Detection Of Biological Molecules Essay Research Paper

Detection Of Biological Molecules Essay, Research Paper

Detection of Biological Molecules

Introduction: Without carbon, nitrogen, hydrogen, sulfur, oxygen and phosphorus,

life wouldn’t exist. These are the most abundant elements in living organisms.

These elements are held together by covalent bonds, ionic bonds, hydrogen bonds,

and disulfide bonds. Covalent bonds are especially strong, thus, are present in

monomers, the building blocks of life. These monomers combine to make polymers,

which is a long chain of monomers strung together. Biological molecules can be

distinguished by their functional groups. For example, an amino group is

present in amino acids, and a carboxyl group can always be found in fatty acids.

The groups can be separated into two more categories, the polar, hydrophilic,

and the nonpolar, hydrophobic. A fatty acid is nonpolar, hence it doesn’t mix

with water. Molecules of a certain class have similar chemical properties

because they have the same functional groups. A chemical test that is sensitive

to these groups can be used to identify molecules that are in that class. This

lab is broken down into four different sections, the Benedict’s test for

reducing sugars, the iodine test for the presence of starch, the Sudan III test

for fatty acids, and the Biuret test for amino groups present in proteins. The

last part of this lab takes an unknown substance and by the four tests,

determine what the substance is.

BENEDICT’S TEST

Introduction: Monosaccharides and disaccharides can be detected because of

their free aldehyde groups, thus, testing positive for the Benedict’s test.

Such sugars act as a reducing agent, and is called a reducing sugar. By mixing

the sugar solution with the Benedict’s solution and adding heat, an oxidation-

reduction reaction will occur. The sugar will oxidize, gaining an oxygen, and

the Benedict’s reagent will reduce, loosing an oxygen. If the resulting solution

is red orange, it tests positive, a change to green indicates a smaller amount

of reducing sugar, and if it remains blue, it tests negative.

Materials: onion juice5 test tubes1 beaker potato juice

rulerhot plate deionized waterpermanent

marker5 tongs glucose solutionlabels starch solution6 barrel

pipettes Benedict’s reagent5 toothpicks

Procedure: 1.Marked 5 test tubes at 1 cm and 3 cm from the bottom. Label test

tubes #1-#5. 2.Used 5 different barrel pipettes, added onion juice up

to the 1 cm mark of the first

test tube, potato juice to the 1 cm mark of the second, deionized water

up to the 1

cm mark of the third, glucose solution to the 1 cm mark of the fourth,

and the

starch solution to the 1 cm mark of the fifth test tube. 3.Used the

last barrel pipette, added Benedict’s Reagent to the 3 cm mark of all 5

test tubes and mix with a toothpick. 4.Heated all 5 tubes for 3

minutes in a boiling water bath, using a beaker, water, and

a hot plate. 5.Removed the tubes using tongs. Recorded colors

on the following table. 6.Cleaned out the 5 test tubes with deionized

water.

Data:

Benedict’s Test Results

Discussion: From the results, the Benedict’s test was successful. Onion juice

contains glucose, and of course, glucose would test positive. Starch doesn’t

have a free aldehyde group, and neither does potato juice, which contains starch.

Water doesn’t have glucose monomers in it, and was tested to make sure the end

result would be negative, a blue color.

IODINE TEST

Introduction:The iodine test is used to distinguish starch from

monosaccharides, disaccharides, and other polysaccharides. Because of it’s

unique coiled geometric configuration, it reacts with iodine to produce a blue-

black color and tests positive. A yellowish brown color indicates that the test

is negative.

Materials: 6 barrel pipettespotato juicestarch solution 5 test

tubeswateriodine solution onion juice

glucose solution5 toothpicks

Procedure: 1.Used 5 barrel pipettes, filled test tube #1 with onion juice,

second with potato

juice, third with water, fourth with glucose solution, and fifth with

starch solution. 2.Added 3 drops of iodine solution with a barrel pipette,

to each test tube. Mixed

with 5 different toothpicks. 3.Observed reactions and recorded

in the table below. Cleaned out the 5 test tubes. Data:

Iodine Test Results

Discussion:The iodine test was successful. Potato juice and starch were

the only two substances containing starch. Again, glucose and onion juice

contains glucose, while water doesn’t contain starch or glucose and was just

tested to make sure the test was done properly.

SUDAN III TEST

Introduction: Sudan III test detects the hydrocarbon groups that are remaining

in the molecule. Due to the fact that the hydrocarbon groups are nonpolar, and

stick tightly

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