Download Planning an Experiment—Bacteria/Mold Growth

Annie Dai
Digestive Enzymes Act on the Egg White
Introduction:
Relevance:
Every human and animals need to eat food. We need to get nutrition to make the body
work. How can body get nutrition form big piece of food? The enzymes can break down
the food into small pieces for body to absorption. Different enzymes break down different
nutrition, if one of the enzymes disappear, our body will be weak because the lack of
nutrition. My investigation is use different enzymes to break down protein (egg white). In
my investigation, you can find out which enzyme can break down the protein.
Goals: Find out the difference of different enzymes act on egg white (protein).
General expectations and models:
My expectation is the protein in text tube 3 will be the first one disappears because the
pepsin is a digestive enzyme that catalyzes the breakdown of protein to peptides. Protein
can be found in gastric juice, it helps the body to break down the protein in the food and
help the body to ingestion, digestion, and absorption.
Variable:
The enzymes is independent variable, it measured in ml.
Egg white is dependent variable, it measured in mm cubes.
Materials：

Cooked egg white
Annie Dai

6 large text tubes

6 stoppers for test tubes

Test-tube rack

10-ml graduated cylinder

1% pepsin solution

0.2% hydrochloric acid

1% pancreatin

1% trypsin
Method/Procedure：
1. Label three test tubes 1、2and 3. Put them in a test-tube rack. Cut three 5-mm cubes
of cooked egg white and add one to each tube.
2. Use a graduated cylinder to add 6ml of water to test tube 1,
3. And 3ml of water and 3ml 0.2% hydrochloric acid to test tube 2.
4. To test tube 3, add 3ml 1% pepsin solution and 3ml hydrochloric acid.
5. To test tube 4, add 3ml water and 3ml 1% pancreatin.
6. To test tube 5, add 3ml water and 3ml 1% trypsin.
7. Put a stopper in each test tube, and turn the tubes upside down several times to mix
the contents.
8. Put the test tubes back in the test-tube rack. Set the test-tube rack where it will not be
disturbed.
9. After 2days, examine the contents of each test tube. Record your observations in your
copy of the table.
10. After 7 days, I haven’t seen any change in text tube 2 so I add 10ml 1% pepsin
solution in it to see if there will be any change.
Annie Dai
Figure 1：This is the Procedure of the investigation.
Expectations (Experiment)
I think there will be no change in tube 1 because there is no enzyme in the text tube.
In tube 2 the egg white will be smaller.
In tube 3, the egg white will be smaller than tube 2 because is has pepsin in it which
break down the protein into peptides.
Tube 4 may be same as tube 2.
Text tube 5 may be smaller than tube 2 and 4 because the trypsin in it can hydrolyze
proteins to form smaller polypeptide units.
I think the one have more enzymes will be break down faster because the enzymes
break down the food into molecules.
Annie Dai
After 7 days, I add 10ml 1% pepsin solution in text tube 2. If it has the same change
as tube 3, it means the pepsin solution can break down protein well.
Other results might the liquid in the tubes will be cloudy because the molecules of
protein (egg white). It means the egg white isn’t disappear, it just become many
molecules.
Results:
After 2 days (May 11): There are difficult to see the changes in text tube 1 and 2, text
tube 4 and 5 became a little cloudy. But I can see that the egg white in test tube 3
become very small.
Test Tube
Compound Tested
Liquid(s) Added
Observations
1
Protein(egg white)
6ml water
Cannot see any change
2
Protein(egg white)
3ml water,
Cannot see any change
3ml hydrochloric acid
3
4
Protein(egg white)
3ml pepsin,
The egg white become very
3ml hydrochloric acid
small
3ml water,
cloudy
Protein(egg white)
3ml pancreatin
5
Protein(egg white)
3ml water,
cloudy
3ml trypsin
Table 1: This is the table that I plan to fill out after 2 days. (May 11)
After 5 days (May 15): In text tube 1, there are still difficult to see the changes, text tube
become cloudy. The egg white in test tube 3 is already disappearing. In test tube 4, I can
clearly see that the egg white become smaller. In test tube 5, the egg white become very
small, I think it will disappear tomorrow.
Annie Dai
Test Tube
Compound Tested
Liquid(s) Added
Observations
1
Protein(egg white)
6ml water
Cannot see any change
2
Protein(egg white)
3ml water,
cloudy
3ml hydrochloric acid
3
Protein(egg white)
3ml pepsin,
Disappear
3ml hydrochloric acid
4
5
Protein(egg white)
Protein(egg white)
3ml water,
The egg white become smaller,
3ml pancreatin
cloudy
3ml water,
Egg white almost disappear, a
3ml trypsin
little cloudy
Table 2: This is the table that I plan to fill out after 5 days. (May 15)
After 7 days (May 17): I cannot see any change with the egg white in text tube 1, but the
water in it become a little cloudy. There is still hard to see the changeb in text tube 2. In
test tube 3, the egg white is already disappearing 5 days ago. In test tube 4, the egg white
become very small and the liquid become very cloudy. In test tube 5, the egg white
disappears and the liquid become as cloudy as text tube 4.
Test Tube
Compound Tested
Liquid(s) Added
Observations
1
Protein(egg white)
6ml water
Very little cloudy
2
Protein(egg white)
3ml water,
Cannot see any change
3ml hydrochloric acid
3
Protein(egg white)
3ml pepsin,
The egg white disappear
3ml hydrochloric acid
4
5
Protein(egg white)
Protein(egg white)
3ml water,
Very cloudy, egg white almost
3ml pancreatin
disappear
3ml water,
Very cloudy, egg white
3ml trypsin
disappear
Table 3: This is the table that I plan to fill out after 7 days. (May 17)
Annie Dai
After 11 days: Cloudy in text tube 1. Egg white becomes much smaller in text tube 2 after
I add 10ml 1% pepsin solution. In text tube 4, egg white almost disappears.
Test Tube
Compound Tested
Liquid(s) Added
Observations
1
Protein(egg white)
6ml water
Cloudy
2
Protein(egg white)
3ml water,
Egg white becomes much
3ml hydrochloric acid,
smaller, a little cloudy
10ml 1% pepsin
solution
4
Protein(egg white)
3ml water,
Egg white almost
3ml pancreatin
disappears
Table 4: This is the table that I plan to fill out after 11 days. (May 21)
Discussion:
In my investigation, the expectation of text tube 3 is similar to my observations.
But in text tube 2, 4 and 5, the expectations are different form observations. In my
expectation, the egg white in tube 2 will be smaller, but the observation is the egg white
doesn’t change until I add some pepsin in it. Tube 4 and 5 are similar in the observation.
I learn that HCl cannot break down protein, but the pepsin can break down protein
very well.
I think if I try to use pepsin only in a text tube, the egg white will break down faster.
It will give me more information about how well can pepsin break down protein.
Next time, I think I can use potato rather than egg white, to see which enzymes can
break down starch better.
Annie Dai
Appendix I: Scientific Terminology
Amino acids: An organic compound containing both an amino group (NH2) and a
carboxylic acid group (COOH), especially any of the 20 compounds that have the basic
formula NH 2CHRCOOH, and that link together by peptide bonds to form proteins. The
peptidase breaks down dipeptide into amino acids.
Amylase: From Greek ‘amylon’ starch + -ase. A group of enzymes that are present in
saliva, pancreatic juice, and parts of plants and help convert starch to sugar. The salivary
amylase in the mouth breaks down starches into disaccharides.
Dependent variable: The observed variable in an experiment or study whose changes
are determined by the presence or degree of one or more independent variables. The
dependent variable in my Investigation is egg white.
Digestive System: The alimentary canal and digestive glands regarded as an integrated
system responsible for the ingestion, digestion, and absorption of food. The enzymes that
I use can be finding from the digestive system.
Dipeptide: A peptide that, on hydrolysis, yields two amino acid molecules. The
peptidase breaks down dipeptide into amino acids.
Disaccharide: Any of a class of carbohydrates, including lactose and sucrose that yield
two monosaccharides upon hydrolysis. The salivary amylase in the mouth breaks down
starches into disaccharides.
Enzymes: German ‘Enzym’ or from Medieval Greek enzumos [leavened]. Any of
numerous proteins or conjugated proteins produced by living organisms and functioning
as biochemical catalysts. I use enzymes in my investigation to break down the protein.
Annie Dai
Hydrochloric acid: A clear, colorless, fuming, poisonous, highly acidic aqueous solution
of hydrogen chloride, HCl. It is found in the stomach in dilute form. Hydrochloric acid is
one of the enzymes that I use in my investigation.
Independent variable: A manipulated variable in an experiment or a study whose
presence or degree determines the change in the dependent variable. The independent
variable in my Investigation are the enzymes.
Lactase: An enzyme occurring in certain yeasts and in the intestinal juices of mammals
that is capable of splitting lactose into glucose and galactose. Lactase in small intestine
breaks down remaining disaccharides into monosaccharide.
Lipase: Any of a group of enzymes that catalyze the hydrolysis of fats into glycerol and
fatty acids. The lipase breaks down fat when the food past thought small intestine.
Maltase: An enzyme that catalyzes the hydrolysis of maltose to glucose. The maltase in
small intestine breaks down remaining disaccharides into monosaccharide
Monosaccharide: A carbohydrate that cannot be decomposed by hydrolysis, especially
one of the hexoses, having the general formula C6H 12O 6. It also called simple sugar.
The maltase, sucrase and lactase in small intestine breaks down remaining disaccharides
into monosaccharide
Pancreatin: A mixture of the enzymes of pancreatic juice, such as amylase, lipase, and
trypsin, used as a digestive aid. It is one of the enzymes that I use in my investigation.
Pepsin: Greek ‘pepsis’ [digestion] from ‘peptein’ [to digest]. A digestive enzyme found
in gastric juice that catalyzes the breakdown of protein to peptides. Pepsin is one of the
enzymes that I use in my investigation.
Annie Dai
Peptidase: An enzyme that hydrolyzes peptides into amino acids. The peptidase breaks
down dipeptide into amino acids. The peptidase breaks down dipeptide into amino acids.
Peptide: from Greek ‘pepsis’ digestion. Any of various natural or synthetic compounds
containing two or more amino acids linked by the carboxyl group of one amino acid and
the amino group of another. The pepsin in the stomach breaks down proteins into large
peptides.
Protein (egg white): French ‘protéine’. It contains carbon, hydrogen, oxygen and
nitrogen. Proteins include many substances, such as enzymes, hormones, and antibodies.
They are need by the animals for the growth and repair of tissue and can be obtained
from foods such as meat, fish, eggs, milk, and legumes. It is the dependent variable in my
Investigation.
Starch: Middle English ‘starche’ [substance used to stiffen cloth (sense uncertain)]. A
naturally abundant nutrient carbohydrate, (C6H 10O 5) n, found chiefly in the seeds,
fruits, tubers, roots, and stem pith of plants, notably in corn, potatoes, wheat, and rice,
and varying widely in appearance according to source but commonly prepared as a white,
amorphous, tasteless powder. The salivary amylase in the mouth breaks down starches
into disaccharides.
Sucrase: French ‘sucre’ [sugar] from Old French ‘sukere’. An enzyme that catalyzes
the hydrolysis of sucrose into glucose and fructose. The sucrase in small intestine breaks
down remaining disaccharides into monosaccharide
Trypsin: Perhaps Greek ‘tripsis’ [a rubbing (from its having been first obtained by
rubbing a pancreas with glycerin)]. An enzyme of pancreatic juice that hydrolyzes
proteins to form smaller polypeptide units. Trypsin is one of the enzymes that I use in my
investigation.
Annie Dai
Appendix II: Key Concepts, Models, "Big Ideas"
Digestive system is an integrated system responsible for the ingestion, digestion,
and absorption of food. It includes the mouth, pharynx, esophagus, stomach, small
intestine, and large intestine. Several major accessory structures, including the salivary
glands, the pancreas, and the liver, add secretions to the digestive system.
Each structure adds different secretions to the digestive system, and each secretion
break down different nutrition into small piece to help the body easier to absorb.
First the food goes into mouth, and then the salivary amylase in the mouth breaks
down starches into disaccharides. This is called chemical digestion. Then the food past
though esophagus and goes into stomach. The pepsin in the stomach breaks down
proteins into large peptides. In the small intestine, the amylase and trypsin from pancreas
continues the breakdown of starch and protein, the lipase breaks down fat. The maltase,
sucrase and lactase in small intestine breaks down remaining disaccharides into
monosaccharide and the peptidase breaks down dipeptide into amino acids.
Because different enzymes can break down different thing, my investigation is
found out which enzyme can break down protein the best.
Annie Dai
Picture 1: This is the picture of digestive system.
Annie Dai
Figure 2: Digestive enzymes break down foods and make nutrients available to the body.
References: