Exploring Enzyme Activity

ExploringEnzyme Activity


Investigationof Catalase Activity in Potato Tissues


  • To determine the presence of catalase in potato tissues

  • To correlate the substrate concentration to the amount of catalase present on the tissue


Catalasereaction is the breakdown of toxic hydrogen peroxide usuallyproduced in tissues into less harmful products, which is water andoxygen in the presence of an enzyme catalase. Catalase acts as acatalyst to speed up the rate of a reaction. The reaction is asfollows:

2H2O22H2O+ O2

Productionof oxygen observed in the form of fizzing and foam formation. Therate of product formation describes the enzyme activity of thereaction. However, this is affected by environmental factors as well.


  • Test tubes

  • Potatoes

  • Water


Catalasereaction was measured by placing tissues varying in length in a testtube containing equal amounts of hydrogen peroxide and observing thebubbling. The height of foam as a result of bubbling in each tube ismeasured and the more the bubbles, the higher the rate of thereaction.



Potato Piece

Frizzing Results


No potato











DataAnalysis and Interpretation

Fromthe results, it was deduced that the frizzing increased with increasein the potato length. Since the potato contains catalase, this meansthat the enzyme concentration affects the rate of reaction providedthe substrate (hydrogen peroxide) is kept constant.


Manyother factors affect enzyme activity, they include


Whenthe protein level is kept constant, and the substrate concentrationis gradually increased, the rate of reaction increases until itreaches the maximum whereby there is no further increase resulting toa sigmoid curve. This is because as the concentration increases, theenzyme becomes saturated with the substrate hence affecting theturnover rate

Environmentalfactors like pH, temperature, high heat treatment, salt, inhibitorsand other treatments

Enzymeswork well under optimum conditions. High temperatures and exposure toheat act to denature the protein while low temperatures inactivatethe enzyme. Change in pH alters the ionic bonds in the amino acidsresulting to inactivity. Various enzymes work at different pH levels.Competitive inhibitors bind to the active site of the enzymepreventing the substrate from binding hence inhibiting the reaction.Non- competitive inhibitors binds to the allosteric site of theenzyme thus changing the shape of the active site disabling thesubstrate from binding hence reduced enzyme activities. Other organicsalts can also result in enzyme inactivation.

Therole of activation energy in enzyme-catalyzed reactions

Chemicalreactions involve bond breaking in the reactants and bond formationto develop new products. However, reactants exist in a ground statelevel and therefore needs to be excited for the reaction to occur.The energy required to raise the reactants ground state to a higherenergy level, transition state is referred to as activation energy.Activation energy acts as a limiting step for the reaction since itdefines the rate of reaction. A higher activation energy correspondsto slower responses and vice versa.

Howactivation energy is provided to a reaction

Activationenergy is supplied to the reaction by absorption of thermal heat bythe reactants from the surroundings. This heat then speeds up thekinetic energy of the reactants resulting in more collision, whichknocks the atoms and bonds within the individual molecules,increasing the probability of bond breakage.

Definedenaturation and give examples of ways that enzymes can be denatured

Denaturationcan be defined as the alteration of the enzyme`s active siteresulting in losing of the biological activity. Since enzymes areproteinous in nature, this could be due to exposure to heat or hightemperatures, some inorganic salts or extremely high pH levels


Nelson,D., Nelson, D., Lehninger, A., &amp Cox, M. (2008). Lehningerprinciples of biochemistry.New York: W.H. Freeman.

Schomburg,D. &amp Schomburg, I. (2006). SpringerHandbook of Enzymes.Berlin, Heidelberg.