TO TEST THE EFFECTS OF ANTACIDS ON PEPSIN'S ABILITY TO DIGEST PROTEIN. Biology report - minus introduction, discussion & conclusion.

Essay by kate123High School, 12th gradeB-, May 2008

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Kate Fitzpatrick

Year Twelve Biology

Term One

(www.happycow.net)

"To test the effects of antacids on pepsin's ability to digest protein."

Contents

1.0 Abstract

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2.0 Introduction

· 2.1 Aim

· 2.2 Background Information

· 2.3 Hypothesis

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3.0 Materials

· 3.1 Equipment

· 3.2 Chemicals

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4.0 Method

· 4.1 Variables

· 4.2 Procedure

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5.0 Results

· 5.1 Sample calculation

· 5.2 Tables

· 5.3 Graphs

· 5.4 Photos

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6.0 Discussion

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7.0 Conclusion

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8.0 References

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9.0 Acknowledgements

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10.0 Appendices

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2.0 Introduction

2.1 Aim

To test the effects of antacids on pepsin's ability to digest protein.

2.2 Background information

Pepsin is an active form of pepsinogen which is released into the stomach. Hydrochloric acid is also released into the stomach from parietal cells and makes the pH acidic, of a pH 1-3.

This then activates chief cells to release pepsinogen, which functions in an autocatalyctic fashion. The hydrochloric acid mixed with pepsinogen generates pepsin, which can digest 20% of ingested carbon bonds. The primary structure of pepsin has an additional 44 amino acids which is useful in breaking proteins into smaller pieces called polypeptides (Whitman, 2002). The peptides are further digested by other protease in the duodenum and then absorbed by the body. However pepsin can only break certain amino acid bonds into shorter chains, and as other bonds are broken in the small intestines.

Pepsin is stored as pepsinogen and released when needed to ensure that it doesn't digest proteins in the stomach lining, as that would mean it is digesting the cell it makes. Therefore it synthesizes and is secreted inactively to the. stomach. Once pepsin is converted into pepsinogen, a chain reaction takes place. Pepsin triggers the formation of more pepsin, which represents a positive feedback loop. Dually, a negative feedback loop is shown when food enters the stomach. After the salivary amylase partially breaks down the food, it enters the stomach and dilutes it, which simulates more gastric juice to be secreted. According to Wikipedia, the result of this is that the pH decreases, altering the homeostasis of the stomach.

Pepsin functions best in an acidic environment, with a pH of 1.5-2 and optimum temperature 60C. The stomach is a perfect environment for this. The hydrochloric acid secreted in the stomach denatures proteins in food, making them more vulnerable to attack by pepsin. It is a fact that the average person secretes 400mL of gastric juice per meal (50-300mg of pepsin/mL) and therefore 80mg pepsin per meal.

Antacids refer to medication prescribed to neutralise the stomachs pH after ingestion, heartburn, overeating and stomach imbalance. However a change in the stomachs pH can denature proteins and cease functioning. Antacids aim to neutralize the stomachs pH to around a 6-7 and show a negative feedback loop as it buffers gastric acid. However pepsin stops functioning after it reaches a pH of 4. A pH imbalance can also cause kidney imbalance and further health problems (Stein Carter, 2004). Regular consumption of antacids increases the amount of acid secreted to restore the stomach to a normal pH which can prevent proper digestion and interfere with the absorption of nutrients. This can cause indigestion and thus makes it unfavourable for the casual use of antacids.

2.3 Hypothesis

Antacids will hinder pepsin's ability to digest protein depending on their concentration.

It can be suggested that the more basic antacids are likely to neutralise the pepsin better, and the more acidic antacids will digest more effectively.

3.0 Materials

3.1 Equipment

1 boiled egg

10 test tubes

Test tube rack

pH paper

Measuring cylinders

Two beakers

Heating equipment

3.2 Chemicals

Chemical

Quantity (conc.)

pH

Description

Risk

Gaviscon Cool

5 mL

9

A form of medication that aims to relieve heartburn. Its main three components are sodium bicarb, calcium carbonate and sodium alginate.

Not suitable for people on a salt restricted diet or young children.

Mylanta liquid

5 mL

8

Also medicine to relieve heartburn and neutralize the stomach's pH. Contains calcium, magnesium hydroxide and calcium carbonate. Is used in both tablet and liquid form.

Keep out of reach of children and do not digest. Do not freeze.

Pepsin solution

60 mL (0.1%)

6

A form of the liquid protease pepsinogen which changes to pepsin when activated with hydrochloric acid.

Should be stored at cold temperatures (20-80C) to prevent autolysis.

Sodium Bicarbonate

(NaHCO3)

5 mg

8

Primarily a cooking ingredient, sodium bicarb also neutralizes acids and bases and can be used as a deoderizer, an antacid, for bites and rashes and in other medicine.

Avoid digestion - can irritate respiratory system.

Mylanta tablet

5

See Mylanta liquid above. ^

Avoid heat.

Alka Seltzer tablet

5

An antacid containing aspirin, sodium bicarb and citric acid used for headaches, gas and heatburn.

Caution - produces carbon dioxide when dissolved with water

Hydrochloric Acid

60mL (0.1%)

1

A corrosive chemical, is incompatible to most common metals, amines, metal oxides, alkalies, carbonates, strong bases and sulphuric acid according to its MSDS.

Avoid contact with eyes, skin, heat and flames, and avoid inhaling.

4.0 Method

4.1 Variables

Independent variables

- Temperature

- Antacids being tested

Dependent variables

- the rate of change of digestion of the protein over time

- the PH over time

Controlled variables

- mass of protein

- amount of hydrochloric acid (to activate pepsin)

- amount of pepsin solution

- pH of initial protein

- Strength of the antacids

- Temperature of the storage place

Uncontrolled variables

- the degree of digestion

- strength of protein

4.2 Procedure

This procedure is based upon one previously created by Meredith Kirchheimer, 2005. It was amended due to accessibility of materials and resources. This is the procedure used for experiment two, as the experimental design for the first experiment was not successful, so it was amended to the following.

PROCEDURE

1. Label seven test tubes 1-7

2. In the test tubes place the antacids from the following table.

Test tube #

Pepsin Solution

0.1% hydrochloric acid

Antacid

Other information

1

5ml

5ml

None

Control experiment

2

5ml

5ml

5 mg Sodium Bicarbonate

3

5ml

5ml

5ml Gaviscon Cool

4

5ml

5ml

5ml Mylanta liquid

5

5ml

5ml

1 Alka Seltzer tablet dissolved in 5ml of water

6

5ml

5ml

1 Mylanta tablet dissolved in 5ml of water

7

5ml

5ml

None

Heated pepsin solution

3. Use the pH paper to determine the pH for each antacid in each test tube and record it.

4. In a beaker, place 40ml of pepsin solution and 40ml of hydrochloric acid. Record the pH of this

5. Add 10ml of pepsin/Hcl solution to each test tube. Record new pH.

6. Place boiling water into a beaker then place test tube #8 into this

7. Cut a boiled egg into relatively equal slices weighing approximately 3grams

8. Add these slices of egg to the test tubes

9. Record any observations and place all the test tubes bar #8 in the incubator at 37C overnight. Keep test tube #8 at room temperature.

10. After 24 and 48 hour record the pHs, rate of digestion and any observations. Comment on egg white, colour and odour. When indicating the rate of digestion, use the following system

3 - No egg white observed 2 - Some egg white present but decreased mass and very transparent 1 - Egg white slightly transparent and slightly changed in size 0 - No change in condition of egg white

11. After 48 hours retrieve the egg white from the test tube and weigh this. Record the new mass of the protein.

12. Make sure you clean up afterwards and fill out table of results.

Alterations in experimental design from experiment 1 to experiment 2

· Experiments stored in incubator (37C)

· Test tube caps used

· Egg weighed before and after experiment

· Tablets dissolved in water

Test tube #

Contents

pH of antacids

First pH

pH after 24hrs

AVG PH

Avg reaction rate

1

Pepsin + Hcl (control)

1

1

1

0

2

Pepsin + Hcl + NaHCO3

9

9

9

9

3

3

Pepsin + Hcl + Gaviscon cool

10

1

7.5

6.17

0

4

Pepsin + Hcl + Mylanta liquid

9

1

6

5.33

3

5

6

Pepsin + Hcl + Alka seltzer

1

1

6.5

2.83

1

7

Pepsin + Hcl + Mylanta tablet

1

1

5

2.33

0

8

Heated pepsin + Hcl

1

1

1

0

Test tube #

Contents

pH of antacids

First pH

pH after 24hrs

AVG PH

First reaction rate

Second reaction rate

Avg reaction

Original Mass

Mass after experiment

% Decrease

1

Pepsin + Hcl (control)

1

1.5

1.25

2.5

1

1.75

3

0.6

80

2

Pepsin + Hcl + NaHCO3

9

8

7.5

8.17

3

0

1.5

3

2.5

16.67

3

Pepsin + Hcl + Gaviscon cool

8

6

7.5

7.17

0

3

1.5

3

2.6

13.33

4

Pepsin + Hcl + Mylanta liquid

7

3

6

5.33

1.5

3

2.25

3

2

33.33

6

Pepsin + Hcl + Alka seltzer

5

6

6.5

5.83

1

2

1.5

3

2.1

30

7

Pepsin + Hcl + Mylanta tablet

5

3

5

4.33

0

1

0.5

3

1

66.67

8

Heated pepsin + Hcl

1

1.7

1.35

2.22

3

2.61

3

0

100

8.0 Appendices

5.0 Results

5.1 Sample Calculation

5.2 Tables

Results of experiment two

This outlines the data collected from the second, successful experiment and some calculations such as averages and % decrease of mass. Explanations of how the calculations were accomplished can be found in 10.0 Appendix .

Test tube #

Contents

pH of

antacids

First pH

pH after 24hrs

AVG PH

First reaction rate

Second reaction rate

Avg reaction rate

Original Mass

Mass after experiement

% Decrease

1

Pepsin + Hcl (control)

1

1.5

1.25

2.5

1

1.75

3

2.7

10

2

Pepsin + Hcl + NaHCO3

9

8

7.5

8.17

3

0

1.5

3

2.5

16.67

3

Pepsin + Hcl + Gaviscon cool

8

6

7.5

7.17

0

3

1.5

3

2.6

13.33

4

Pepsin + Hcl + Mylanta liquid

7

3

6

5.33

1.5

3

2.25

3

2

33.33

6

Pepsin + Hcl + Alka seltzer

5

6

6.5

5.83

1

2

1.5

3

2.1

30

7

Pepsin + Hcl + Mylanta tablet

5

3

5

4.33

0

1

0.5

3

1

66.67

8

Heated pepsin + Hcl

1

1.7

1.35

2.22

3

2.61

3

0

100

Results of original experiment (discarded)

These are the results of the first experiment. As you can see there was less monitoring than the second experiment therefore fewer calculations involved.

Test tube #

Contents

pH of antacids

First pH

pH after 24hrs

AVG PH

First reaction rate

2nd Reaction rate

Avg Reaction rate

1

Pepsin + Hcl (control)

1

1

1

0

1

0.5

2

Pepsin + Hcl + NaHCO3

9

1

9

5

3

0

1.5

3

Pepsin + Hcl + Gaviscon cool

10

1

7.5

4.25

0

2

1

4

Pepsin + Hcl + Mylanta liquid

9

1

6

3.5

3

3

3

6

Pepsin + Hcl + Alka seltzer

1

1

6.5

3.75

1

0

0.5

7

Pepsin + Hcl + Mylanta tablet

1

1

5

3

0

0

0

8

Heated pepsin + Hcl

1

1

1

0

0

0

5.3 Graphs

1)

This graphs shows the mass remaining of each solution after the experiment (the mass was originally 3g).

2)

This graph represents the % decrease in mass compared to the average pH of the test tubes.

3.)

This graph shows the average rate of reaction for different solutions. This was calculated from the aforementioned rating system. (see 4.2 Procedure )

4.)

This graph illustrates any correlation between the average pH of the substances and the reaction rate. The dots represent the different test tubes from 1-7.

5.4 Photos

Test tube #1

Nothing out of the ordinary

Test tube #2

More volume, greeny transparent, egg on top, strong odour

Test tube #3

Gluggy, thick blue colour at bottom, layer of bubbles on top

Test tube #4

Looks like clouds, transparent yet green tinge, gluggly particles and egg is slightly smaller

Observations after 24 hours

Test tube #5

Was empty and not used. I just can't count properly.

Test tube #6

Had some sort of reaction going on. Egg had less volume

Test tube #7

Murky white, egg sunk to bottom, transparent on top

Test tube #8

Nothing out of the ordinary. Looks like solution and egg in it.

9.0 Acknowledgements

I would like to thank

· Ms Di Bella - for her tireless efforts in helping me with this experiment and patience with me, even when I didn't know how to peel an egg

· Ms Murray - for going to all extremes to find the materials for my experiment

· Fellow students - for lending me their cameras in the absence of my own

· Big brother - for teaching me how to calculate percentages

· Tim Rossow and Daniel Bradford - for explaining what my brother could not

· Google - for once again, being a reliable and trustworthy search engine

· The Information Technology crew at LHC - for leaving a small minority of websites needed to conduct research for this assignment unblocked

· Danny & Anne Fitzpatrick - for giving me the better half of their EEI writing genes

· Foodworks Wynnum - for firing me via text message and thereby giving me more time to spend on this assignment

8.0 References

1. Kirchheimer, Meredith. "Concentration of Pepsin and Protein Digestion." California State Science Fair. Sept.-Oct. 2005. 6 Feb. 2008 <http://www.usc.edu/CSSF/History/2005/Projects/S0413.pdf>.

2. "Online Bibliography." Easybib.Com. 21 Mar. 2008. 21 Mar. 2008 <www.easybib.com>.

3. "Pepsin." Wikipedia. 08 Feb. 2008. 8 Feb. 2008 <www.wikipedia.org/pepsin>.

4. Stein Carter, J. "Effects of Antacids on Pepsin." 3 Nov. 2004. Clermont College. 12 Feb. 2008 <http://biology.clc.uc.edu/courses/bio115/pepsin.htm>.

5. Sutliffe, Jimmy. "Antacids." Xnet. 31 Feb. 2006. 25 Feb. 2008 <www.xnet.com/sciencefairexperiements/biology/72_#77/sutliffe.htm>.

6. Whitman, Cory. "Pepsin and Protein Digestion." July 2002. Australian Academy of Science. 6 Feb. 2008 <www.science.org.au/archives/55FTL/17.htm>.