Ccea as Biology Coursework: an Investigation to Measure the Percentage Light Transmission Through a Solution in Which Jelly Cubes Were Immersed over a 24 Hour Period

Only available on StudyMode
  • Download(s) : 362
  • Published : March 22, 2013
Open Document
Text Preview
An investigation to measure the percentage light transmission, using a colorimeter, through a solution, from pH 2 – pH 9, in which jelly cubes were immersed over a 24 hour period

Interpretation

Written Communication of the Data
C1

Pepsin is an enzyme that works in the stomach and has an optimal pH between pH 1 and 4 or in acidic conditions. From our graph it can be seen that that the lowest mean percentage light transmission for pepsin is when the buffer has a pH of 2. Trypsin is an enzyme that works in the small intestine and has an optimum pH between pH 7 and 8 or in neutral conditions. From our graph it can be seen that the lowest mean percentage light transmission for trypsin is when the buffer has a pH of 8.

C2 and C3

As the pH of the pepsin buffer increases from pH 2 to pH 9 so too does the percentage light transmission through the buffer solution after a 24 hour period. Although when the trypsin buffer has a pH between pH 2 and 8 the percentage light transmission through the buffer solution after a 24 hour period decreases, but from pH 8 to pH 9 the percentage light transmission through the buffer solution after a 24 hour period increases. At a low pH (pH 2) the amount of gelatine broken down by the pepsin is high. We can tell this as this is when there is a low mean percentage light transmission (16.86%) because a lot of colour of the jelly will leak in the solution causing the colour to be deeper. But at a higher pH (pH 9) the amount of gelatine broken down by the pepsin is low. We can tell this as this as there is a low mean percentage light transmission is high (34.14%) because a little colour of the jelly will leak in the solution causing the colour to be lighter. At a low pH (pH 2) the amount of gelatine broken down by the trypsin is low so this means there is a high mean percentage light transmission (41.75%) because a little colour of the jelly will leak in the solution causing the colour to be lighter. At a high pH (pH9) the amount of gelatine broken down by the trypsin is high so this means that there is a low mean percentage light transmission (29%) because a lot of colour of the jelly will leak in the solution causing the colour to be deeper.

C4 and C5

An enzyme is a biological catalyst which speeds up a chemical reaction without itself undergoing a permanent change. Most enzymes are globular proteins and contain active sites. The active site is the part of the enzyme which combines with the substrate. Enzymes are specific which means that one enzyme will work on one substrate.

All enzymes work best at a particular pH, their optimum pH. The proteins structure of the enzyme is altered in a more alkaline or acidic solution than the specific optimum pH. When an enzyme structure is altered it cannot fit successfully with the substrate. Activity is therefore limited to a few enzyme molecules that are still unaltered or may totally stop. The protein digesting enzymes, pepsin and trypsin, will hydrolyse the substrate, gelatine. This substrate is a major component of jelly. When a coloured jelly, such as raspberry, is exposed to a protein digesting enzyme, the colour is released into the solution as the gelatine is broken down.

The intensity of the colouring released into the buffer can be estimated with a colorimeter. Trypsin is often found naturally in neutral or slightly alkaline conditions. Therefore the most enzyme activity and most colour is released from the jelly would be expected at a pH 7 or 8 and in solutions above or below this pH there would be less colour released. Pepsin is often found naturally in very acidic conditions. Therefore the most enzyme activity and most colour is released from the jelly would be expected at a pH 1 or 2 and in solutions above or below this pH there would be less colour released.

Evaluation

D1

I consider my results to be appropriate in meeting the aims of the investigation because we used a colorimeter. This measures the percentage...
tracking img