CHAPTER I

INTRODUCTION

A. Background

Proteins are composed of peptides to form a polymer called polypeptides.

Each monomer is composed of amino acids. The role of proteins such as

catalysts, support, backup, immune system, etc.

Almost all amino acids except glycine have chiral carbon atoms. Chiral

amino acids have two forms isomeri. Have similar physical and chemical

properties, except the ability to distinguish the polarization direction of the play

field.

Proteins are composed of amino acid chains will have a wide variety of

typical structure of each protein. The protein structure includes primary

structure, secondary structure, tertiary structure and quaternary structure. The

primary structure is a structure composed of amino acid sequence does not

occur linearly and chain branching. Secondary structure is a combination of the

primary structure of the linear and has segments in polypeptide entwined. The

tertiary structure of a protein is an overlapping layer above the secondary

structure pattern consisting of irregular distortion of the bond between the side

chain (R group) of various amino acids are quaternary structure of proteins to

form complex molecules, some protein chains joined together to form a ball

(Carey , 2006).

B. Formulation of the problem

How the peptide bonds that form proteins?

C. Purpose

Students can provd there are amino acid

CHAPTER II

LITERATURE

Amino acids derived from the hydrolysis of amino acid α protein is also

called acid or α-aminokarboksilat. Amino acid that occurs naturally as the building

blocks of protein has an amino group (NH2) and the carboxylic group (COOH) are

bound to the same atom, namely the carbon atom alpha.

Amino acid is a carboxylic acid having an amino group. Amino acids

contained as protein components have -NH2 the α carbon atom of position -COOH

group.

The general formula for amino acids is: R - CH - COOH

NH2

Of the general formula can be seen that the α carbon atom is asymmetric

carbon atoms, except when R is atomic H. The difference between an amino acid

with another amino acid that is caused by differences in the R group called side

chains. There are 20 amino acids that act as the builder of a protein molecule,

namely glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine,

threonine, cysteine, methionine, proline, phenylalanine, tyrosine, tryptophan,

aspartic acid, glutamic acid, asparagine, glutamine, lysine, arginine and histidine.

In general, the amino acid is soluble in water and insoluble in non-polar

organic solvents such as ether, acetone and chloroform. Amino acids have a higher

melting point than the carboxylic acid or amine. Both of these physical properties

indicate that the amino acids tend to have a structure that is charged and has a high

polarity and not just a compound having -COOH and -NH2 groups. It also appears

on the nature of the amino acid as the electrolyte.

Amino acid containing an amino group which is alkaline and acidic karoksil

group in the same molecule. Amino acids undergo an acid-base reaction that

generates an internal dipolar ions, which are also called zwitterionic or amphoteric

ion.

If the water-soluble amino acids, carboxylic group will release H + ions,

while the amine group will accept H + ions, as written below:

-COOH -COO- + H +

-NH2 + H + -NH3 +

At the amino acid test there is general test and the test is specifically based

on the type of amino acid. Ninhydrin test of a general nature which reacted

positively to produce a violet color of all amino acids with primary amino groups.

And xantroproteat test positive reaction for amino acids containing a benzene

nucleus.

If ninhydrin heated with amino acids, it will form a color complex. For one

amino acid can be determined quantitatively by observing the intensity of the color

formed is proportional to the concentration of the amino acids. In this case NH3

and CO2 removed so that the possibility can be measured quantitatively. reaction:

RCH (NH2) COOH RCHO + NH3 + CO2 (purple)

Such as alanine, valine, leucine, isoleucine, phenylalanine and methionine

produce different colored complex with other amino acids. Color complex formed

contains 2 ninhydrin molecules that react with ammonia after amino acids are

oxidized.

Ninhydrin compound is a hydrate of triketon cyclic, and when it reacts with

amino acids, produces a purple color. Only the nitrogen atom of purple dye

derived from amino acids, amino acids and the rest is converted into aldehyde

carbon dioxide. Thus, the same purple dye produced from all α amino acids with

primary amino groups and the intensity of the color is directly proportional to the

concentration of the amino acid. Only proline, which has a secondary amino

group, react differently and resulted in a yellow dye, but it also can be used for

analysis.

CHAPTER III

RESEARCH METHODS

A. Tools and Materials

Tools :

Reaction tube

pipette

test tube rack

clamp test tube

measuring cup

Bunsen

Materials :

Protein solution

Solution of ninhidrin 0,1 %

B. Procedures

1. Add 5 drops of 0.1% ninhydrin solution in 1 ml of protein solution in a test tube

2. Heat until boiling, then let it cool and observe the color change.

CHAPTER IV

RESULT AND DISCUSSION

A. Results

No ActivityResult of Observed

Before After1. Arginin + ninhidrin

solution,heatedArginin : colorless

Ninhidrin : blue

Arginin + ninhidrin solution = colorless

Arginin + ninhidrin solution,heated = soft purple (+)

2. Albumin + ninhidrin solution,heated

Albumin : colorless

Ninhidrin : blue

Albumin + ninhidrin solution = colorless

Albumin + ninhidrin solution,heated =purple (++)

3. Tofu extract + ninhidrin solution,heated

Tofu extract :white

Ninhidrin : Blue

Tofu extract + ninhidrin solution = colorless

Tofu extract + ninhidrin solution,heated = white

4. mung bean extract + 5 drops of 0.01% ninhidrin solution,Then boiled it

Mungbean extract color:White

Ninhidrin: light turqoise

Mungbean extract + ninhidrin : white

after heated :dark purple with brownie color.

5. Chicken heart extract + ninhidrine,heated

Chicken heart extract color: maroon

Ninhidrine color: ligth turqoise

Chicken heart extract + ninhidrine + heated =purple

6. peanut extract + ninhidrine,heated

Color extract = white muddy solution

Ninhidrin = colorless

Extract tempe+ ninhidrin solution + heated:purple muddy

Many vapor (+++)

7. Extract tempe+ ninhidrin solution ,heated

extract tempe color:white muddy

Extract tempe+ ninhidrin solution + heated: grey purple

Ninhidrin solution color:clear

8. Fish meat extract + ninhidrin solution ,heated

Fish meat extract color: cream muddy

Ninhidrine color: colorless

Fish meat extract + ninhidrin solution + heated: purplish blue

9. chicken meat extract + ninhidrin solution ,heated

Chicken heart extract color: muddy,cream pinkish

Ninhidrine color: colorless

chicken meat extract + ninhidrin solution ,heated:blue purplelishthere is precipitation (++)water vapor (+)

B. Analysis

Based on the above observations obtained results that are arginine

indicator changes color to purple after undergoing a process of combustion or

dipanaskan.kemudian for albumin indicator is also changing to purple color but

the color purple in albumin solution is darker than the laruran arginine. While in

ekstract ekstract we tested using ninhydrin test produces visible changes, such as a

change in color and there is water vapor.

In ekstract maroon colored chicken livers, if added to a solution of

ninhydrin after it is heated will produce a brown color which has not shown the

presence of amino acids. In peanut extract white when added to a solution of

ninhydrin after it is heated will produce muddy purple color and many vapor

which indicates amino acids on these materials. In the fish meat extract white

colored muddy when added to a solution of ninhydrin after it is heated will

produce purplish blue color which indicates the presence of amino acids.

In tempeh extract cream colored when added to a solution of ninhydrin

after it is heated will produce a purple color which also showed the presence of

amino acids in the soybean extract and the extract of chicken meat soft pink color

produces a color change to purple after adding 0.1% ninhydrin solution and

heated, the color change indicates the presence of amino acids. In extracts of

white tofu did not produce a change in color to white after adding 0.1% ninhydrin

solution and heated, the color change has not shown the presence of amino acids

in the tofu extracts. And on the white colored mungbean extract produces a color

change into dark purple after adding 0.1% ninhydrin solution and heated, the color

perubabahan indicate amino acids.

C. Discussion of the result

Can we know that ekstract that changes color to purple to prove that the

protein solution containing amino acids. The darker the purple color of the peptide

bond in the solution more and kuat.akan but if the color is not dark purple then

show the peptide bond in the solution is not much and not as strong as the solution

changed color to a darker purple.

However, in our experiments that use ekstract know to get the color

changes to white after adding 5 drops of 0.1% ninhydrin solution. And on chicken

liver extract obtain Warne change into brown. The possibility that happened was

during the making of the state ekstract know know at the time is not good or is

already happening fermentasi.sehingga process causes the loss of peptide bond

know that amino acids in the know is missing too. And what happened to the

chicken liver extract, at the time of making the chicken liver extract, not stirred

first but took on the bottom / top of the chicken liver extracts, which could result

in the loss of chicken liver extract amino acids.

D. Question

1. Why ninhydrin reagent can be used to determine the presence of amino

acids? Explain!

Because ninhydrin an oxidizing cause oxidative decarboxylation

and amino acid by removing the CO2, NH3, and aldehydes, so that the

reduced ninhydrin reacts with NH3-free form of Compounds blue

complex. And ninhydrin a very strong oxidizing agent that can cause

oxidative decarboxylation of α-amino acids. Ninhydrin reduced, then

reacts with amino loose form complexes purple blue. The intensity of the

resulting blue color purple in a raw state is the basis for quantitative ter

very useful for amino acids and amines are not α-amino acids.

CHAPTER V

CLOSING

A. Conclusion

Based on the observation that has been done got the result that most of the

extracts proved the presence of an amino acid, the extract of chicken meat, fish,

tempeh, beans, and mung bean, because at the moment with the addition of 0.1%

ninhydrin solution and heated produces purple because Ninhydrin compound is a

hydrate of triketon cyclic, and when it reacts with amino acids, produces a purple

color. Tus, the same purple dye produced from all α amino acids with primary

amino groups and the intensity of the color is proportional to the concentration

Directly of the amino acid. But the tofu and chicken liver extract did not produce

a purple color which indicates the absence of amino asm, due to errors and lack of

prudence in the lab.

B. Suggestion

Next to the lab work was recommended to one who performs lab work to be

more careful in conducting a particular experiment, either in pouring reagent

solution, and in terms of reacting solutions of further maintaining the

cleanliness examiners.And of lab work tools so as not Contaminated by

another chemical solution. And 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

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