Biology Lab Report 5 Title Appa Appara ratu tuss Mate Materrial ial Method
: Id Identification of of Some ome Bi Biologic gical Import ortant Ch Chemi emical Compounds nds : Ple Pleas asee ref refer er to Biol Biolog ogy y Han Handb dboo ook k pag pagee 112 112 : Plea Please se refer efer to Biol Biolog ogy y Hand Handbo book ok page page 112 112 : Ple Please refer to Biology Handb ndbook page 112
Starch Hypothesis Result
: The colour of iodine iodine will change from from yellow to blue. :
Figure 2: Image of potato after dropping dilute iodine; 100x Discussion
: The blue-black colour of iodine shows that starch is present in the food.
Glucose Hypothesis : The glucose solution will change colour from blue to brick-red colour after testing with Benedict's reagent. Result :
Figure 3: Image of apple after heating.
Discussion : All monosaccharide sugars and certain disaccharides will reduce copper sulphate, producing a precipitate of cuprous oxide on heating. The colour and and density of the precipitate gives rough indication of the amount of sugar; a brown or red precipitate means progressively that more sugar is present while green precipitate indicates lower sugar content.
Sucrose Hypothesis : The sucrose solution will change colour from blue to brick-red colour after being hydrolyse into its constituent monosaccharides and then testing with Benedict's reagent. Result :
Figure 5: Image of sucrose solution after heating. : Sucrose which is disaccharide does not reduce copper sulphate. By Discussion hydrolysing it into monosaccharides, sugar can be detected using Benedict reagent. Cellulose Hypothesis added.
: The wool will change colour into purple when Schultz's solution is
Result
:
Discussion
Figure 7: Image of the wool after dropping Schultz's solution. : Cellulose will stain purple with Shultz’ solution.
Lignin Hypothesis Result
: The colour of the match will turn into red after phloroglucinol is added . :
Discussion
: Lignin or wood will stains red with acidified phloroglucinol
Lipid Hypothesis : Olive oil will produce red stain with Sudan III : Result : Lipid or wood stains red after dipping it into a mixture of phloroglucinol Discussion and hydrochloric acid.. Protein Hypothesis Result
: A brick-red colour precipitate will show up in food that contains protein. :
Discussion : About six drops of Millon’s reagent is added to 2cm³ of an egg albumen and boiled. A brick-red colour indicated presence of protein.
Investigating Unknowns Lipid
Eight more solutions are used to test presence of lipid. Solution Oil palmseed Starch solution Potato tuber Glucose Sucrose Plant Egg albumen Soaked peas
Red stain appears
Protein
LIMITATIONS AND RECOMENDATIONS
1. The test on starch and protein must be carried out at room temperature and for the solution used (biuret and iodide) must not be heated. 2. The test for lipids required dry and grease free test tube. 3. Because Millon Reagent contains mercury salt that is dangerous, we must handle it carefully. 4. The Benedict and Millon test should not be heated directly under the flame because it may spills the solution. 5. For the sucrose, we need to neutralize the acid carefully because we don’t want to turn it into an alkali solution. 6. If the apple is sliced too thick, we might not see the tissue under the microscope, so the apple need to be sliced as thin as possible. 7. For the wood, use the older part of the tree to get a better result. IB DIPLOMA BIOLOGY LAB REPORT PRACTICAL 5 : Identification of some biological important chemical compound : a) To identify some biological important chemical compound b) To know the specific reagent for certain chemical constituent Apparatus : Refer to Biology handbook page 112 Materials : Refer to Biology handbook page 112 Procedure : Refer to Biology handbook from page 113 to page 115 Title Objective
Data Collection: A. STARCH
Reagent Dilute Iodine
Observation The solution’s colour changes from yellow to blue-black
Details 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.
B. GLUCOSE AND FRUCTOSE
Reagent Benedict’s reagent
Observation
Details For glucose Aqueous glucose/fructose is The solution’s colour changes mixed with Benedict's • from blue to brick-red reagent, a solution of copper sulfate, sodium hydroxide, For fructose and tartaric acid. The The solution’s colour changes mixture is heated. • from blue to brick-red 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. SUKROSE
Reagent Benedict’s reagent
Observation With no hydrolysing No colour change •
With hydrolysing The solution’s col• our changes from blue to brick-red
Details 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.
D. CELLULOSE
Reagent Schultz’ solution
Observation The solution’s colour changes from colourless to purple
Details 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 purplecoloured stains indicating that both of them possess cellulose.
E. LIGNIN
Reagent Acidified Phloroglucinol
Observation 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
Details 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.
F. LIPIDS
Reagent
Substances
Sudan Ш
Oil palm and water
Observation Initial Colour Final Colour Two separTwo layers are ate layers are formed formed Top red and botThe top one yeltom dark red low (oil) the bottom colourless (water)
Details
Basically, when Sudan III reacted with lipid, a redstained oil layer separate out and floats
Sudan Ш
Pure oil palm oil
Ethanol
Palm oil and water
The oil palm is pale yellow in colour The entire solution is red in colour
Initially clear, slightly cloudy when water is added
The red settles at the base of the test tube, whilst the top layer is a dark yellow with red droplets suspended in it
on the water surface.
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 precipate. In the experiments, cloudy white precipate formed after some time representing that the palm oil contained lipid.
G. PROTEIN
Reagent Millon’s Reagent
•
Observation Details The solution’s colour changes from Millon tests for phenolic colourless to brick-red -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
Xanthoproteic test
•
Biuret test
•
• •
brick red. The solution’s colour which is deep- Xanthoproteic Acid Test yellow disappears 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. A blue ring appears at the surface of Biuret array is a test for the solution. peptide bonds present in the On shaking, the blue ring disappears. sample such as protein. The solution’s colour turns purple Under alkaline conditions, peptide bonds are cleaved and react with a copper reagent to yield a purple colour.
H. INVESTIGATING UNKNOWNS
Reagent Dilute Iodine
•
Benedict
•
Schultz’ Solution
•
Observation Details No colour changes spotted. The solu- Basically, if starch is mixed tion remains yellow 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. The solution’s colour changes from When benedict reagent is blue to brick-red 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. The solution’s colour changes from Cellulose stained purple colourless to 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.
Acidified Phloroglucinol
•
Sudan III
•
Millon’s Reagent
•
No colour changes spotted. The solu- Acidified phloroglucinol tion colour remains red. can react with lignin to produce red stain. However, not all structure in the unknown actually reacted with the reagent to produce red stained. Only certain part such as skin and pips stained red with the reagent The solution’s colour changes to Fundamentally, a red blurred red. stained oil layer that separate out and float on the water surface indicates the existence of protein in the solution. Still, when Sudan III is added up to the solution, a blurred redstained oil layer appears. This mean, there is not much lipid exist in the unknown. The solution’s colour changes from Hypothetically, when colourless to blurred brick-red 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.
MICROSCOPE OBSERVATION
Chemical compound
Reagent
Fructose
Benedict’s reagent
Observation under magnification of x100
The Light photomicrograph drawing of cell of apple
Lignin
Sudan III
The Light photomicrograph drawing of xilem of plant stem
Protein
Millon’s reagent
Light photomicrograph drawing of cell of pea
Benedict’s reagent
The Light photomicrograph drawing of unknown cell
Unknown
Sudan III
The Light photomicrograph drawing of unknown cell
Millon’s reagent
The Light photomicrograph drawing of unknown cell
DISCUSSION
1) Benedict’s reagent was used to determine the presence of reducing sugar in the substances that had been tested. 2) Millon’s reagent was used to determine the presence of protein in the substances that had been tested. 3) Iodine was used to determine the presence of starch in the substances that had been tested. 4) Schultz’ solution was used to determine the presence of cellulose in the substances that had been tested. 5) Hydrochloric acid was used to hydrolyse sucrose to glucose which is a reducing sugar. 6) Acidified phloroglucinol was used to determine the presence of lignin in the substances that had been tested. 7) Sudan III reagent was used to determine the presence of lipid in the substances that had been tested.
LIMITATIONS AND RECOMENDATIONS
8. The test on starch and protein must be carried out at room temperature and for the solution used (biuret and iodide) must not be heated. 9. The test for lipids required dry and grease free test tube. 10. Because Millon Reagent contains mercury salt that is dangerous, we must handle it carefully. 11. The Benedict and Millon test should not be heated directly under the flame because it may spills the solution. 12. For the sucrose, we need to neutralize the acid carefully because we don’t want to turn it into an alkali solution. 13. If the apple is sliced too thick, we might not see the tissue under the microscope, so the apple need to be sliced as thin as possible. 14. For the wood, use the older part of the tree to get a better result.
CONCLUSION
Biological chemical compounds can be identified by using certain scientific methods.
