SAINT MATHEW SCHOOL

LAB REPORT

BIOLOGY

BENEDICT´S TEST

FROM: Santiago Alvafrez García, Christian Caycedo Vasquez, Edgar Florez Caro, Santiago Rojas Sarmiento

TO: Santiago Schmidt.

9º A

2010-2011

1. INTRODUCTION

The carbohydrates are sugars that can be monosaccharides, disaccharides or polysaccharides. Their function consists on being the sources of energy in the cell. They are composed of carbon, hydrogen and are divided in different groups. They are: hydroxyl group, the ketone group and the aldohyde group. Hydroxyl (-OH) is joined to most of the carbon atoms in the monosaccharide.

The simplest type of carbohydrate is called the monosaccharides, which are crystalline compounds which are dissolved into water. They are sweeter than other types of carbohydrates, in other words they are the simplest sugars (glucose). Their function is to produce fast energy. Some examples are glucose and other simple sugars.

Another type of carbohydrates are the disaccharides which their function is also to produce fast energy as monosaccarides. In other words, they are two monosaccharides joined by dehydratation synthesis. They are more complex sugars which mean they are also sweet to taste like the monosaccharides. Some examples are maltose and sucrose.

The most complex form of sugars of carbohydrates is called polysaccharides. They are composed of thousands of monosaccharides formed by dehydratation reactions. They are not formed of crystalline compounds as monosaccharides and disaccharides. Their function is the storage of energy. Some examples are glycogen and starch.

The Benedict’s test consists on identifying the presence of simple sugars, most of the times you will be asked to identify two or more unknown solutions of different types. The Benedict’s test will always have the same procedure with any solutions that can be compatible with this test.

When comparing two or more solutions, for example two unknown substances A, B and C as the laboratory made in class in the Benedict’s test, sweetness is refered to what solution is sweeter than the other. This changes depending on the types of carbohydrates that are compared.

1. MATERIALS

The materials used in the laboratory were:

Lab Coat

Tape

Benedict’s solution

Water

Test tubes

Fire

Plastic recipient

Pipette

2. OBJECTIVES

To recognize the types of sugars in the unknown solutions A, B, and C using the Benedict’s test, compare them and see what substance is sweeter, what is the intermediate one and what is the lees sweet substance.

3. PROCEDURE

First of all tape was used to mark each of the 3 test tubes,

with A, B and C.

Then Solution A was introduced in test tube A. Then the

same procedure with solutions B and C introduced in test

tubes B and C respectively.

After that step the next one is to introduce five Benedict´s

solution drops in each of the test tubes, A, B and C.

Test tubes are passed to a recipe where all of them

are heated.

Then each of the solutions is taste by one member of

the group.

Finally the last step is to observed changes on the test tubes

and pass to conclude.

4. RESULTS

UNKNOWN BENEDICT´S

Solution A Sweeter - orange

Solution B Normal - yellow

Solution C Less Sweet - blue

5. CONCLUSIONS

With the Benedict´s test the things that can be concluded about it is that the solutions A, B and C change their color depending on how sweet the solution is, the sweeter solution (A) change from its original color blue to orange, the normal solution (B) change from blue to yellow, and the less sweeter one (C) stay on the same color. With that information we can say that the solutions A and B are monosaccharide carbohydrates because they both change their color from its original one, but the C solution doesn´t change its color, it remain as it is because is a polysaccharide.