The Factors Affecting Enzyme Activity

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Title: The Factors Affecting Enzyme Activity Speeds


How do the factors of temperature, pH level, substrate concentration and enzyme concentration specifically and significantly alter the rate of enzymatic reactions?

Background Information:

Enzymes are critical to the function of human life. They are the controllers of all the chemical reactions within our bodies – they catalyze relatively unreactive metabolic reactions, making them reactive. With very rare exception, enzymes are proteins; more importantly, they are catalysts (chemical agents). The function of catalysts is to accelerate the rate of a reaction without being consumed by the reaction. They accomplish this by binding to the reacting molecules, called the substrate, which forms an enzyme-substrate complex. Thus, enzymes are substrate-specific. Of extreme importance to the enzyme’s function is its active site; it is a pocket of sorts, an indentation whose shape is absolutely critical – the substrate must fit it perfectly, or the enzyme cannot bind to it, and thus it will remain unreactive. Furthermore, the enzyme can have an induced fit, which brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction (usually stressing a bond reducing activation energy). That activation energy is supplied by the enzyme and is the initial investment of energy required for starting a reaction; it triggers the more reactive transition state of the substrate. Enzymes, like anything else biological, are not perfect. They rely heavily on their tertiary shape to function correctly – denaturation (via structural change, which could likely occur through factors taken to extremes, some of which we will be testing) will destroy them. In addition to denaturation, there are inhibitors which can be affective in counteracting the effects of an enzyme. For example, the allosteric site of an enzyme acts as an on/off switch for the enzyme. Allosteric regulation occurs when the enzyme binds to the allosteric site, which either stabilizes conformation or stabilizes the inactive form of the substrate. In other words, the substrate is completed with enough of the product that it does not require any more. Another form of inhibition is feedback inhibition, which is the switching off of a metabolic pathway by its end-product, which acts as an inhibitor of the enzyme within that pathway. All of these characteristics and potentialities of enzymes are critical in predicting the affect various factors might upon the enzymatic reaction (in this case, the hydrolysis of starch). In this particular reaction, amylase (the enzyme) breaks the bond between adjacent glucose units and inserts water molecule ions, thus breaking the glucose down into monosaccharides called maltose. Enzymes have a preferred range of values for any of the variables in this experiment – a range of optimal conditions. When these optimal conditions are exceeded or failed to be met, the enzyme will be much less effective. Thus, we will be testing for the optimal conditions of amylase, and how drastically or not drastically the four independent variables affect amylase’s efficiency.


If the temperature is increased, than the enzymatic rate will also increase.

If the pH level is increased, than the enzymatic rate will decrease.

If the substrate concentration is increased, than the enzymatic rate will increase.

If the enzyme concentration is increased, than the enzymatic rate will decrease.


The general procedure to be used to observe the enzymatic reaction (the hydrolysis of starch) will be the detection of starch in the substance. If there is no starch remaining, it has all been hydrolyzed, and the amylase was successful. The rate it takes for that to occur is the efficiency of the enzyme, and will vary as we vary the independent variables. The dependent variable in all the...
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