NAME: MOHD SAFWAN BIN MOHD SHAFIECLASS:M04N

PRACTICAL 5

Title : Identification of some biological important chemical compoundObjective : a) To identify some biological important chemical compound

b) To know the specific reagent for certain chemical constituentApparatus : Refer to Biology handbook page 112Materials : Refer to Biology handbook page 112Procedure : Refer to Biology handbook from page 113 to page 115

Data collection:

PART 1

A.STARCH

Reagent Substances Observation Details

Dilute iodine

Starch suspension The solution’s colour changes from yellow to blue-black.

When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. But it seems that the iodine gets stuck in the soluble starch. The starch forces the iodine atoms into a linear arrangement in the central groove of the soluble starch coil, giving the complex its intense blue color.

Potato Tuber Potato tuber were coloured to blue-black

Under microscope observation, all cells were coloured into blue-black

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B.GLUCOSE

Reagent Subtances Observation DetailsBenedict’s

reagentGlucose solution The solution’s colour

changes from clear blue to cloudy green to yellow and finally to a red precipitate when boiled.

Aqueous glucose is mixed with Benedict's reagent, a solution of copper sulfate, sodium hydroxide, and tartaric acid. The mixture is heated. Carbohydrates which react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitate of copper (I) oxide are classified as reducing sugars.

C. FRUCTOSE

Reagent Subtances Observation Details Benedict’s reagent

Apple Cell change colour from blue-black to brown

The microscope observation is attached at the back.

Aqueous fructose is mixed with Benedict's reagent, a solution of copper sulfate, sodium hydroxide, and tartaric acid. The mixture is heated. Carbohydrates which react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitate of copper (I) oxide are classified as reducing sugars.

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D. SUCROSE

Reagent Subtances Observation DetailsBenedict’s

reagentSucrose solution With no hydrolysing

No colour change

With hydrolysing The solution’s

colour changes from blue to green to yellow and finally to brick-red

Sucrose is disaccharide that does not reduce copper sulphate. Therefore, it should be hydrolysed into its constituent monosaccharides before testing it with benedict’s reagent. Sucrose then will react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitate of copper (I) oxide.

E. CELLULOSE

Reagent Subtances Observation DetailsSchultz’ solution

Cotton wool Cotton is high of cellulose. Therefore it should be stained to purple. However, the changes of colour of cotton are not clear.

When the solutions tested on a plant tissue and observed under microscope cell walls of the tissue is purple in colour

Schultz’ solution reacted with cellulose to produced purple stained. In the experiment, when the reagent is put on the cotton and also in the solution, both of the produce purple-coloured stains indicating that both of them possess cellulose.

F. LIGNIN

Reagent Subtances Observation DetailsAcidified

phloroglucinolWood When tested on

toothpick, colour of toothpick becomes red

When solution is tested on plants item, colour of xilem seen to be red in colour

Acidified phloroglucinol can react with lignin to produce red stain. After testing with toothpick and xilem, both of them stained red indicating that both of them contain lignin.

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G. LIPIDS

Reagent Substances Observation Details

Sudan Ш Oil palm and water

Colour (initial) Colour (final)Basically, when Sudan III reacted with lipid, a red-stained oil layer separate out and floats on the water surface.

Two separate layers are formed

The top one yellow (oil) the bottom colourless (water)

Two layers are formed

Top red and bottom dark red

Sudan Ш Pure oil and palm oil

The oil palm is pale yellow in colour

The entire solution is red in colour

The red settles at the base of the test tube, whilst the top layer is a dark yellow with red droplets suspended in it

Ethanol Palm oil and water

Initially clear, slightly cloudy when water is added

A thin top, layer of cloudy, light yellow, followed by a long rung of cloudy white and a thin bottom layer of dear yellow

Ethanol reacted with lipids to form a cloudy white precipitate. In the experiments, cloudy white precipitate formed after some time representing that the palm oil contained lipid.

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H. PROTEIN

Reagent Substances Observation DetailsMillon’s reagent

Albumen Brick-red precipitate appears. Millon tests for phenolic -OH group present in sample such as protein. Millon’s reagent is prepared from mercuric and mercurous nitrate in nitric acid. When protein is heated with Millon's reagent, a white precipitate is formed and on heating changes to brick red.

Pea Before heated, the sample was creamy white in colour. However, after heated, the colour of the sample change to yellowish browning.

Xanthoproteic test

Nitric acid

The solution’s colour which is deep-yellow disappears.

Xanthoproteic Acid Test tests R Group. This is a test for specific functional groups that a positive test is formation of a deep-yellow orange or orange-red color. A deep-yellow partial precipitate, which disappears, on shaking, indicates protein.

Biuret test Potassium hydroxide

A blue ring appears at the surface of the solution.

On shaking, the blue ring disappears.

The solution’s colour turns purple

Biuret array is a test for peptide bonds present in the sample such as protein. Under alkaline conditions, peptide bonds are cleaved and react with a copper reagent to yield a purple colour.

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I. INVESTIGATING UNKNOWN

Reagent Component Observation DetailsDilute iodine Content No colour changes

spotted. The solution remains yellow

Basically, if starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. However, when iodine is dropped into the unknown solution, no colour changes which is from yellow to blue-black is spotted. Therefore, there is no starch in the unknown.

Husk No colour changes spotted. The solution remains yellow

Seeds No colour changes spotted. The solution remains yellow

Benedict reagent

Content The solution’s colour changes from blue to green to yellow to brick-red

When benedict reagent is dropped into the unknown solution, the colour changes. This mean the unknown do has glucose/carbohydrates in it. This is because Carbohydrates react with Benedict's reagent to reduce the blue copper (II) ion to form a brick red precipitate of copper (I) oxide. Even so, the unknown solution does not have sucrose in it because red-brick precipitate can be obtained without hydrolysing it.

Husk The solution’s colour changes from blue to green to yellow to brick-red

Seeds The solution’s colour changes from blue to green to yellow to brick-red

Schultz’s solution

Content The solution’s colour changes from colourless to purple

Cellulose stained purple with Schultz’ solution. Then, when the reagent is being tested with the unknown solution, the solution’s colour changes from colourless to purple. For this reason, the unknown should comprise cellulose in it.

Husk No colour changes spotted. The solution remains colourless.

Seeds No colour changes spotted. The solution remains colourless.

Acidified phloroglucinol

Content No colour changes spotted. The solution colour remains red.

Acidified phloroglucinol can react with lignin to produce red stain. However, not all structure Husk No colour changes

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spotted. The solution colour remains red.

in the unknown actually reacted with the reagent to produce red stained. Only certain part such as content and husk stained red with the reagent

Seeds The solution changes colour from red to colourless.

Sudan III Content The solution changes colour from paint yellow to blurred red.

Fundamentally, a red-stained oil layer that separate out and float on the water surface indicates the existence of lipid in the solution. Still, when Sudan III is added up to the solution, a blurred red-stained oil layer appears. This mean, there is not much lipid exist in the unknown.

Husk No colour changes spotted. The solution remains paint yellow

Seeds No colour changes spotted. The solution remains paint yellow

Millon’s reagent

Content The solution’s colour changes from colourless to blurred brick-red

Hypothetically, when protein is heated with Millon's reagent, a white precipitate is formed and on heating changes to brick red. However, when the unknown is heated, a blurred brick-red precipitate produced, meaning that the amount of protein in the unknown is not much.

Husk No colour changes spotted. The solution remains colourless.

Seeds The solution’s colour changes from colourless to blurred brick-red

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PART 2

Chemical compound

Reagent Observation

Fructose Benedict’s reagent

Title: Light photomicrograph drawing of cell of apple

Magnification: x100Lignin Sudan III Title: Light photomicrograph drawing of xilem of

plant stem

Magnification: x100Protein Millon’s

reagentTitle: Light photomicrograph drawing of cell of pea

Magnification: x100

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Unknown Benedict’s reagent

Title: Light photomicrograph drawing of unknown cell

Magnification: x100 Sudan III Title: Light photomicrograph drawing of unknown cell

Magnification: x100 Millon’s

reagentTitle: Light photomicrograph drawing of unknown cell

Magnification: x100

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PART 3

Conclusion

1. Potato tuber contained starch because the dilute iodine change colour from yellow to blue-black

2. Apple contained glucose and sucrose when brick red precipitates appear when tested with benedict’s reagent

3. Apple contained fructose because the cells change colour from blue to brown after heated

4. Stem cells containing cellulose since the cell stained in purple.5. Stem cells contained lignin since the cell stained red in colour.6. Oil palm seeds contained lipids7. Albumen and pea contained lipid because brick red precipitate appears when tested

with Millon’s reagent.8. For the unknown test, the unknown contained high concentration of fructose, glucose

and sucrose because brick red precipitates appear when tested with Benedict’s reagent. However, apple contained low quantity of cellulose and lignin since the change of colour of the indicators are blurred. Apple also contained low quantity of lipid and protein.

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