Ib Biology Digestion Prac

Only available on StudyMode
  • Download(s) : 122
  • Published : March 10, 2013
Open Document
Text Preview
Digestion Self-design Practical: The effect of pH on enzyme activity

Rationale
Amylase is an enzyme involved in the digestion system which catalyses the breakdown of starch into sugars. It is not only present in human saliva but also in the pancreas, where it hydrolyses dietary starch into disaccharides and trisaccharides which are converted by other enzymes to glucose to supply the body with energy. pH has an effect on the activity of all enzymes, including amylase. As the pH level increases, the enzyme activity increases, up until an optimum pH level where enzyme activity plateaus. For amylase, this optimum pH levels is usually about pH7. The present study investigates this relationship between pH levels and enzyme activity.

Aim
The aim of the present study is to examine the effect of different pH levels on the rate of amylase activity.

Research Question
What is the effect of varying pH levels on the rate of amylase activity?

Hypothesis
The hypothesis of the present study is that increasing pH levels will increase the rate of amylase activity; pH levels at 7 or higher will show a fast rate of amylase activity.

Variables:
Independent Variable: The independent variable was the varied pH levels manipulated by using a buffer solution of different pH levels. The different pH levels were pH0, pH4, pH6, pH8 and pH10

Dependent Variable: The dependent variable is the amylase activity. Amylase activity was measured by recording the concentration of starch in each test tube at 0minutes, 5minutes, 10 minutes and after the weekend. This was done by adding 2 drops of iodine to each test solution at the end of each interval and recording the colour of the solution using a colour chart.

Controlled Variable: A controlled variable was the time of measurements, timed with a timer on a mobile phone. The measurements were taken at 0 minutes, 5 minutes and 10 minutes. This needed to be controlled in order for the rate of enzyme activity to be measured accurately.

Materials/Apparatus
100mL of starch
20mL of buffer pH 0
20mL of buffer pH 4
20mL of buffer pH 6
20mL of buffer pH 8
20mL of buffer pH 10
pipette
20 test tubes
100mL of amylase
Iodine solution
measuring cylinder to measure 5mL
Colour Scale
Method
With the measuring cylinder, 5mL of each pH buffer solution was measured (5mL of pH0, 5mL of pH4, 5mL of pH6, 5mL of pH8 and 5mL of pH10) and poured into 5 different test tubes. Using the measuring cylinder again, 5mL of starch was measured. 5mL of starch was poured into each test tube with each buffer solution. 2 drops of iodine was added to each test solution.

Using the measuring cylinder again, 5mL of amylase for each test solution was measured and, as simultaneously as possible, 5mL of amylase was poured into each test tube. As soon as amylase was added, the timer was started, and the first colour measurements were taken at 0 minutes. After 5 minutes on the timer, the colour of each test solution was measured again. After 10 minutes on the timer, the colour of each test solution was measured again. Out of interest, after the weekend (approximately 48 hours), the colour of each test solution was measured again. This method was repeated for 4 trials.

Precautions
Precautions that were taken in order to attain the most accurate results were the control of the time intervals. Safety precautions included washing our hands after the experiment.

Data Collection and Processing

TRIAL 1 - Colour measurements of test solutions

|0 minutes |5 minutes |10 minutes |following weekend (approx. 48hrs) | |pH0 |black |black |black |very dark blue | |pH4 |black |black |black |dark blue | |pH6 |black |black |black |light blue | |pH8 |black |black |light blue |no colour | |pH10 |white |white |white |no colour | |

TRIAL 2 - Colour measurements of test solutions

|0 minutes |5 minutes |10 minutes |following weekend (approx. 48hrs) | |pH0 |black |black |black |very dark blue | |pH4...
tracking img