Ensayista

Design practice: Enzyme action
Title: Difference in the action of the enzyme catalase from raw cow’s liver and liver boiled to two different times and temperatures

Introduction: Enzymes are globular proteins that are found in very living cell. They work as a catalyst by speeding up chemical reactions without being altered themselves. Catalase is an enzyme found in the tissue cells of nearlyall-living organisms. The function of this enzyme is to catalyze the decomposition of hydrogen peroxide to water and oxygen. The chemical reaction is as follows:

 catalase 2 H 2 O 2 (l)  2 H 2 O (l) + O 2 (g)

Hº 1960kJ

As this is an exothermic reaction that releases 1960 kJ of heat, the amount of molecules that are           being decomposed by the enzymewill be directly proportional to the amount of energy released as heat. Denaturation of enzyme varies for catalase enzymes from different organisms, and depends on several factors, such as pH, but in this practice we will look closer to temperature as a factor. The denaturation temperature depends on the composition of the protein (it's amino acid sequence). For most land mammals (cow, pig, humanetc) the optimum temperature for any enzyme is likely to be between 36 Celsius and 39 Celsius (most often 37 Celsius). Mammalian catalase has an optimum temperature of about 37 Celsius.

The objective of this practice is to observe the difference in temperature in the reaction (to obtain the energy released) of catalase present in cow’s liver boiled at two different temperatures in decomposinghydrogen peroxide and comparing these reactions with the ideal reaction with raw liver.

Research question: What is the difference in the action of the enzyme catalase from raw cow’s liver and boiled liver to different times and temperatures? What is the difference in the action of enzyme catalase from raw liver and liver boiled for 20 minutes that reached a temperature of 90 (±0.5 Celsius)? 1What is the difference if the liver is boiled for 10 minutes reaching a temperature of 75 (±0.5 Celsius)?

Hypothesis: I suppose that catalase enzyme present in cow’s liver will suffer denaturalization reaching the temperature of 90 (±0.5 Celsius) being boiled for 20 minutes. The exposure of the liver to such temperature would probably change the shape of the active site of the catalasecontained. So probably in this reaction there will no be a significative change of temperature. As the liver boiled at a temperature of 75 degrees (±0.5 Celsius) for 10 minutes is not plenty baked it might still be active sites that were not deformed by the action of the temperature. This reaction would still release some heat but there probably be a large difference from the raw liver.

VariablesIndependent

Different points of baking cow’s liver

Units/control method -Raw liver -Baked in water 20 minutes at 90 (±0.5 Celsius) -Baked in water 10 minutes at 75 (±0.5 Celsius) Measured using the temperature sensor of the Logger Pro 3 Covering the flask with aluminum paper, building a calorimeter with a foam glass and filling the inside with isolating materials. 50 ml of hydrogen peroxide at 1%3 grams of cow’s liver

Dependent

Controlled

Temperature release as heat by the exothermic reaction External temperature

Concentration of substrate Concentration of the enzyme

Materials:  Raw cow liver

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Universal support Aluminum paper Double-perforated stopper Data Logger software (Logger Pro 3) Logger Pro 3 temperature sensor LoggerPro 3 interphase Computer Triple beam balance (±0.50) 500 ml of Hydrogen peroxide (H2O2) at 1% 2 petri dishes Dissection scissors Knife 50 ml Burette (±10 sec) Thermometer (±0.5 Celsius) Big Beaker Hot plate Big foam glass 125 ml earlenmayer flask (5) Latex gloves

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Methodology: Several trials were carried out in order to select the adequate quantities of substrate and the adequate...