biology amylase

Topics: Enzyme, PH, Starch Pages: 10 (1508 words) Published: July 24, 2014
Biology- Change in pH

Aim: To investigate the affect that change in pH levels has on a particular enzyme, in this case amylase.

Hypothesis: In this investigation I expect as the pH reaches the optimum level, the rate of reaction will be fastest, compared to other pH levels. It is also suspected that after the enzyme has reached optimum level the enzyme activity will decrease. Through further study of the optimum level of amylase I found that the enzyme usually has an optima pH of 8. It is known that the pH of an enzymes environment will affect its activity rate.


In order to identify the dependent and independent variable and describe the difference between them, I will first define what an independent variable is. An independent variable is the variable you have control over and is what you can choose and manipulate. It is usually what you think will affect the dependent variable. In some cases, you may not be able to manipulate the independent variable. It may be something that is already there and is fixed, something you would like to evaluate with respect to how it affects something else, the dependent variable for example colour, kind, time. For this investigation the independent variable would be the pH level. As I have control over it which subsequently has an affect on the dependent variable.

A dependent variable is what you measure in the experiment and what is affected during the experiment. It is called dependent because it ‘depends’ on the independent variable. In an experiment, you cannot have a dependent variable without an independent one. In my investigation the dependent variable would be the time for disappearance of colour as the varying pH levels affect it. Therefore it ‘depends’ on an independent variable for the experiment to work.

The difference between the independent (pH) and dependent (time for disappearance of colour) variables is that the time for disappearance of colour relies on the pH to actually determine the rate of reaction.

Two controlled variables include the volume of amylase solution in each test tube, as it needs to be a constant because we don’t know if this variable will affect the result. To ensure an accurate result, it is key maintain the same volume of amylase solution in each test tube. Another controlled variable is the volume of starch solution, in each test tube. Although if the volume of starch solution were not the same, it would mean that the rate of reaction between the amylase and starch would not be true. An uncontrolled variable of this experiment would be possible contamination. This could pollute and affect the end result. It is essential to sanitize equipment and wear protective clothing.

In knowing this I can base my investigation around the fact that as I know the optima pH level I can determine the level of maximum reaction rate should occur at a pH level of 8. However if my results are inconclusive then something in the experiment has gone wrong (i.e.: the pH medium or amylase may have been contaminated).

In discussing the structure of an Enzyme and how this may impact on the results from my experiment. Enzymes are a type of protein called catalysts that start or speed up chemical reactions. They break down complex chemical compounds into smaller molecules. Molecules of starch consist of links of glucose polymers formed by glycosidic bonds. The amylase as an enzyme breaks those glycosidic bonds and the starch into glucose molecules. Subsequently I can predict the result of my investigation by recognising that I should have some kind of change in reaction rate, in association with different levels of pH.

In this investigation I am going to consider how different pH levels affect the activity rate of amylase. It is expected that the amylase will break down the starch molecules in the starch solution. In turn I will be measuring the time it takes for amylase to break down the starch in accordance with different pH...
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