Annie Dai
Relevance:
Human and animals need to eat food because 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 doesn’t work, our body will become weak because the lack of nutrition. My investigation is use different enzymes to break down protein (egg white). In my investigation, I want to 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.
：

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
：
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.
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.
The egg white in 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.
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
1
2
Protein(egg white)
Protein(egg white)
Liquid(s) Added
6ml water
3ml water,
Observations
Cannot see any change
Cannot see any change
3
4
5
Protein(egg white)
Protein(egg white)
Protein(egg white)
3ml hydrochloric acid
3ml pepsin,
3ml hydrochloric acid
3ml water,
3ml pancreatin
3ml water,
3ml trypsin
The egg white become very
Table 1: This is the table that I plan to fill out after 2 days. (May 11) small cloudy cloudy
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
1
2
3
Protein(egg white)
Protein(egg white)
Protein(egg white)
Liquid(s) Added
6ml water
3ml water,
3ml hydrochloric acid
3ml pepsin,
3ml hydrochloric acid
Observations
Cannot see any change cloudy
Disappear
4
5
Protein(egg white)
Protein(egg white)
3ml water,
3ml pancreatin
3ml water,
3ml trypsin
The egg white become smaller, cloudy
Egg white almost disappear, a 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
1 Protein(egg white)
2
3
Protein(egg white)
Protein(egg white)
Liquid(s) Added
6ml water
3ml water,
3ml hydrochloric acid
3ml pepsin,
Observations
Very little cloudy
Cannot see any change
The egg white disappear
4 Protein(egg white)
3ml hydrochloric acid
3ml water,
3ml pancreatin
Very cloudy, egg white almost disappear
5 Protein(egg white) 3ml water,
3ml trypsin
Table 3: This is the table that I plan to fill out after 7 days. (May 17)
Very cloudy, egg white disappear

Annie Dai
After 11 days 9 (May 21): 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
1 Protein(egg white)
2 Protein(egg white)
Liquid(s) Added
6ml water
3ml water,
10ml 1% pepsin solution
3ml hydrochloric acid,
Observations
Cloudy
Egg white becomes much smaller, a little cloudy
4 Protein(egg white) 3ml water,
3ml pancreatin
Egg white almost disappears
Table 4: This is the table that I plan to fill out after 11 days. (May 21)
In my investigation, the expectation of text tube 3 is similar to my observations.
The 1% pepsin with 0.2% HCl can break down protein as well as I want. But in text tube
2 and 4, the expectations are different form observations.
In my expectation, the egg white in tube 2 will be smaller, but the observation is that the egg white doesn’t change until I add 1% pepsin in it.
In the observation, the egg white in tube 4 is much smaller than the one in tube 2, but in the expectation, Tube 4 may be same as tube 2.
My expectation of tube 5 is alike the observation. The egg white in text tube 5 is smaller than tube 2 and 4 because the trypsin in it can hydrolyze proteins to form smaller polypeptide units.
I learn that 0.2% HCl cannot break down protein, but the 1% pepsin with 0.2% HCl can break down protein very well. Also 1% pancreatin and 1% trypsin can break down protein.

Annie Dai
If I use pepsin only in a test tube, will it break down protein as well as the one in tube 3? 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.
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.

Annie Dai
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.
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

Annie Dai
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] or 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.
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

Annie Dai
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.
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.
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. Then they will go past the large intestine.
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. In my investigation, I want to find out which enzyme can break down the protein, which are the pepsin from stomach and the trypsin from pancreas.

Annie Dai
Picture 1: This is the picture of digestive system.
Figure 2: Digestive enzymes break down foods and make nutrients available to the body.

Annie Dai
Miller KR, Levine JS. Biology.
Upper Saddle River, New Jersey: Prentice Hall; 2006:
Page 978, 981, 990.
Picture 1: http://cache.eb.com/eb/image?id=8039&rendTypeId=4