Unit 13: Biochemistry and Biochemical Techniques
Assignment title: Enzymes
Name: Hani Oladeinde
Student I.D: OLA17005525
Experiment 1: The effects of Temperature on Enzyme Activity
Test tube holder
Egg white suspension
pH 2 buffer solution
Label 5 test tubes 1-5.
Using a graduated pipette place 3cm3 of egg white suspension into each of the test tubes.
Using a clean graduated pipette place 3cm3 of the pH 2 buffer solution to each test tube.
Leave test tube 1 in the test tube holder and place test tube 2-5 in water baths with 30-60oC respectively for five minutes.
After 5 minutes remove the test tubes 2-5 from the water baths.
Using the 1ml graduated pipette place 1ml of pepsin into each of the test tubes 1-5 and place the test tubes 2-5 into their respective water baths immediately and leave for five minutes
Remove the test tubes from the water baths after the 5 minutes have elapsed and record their appearance in the table below.
Use indicator paper to test the pH of each sample using a dropping pipette and record the pH.Errors:
Other students took my test tube samples so this effect my results because everyone had different amounts in their test tube. To avoid this error, label the test tubes with your name on it or put your samples in separate water baths from other samples.
Reading the measurement from the graduated pipette was hard to see so this affect my results. This error can be avoided by having two or more people reading the graduated pipette.
I didn’t use a clean graduated pipette for the different substances that I used so this affected my results because it cross contaminated the sample. And to avoid this error, you must use clean graduated pipettes for each substance that you are measuring.
Every enzyme has a temperature at which it works fastest. For most human enzymes this is about 37.5oC (optimum temperature). If the temperature is increased up to this optimum value then the rate of the reaction it controls also increases. The temperature increase means that the substrate and enzyme molecules have more energy so are more likely to collide with each other. More molecules also have the minimum amount of energy that is needed for a reaction to occur upon collision is called the activation energy.
Below the optimum temperature enzyme and substrate molecules have less energy so fewer collisions occur and the rate of reaction is slower. Above the optimum temperature the rate of reaction also decreases. The heat energy breaks the hydrogen bonds which form the active site and loses its shape. The substrate can’t fit into the active site so the reaction can’t be catalysed. At very high temperatures this change is permanent. When this change in shape happens the enzyme is said to be denatured.
Enzymes also have an optimum pH at which they work fastest which increases the rate of reaction. This is about pH 7-8 (optimum pH). Some enzymes can work at more extreme pH values such as protease enzymes in the stomach. These need to work in acidic conditions so they have an optimum pH of 1. Enzymes’ tertiary structure is fixed in position by H bonds and ionic bonds. Hydrogen ions have a + charge and are drawn to negative charged sets on amino acids affecting with the H bonds and ionic bonds that clutch the tertiary structure and the active site in position. The pH affects the charge on the amino acids that make the active site on the enzyme. If the pH value is above or below the optimum this will quickly decrease the rate of reaction. If the pH changes then the charges on the active site change and the substrate may no longer be attracted to the active site. For example an amino acid containing a carboxyl group will be uncharged at low pH (COOH) but charged at high pH (COO-). So a substrate with a positive charge can’t be made to react quickly at a low pH. At very acidic and vey alkaline conditions an enzyme can be denatured. Also at very minimal pH quantities this restriction triggers the enzyme to unroll the form of the active site can’t match to the substrate anymore and the reaction can’t be catalysed by the enzyme. This also denatures the enzyme.