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Enzyme Activity |
Enzymes are proteins which act as biological catalysts. They speed up chemical reactions in living cells without being permanently changed or used up by those reactions. Without enzymes, cells would cease to function.
Remember that proteins are large, three dimensional molecules. The 3-D shape of a protein has a big effect on its function. Anything that can change the shape of a protein molecule can influence how well an enzyme works. Also, anything that might effect how fast a chemical reaction runs could also effect how enzyme catalyzed reactions work. In this lab, we observed how three factors influence enzyme catalyzed reactions: concentration of the enzyme, pH, and temperature.
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The enzyme catalase is found in bacteria, plant cells, and your cells. Hydrogen peroxide (H2O2) is a toxic end product of cellular respiration reactions. If it builds up, it can cause damage. Catalase breaks down hydrogen peroxide into water (H2O) and oxygen (O2), which are harmless.
In lab we used blended beef liver and water (a.k.a. homogenate) as our enzyme source. (Running the beef liver through a blender broke the cells and released their catalase).
To the left is a tube of homogenate. Adding hydrogen peroxide results in vigorous bubbling (right), as the catalase in the homogenate breaks down the hydrogen peroxide, releasing oxygen bubbles.
The chemical reaction is as follows:
substrate --enzyme--> end products
2 H2O2 --catalase--> 2 H2O + O2
We will rank reactions on the basis of how fast they are and how many oxygen bubbles they make. The reaction shown to the right is a 4 (fastest/strongest). A 0 would be no reaction.
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