The Effect of Hydrogen Peroxide Ph Levels on Reaction Rate of Catalayse Enzyme

STAGE 2 BIOLOGY

INVESTIGATIONS FOLIO

TASK 1: ENZYME PRACTICAL (COMPLETION)

NAME: CHLOE MATZ

[pic 2]

THE EFFECT OF HYDROGEN PEROXIDE PH LEVELS ON REACTION RATE OF      CATALAYSE ENZYME.[pic 3]

INTRODUCTION:

Chemical reactions are the underlying biological processes in which one or more reactants are converted into a product, (Triechel and Kotz, 2018). There are two main types of chemical reactions; these are catabolic and anabolic. Anabolic reactions, (see figure 1) are endergonic and use energy through chemical bonds to join two or more smaller molecules into a larger one, (RSC Organisation, n.d.). Catabolic reactions however, (see figure 2) are exergonic and break down a large molecule into two or more smaller ones, (RSC Organisation, n.d.). The rate of cellular chemical reactions can be accelerated with a type of protein known as enzymes. Enzymes are the biological catalysts located in living cells and are capable of accelarating chemical reactions without being permanently altered, (BBC, 2014). Enzymes are proteins composed of one or more polypeptide chains. The amino acid sequence on these polypeptide chains determines the characteristic folding patterns of the protein’s tertiary structure, (see figure 3) which is essential to enzyme specificity, (what the function of the enzyme will be), (BBC, 2014). [pic 4][pic 5][pic 6]

Enzymes accelerate the rate of chemical reactions through the induced-fit model. This model states that the active site of an enzyme chemically attracts substrate molecules which temporarily bind to each other at the active site (Khan Academy, 2018). This binding between enzymes and substrates isn’t exact, but rather induces a change in the 3-dimensional structure of the enzyme when it binds (see figure 4) so that the active sight moulds around the substrate, (Khan Academy, 2018). For a chemical reaction to take place the required amount of activation energy must be obtained. Enzymes function by lowering the activation energy needed to initiate a chemical reaction, consequently accelerating the reaction rate, (Biology Arizona, 2004).[pic 7][pic 8]

Various factors influence enzyme activity, including; pH, temperature, enzyme and substrate concentration, and the presence of inhibitors. Firstly, enzymes are influenced by changes in pH. Extremely high or low pH values outside the optimum pH result in complete loss or minimisation of activity for enzymes, (Pfeiffer, 1954). Additionally, temperature can influence enzyme activity because as temperature increases, so does the activity of enzymes until the optimum temperature is surpassed in which the enzyme denatures, (see figure 5). Additionally, an increase in enzyme and substrate concentration increases the activity of enzymes. This is because more substrate molecules will be colliding with enzyme molecules, so more product will be formed, (reference). Finally, enzymes may be deactivated temporarily or permanently by chemical inhibitors.  Chemical inhibitors are molecules that bind to the enzyme and interrupt its ability to catalyse a reaction.  These can be competitive and non-competitive. Competitive inhibitors compete with the substrate for binding to the active site, reducing the activity of the enzyme.  Whereas non-competitive inhibitors reduce enzyme activity by binding to a region other than the active site.  [pic 9][pic 10][pic 11][pic 12]

[pic 13]

THE EFFECT OF HYDROGEN PEROXIDE PH LEVELS ON REACTION RATE OF CATALAYSE ENZYME.

INTRODUCTION CONTINUED:

In this investigation the effect of pH on the catalyse enzyme’s activity will be tested. Catalase is an enzyme found in most living cell’s tissue. It catalyses the reaction in which hydrogen peroxide is broken down into water and oxygen (catabolic reaction). As peroxide is continuously developed in numerous metabolic reactions, catalyse functions by preventing the accumulation of peroxide and by protecting cellular organelles and tissues from damage, (Augustyn, 2017). The equation for catalase’s reaction is shown below:

Catalase

Hydrogen Peroxide         Water + Oxygen[pic 14]

2H₂O₂                                                                                2H₂O +O₂[pic 15]

As catalyse is an enzyme it is affected by the factors previously discussed, (e.g. pH, temperature, enzyme and substrate concentration, and the presence of inhibitors). In this experiment the pH levels of hydrogen peroxide will be altered, with pH’s of 0.96, 3.02, 5.28, 6.62, 9.17 and 11. The application of a timer will be utilised to calculate the time taken for the disks to reach the surface, with reaction rate calculated following the experiment using the formula:

Reaction rate = [pic 16](mgO2/min)

Consequently, the effect of pH on the catalyse enzyme’s activity will be examined and analysed through tables and graphs in this practical report.

AIM: to investigate the effect of 0.1% hydrogen peroxide solution pH levels on the reaction rate of catalase enzymes.

HYPOTHESIS: It is hypothesised that if the pH levels of 0.1% hydrogen peroxide solution is increased, the reaction rate of catalase enzymes will also increase until an optimum pH of 7 is reached.

INDEPENDENT VARIABLE: the independent variable will be the pH level of 0.1% hydrogen peroxide solutions. This will be altered by conducting 20 trials for each different pH level. Including a pH of 0.96, 3.02, 5.28, 6.62, 9.17 and 11.