Fehling's Test

Comparative test reactions ofCarbohydrates

Procedure

Procedure

• In a 10ml vial, put 2ml of Fehling's A solution

• Add 2ml of Fehling's B solution and mix

• This serves as Fehling's reagent. Note and record the color of the resulting agent.

Procedure

• Divide the Fehling's reagent into 4 test tubes of 1ml (15 drops) each.

• Label tubes as: Glucose, Sucrose, Fructose, Lactose

• Add into each tube 1ml(15 drops) of 10% sugar solution respectively and mix thoroughly

Procedure

• Note any changes

• Place all tubes in warm water bath of 60 C⁰

• Remove all tubes once a change is observed in some of the sample.

• Note the changes and record observations.

Results and Observation

Specific Objective

To determine the presence of aldehydes

Color of Reagent

Deep alkaline blue color

• GLUCOSE

• Brick red precipitation

• SUCROSE

• Blue colored solution

• LACTOSE

• Brownish color is formed

Guide Questions

What is the principle involved in Fehling's test?

The presence of aldehydes but not ketones is detected

Cupric ion is reduced to Cuprous ion by the aldehyde and precipitates Cuprous Oxide

Reduction of the deep blue solution of copper(II) to a red precipitate of insoluble copper oxide.

What is the purpose of these tests?

The test is commonly used to determine reducing sugars but is known to be NOT specific for aldehydes.

Brick-red precipitate indicates presence of aldehyde group.

C.What components make up the Fehling's reagent?

• Fehlings reagent consists of two solutions– Soln. A – contains 7% CuSO4 dissolved in distilled

water containing 2 drops of dilute sulfuric acid.– Soln. B – contains 25% KOH and 35% NaOH and

35g of potassium tartarate.• In this test the presence of aldehydes but not

ketones is detected by the reduction of the deep blue soln. Of copper (II) to red precipitate of insoluble copper oxide.

D. Provide the type of equations used in the test

E. Present the sample equation involved in the reaction between Fehling's and the

sample w/c gave positive result

F. PROVIDE OF EXPLAINATION FOR:•The positive results obtained with your samples

RED PRECIPITATE GlucoseLactose

•The negative results obtained with your samplesBLUE SOLUTION

sucrose

POSSIBLE EXPLAINATION:FEHLING A SOLUTION + FEHLING B SOLUTION = BITARTRATOCUPRATE (II) COMPLEX

Positive result indicated by a precipitate of COPPER (I) OXIDE that exihibit red color•Presence of aldehyde groupNegative result do not react•Ring chain

• COPPER (II) SULFATE PENTAHYDRATE

• DISTILLED WATER

• POTASSIUM SODIM TARTRATE

• SODIUM HYDROXIDE• DISTILLED WATER

• DEEP BLUE COMPLEX

GLUCOSE

Has positive result because it has aldehyde group in its open chain

LACTOSE

The ring of the glucose able to open even though the glycosidic bond is present.

So aldehyde is provided

SUCROSE

It did not react because the ring of glucose cannot open due to the glycosidic bond.

It is not a reducing sugar

G. Why is there a need to freshly prepare the Fehling's reagent?

Fehling's solution must be freshly prepared, for, like all other copper test solutions it becomes unreliable in a short time, thereafter indicating sugar where none exists.

H. Why is the Fehling's test not used in analyzing carbohydrates in clinical samples.

Fehling's solution is made up out of two separate solutions, is caustic, and doesn't keep well.

I. Advantages of using Benedict’s reagent instead of Fehling’s reagent:

• More stable• Single solution• No caustic properties

State other disadvantages of using the Benedict's reagent instead of the

Fehling's reagent

Differentiate the 3 kinds of urine: Fasting, Post-Prandial, Random

J. Which sample is the most suitable for use in clinical laboratory test. Why?

K. What is diabetes Milletus?

-Diabetes mellitus (or diabetes) is a chronic, lifelong condition that affects your body's ability to use the energy found in food. Normally, your body breaks down the sugars and carbohydrates you eat into a special sugar called glucose.

-Glucose fuels the cells in your body. But the cells need insulin, a hormone, in your bloodstream in order to take in the glucose and use it for energy.

-With diabetes mellitus, either your body doesn't make enough insulin, it can't use the insulin it does produce, or a combination of both.

K. Differentiate Type 1 from Type 2 diabetes.

Type 1 diabetes is usually diagnosed in children and young adults, and was previously known as juvenile diabetes. Only 5% of people with diabetes have this form of the disease.

-Type 1 diabetes occurs when the immune system mistakenly attacks and kills the beta cells of the pancreas. No, or very little, insulin is released into the body. As a result, sugar builds up in the blood instead of being used as energy.

Type 2 diabetes occurs when the body can’t properly use the insulin that is released (called insulin insensitivity) or does not make enough insulin. As a result, sugar builds up in the blood instead of being used as energy. About 90 per cent of people with diabetes have type 2 diabetes. Type 2 diabetes more often develops in adults, but children can be affected.

K. Is it possible to have sugar diabetes even if no member of your family had

it?

Unlike some traits, diabetes does not seem to be inherited in a simple pattern. Yet clearly, some people are born more likely to develop diabetes than others.

L. Is one considered a diabetic if one obtains a positive result for sugar in a

fasting urine sample. The most common cause of sugar in the

urine, by far, is the presence of diabetes mellitus. There is other potential cause for sugar in the urine which includes the use of certain drugs that may increase urine glucose measurements; and renal glycosuria which is a rare condition in which glucose is excreted in the urine, even when blood glucose levels are normal or low, due to improper functioning of the renal tubules in the kidneys.

Other symptoms of diabetes-sudden weight loss-extreme thirst-feeling tired all the time-feeling very hungry, even after eating-difficulty seeing-urinating more often than usual