Carbohydrate Biochemical Report

1. Basic Theory   

      Carbohydrates are aldehydes or ketones which have hydroxyl groups. These compounds make up most of the organic matter in the world because of their multiple roles in all forms of life. Carbohydrates act as a source of energy, fuel, and metabolic intermediates. Example: starch in plants and glycogen in animals are polysaccharides that can be mobilized to produce glucose (the main fuel for energy formation). Ribose sugar and ribose deoxy form part of the skeletal structure of RNA and DNA. The flexibility of the second ring of sugar is important in the storage and expression of genetic information.    

      The various kinds of carbohydrates found in food include starch or starch and sucrose (cane sugar). Carbohydrates (glucose) are formed from carbon dioxide and water with the help of sunlight and chlorophyll in the leaves. Furthermore, the resulting glucose is converted into starch and stored in fruit or tubers. The reaction is:

6CO 2 + H 2 O C 6 H 12 O 6 + 60 2           

      Carbohydrates or saccharides are hydroxyl groups (-OH), aldehyde groups or ketone groups. Then it can be defined that carbohydrates as polyhydrochaldehyde or polyhydroxetone compounds, or compounds that are hydrolyzed from both. Carbohydrates can be classified based on the number of constituent monomers. There are 3 types of carbohydrates based on this classification, namely:

1. Monosaccharides     

2. Disaccharides (Oligosaccharides)     

3. Polysaccharides     

 

§ Monosaccharides  

      Monosaccharides are the simplest carbohydrate compounds that cannot be hydrolyzed anymore. Generally these compounds are aldehydes or ketones that have 2 or more hydroxyl groups. Some carbohydrate molecules contain nitrogen and sulfur. The empirical formula for carbohydrate is (CH2O ) n . If the carbonyl group at the end of the monosaccharide chain is an aldehyde derivative, this monosaccharide is called aldose. If the carbonyl group at the end of the monosaccharide chain is a derivative of ketones, this monosaccharide is called ketose. The smallest monosaccharide n = 3 is glyceraldehyde and dihydroxyacetone.

 

§ Disaccharides (Oligosaccharides)  

      Disaccharides are carbohydrates that are formed from 2 to 10 monosaccharides. Included in this group are disaccharides, trisaccharides, and so on. Disaccharides consist of 2 monosaccharides that are bound to O-Glycosidic. The 3 main disaccharide compounds that are important and abundant in nature are sucrose, lactose and maltose. These three compounds have the same molecular formula (C12H22O11) but the molecular structure is different.

      Sucrose or sugar is made from sugar cane drops. Cyclopsa is sweeter than glucose, but less sweet compared to fructose, it is very soluble in water. This sugar is used to make syrup, confectionery and food sweeteners. If this compound is hydrolyzed one glucose molecule and one fructose molecule will be produced. 

      Lactose is called milk sugar because there is a lot of milk. Usually obtained from milk. This sugar is the sugar that is the most soluble in water and the least sweet. Enzymes in certain bacteria will turn lactose into lactic acid, this happens when milk turns sour. Lactose is used to make baby food and special diets. If hydrolyzed 1 glucose molecule and 1 galactose molecule will be produced.

      Maltose is called sugar mout, which is found in many germinating barley. This compound is the result of partial hydrolysis of starch. Compared with sucrose this substance is more difficult to dissolve and less sweet. This compound is used for making baby food, milk powder, and other food ingredients. If hydrolyzed 2 glucose molecules will be produced.

 

 

§ Poisaccharides  

      Polysaccharides are composed of monosaccharides that are joined by glucoside bonds. Starch is an example of a polysaccharide composed of glucose. Viewed from its structure, starch grains consist of 2 parts, namely: the amylose part which is a straight chain of glucose polymer, and the amylopectin part consisting of a branched chain of glucose polymer which, when hydrolyzed completely, will produce glucose molecules. 

      Monosaccharide identification is based on the nature of its ability to reduce, which is done using the Benedict test. Molicsch test is used to recognize carbohydrates that are easily dehydrated to form furfural or dihydrosifurfural which further condenses with resorcinol, orsinol or a-naphthol. Seliwanof reagents are used to recognize carbohydrates that contain aldehyde functional groups such as fructose and sucrose. Barfoed reagents are commonly used to recognize the presence of monosaccharides. The iodine test is specifically used to identify the presence of starch polysaccharides. 

2. TOOLS AND MATERIALS     

      a. material

- Carbohydrate Solution         

- Seliwanof reagent                    

- Barfoed reagents                                                           

- Concentrated HCl solution         

- HCl 6 M solution         

- 6 M NaOH Solution                                           

- Solution I 2 0.01 M                                   

- Molisch Pereksi              

- Benedict's reagent         

             b. Tool

3. Working Procedure     

      a. Molisch Test

2 mL carbohydrate solution

- + 2 drops of molisch reagent   

- + 1 drop of concentrated H2SO4    

- observe   

     

Observation result

      b. Barfoed Test

1 mL carbohydrate solution

- + 3 mL barfoed reagents   

- Heated in a water bath for 1 minute or more   

- observe    

                                                    Observation result

      c. Seliwanof Test              

3 mL of the Seliwanof reagent

- + 3 drops of carbohydrate solution   

- Heated in a water bath until the color changes   

- observe    

                                                    Observation result 

      c. Iodine Test                 

3 mL of starch solution

- In 2 test tubes   

- + 2 drops of water - + 2 drops of HCL                                                                

- Shaken - Shaken                                                               

- + iodine - + iodine                                                                 

        Color change. Color change                                                               

                          

- Heated - Heated                                                           

- Refrigerated - Refrigerated                                                          

- Observing - Observing                                                               

        Observation Results Observation Results                                                       

4. Observation Results     

TEST / TEST	PROCEDURE	OBSERVATION
Molisch	Carbohydrate solution + Reaction molisch + concentrated sulfuric acid	Purple ring formed
Barfoed	Carbohydrate + Barfoed reagent + Heated	Red brick deposits are formed in fructose and galactose carbohydrates while in other carbohydrates are not formed
Seliwanof	Seliwanof reagents + sugar solution + Heated	Pink brick color
Iodine	Tube I: Starch + water + iodine + heated solution Tube 2: Starch + HCL + iodine + heated solution	Blue     Light blue color

5. Discussion   

      Carbohydrates can be defined as polyhydrochaldehyde or polyhydroxetone compounds, as well as compounds that are hydrolyzed from both. This is because carbohydrates contain hydroxyl groups (-OH), aldehyde groups or ketone groups.  

      Sir Walter Norman Howarth, an English chemist, argues that in the first five glucose molecules the first carbon atom with an oxyent atom can form a hexagon ring. Therefore the structure of carbohydrates as a form of furan or piran ring. Based on this, the structure and configuration of carbohydrates are written based on the shape of the cyclic ring, namely: the furanose group (carbohydrates have a five-membered ring) and the piranose group (carbohydrates have a six-membered ring).

            Furan Piran                                                               

      The carbon atom of a sugar molecule is numbered starting from the tip closest to the aldfehid or ketone. The main forms of glucose and fructose in solution are not open chains but in the form of rings.

      Carbohydrates can be classified based on the number of constituent monomers. Based on this classification carbohydrates are divided into 3 namely: Monosaccharides, Disaccharides (Oligosaccharides) and Polysaccharides.

      As for what was done in this experiment are as follows:

1. Molisch Test     

            The Molisch test is a general test for carbohydrates. This test is effective for compounds which can be dehydrated by concentrated acid into furfural compounds or substituted furfural compounds, such as hydroxymethyl furfural.

The observations show that all carbohydrates produce purple rings. Color that occurs due to furfural condensation or its properties with a-Naphthol produces the following compounds: 

            In dilute acid solutions, even though heated, monosaccharides are generally stable. But when it is heated with strong strong acid in this case the above carbohydrate test, monosaccharides produce furfural or derifat. This furfural formation reaction is: dehydration reaction or the release of water molecules from a compound.

Question

1. The color of the ring formed is purple     

2. The carbohydrate group that provides the molisch test is hydroxymethylfurfural     

3. Because molisch reagents are a mixture of a- Naphthol solution in alcohol or a reaction between a-Naphthol and furfural.       

2. Barfoed Test     

      Barfoed reagents Made from Coper Acetate and acetic acid solutions in water. This reagent is used to distinguish monosaccharides and disaccharides by controlling conditions, such as pH and heating time.

      From the observations it was found that when mixing the solution is dark blue and after the heating process the color of the mixture becomes bright blue. For the fructose and galactose (Monosaccharide) carbohydrates, brick red deposits are formed. Monosaccharides can reduce faster than disaccharides. So Cu2O is formed more quickly by monosaccharides than disaccharides. By Tauber and Kleiner made modification of the reagents and turned out to produce a blue color that indicates the presence of monosaccharides. 

Answer the question

1. Carbohydrates monosaccharides namely fructose and galactose     

2. Warming for too long will cause more red brick deposits formed.     

3. Barfoed reagents can be used in tests of sugar in urine, this is because barfoed reagents consist of an acetate suitcase and acetic acid in water.     

3. Seliwanof Test     

      Another specific reaction for certain carbohydrates is the seliwanof test. The seliwanof reaction is caused by the change in fructose by hot hydrochloric acid to the origin of levulinates and hydroxymethylfurfural, then hydroxymethylfurfural condensation with resorcinol produces the following compounds:

      Sucrose is easily hydrolyzed into gluose and fructose, giving a positive reaction with seliwanof test. On further boiling, aldoses give red color with seliwanof reagents because they are converted by HCl to Ketose.  

      The brick red color produced in this experiment indicates that the positive sugar solution contains ketose compounds. The color is caused by the reaction of resorcinol condensation with furfural or hydroxymethylfurfural.  

Question Answer

1. Ketosa carbohydrates     

2. seliwanof test cannot be used in distinguishing fructose from sucrose because it requires a long time in color formation.     

3. If a glucose or maltose solution is heated in a seliwanof reagent for a sufficiently long period of time, a red color will form. These results indicate that the test is negative because in seliwanof reagents it only requires fast time to experience color changes.     

4. Iodine Test     

      Iodine test is used to distinguish starch from glycogen. From the observations it was found that a tube containing 3 mL of starch solution added with 2 drops of water and iodine produced a blue color whereas in a tube containing 3 mL of starch solution added with 2 drops of HCl and iodine produced a light blue color.

6. Conclusion   

§ Molsch test gives positive results on all carbohydrates  

§ Barfoed test gives positive results on monosaccharides namely galactose and fructose.  

§ Seliwanof test gives positive results on carbohydrates containing ketose compounds  

7. Possible Mistakes   

§ When reacting to a solution  

§ When heating the solution  

§ When measuring solutions  

§ At the time of color observation