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GENERAL TEST FOR

CARBOHYDRATES: MOLISCHTEST AND IODINE TEST

Performed by: Group 3

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SPECIFIC OBJECTIVE:

To test for the presence ofcarbohydrates.

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Preparation of Sap!e "C#i$%en !i&er e'tra$t(

a. Get a thumb-sized portion of chicken liver and nely cut orshred it with scissors.

b. Transfer the cut liver into a mortar and rind it with a pestleuntil it reaches a semi-li!uid consistency.

c. Transfer the liver into a test tube and add "#ml water and"ml of #."$ acetic acid.

d. %eat the mi&ture for 3# mins in a boilin water bath toprecipitate the proteins.

e. 'hile warm( the mi&ture should be ltered usin lter

paper. )ollect the ltrate to be used in the *olisch and +odinetests.

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)* Mo!i+$# Te+t

a. Prepare 3 test tubes and label them as follows:,lucose( ,carraeenan( and ,chicken liver

b. +n the "sttube( put ml of the "#$ lucosesolution.

c. +n the ndtube( put a pinch /mono size0 ofelatin and add ml of hot distilled water todissolve. )ool to room temperature.

1. +n the 3rdtube.( put ml of chicken liver e&tract.

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e. 2dd two drops of the *olischreaent into each tube and mi&thorouhly.

f. sin a dropper( slowly add "ml/"4 drops0 of concentrated sulfuric

acid alonside each tube to create aninterface with the mi&ture.

. 5ote what is formed in the

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RES,LTS

Glucose)araeenan )hicken 7iver

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RES,LTS

SAMPLES OBSERVATIONS

Glucose 8iolet9purple rin

)arraeenan 8iolet rin

)hicken liver e&tract 7iht violet rin

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-* Io.ine Te+t

a. Prepare 3 test tubes and label them as follows:,starch( ,carraeenan( and ,chicken liver

b. +n the "sttube( put "ml of cooked potato starch

mi&ture.

c. +n the ndtube( put a pinch /mono size0 ofelatin and add ml of hot distilled water to

dissolve.

d. +n the 3rdtube( put ml of chicken liver e&tract.

e. 2dd a drop of iodine solution to each of the tubesand mi& thorouhly.

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f. 5ote the color of the resultin

mi&ture.

. 'arm the 3 tubes in water bath

/#;c0 until a chane is observed inone of the tubes.

h.

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RES,LTS

+odine was combinedTube "/starch0: =lack precipitate

Tube /)arraeenan0: Green color

Tube 3/)hicken 7iver0:7iht

>ellow

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?amples were heated and cooled:Tube "/starch0: >ellow with =lack

precipitate

Tube /)arraeenan0: Green color

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Tube 3/)hicken 7iver0:7iht yellow

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RES,LTS

SAMPLES

OBSERVATIONS

=efore%eatin

2fter %eatin ;n )oolin

Potato starch black>ellow w9

blackprecipitate

>ellow w9 blackprecipitate

)arraeenan reen reen reen

)hicken 7iver @&tract7iht

yellow7iht yellow 7iht yellow

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MOLISCH TEST

2. 'hat is the principle involved in the*olisch testA

)oncentrated sulphuric acid causes

dehydration of all carbohydrates to ive,f/rf/ra! compounds( that react with 01

nap#t#o!/*olischBs reaent0 ivin aviolet or purple colored comple&.

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=. 'hat is the purpose of this testA

+t is a eneral test for the presence ofcarbohydrates.

+t is used widely as compared to other tests

because before every specic test fordiCerent carbohydrates( a eneral test isimportant and is performed via *olisch test.

This test is positive for all types ofcarbohydrates whether free or in combinedform like lycoproteins( lycolipids( etc.

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). Provide the type of e!uation used inthe test.

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1. 'hat reaents were used in the *olischBstestA ?tate the purpose of each component.

The Mo!i+$# rea2ent contains alpha-naphtholdissolved in ethanol. )arbohydrates( specicallymonosaccharides are dehydrated in the presenceof $on$entrate. +/!p#/ri$ a$i. to form analdehyde known as f/rf/ra! /pentoses0 orhydro&ymethyl furfural /he&oses0 derivatives.Polysaccharides and disaccharides are convertedto monosaccharides via hydrolysis of the

lycosidic bonds. The monosaccharide9furfuralderivatives then react with "-naphthol in *olischreaent via a condensation reaction to form apurple coloured compound.

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@. Provide a possible e&planation for:

the positive results obtained with yoursamples9s

- 2 positive result is indicated by theappearance of a purple rin in the interface

between the acid and test layers. +t indicatesthe presence of carbohydrates.

the neative results obtained with your

sample9s- There is no formation of a purple rin. Thismeans that there is no carbohydrate present inthe sample.

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IODINE TEST

=a. 'hat is the principle involved in the iodine testA

1istinuish between monosaccharide(disaccharides and polysaccharide( you shouldperform iodine test. This test would be positive forpolysaccharide and neative for mono anddisaccharides.

'hen iodine dissolved in potassium iodidesolution react with starch or lycoen( it reactwith it and the color of solution is chanes(indicatin the presence of these polysaccharides.

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?ome polysaccharides have have theproperty of adsorption for iodine. ?o(

they adsorb iodine and ivecoloration.

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=. @&plain the color noted when:

+odine was combined with the samplesD ". Eirst test tube : =lack color

. ?econd test tube : Green color

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3. Third test tube : 7iht >ellow

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the mi&ture of iodine and eachsample were heatedD

Eirst test tube : >ellow with blackprecipitate

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. ?econd test tube : Green

3. Third test tube : liht yellow

the heated mi&ture of iodine and each sample were cooled.The same with the heated samples

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). 'hat is the importance of the iodine testA 'hatcarbohydrates were identied in you samplesA

+odine test is done to test for the presence of starch.The basic principle of this test is that when an iodinesolution /i.e.( a!ueous solution of potassium iodide0

comes in contact with starch( the solution turns blueblack in color. ?tarch( which is found in carbohydraterich foods like potatoes( rice( corn( and barley can beseparated into two fractions .

The )arbohydrates found in the sample were amyloseand amylopectin. +n the presence of iodine( amylose instarch forms a deep blue color. 2s starch is nothin butcarbohydrates( the test for carbohydrates is same as

that of starch.

1 ?tructurally how are amylose and

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1. ?tructurally( how are amylose andamylopectin diCerent from each anotherAErom lycoenA Erom celluloseA %ow do

their structural characteristics aCect theirsolubility in waterA

2mylose is known to be continuous. ;n the otherhand( 2mylopectin is branchin. +t is also foundonly on plants.

?imilarities: They are all POLYSACCHARIDES Eormed in lycosidic bonds

Primary functions are enery storae and food reserve.

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1iCerence: the diCerence has to do with the branchin.

Glucose molecules are linked in straiht chainsvia the alpha "(F bond.

Glycoen is more hihly branched thanamylopectin.

%umans can make their own lycoen in the liverand muscles. =ut it can also be made bylycoenesis within the brain and stomach.

)ellulose is the main component in cell walls

which ives plant their structure. )ellulose is made up of o&yen( hydroen and

carbon as well as a derivation of lucose. Theirstructural characteristic is aCected by their

hydroen bondin.

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Their structural characteristic is aCected bytheir hydroen bondin.