NAME: Michael Timson

DATE: 11/09/2014

FORM: L6-4

LAB: #1

SUBJECT: Biology

TEACHER’S NAME: Miss Sarjeant

TOPIC: Food Test

AIM: To determine the nutrients present in various solutions tested.

INTRODUCTION:

Carbohydrates (hydrated carbon) are organic compounds. Their molecules contain

carbon together with hydrogen and oxygen and have a general formula Cx(H2O)y. There are

three groups of carbohydrates. These groups are monosaccharaides, disaccharides and

polysaccharides. Monosaccharaides (e.g. glucose) are reducing sugars. They readily reduce

other chemicals. Unlike monosaccharaides, some disaccharides (e.g. sucrose) are non-

reducing sugars while maltose and lactose are reducing sugars. They are molecules whose are

formed when two hexose sugar molecules react together by means of a condensation reaction

(a reaction in which two smaller molecules join together to form a larger one and releases a

molecule of H2O. Polysaccharides (e.g. starch) are carbohydrates whose molecules condenses

together to form long chain also known as condensation polymers (a substance with

molecules which are long chains built up by the condensation of many similar units.

Similar to carbohydrates, lipids are organic compounds whose molecules are

composed of carbon, hydrogen and oxygen atoms. Common Lipids are fats and oils. They are

also known as triglycerides. A molecule of glycerol condenses and combines with three fatty

acid molecules to form triglycerides. SSS, also known as Saturated lipids, are lipids with

Single bonds and is found in the Solid state at room temperature. DUL are lipids with Double

bonds and thus are Unsaturated lipids. They are found in the Liquid state at room

temperature.

Proteins are large biological molecules, or macromolecules, consisting of one or more

long chains of amino acid residues. The monomers of protein are amino acids and are the

composed of carbon, hydrogen and oxygen as well as nitrogen atoms. Some amino acids

contain atoms of sulphur. These long chains are known as polypeptide. Two amino acids

condense together to form a dipeptide and the bond linking the amino acids are known as a

peptide bond. Further condensation between amino acids leads to the formation of the long

chains.

All organisms must be supplied with a source of energy. This energy can be used for

different reasons. Such reasons include maintenance, growth and repair of the body. Animals

can only obtain energy from the food they consume. By consuming different foods they

obtain different materials called nutrients. These nutrients comprises of protein,

carbohydrates, lipids/fat, minerals, vitamins, water and fibre. It is important to test food in

order to know what types of nutrients and minerals are located in the various foods that are

consumed. By knowing what are the major organic nutrients found in foods, there is now a

better understanding of what and how much is the right mount to consume of each food.

APPARATUS/MATERIALS

5 test tubes Water Bath

Dilute HCl Sodium bicarbonate

Sodium Hydroxide Copper (II) Sulphate

Ethanol Iodine

Benedict’s Solution 2 Droppers

3 Syringes Test Tube Holder

Test Tube Rack 2 Beakers

Measuring cylinder Distilled Water

Solution X Stirring Rod

METHOD:

Reducing Sugar

1. 2cm3 of Solution X was placed into a test tube and 2cm3 of Benedict’s solution was added

2. The mixture was shaken and brought to boil.

Non Reducing Sugar

1. 2cm3 of Solution X was placed into a test tube and 1cm3 of dilute HCl was added

2. A small amount of NaHCO3 was added to neutralize the mixture and 2cm3 of benedict’s solution was then added.

3. The mixture was shaken and brought to a boil.

Iodine Test

1. 2cm3 of Solution X was added in a test tube then 2 drops of iodine.

Emulsion Test

1. 2cm3 of Solution X was added in a test tube containing 2cm3 of ethanol.

2. It was then shaken vigorously to dissolve the lipid.

3. 2cm3of H2O was then added.

BIURET TEST

1. 2cm3 of Solution X was added into a test tube.

2. 2cm3 of NaOH was then added.

3. 1 drop of CuSO4 was added and mixed.

RESULTS

TABLE SHOWING TEST DONE ON THE SOLUTIONS AND THEIR OBSERVATIONS

Food Test Observation Conclusion

Reducing Sugar A brick red solution is formed in the original blue solution

Presence of a reducing sugar

Non reducing No changes occurred No reducing sugar present

Iodine Test A blue black colour is produced Presence of Starch

Emulation Test A cloudy white suspension is seen after the water was added

Fats and lipids

Biuret Test Solution turns from blue to violet (purple).

Protein

DISCUSSION:

In the first test, solution x was tested for reducing sugars. After the test was conducted a brick

red solution was formed in the original blue solution. This indicated the presence of glucose

thus indicates that glucose was present in the first sample of solution x. The chemistry behind

Benedict's test involves reduction of Cu2+ ions present in Benedicts solution to Cu+ by

reducing sugars. These substances reduce the cupric (Cu2+) ions present in Benedict's

solution to cuprous (Cu+) ions, which can be detected by the formation of a brick red

precipitate of Cu2O. Benedict’s test was also used to test the presence of a non-reducing

sugar. After the test, no changes occurred. This indicated that no non-reducing sugars were

present in solution X and thus the solution remained blue. After, solution X was tested for

reducing sugars; it was later tested for starch by conducting the iodine test. From this test, a

blue black colour was produced. This clearly showed the presence of starch in the solution.

Amylose in starch is responsible for the formation of a deep blue color in the presence of

iodine. The iodine molecule slips inside of the amylose coil. Iodine - KI Reagent: Iodine is

not very soluble in water; therefore the iodine reagent is made by dissolving iodine in water

in the presence of potassium iodide. This makes a linear tri-iodide ion complex with is

soluble that slips into the coil of the starch causing an intense blue-black colour. After the

iodine test, the emulsion test was then conducted. From this test, a white suspension was seen

after the water was added. This observation was a result of the fats and lipids present in the

solution. After the emulsion test followed the biuret test. This test was used to test the

presence of protein. The solution turned from blue to violet (purple) which meant that the

presence of protein was positive. The biuret reaction is based on the reduction of Cu2+ to

Cu+ which then complexes with the nitrogen atoms on the peptide bonds. This reaction is

carried out at high pH and gives a violet colour. It is the amide bond (common to all proteins)

which is responsible for the colour.

CONCLUSION: Based upon the experiment conducted and the results obtained, it is

concluded that Solution X contained no non-reducing sugars but contain reducing sugars,

starch, fats and lipids and protein.