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Topics: Enzyme, PH, Chemical reaction Pages: 10 (1752 words) Published: February 23, 2014
I1, I3, I4
AE2
A3
KU1

Stage 2 Biology

Sacred Heart College Senior

Catalase Enzyme Practical

Background
Chemical reactions in general can be accelerated in a number of ways. Two important ways are by an increase in temperature up to the optimum and by the use of a catalyst. A catalyst is a substance that increases the rate of a reaction without being used up itself. Enzymes are protein molecules which function as catalysts and speed up chemical reactions in living organisms without the need to raise the temperature of the reaction.

Enzymes are usually specific for particular reactions and work best when conditions such as pH, temperature and ion concentration are most suitable. If these conditions are inappropriate for the enzyme, the reaction will proceed at a slower rate or not at all. The model that helps understand the functioning of enzymes is called the Induced Fit Model (see diagram below).

Hydrogen peroxide (H2O2) is a very reactive chemical which is formed as a by-product in cellular reactions. It is highly toxic and must be removed or it will disrupt chemical reactions in the cell. An enzyme, catalase, found in most tissue from living organisms, breaks the substrate (H2O2) down into harmless substances of water and oxygen according to this equation: 2H2O2 2H2O + O2

In this experiment liver will be used as a source of catalase. The oxygen is given off as a gas, and if detergent is added to the substrate, foam is formed. The volume of foam produced in a given time can be used as a measure of the enzyme activity.

Aim
The aim in this experiment is to use this reaction to investigate how the pH of the substrate may influence the rate of the above reaction. pH affects the charges on the active site and substrates (see diagram below).

Materials
Hydrogen peroxide (H2O2) solution at different pH levels.
Detergent
Stop watch
1 x 10mL measuring cylinder
Sharp knife

Forceps
Fresh liver or potato
1 x 100mL measuring cylinder
2 x teat pipettes
Distilled water
Cutting tile
Method
Cut 6 cubes of liver/potato each approximately 1cm x 1cm x 1cm.

Use the 10mL measuring cylinder and teat pipette to measure 9mL of H2O2 with pH of 1 into 100mL measuring cylinder. Add 1 drop of detergent and swirl to mix.

Using the forceps, take one cube of liver/potato and place it in the measuring cylinder. After 2 minutes, record the total volume of the foam in the cylinder and record your data in the table below (Table 1).

Repeat steps 1 - 3 with the other 5 solutions of H2O2. Make sure you rinse and dry your cylinders and pipettes carefully between procedures.

Obtain the results from two other groups and enter them in the table.

Use this data to calculate average volumes and then calculate reaction rates using the formula given below.

Reaction Rate (mL/min) =

Average Total Volume – 10

2
Use the data to draw a graph and then write a discussion about this practical. Table 1: Results of catalase enzyme reactivity measured as volume of foam at different pH levels of H2O2

Total Volume (mL) in 2 minutes
pH
of
H2O2
Group 1
Group 2
Group 3
Av. total vol. (mL)
Av. vol. - 10 (mL)
Reaction Rate (mL/ min)

ASSESSMENT DESIGN CRITERIA AND PERFORMANCE STANDARDS
ASSESSMENT DESIGN CRITERIA
EVIDENCE
PERFORMANCE STANDARD
I1Design of biological investigations.

I3Manipulation of apparatus and technological tools to implement safe and ethical investigation procedures.

I4The obtaining, recording, and display of findings of investigations, using appropriate conventions and formats.

Understand the structure of an experiment such as the hypothesis, experimental control, variables (IV, DV, controlled).

Correct and safe use of apparatus specific for the practical investigation

Correct labeling of tables and graphs with headings and units.

AE2...

References: KU1 Demonstrates some limited recognition and awareness of biological concepts.
2013 Performance Standards for Stage 2 Biology Enzyme Practical
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