pyruvic acid. Upon entering the mitochondrion, the pyruvate converts to Acetyl CoA for use later in the Krebs cycle that occurs in the mitochondrial matrix. In the Krebs cycle, each pyruvate yields 4 NADH, 1 FADH2, and 1 ATP molecule. NADH and FADH2 go to the electron transport chain to produce more ATP molecules. The electron transport chain is the chain of molecules, located in the inner mitochondrial membrane, that passes electrons along during the process of chemiosmosis to regenerate NAD+ or FAD+2 to form the ATP molecule. Chemiosmosis is the coupling of the movement of electrons down the electron transport chain with the formation of ATP driven by a proton gradient. The result of the electron transport chain is a contribution of about 34 ATP molecules. Overall, cellular respiration produces the maximum of 38 ATP molecules per glucose.(World of chemistry 2006) However, if there is no presence of oxygen in glycolysis, the process still goes on by replacing the oxygen to NAD+. That process is called fermentation.

The balanced chemical equation for cellular respiration is shown below. Notice that oxygen is proportional to carbon dioxide by 1:1, therefore, during the experiment, measuring the amount of oxygen consumed can determine the amount of carbon dioxide produced. C6H12O6 + 6O2 --> 6CO2 + H2O + Energy

It is important to understand how the general gas law applies to the apparatus. The gas law states:
where P is the pressure of the gas, V is the volume of the gas, n is the number of molecules of gas, R is the gas constant, and T is the temperature of the gas. For this experiment, if the temperature and volume of the water remain constant, the water will move toward the region of lower pressure due to the consumption of O2 because...

References: AP Biology Lab Handout: Cellular Respiration
Holtzclaw, Theresa Knapp. LabBench Activities: Cellular Respiration. from http://www.phschool.com/science/biology_place/labbench/lab5/intro.html
Hermans-Kilam, Linda. Warm and Cold Blooded., from http://coolcosmos.ipac. caltech.edu/image_galleries/ir_zoo/coldwarm.html
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