Experiment to investigate the affect of temp on the respiration rate of small invertebrate.

Experiment to investigate the affect of temp on the respiration rate of small invertebrate

Task

I will measure the oxygen consumption during respiration as the change in gas volume in respirometer containing the invertebrate. In addition I will measure the respiration of these invertebrate at two different temperatures.

Background Information and Knowledge

Cellular respiration is the release of energy from organic compounds by metabolic chemical oxidation in the mitochondria within a cell. There are a number of physical laws that relate to gases and are important in the understanding of how the equipment in this lab works. These are summarized as general gas laws that state: PV=nRT where: P stands for pressure of the gas, V stands for the volume of the gas, n stands for the number of molecules of gas there are, R stands for the gas constant, and T stands for the temperature of the gas. A respirometer is the system used to measure cellular respiration. Pressure changes in the respirometer are directly relative to a change in the amount of gas there is in the respirometer as long as the volume and the temperature of the respirometer do not change.

C6H12O6 + 6O2 → 6CO2 + 6H2O + 686 kilocalories of energy/mole of glucose oxidised.

Carbon dioxide is formed as oxygen is used. The pressure due to CO2 might cancel out any changes due to the consumption of oxygen. To get rid of this problem, a chemical will be added that will selectively take out the carbon dioxide put off. Potassium hydroxide will chemically react with the carbon dioxide by this equation: CO2 + 2KOH → K2CO3 + H2O.

The number of oxygen molecules consumed during respiration by the invertebrate will be directly related to the decrease in the volume occupied by gas within the respirometer, The water in the pipette will move towards the region of lower pressure, which is created within the respirometer due to oxygen consumption.

Respiration involves a number of enzymes, which, work with a number of substances in order to make ATP.

Enzymes are biological catalysts, which lower the activation energy of a chemical reaction. Enzymes have a specific active site, which only fit a particular substrate. The shape of the active site allows the substrate to fit perfectly and to be held by temporary bonds. A combined structure is called the enzyme substrate complex.

Enzyme activity is affected by temperature. At low temperature, the reaction takes place only very slowly. This is because molecules are moving relatively slowly. Substrate molecules will not often collide with the active sit, and so binding between substrate and enzyme is a rare event. As the temperature increases, the enzyme and substrate molecules move faster thus more collisions, with more energy. This makes it easier for bonds to be broken so that the reaction can occur. However above a certain temperature the structure of the enzyme molecule in its precise shape begins to break: hydrogen bonds begin to break and the enzyme molecule begins to loose its shape and activity is said to be denatured. The substrate can no longer fit in to the activity site so the rate of reaction slows down. The temperature at which, an enzyme catalyses a reaction at the maximum rate is called the optimum temperature. Most human enzymes have an optimum temperature of around 40c.

In order for ATP to be successfully made there are a number of chemical reactions that occur. These include glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation and the electron transport chain.

Glycolysis is the splitting of glucose. Glucose is eventually split in 2 molecules of pyruvate. ATP is needed for this, however ATP is released in later stager. There is a net gain of two ATP molecules per glucose molecule.