Investigating a Factor That Affects an Enzymatic Reaction

Science

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November 2010 1493014

INVESTIGATION #14

INSTRUCTION:

INVESTIGATING A FACTOR THAT AFFECTS AN ENZYMATIC REACTION

TOPIC:

C2

DATE:

May /2010

TIME:

3

ASSESSMENT:

D, DCP AND CE

Catalase

Introduction:

An enzyme is a protein (or protein-based molecule) that speeds up a chemical reaction in a living organism[1]. During an enzymatic reaction a substance called substrate binds to the enzyme and at the end of the reaction the enzyme releases a substance called product. Enzymes accelerate almost all the reactions that occur in cells. They do this by decreasing the initiation energy needed, which makes the reaction faster. The enzyme-substrate specificity states that one enzyme can only work with one kind of substrate to produce one product. Inhibitors are substances that can affect the enzymatic reaction. Enzymes activity can be affected principally by pH, temperature and substrate concentration.

PH can have an effect on the state of ionization of acid or basic amino acids. Acid amino acids have carboxyl functional groups in their side chains. Basic amino acids have amine functional groups in their side chains. If the state of ionization of amino acids in a protein is altered then the ionic bonds that help to determine the 3-D shape of the protein can be altered. This can occur by adding basic or acid substances to the enzyme. This can lead to alter protein recognition or an enzyme might become inactive. In general enzyme has an optimum pH. However the optimum is not the same for each enzyme.

Catalase is an enzyme that can be found in all organisms that are exposed to oxygen. Its substrate is hydrogen peroxide which the enzyme catalyzes and separates into water and oxygen. This process is important because hydrogen peroxide can be harmful to almost all organisms and they need to break it down. Catalase also uses hydrogen peroxide as a resource to oxide toxins including Phenols, Formic Acid, Formaldehyde and Alcohols. Catalase’s optimum pH is 7.6 and its optimum temperature is 37 ° C in mammals.

Design

AIM

Analyze the effect of acid pH on the enzymatic rate (amount of bubbles produce) of Catalase in liver.

Problem

What is the effect of acid pH on the enzymatic rate of Catalase in liver? Six different rates of pH (7, 6, 5, 4, 3 and 2) will be used to analyze how the enzymatic reaction changes. The enzymatic reaction of Catalase will be measure by the amount of bubbles of oxygen produce (ml ± 1 ml). Hydrogen peroxide will be used to test this reaction.

Hypothesis

If the pH of the blended liver is more acid, then the enzymatic reaction of Catalase will decrease[2]. This will occur because with an acid pH the amino acids that build up the enzyme will be unbalanced, having more carboxyl groups than amino groups. This will cause the ionic bonding of the three-dimensional structure of the enzyme to be weaker, until the bonds break down. This will deform the active site of the enzyme[3]. As a result, the substrate will not be able to enter the enzyme as fast and the rate of reaction will decrease until the enzyme becomes denaturized.

Variables

* Independent variable: rate of pH: pH 7, 6, 5, 4, 3 and 2.

* Dependent variable: the amount of bubbles produced during the enzymatic reaction / ml ± 1 ml

Control variables

Table #1: Controlled variables, method to controlled them and justification

Variable

Amount

Method to control it / justification

Amount of liver

6 ml ± 1 ml

This amount of liver will be measure using a 25 ml graduated cylinder (± 1 ml). This amount was chosen because it can produce a significant amount of reaction without overflowing the 50 ml graduated cylinder.

Amount of hydrogen peroxide

2 ml ± 0.1 ml

The optimum substrate concentration for the enzyme Catalase is 30%[4]. The amount of substrate (hydrogen peroxide) will be calculate using the next formula:

2 ml of hydrogen peroxide will be measure using a 5 ml pipette (± 0.1 ml).

Time

2 minutes (120 seconds ± 0.01 second)

This time will be measure using a chronometer. In this, Catalase will produce a significant amount of reaction without overflowing the 50 ml graduated cylinder.

Kind of liver

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The liver used for every trial will be fresh chicken liver. It was chose because it has a great amount of Catalase[5].

State of the liver

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All liver will be blended. Hydrogen peroxide will be able to penetrate better the liver if it is liquid than if it is solid. As a result the amount of reaction will be greater if the liver is blended. Also if the liver is blended all trials will have the same superficial area.

Hydrogen Peroxide

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The