CHAPTER I

INTRODUCTION

A. Background

Protein is the most organic molecules in the cell. This substance is

found in all parts of the bodies of living and a group of the most diverse

kinds of compounds important in biology. (Pine, 1988)

Humans need energy to perform activities and everyday activities, the

energy can be obtained from a variety of foodstuffs. Protein is a polypeptide

biopolymer composed of a number of amino acids linked by peptide bonds.

Protein is a multifunctional biopolymers, namely as structural cells and

tissues and organs, as a biocatalyst enzyme, as a carrier or carrier when the

compound or substance through biomembran cells, and as a regulator.

(Hawab, 2004). Protein is contained in foods commonly consumed by

humans. As the eggs, tempeh, fish and others. In general, a protein derived

from vegetable and animal. Protein is essential for living organisms in

general, because it serves to improve the body's cells are damaged and the

supply of nutrients the body needs.

There are various ways in which the protein test to prove the

elements contained in proteins, one of which biuret test to demonstrate or

prove the peptide bonds that make up proteins.

B. Formulation of the problem

1. How to show or prove the peptide bonds that form proteins?

2. Are in all materials tested contained the peptide bonds that form proteins?

C. Purpose

1. Students can demonstrate or prove the peptide bonds that make up proteins.

CHAPTER II

LITERATURE

The word protein comes from the Greek word which means first and

foremost, the origin of the word protos. Proteins are composed of various classes

of heterogeneous macromolecules. Protein is a natural polymer composed of

various amino acids by peptide bonds. (Hart, 1987).

Protein is a source of amino acids containing the elements C, H, O and N are

not owned by fat and carbohydrates. Terpor sugar molecules containing sulfur

proteins, and there is a type of protein that contain metals such as iron and copper.

(Winarnno, 1997).

Key thousands of different proteins in the molecular structure is cluster

development units are relatively simple proteins are built from the same basic

circuit, of 20 amino acids having a side chain specific, covalent bonds in a typical

sequence. Because each amino acid side chains which have a special that gives the

chemical nature of each individual, a group of 20 units of this development can be

considered as the alphabet of protein structure. (Lehninger, 1996).

1. Protein function

As Enzymes

Tool Carrier and Storage

Regulatory Movement

Supporting Mechanics

Body Defense or Immunization

Media Propagation Neural Impulses

Control of Growth (Lehninger, 1996)

2. Protein structure

There are four levels of protein structure are:

1. The primary structure shows the number, type and sequence of

amino acids in a protein molecule (sequence of amino acids in a

protein molecule)

2. The secondary structure showed many properties of a protein is

determined by the orientation of the molecule as a whole, form a

protein molecule (eg spiral) and spatial arrangement skeleton (a

hydrogen bond between the NH group, one amino acid residue with

a carbonyl group C = O acid residues others).

3. Tertiary structure shows a tendency circumstances polypeptide

folds combined strap (more like terlipatnya interaction framework

to form a circle).

4. quaternary structure indicates the degree of partnership units of

proteins. (Winarno, 1997).

In terms of its structure, the protein can be divided into two groups, namely:

1. Simple Protein is a protein that is only made up of amino acid

molecules

2. Protein is a protein composite that consists of protein and not the

protein group. This group is called the prosthetic group and consist of

carbohydrates, lipids or nucleic acids.

Simple proteins according to their molecular shape is divided into two

groups, namely:

1. Protein fiber. The protein molecule consists of several polypeptide

chains are elongated and connected to each other by some

crosslinking to the fiber or fibers that form stable. Protein fiber is

insoluble in aqueous solvents, either saline, acidic, alkaline or

alcohol. Large molecular weight could not be determined with

purified starch and difficult. The usefulness of this protein only to

form a network structure and materials, for example, is the keratin in

the hair.

2. globular proteins. Globular proteins are generally spherical or

elliptical and consists of polypeptide chains involved. Globular

protein / speroprotein spherical, this protein dissolved in saline

solution and dilute acid, is also easier to change under the influence

of temperature, acid concentration and dilute acid. This protein is

denatured. Many are in milk, eggs and meat. (Fessenden, 1982)

To test the protein there are several ways one biuret test means a way to give

a clear result of the compounds are believed to have a peptide bond. Biuret test is

used as a way to determine the protein compounds. (Syakur, 2012).

To determine the presence of protein or peptide bonds including protein

hydrolysis as metaprotein, proteosa, peptone, amino acid polypeptide except the

biuret test. In alkaline conditions, CuSO4 react with compounds containing two or

more peptide bonds to form a purple complex. Biuret is a compound with two

peptide bonds formed on heating two urea molecules.

(NH2) 2C = O + (NH2) 2C = O ----> H2N-CO-NH-CO-NH2 + NH3. The

positive reaction occurs in the presence of a color change to purple or pink due to

the compounding of reserves of peptide N and O of the water. Colors that occur

depending on the length of the peptide bond. When the peptide bond length in

purple, otherwise if short color to pink.

Biuret reagent containing ions of copper (II) under alkaline conditions which

will react with the polypeptide or peptide bonds that make up proteins form a

complex compound purple (violet). Positive biuret reaction against two or more

peptide bonds, but negative for the free amino acid or dipeptide. The reaction was

positive for compounds containing two groups -CH2NH2, -CSNH2, -C (NH) NH2

and -CONH2.

CHAPTER III

METHODS

A. Tools and materials

Tools :

1. Test tube 5 pieces

2. Pipette drops 3 pieces

3. The test tube rack 1 piece

4. Clamp the test tube 1 piece

5. Measuring cup 1 piece

6. vortex 1 piece

Materials :

1. 10% NaOH

2. CuSO4 0.01m

3. albumin solution

4. 7 kinds of protein test :

Tempe

Tofu

Chicken liver

Chicken

Meat fish

Peanuts

Green beans

B. Step work

1. Prepare 7 kinds of protein solution and 1 solution of albumin.

2. Insert each protein solution into a test tube, each 3 ml.

3. Add 1 ml of 10% NaOH solution into each reaction tube containing any

type of protein solution, homogen with vortex.

4. Insert 3 drops of 0.01 M CuSO4 solution, then stir. If not arise color, add

1-2 drops of CuSO4.

5. Observe the changes that occur.

BAB III

RESULT AND DISCUSSION

A. Result

No. Procedure Result

Before After

1 Albumin + NaOH

10% + CuSO4

0,01 M

Albumin color:

Colorless

NaOH: Colorless

CuSO4 : Blue

Albumin + NaOH :

Colorless

After mixed with vortex :

colorless

Albumin + NaOH

+CuSO4:

Purple + blue sediment

2 Extract tempe +

NaOH 10% +

CuSO4 0,01 M

Extract tempe

color : cream

NaOH: Colorless

CuSO4 : Blue

Tempe Extract + NaOH:

Yellow

After mixed with vortex :

yellow

Tempe Extract + NaOH

+CuSO4: dark Purple, No

sediment.

3 Extract tofu +

NaOH 10% +

CuSO4 0,01 M

Extract tahu

color:

White

NaOH: Colorless

CuSO4 : Blue

Tofu extract + NaOH =

yellow wisk

After mixed with vortex :

white

Tofu extract + NaOH +

CuSO4=purple (+)

4 Extract fish meat +

NaOH 10% +

CuSO4 0,01 M

Extract fish meat

color : white

NaOH: Colorless

CuSO4 : Blue

Fish meat extract +

NaOH= cream

muddy,white sediment

After mixed with vortex :

Muddy yellow

Fish meat extract + NaOH

+ CuSO4= muddy

purple,purple sediment

5 Extract chicken

meat + NaOH

10% + CuSO4

0,01 M

Exract chicken

meat color:

Soft pink

NaOH: Colorless

CuSO4 : Blue

chicken meat extract +

NaOH= cream

After mixed with vortex :

Cream

chicken meat extract +

NaOH + CuSO4= muddy

purple(++)

6 Extract chicken

heart + NaOH

10% + CuSO4

0,01 M

Extract chicken

heart

color:maroon

NaOH: Colorless

CuSO4 : Blue

Chicken heart extract +

NaOH 10% + CuSO4

0,01 M : deep brown

After mixed with vortex :

Deep brown

7 Extract peanut +

NaOH 10% +

CuSO4 0,01 M

Extract peanut

color : white

muddy solution

NaOH: Colorless

Peanut extract + NaOH =

yellow white muddy

After mixed with vortex :

Yellow white

CuSO4 : Blue Peanut extract + NaOH +

CuSO4 = muddy purple

8 Extract mungbean

+ NaOH 10% +

CuSO4 0,01 M

Extract

mungbean color:

white

NaOH: Colorless

CuSO4 : Blue

Mungbean extract +

NaOH:

light yellow

After mixed with vortex :

Light yellow

Added CuSO4 :

Blackish purple, blue

precipitate.

B. Anallysis

From the data table above, the biuret test the addition of NaOH

solution and CuSO4 in setap materials tested. Color albumin and NaOH

solution is colorless, to color CuSOA 0.01 M solution is blue, as well as for

color 7 containing material that is extracted soybean protein: cream, tofu

extract: white, fish meat extract color: white, Exract chicken meat color:

soft pink, Extract chicken heart color: maroon, peanut Extract color: white

muddy solution, mungbean Extract color: white.

When Albumin + NaOH: Colorless, After mixed with vortex:

colorless and after Albumin CuSO4 + NaOH + Purple + Blue sediment

yield.

And to test materials containing protein 7. First, Tempe Extract +

NaOH: Yellow, After mixed with vortex: yellow and after Tempe Extract +

NaOH + CuSO4 produce dark color Purple, No sediment. In the extract

tofu, when Tofu extract + NaOH = yellow wisk, After mixed with a vortex:

white And after Tofu extract + NaOH + CuSO4 produce color purple (+).

To extract fish meat, when Fish meat extract + NaOH = cream muddy,

white sediment, After mixed with a vortex: Muddy yellow, and after Fish

meat extract + NaOH + CuSO4 produce muddy color purple, purple

sediment. In the test chicken meat, when chicken meat extract + NaOH =

cream, After mixed with vortex: Cream, and after chicken meat extract +

NaOH + CuSO4 produce muddy purple color (++).

In chicken liver extract test when Chicken liver extract + 10%

NaOH + 0.01 M CuSO4: deep brown, mixed with a vortex After: Deep

brown. To test the peanut extract when Peanut extract + NaOH = yellow

white muddy, After mixed with a vortex: Yellow white, Peanut extract +

NaOH + CuSO4 produce muddy purple color. In the last test protein bhan

ie extract mungbean, when mungbean extract + NaOH: light yellow, After

mixed with a vortex: Light yellow, CuSO4 Added produce color Blackish

purple, blue precipitate.

In all test produces a peptide bond, and if at the end of the results

when adding 0.01 M CuSO4 solution produces purple, peptide bond length,

but of some of the material tested produce a dense purple color, meaning

the longer the peptide bond.

C. Discussion Of The Result

To determine the presence of protein or peptide bonds including

protein hydrolysis as metaprotein, proteosa, peptone, amino acid

polypeptide their biuret test. In alkaline conditions, CuSO4 react with

compounds containing two or more peptide bonds form a purple complex.

Biuret is a compound with two peptide bonds formed on heating two urea

molecules.

(NH2) 2C = O + (NH2) 2C = O ----> H2N-CO-NH-CO-NH2 + NH3.

Positive reactions occur with a change in the color purple or pink for

backup compounding peptide N and O of the water. Colors that occur

depending on the length of the peptide bond. When the length of the

peptide bond in purple, otherwise if short color to pink.

And the results of the materials tested, all were found to contain a

peptide bond but on every test produces a peptide bond different, as in

soybean extract produces dark color Purple meaning peptide bond is very

long, the tofu and fish meat extract extract produces the color purple mean

bond length but not along in soybean extract. That is because the protein

content in each test is different, because the protein in soybean

literaturekandungan indeed very much.

But the chicken liver extract produces deep brown color that should if

formed their peptide bonds when the length of the peptide bond in purple,

otherwise if short color to pink. Probably within experimental apparatus

and the solution was contaminated with other materials to produce a deep

brown color. Biuret test on chicken liver showed negative results. It shows

the lack of peptide bonds.

D. Discussion

1. Can the biuret test is used to determine the hydrolysis of such

proteins has been completed?

Biuret test may be used to determine the protein hydrolysis has been

completed or not. Hydrolysis of proteins characterized by a color

change to blue keunguan.Warna purple indicates that the protein has

an alkaline and biuret test itself reacted positively to the formation

of complex compounds of Cu on -CO and -NH group of the peptide

chain under alkaline conditions. Biuret test is done to determine the

presence of protein or peptide bond. including the results of

hydrolysis of proteins such as metaprotein, proteosa, peptone,

except the amino acid polypeptide.

CHAPTER V

CLOSING

A. Conclusions

Protein solution has a kind of bond that is different, there are composed

of a peptide bond length and there are composed of a short peptide bonds. In

alkaline conditions, CuSO4 react with compounds containing two or more

peptide bonds form a purple complex. Biuret is a compound with two peptide

bonds formed on heating two urea molecules.

(NH2) 2C = O + (NH2) 2C = O ----> H2N-CO-NH-CO-NH2 + NH3.

Positive reactions occur with a change in the color purple or pink for backup

compounding peptide N and O of the water. Colors that occur depending on

the length of the peptide bond. When the length of the peptide bond in purple,

otherwise if short color to pink.

In soybean extract produces dark purple color, the tofu and fish meat

extract produces purple color, the chicken meat extract produce muddy purple

color ++, to extract the beans produce a muddy color purple, to extract

mungbean yield Blackish color purple, blue precipitate. Which indicates that

the presence of the peptide bond panjangt. But the chicken liver extract

produces deep brown color that shows on chicken liver showed negative

results. It shows the lack of peptide bonds.

B. Suggestions

As for suggestions to improve the quality of research:

a. It should be more careful in mixing the ingredients so that the results

agree with the theory that has been taught.

b. Tools and materials need to be added Because The test process must

use a considerable reaction tube, so do not spend a lot of time.

c. Maintain hygiene before and after use laboratory.

d. The existence of material preparation before entering the study