Enzyme Activity Test Tube

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EnzymeActivity

Test Tube

Hydrogen peroxide (3%) (substrate)

Water tsp for a final volume of 2 tsp in each tube

(student to fill in)

Liver homogenate (catalase enzyme)

Total volume in test tube

Bubble observation (on a scale of 0-5, 0 is the lowest and 5 is the highest)

A

1 tsp

1 tsp

0

2 tsp

0

B

1 tsp

7/8 tsp

1/8 tsp

2 tsp

1

C

1 tsp

¾ tsp

1/4 tsp

2 tsp

2

D

1 tsp

½ tsp

1/2 tsp

2 tsp

3

E

1 tsp

0

1 tsp

2 tsp

5

  1. What happens to the reaction when the amount of enzyme (liver homogenate) is increased in it? Why does that happen?

  • The reaction rate increases as the amount of enzyme is increased. This happens since more enzymes mean that more substrate will be bound hence a fast rate of turning substrate into product (Moore, 2012).

  1. Is there a “control” (control group or control sample) in this experiment? What is it?

  • It is a good practice to use control groups in experiments since they provide a point of reference to determine if indeed the experiment was a success (Moore, 2012). There was one control sample for our experiment this control sample was test tube A where no enzyme was added.

  1. What information does this control provide?

  • Controls provide baseline data that the researcher can use to compare the results of other experiments (Moore, 2012). For instance, the first control without enzyme gave the results to expect when there was no enzyme activity in the test tube as such, any results that differ from this control will mean that there was some enzyme activity.

  1. Why do we add water to some of the test tubes in this experiment?

  • Water is added to the test tubes in order to achieve a uniform volume of mixture in each and every test tube. Such uniformity is important in enzyme-substrate reactions so as ensure that the results are also uniform (Seager, 2011). Using unequal volumes of the mixture will lead to inconclusive results.

  1. Line graph, which describes the effect of adding different volumes of liver homogenate to a test tube for the enzymatic reaction.

Graph1: effects of enzyme concentration on reaction rate

Test Tube

Water bath

Temperature (C)

Hydrogen peroxide (3%)

(substrate)

Liver homogenate (catalase enzyme)

Bubble observation (on a scale of 0-5, 0 is the lowest and 5 is the highest)

A

Ice water

-4

1/2 tsp

1/2 tsp

0

B

Room temperature

27

1/2 tsp

1/2 tsp

3

C

Heated water bath

97

1/2 tsp

1/2 tsp

1

D

Heated water bath, phase 2

40

1/2 tsp

1/2 tsp

0

  1. Which temperature condition is normally the most appropriate for catalase activity?

  • The most appropriate temperature for catalase enzyme activity is 37oC since it is a body enzyme used to break down hydrogen peroxide into harmless components (Eed, 2012).

  1. What happened to the enzyme reaction in the ice water bath?

  • There was no enzyme reaction in the ice water bath this happened since enzymes are deactivated at low temperatures. Deactivated enzymes cannot bind substrate and hence there was no enzyme substrate reaction in the ice water bath (Seager, 2011).

  1. a) What effect does an extremely high temperature have on enzyme function?

  • Extremely high temperatures tend to slow down enzyme reaction as we observed in our experiment.

(b)What is the cause of this effect, in other words, what exactlyhappens to the enzyme molecules due to extremely high temperature?

  • The enzyme molecules get denatured at extremely high temperatures denatured enzyme molecules, on the other hand, cannot bind substrate and hence the reduced reaction rate (Eed, 2012).

  1. What happens to the liver homogenate when you cool it back down to room temperature and add more hydrogen peroxide?

  • There was no reaction after cooling down the liver homogenate and adding more substrate. The reason for this is because the enzymes got denatured by the extreme heat and therefore it could not bind substrate (Starr, 2011).

  1. bar graph describing observations of the effect of temperature on catalase activity

Graph2: effects of temperature on reaction rate

Questions

  1. Write an explanation of the function of the enzyme catalase.

  • The function of the enzyme catalase is to break down hydrogen peroxide which is harmful to the body hydrogen peroxide is broken down into the harmless substances water and oxygen (Starr, 2011). The production of oxygen is evident because in our experiment bubbles are observed.

  1. Why are the functions of enzymes in general important to cellular homeostasis?

  • They break down the harmful substances in the body for instance, catalase breaks down hydrogen peroxide.

  • Complex molecules are broken down by enzymes into less complex substances that can be directly used by the body. Examples of complex molecules broken down by enzymes include lipids and starch.

  • They also speed up the rate of chemical reactions in a bid to maintain homeostasis (Starr, 2011).

  1. Are enzymes normally reusable in cells or the body of organisms? Explain your answer.

  • Enzymes are reusable after every reaction. Enzymes have active sites where the substrate is bound after the substrate is turned into product, it leaves the active site so that more substrate may be broken down. In this way, the enzyme is not worn out and hence it can be reused in cells or the body of organisms (Starr, 2011). However, in cases of extreme temperatures, then the enzymes cannot be reused since they are denatured.

  1. In this lab, the amount of substrate (hydrogen peroxide) was not varied. If the concentration of substrate continues to increase, would the rate of the enzymatic reaction (catalase activity) continue to increase at all increasing substrate concentrations?

  • There is an inverse relationship between enzyme rate and substrate concentration. Increasing the amount of substrate causes a decrease in reaction rate. This happens since as substrate increases, all the active sites in the enzyme are filled hence there is no more room to bind more substrate for this reason, the rate of enzyme activity reduces (Starr, 2011).

  1. List two specific substances that can act as inhibitors of the enzyme catalase. These two substances can be competitive or noncompetitive inhibitors of catalase.

  • Poison or toxin such as cyanide

  • Drugs such as disulfiram

  1. What is the difference between competitive and noncompetitive inhibitors?

  • A competitive inhibitor binds to the active site of the enzyme. It competes with the substrate so that it can occupy the site on the enzyme (Copeland, 2013).

  • A non-competitive inhibitor binds away from the active site in an enzyme. This results in a change of the structure of the enzyme such that the active site changes shape and hence it cannot bind substrate. This decreases the overall rate of the reaction (Copeland, 2013).

References

Copeland,R. A. (2013). Evaluationof enzyme inhibitors in drug discovery: A guide for medicinalchemists and pharmacologists.Hoboken, N.J: Wiley.

Eed,J. (2012). Factors Affecting Enzyme Activity. ESSAI,10(1),19.

Moore,T. C. (2012). ResearchExperiences in Plant Physiology: A Laboratory Manual.Berlin, Heidelberg: Springer Berlin Heidelberg.

Seager,S. L., &amp Slabaugh, M. R. (2011). Chemistryfor today: General, organic, and biochemistry.Australia: Brooks/Cole CENGAGE Learning.

Starr,C., Evers, C. A., &amp Starr, L. (2011). Biology:A human emphasis.Belmont, CA: Brooks/Cole Cengage Learning.