Gastric Digestion

GASTRIC DIGESTIONACTIVITY NO. 12Amina Zaira Y. Wooton

Fatima Nabeela M. Tungupon

Brion James A. Silveo

OBJECTIVES To be able to determine the reaction of

proteose solution with Biuret’s, Hopkins-cole’s, and Xanthroproteic Test.

To be able to determine the reaction of peptone solution with Biuret’s, Hopkins-cole’s, Xanthroproteic Test, and Tannic Acid Test.

To be able to determine the optimum pH for pepsin activity.

DATA, RESULTS, AND DISCUSSION

DATA RESULTS

Filtrate added with 5% sodium hydroxide

-No precipitate formed-Filtrate neutralized with 5% sodium hydroxide

Test II. Products of Gastric Digestion

DATA RESULTS

Biuret’s Test Produced a dark violet color

Hopkins-cole Test Violet ring formed at the junction of two layers

Xanthroproteic Test Color intensity lessenedBiuret’s Test is used for detecting the presence of peptide bonds on the presence of proteins. This test has a positive result of a violet color which results from the formation of coordination complexes by copper (II) ions in an alkaline solution.

Hopkins-cole Test determines the presence of the amino acid tryptophan. Indication of a positive result is the formation of a violet ring at the junction of two layers of the liquid. Tryptophan has an indole nucleus which is responsible for the violet ring found at the junction of two layers.

Xanthroproteic Test determines the presence of aromatic groups in amino acids. Indication of a positive result is the turning of the solution into dark yellow.

Test III. Separation of Proteoses and PeptonesA. Test for Proteoses

DATA RESULTS

Picric Acid Precipitate formed

Nitric Acid Precipitate formed

Proteose is the result in the breakdown of proteins through hydrolysis (breaking of a bond in a molecule using water).

In picric acid and nitric acid test, if there will be a precipitate, there is a protein content.

For picric acid, it will produce a dark brown or reddish brown precipitate.

For nitric acid, it will produce a white precipitate.

DATA RESULTS

Biuret’s Test Produced a blue violet color

Hopkins-cole Test Violet ring formed at the junction of two layers

Xanthroproteic Test Color intensity lessened

Tannic Acid Test Precipitate formed

Biuret’s Test is used for detecting the presence of peptide bonds on the presence of proteins. This test has a positive result of a violet color which results from the formation of coordination complexes by copper (II) ions in an alkaline solution.


B. Test for Peptones


Tannic Acid The peptones are considered as the final products of the hydrolysis of proteins.

They are readily soluble in water, glacial acetic acid, and in all salt solutions and are not coagulated by heat. The watery solutions are not precipitated by nitric acid, acetic acid and potassium ferrocyanide, picric acid, trichloracetic acid, potassium mercuric iodide, nor by neutral salts and acids.

These reagents, however precipitate peptones in concentrated solutions of calcium chloride, calcium nitrite, and ammonium sulfate. They are precipitated by phosphotungstic acid, phosphomolybdic acid, mercuric chloride, absolute alcohol, and tannic acid, but the precipitate may redissolve on the addition of an excess of the precipitant.

DATA RESULTS

Test Tube 1 (ice water) Least digested

Test Tube 2 (room temp) More digested

Test Tube 3 (40ºC) Most digested

Test Tube 4 (60ºC-70ºC) Less digested

Test IV. Optimum Temperature for Pepsin Action

Pepsin in human beings work best at 40ºC, thus the test tube 3 in a water bath at 40ºC has the most digested coagulated egg white.

Test tube 2 with room temperature is second to test tube 3 because the room temperature is close to 40ºC.

Test tube 1 in an ice water has the least digested coagulated egg white because this has the largest difference in temperature.

Test tube 4 in 60ºC-70ºC has the less digested coagulated egg white because there is big difference in the temperature.

DATA RESULTS

Test tube 1 (water) Egg digested

Test tube 2 (10% HCl) Digested more than test tube with 0.2% HCl

Test tube 3 (0.2% HCl) Digested less than test tube with 10% HCl

Test tube 4 (0.5% Na2CO3) Digested more than test tube with 1% Na2CO3

Test tube 5 (1% Na2CO3) Digested less than test tube with 0.5% Na2CO3

The higher the concentration of the HCl, the lower the pH. Lower pH will maximize pepsin activity better.

The higher concentration of Na2CO3 result in a less digested coagulated egg white.

Test V. Optimum pH for Pepsin Activity

CONCLUSIONSBiuret’s Test is used for detecting the presence of peptide bonds on the presence of proteins. This test has a positive result of a violet color which results from the formation of coordination complexes by copper (II) ions in an alkaline solution.



Proteose is the result in the breakdown of proteins through hydrolysis (breaking of a bond in a molecule using water).

In picric acid and nitric acid test, if there will be a precipitate, there is a protein content.

For picric acid, it will produce a dark brown or reddish brown precipitate.

For nitric acid, it will produce a white precipitate.

Peptones are considered as the final products of hydrolysis of proteins.

The watery solutions are not precipitated by nitric acid, acetic acid, potassium ferrocyanide, picric acid, trichloracetic acid, potassium mercuric iodide, nor by neutral salts and acids.

These reagents, however precipitate peptones in concentrated solutions of calcium chloride, calcium nitrite, and ammonium sulfate. They are precipitated by phosphotungstic acid, phosphomolybdic acid, mercuric chloride, absolute alcohol, and tannic acid, but the precipitate may redissolve on the addition of an excess of the precipitant.

Difference Between Proteoses and peptones

Proteoses are any of various protein derivatives that are formed by the partial hydrolysis of proteins (as by enzymes of the gastric and pancreatic juices), that are not coagulated by heat, and that are soluble in water but are precipitated from solution by ammonium sulphate while peptones any of various protein derivatives that are formed by the partial hydrolysis of proteins (as by enzymes of the gastric and pancreatic juices or by acids or alkalies), that are not coagulated by heat, and that are soluble in water but unlike proteoses are not precipitated from solution by ammonium sulphate .

Proteose and peptone do not indicate any definite compounds. They represent stages of decomposition between that of true proteins and amino acid.

Role of Temperature and ph level on Digesting Proteins

Increasing the temperature increases the kinetic energy of the enzyme and substrate molecules so that they move faster and are more likely to collide. So increasing the temperature increases the rate of the reaction up to a certain temperature. This temperature is known as the enzyme’s optimum temperature. Different enzymes have different optimum temperatures. The enzymes in animal bodies work best at 37ºC-40ºC.

If the temperature is increased beyond the optimum, the enzyme has so much kinetic energy that the bonds holding the enzyme molecule together start to vibrate and eventually break. Very high temperatures denature enzymes.

Changes in pH also alter an enzyme’s shape. Different enzymes work best at different pH values. The optimum pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7.5. Enzymes in the stomach have an optimum pH of about 2.

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Gastric Digestion