How will Concentration affect the Volume and Rate of Oxygen Released when reacting Hydrogen Peroxide with a Potato

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Jay Vyas

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How will Concentration affect the Volume and Rate of Oxygen

Released when reacting Hydrogen Peroxide with a Potato

Introduction

I am going to find out whether the concentration of hydrogen peroxide (H2O2) will affect the rate and volume of oxygen produced by a potato when hydrogen peroxide is added to it.

Plan

Potatoes contain a chemical enzyme called catalase to break down poisonous hydrogen peroxide into harmless water and oxygen. Hydrogen peroxide is produced in certain cell reactions. Without catalase, the potato would not be able to break it down, and the organism would die. The chemical equation for this reaction is:

                                                                   catalase

2H2O2                   2H2O + O2

Enzymes are biological catalysts. They are:

  • Catalysts: they are substances that speed up reactions, without being disfigured or used up themselves. This makes them very useful, because even small amounts can do a big job.
  • Proteins: They have a special shape for each specific substance it works on.

I will now show as diagram how they are specific.

As you can see enzyme A can only react with substance a, and not c. However, enzyme C will not react substance a only c. The substance on which an enzyme acts is called its substrate.

Catalase is a biological enzyme. It is found in foods because it speeds up the disintegration of hydrogen peroxide into water and oxygen as you can see in the above equation. It is able to do this because hydrogen peroxide has a shape that aids the decomposition of it by catalase. This is shown in the diagram above. This type of reaction is called an anabolic reaction. An anabolic reaction is when large molecules are built from smaller molecules. In this case, hydrogen peroxide is a small molecule and when reacted with catalase water is produced which is a bigger molecule.  

There are four factors that affect the rate at which an enzymes works:

  1. Temperature
  2. pH Level
  3. Surface area
  4. Concentration of substrate and enzyme (GSCE BIOLOGY by D.G. MACKEAN)

The temperature of an enzyme is very important. In humans, enzymes work best at 37oc. After this, they are past their optimum, and if the temperature is too high, the enzyme will denature. A graph for this phenomena would resemble this:

Rate of reaction

        Temperature (oc)

The dotted line represents the optimum temperature. Therefore, it is important for the enzyme to be kept at the right temperature. If it is too hot then the enzyme will denature and die. In many cases if the temperature is raised by 10oc, the rate of reaction will double in a cell, until a point. The enzymes denature at high temperatures because their shape changes therefore the enzyme can no longer react with the substrate.

The pH level alters the chemical properties of an enzyme. Most enzymes work best at a certain level of pH. A good example of this is in the stomach where the pH is set at 2, because the protease enzyme works best at that pH. Where an enzyme works, best is called its optimum pH. Unlike in temperature where high temperatures can permanently denature enzymes, high or low levels of pH, will not permanently inactivate the enzyme, however this is not the case with all enzymes.

If there are more substrate for the enzyme to react with then the rate will be faster, because there is more chance for a successful collision if there is an increase of the substrate into a  fixed amount of enzyme. If there is less substrate there is less chance of a successful collision. This is also the case with increasing the concentration of the enzyme. If  there is an increase in enzyme with a fixed amount of substrate then there is more chance of successful collision to occur.

The surface area of the potato will alter the rate of reaction. If the potato has a large surface area, then there is more surface for the hydrogen peroxide around it to react with. If it is a small fat piece then there is a smaller surface area then with a thin tall piece.

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I will be altering the concentration of the substrate. I predict therefore using my above knowledge that as the concentration increases the rate of reaction will increase as well. I believe that the graph I will produce will resemble this.  

Volume of oxygen (cm3)

        Time

I predict that the higher concentration will have a steeper line of best fit, compared to a lower concentration of hydrogen peroxide. I also believe that the line of best fit will not bottom out until more time has passed because there is more ...

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