Temperature on Rate of Pnpp Hydrolysis

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LABORATORY 3
The Effect of Temperature on the Rate of PNPP Hydrolysis

Partners:
Shelby Cruickshanks
Alexis Williamson

Introduction
Most of the chemical reactions, which occur throughout our bodies, would proceed at a much slower rate of reaction without the presence of an enzyme. Cells can not wait for centuries for molecules to break down, if they waited for that, there would be no way for the organism to obtain energy or in turn survive. This is where biological catalyst comes into play. (Ophardt, 2003) In the year of 1836, Jacob Berzelius, introduced the concept of a catalyst (enzyme). By studying the effects of acids and bases in the decomposition of hydrogen peroxide he developed the notion of biochemical catalysts. There were many conflicting thoughts on this, and it wasn’t until Edward Buchner experimented on this topic in 1897 that this notion was generally accepted. (Metzler, 2001)

The term “Enzyme”, derived from the Latin phrase “in yeast”, is an organic catalyst, most often proteins, that accelerate specific chemical reactions by lowering the required activation energy necessary for that reaction to occur. One enzyme in particular, Acid Phosphatase, is a critical enzyme in our every day biological functions. Phosphorus plays a vital role in energy transfer and metabolic regulation and is an important component of phospholipids and nucleic acids. (Hiroshi, 2001, Cavigis, 2001) Furthermore, if molecules need less energy to react because of the lowered activation barrier, a greater amount of enzyme – substrate bindings are able to occur in a shortened amount of time, without being consumed or structurally denatured in the process. This being said, if the reaction happens to reach equilibrium, no catalysts would be able to cause the reaction to proceed. Although most enzymes are soluble globular proteins, research has discovered that some types of RNA molecules have catalytic activity as well. (Ophardt, 2003)

In order for a reaction to occur an enzyme – substrate complex must be formed. Given that an enzymes structure is critical to its function, the enzyme and the substrate must form an induced fit at the active sites, which are grooves or cavities in the enzyme molecule where the substrate binds to form the ES complex. (Freeman, 2011) (Soloman, 2008) If the induced fit does not occur then there is no way for the enzyme to have any effect on the specific reaction. Once the ES complex is formed the substrates structure changes slightly and converts into the reaction product and the enzyme is released, which allows it to move on and form another ES complex with a new substrate molecule; therefore forming more products. (Delgado & Liao, 1995)

Every chemical reaction that takes place is virtually catalyzed by enzymes and because the shape of the active site and the substrate are very similar, it causes the enzymes to be highly specific, in turn they can only react with certain chemicals or molecules. Furthermore, because of their high specificity, each enzyme will perform best under optimal conditions relative to their structure. (Freeman, 2011) Given that its ordered structure is critical to its function, it is not surprising that an enzymes activity is sensitive to conditions which alter its structure, for example, temperature. Temperature effects the movement of the enzyme and substrates as well as their kinetic energy of the substrates. In particular the activity of an enzyme often changes drastically as a function of temperature. During an enzymatic reaction, if the temperature is low then the reaction will only occur either slowly or not at all. Therefore as the temperature increases the molecular motion will increase, resulting in more molecular collisions. However, if exposed to extremely high temperatures the enzyme will be rapidly denatured. Denaturation occurs because the bonding interactions responsible for the secondary and tertiary structures are disrupted....
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