top-rated free essay


By fd123jv May 16, 2013 1119 Words
Department of Pure and Applied Chemistry
College of Arts and Sciences
Visayas State University

Chem 31a
Biochemistry Laboratory

Name: Jayvee A. Garcia
Group #: 1
Lab Schedule: M-F 7-10:20
Date Performed: April 30, 2013
Date Submitted: May 10, 2013

Experiment # 7
Enzyme Activity

1. Associate the presence of enzymes with the catalysts of the chemical reaction in living cells. 2. Determine the effect of enzyme concentration, substrate concentration, temperature, pH and heavy-metal salts upon the activity of salivary amylase. Results:

A. Enzyme Concentration
Test tube| Drops of Enzyme| A-1 Starting Time| A-2Time Blue Color Fades| A-3Time for Starch Hydrolysis| 1| 1| 9:07 am| 9:42 am| 35 minutes|
2| 5| 9:07 am| 9:37 am| 30 minutes|
3| 10| 9:08 am| 9:33 am| 25 minutes|
4| 15| 9:08 am| 9:28 am| 20 minutes|
5| 30| 9:09 am| 9: 24 am| 15 minutes|

Figure 1: Enzyme Activity (Time for Starch Hydrolysis) vs. Enzyme Concentration

B. Effect of pH
pH| B-1Starting Time| Time Blue Color Fades| B-2Time for starch Hydrolysis| 3| 9:17 am| 9:47 am | 30 minutes|
5| 9:19 am| 9:44 am| 25 minutes|
7| 9:19 am| 9:49 am| 20 minutes|
9| 9:20 am| 9:25 am| 5 minutes|
11| 9: 20 am| 9:25 am| 5 minutes|

Figure 2: Enzyme Activity (Time for Starch Hydrolysis) vs. pH

C. Effect of Temperature
Temperature| C-1Starting Time| Time for Blue Color to Fade| C-2Time for starch Hydrolysis| 0⁰C| 9: 25 am| 10: 05 am| 30 minutes|
25⁰C| 9:26 am| 9: 26 am | 0 minute|
37⁰C| 9:28 am| 9:48 am| 20 minutes|
70⁰C| 9:35 am| 10: 00 am| 25 minutes|
100⁰C| 9:36 am| 9:36 am| 0 minute |

Figure 3: Enzyme Activity (Time for Starch Hydrolysis) vs. Temperature

D. Inhibition of Enzyme Activity
Compound| D-1Starting Time| D-2Time for Blue Color to Fade| D-3Time for Starch Hydrolysis| AgNO3| 9: 10 am| 9:48 am| 38 minutes|
NaCl| 9:11 am| 9:25 am| 14 minutes|
Ethanol| 9: 12 am| 9:29 am| 17 minutes|
Water| 9:15 am| 9:24 am| 9 minutes|

1. (A) How does the activity of the enzyme change as its concentration is increased?

As the more of the enzyme is added, the time in minutes for the reaction to happen decreases. This means that enzyme activity is increased as the concentration of the enzyme is increased.

What are some reasons for these changes in activity?

The enzyme binds to or somehow interacts with the substrate to speed up the reaction. There are certain sites on the substrate that the enzyme will act on. So as you increase the concentration of enzymes it increases the number of successful collisions and so to a point the rate of reaction is directly proportional to enzyme concentration and the higher the concentration of the enzyme the faster the reaction.

2. (B) What is the effect of pH upon the relative enzyme activity?

Based on the graph, as the pH was increased, the activity also increased, even when the pH reached a high value. The data is somewhat erroneous since there should be an optimum pH for an enzyme and the graph should look like a mountain, the rate of reaction rising then peaks when reaching the optimum pH then declining beyond that optimum pH. The optimum pH of salivary amylase is 6.8 so the graph should’ve showed the least time in minutes close to pH=7.

What are some reasons for this effect?

pH affects the ionization of the amino acids that make up the active site of an enzyme (active site: where the subtrates are attached to). A change in pH causes a change in the degree of the ionization of the amino acids. The active site might change shape so as not to fit the substrates properly. Hence, less enzyme-substrate complex, enzyme activity decreases.

3. (C) How is the enzyme affected by low temperature? By high temperature?

Low temperatures lessen the activity of the enzyme. Like in pH, there is an optimum temperature; going over that temperature will also lessen enzyme activity. Again, the data is wrong since the optimum temperature for amylase is 37oC.

What are some reasons for these temperature effects?

Enzymes are proteins that catalyze reactions in biological systems. They are typically complex and "flexible". As molecules, their bonds are subject to excitation. At low temperatures, do not flex enough to let in the substrate. Also, the substrates and enzymes do not move around (brownium motion).However, as temperature increases so does the vibration of the molecules and the chance that the enzyme is "denatured" or broken and in need of repair. So reaction rate increases with temperature until a maximum is met. After the optimum temperature is reached, the denaturing effect of temperature is greater than its effect on reaction rate. This is why the graph shows a gradual increase until the optimum where it suddenly drops off.

According to your experiment, what is the optimum temperature for the salivary amylase?

According to the experiment, the optimum temperature for salivary amylase is about 25oC

4. (D) Which of the compounds added to the reaction tubes are inhibitors? Ethanol and AgNO3

Why do these compounds act as inhibitors of enzyme activity?
Enzymes are proteins. Proteins can be easily denatured by heavy metals and alcohols, and this denaturation causes changes in protein properties and can lessen protein activity. NaCl is not an inhibitor. In fact, human salivary α-amylase is often activated by NaCl.

Why is an alcohol swab used prior to giving an injection to a patient? Alcohols can kill microscopic and harmful organisms in the skin around the entry point of the needle. Along with its antiseptic uses, the alcohol also causes the blood vessels to rise to the skin's surface, making it easier to insert the needle.


Enzymes are proteins found in the body that catalyze reactions in the body. It lowers the activation energy of reaction and thus results to faster rate of reaction. Several factors affect the activity of these enzymes and they include enzyme concentration, substrate concentration, temperature, pH and heavy-metal salts. The activity of the enzyme is directly proportional to the enzyme concentration. Enzymes have optimum pH and temperature and below and beyond these optimum conditions, enzyme activity declines. There are also compounds that inhibit the enzymes like alcohol and heavy metals.


Cite This Document

Related Documents

  • What About Bob

    ... Psychological Analysis of What About Bob Danyel Samuel Psy-137 6/18/2014 Abstract The movie “What About Bob” follows the story of the two main protagonists Dr. Leo Marvin (played by Richard Dreyfuss), and Bob Wiley (played by Bill Murray). Throughtout the movie, these two display a number of psychological related problems. ...

    Read More
  • What would You Do ? and Country

    ...your family? o What do you like to do together as a family? o Do you get along well with your family? o Are people in your country generally close to their families? WORK o What do you do? o What are your responsibilities? o How many hours do you work each day? o Do you enjoy your work? o Is there some other kind...

    Read More
  • What About Bob Diagnosis

    ...PSYC 3350 Abnormal Psychology On-Line What About Bob "Multi-phobic personality characterized by acute separation anxiety . . ." This is Dr. Leo Marvin's diagnosis of Bob Wiley in the movie What About Bob. But exactly what does this mean? We all seem to have a vague understanding of what a phobia is, whether is be from watching movies ...

    Read More
  • What About Bob

    ...ELIJAH MOSS PROFESSOR LEONARD JUNE 12, 2013 In the 1991 comedy, What About Bob? Bill Murray portrays a peculiar and anxious man that is isolated by his multiple phobias and excessive dependence on therapists. Bob Wiley’s (Bill Murray’s character) fears range from germs to fear of having a heart attack or his bladder explode sp...

    Read More
  • What Would You Do? Paper

    ...What Would You Do? Episode __ : Helping the Homeless I. Relate the video to conscience Conscience, as defined by the Merriam – Webster Dictionary, is “the part of the mind that makes you aware of your actions as being either morally right or wrong”. It’s that tiny voice inside your head that tells you if what you’re about to do, w...

    Read More
  • What would You Do ? and New Product Design

    ...15. The refreshments are going to be pprepared by Karen. Conjugate the verb in parentheses in the correct tense used in the first or second conditional. 1. If she knows the time, she _____ (come) to the meeting. 2. She _____ (attend) the meeting if she had the time. 3. Peter _____ (say) yes if you ask him. 4. Unless he _____ (fi...

    Read More
  • Everlast Song Argument " What It's Like"

    ...Sydney Sanders English 305 Professor Michael Harrold 1 February 2011 Song Argument Essay “What it’s Like” by Everlast is a song that tells not one but three different stories. It touches on homelessness, abortion and drug violence. Three very relevant topics, despite its 1998 release date. The song cautions those who are quick ...

    Read More
  • what is love

    ...some family history as well. Write down information about your ancestry, your grandparents' lives, your parents' lives, and so on. Having information about your family history will help readers get a sense of how you became the person you are. Write down information about your childhood. What's your earliest memory? What were your mother and fa...

    Read More

Discover the Best Free Essays on StudyMode

Conquer writer's block once and for all.

High Quality Essays

Our library contains thousands of carefully selected free research papers and essays.

Popular Topics

No matter the topic you're researching, chances are we have it covered.