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If benedicts reagent turns red what substance is present?
If Benedict's reagent turns red after adding it to a solution, it indicates the presence of reducing sugars such as glucose or fructose. The red color is a result of the reduction of copper (II) ions in the reagent to copper (I) oxide by the reducing sugars.
Explain the chemical mechanism for detecting indole in a bacterial culture?
Indole is extracted from the medium and into the reagent layer (Kovac's) by the acidified butyl alcohol component and forms a complex with the p-dimethylaminobenzaldehyde, yielding the cherry red color seen when the culture is indole positive.
An unknown sample is tested with both biuret reagent and benedicts reagent both test result in a blue color what has been learned and why are these called negative results?
That the unknown sample is not a monosaccharide and is does not contain peptide bonds (is not a protein). This is because they both produced negative results because Biuret tests positive in solutions that contain peptide bonds and will turn a violet color. Benedict reagent reacts to monosaccharides and will turn green-reddish orange when a monosaccharide is present. Neither of these things happened so the results are negative.
How IMViC tests differentiate Escherichia coli from Enterobacter aerogenes?
Indol Test ( Kovac's Reagent): E.a. = negative = yellow/gold ring at meniscus; as for E.c. = positive = red ring at meniscus (immediate change). Methyl Red Test (Methyl Red Reagent): E.a. = negative = yellow = pH > 7.0; as for E.c. = red color = pH < 5 (immediate change). Vogues-Proskauer Test (Napthol + KOH Reagent): E.a. = positive = reddish color (not immediate change); as for E.c. = negative = brown/yellow (straw color). Citrate (Bromothymol Blue Reagent - alkaline pH): E.a. = positive = blue color + growth; as for E.c. = negative = green color.
What is Oxidase test results for bacillus subtilis?
Bacillus subtilis is positive for the oxidase test. This means that it has the enzyme cytochrome c oxidase, which is needed for the bacterium to produce energy through aerobic respiration. The positive result is indicated by the appearance of a color change (usually dark purple) on the test strip after adding the reagent.
Does using benedicts reagent on honey produce a positive result?
Yes, Benedict's reagent can produce a positive result when used on honey containing reducing sugars, such as glucose or fructose. The reagent will change color from blue to green, yellow, orange, or red depending on the concentration of reducing sugars present in the honey.
Indication of a negative result with Bial's Reagent?
A negative result with Bial's reagent will show no color change, indicating the absence of pentoses in the test sample. This can be confirmed by the lack of a green color formation, which is characteristic of a positive result when pentoses are present.
If benedicts reagent turns red what substance is present?
If Benedict's reagent turns red after adding it to a solution, it indicates the presence of reducing sugars such as glucose or fructose. The red color is a result of the reduction of copper (II) ions in the reagent to copper (I) oxide by the reducing sugars.
What substrate gives a positive reaction for benedicts reagent?
Reduction of Benedict's reagent occurs with reducing sugars such as glucose, fructose, and galactose, giving a positive test result. This test is used to detect the presence of reducing sugars in various food products.
When glycogen is added to benedicts reagent why would it remains blue?
Although glycogen is a carbohydrate, it is classified under POLYSACCHARIDES which are non-reducing sugars. Benedict's reagent is used to test for the presence of non-reducing sugars. The positive result for this is a brick-red precipitate or solution. It remained blue (which is negative) due to fact that ALL POLYSACCHARIDES (such as glycogen) ARE NON-REDUCING SUGARS > I'm a Nursing Student. >M.J.T.M.E.
Will hydrolysed dextrine give positive response to Benedict test?
Yes, it should. Benedicts test will be positive for reducing sugars, and since glucose is such a sugar, and would be a product of dextrin hydrolysis, you should get a positive result with Benedicts reagent.
Why Tollens reagent does not react with ketone?
Tollens reagent is a mild oxidizing agent that reacts with aldehydes to produce a silver mirror. Ketones, however, do not have a hydrogen atom bonded to the carbonyl group, making them resistant to oxidation by Tollens reagent. As a result, ketones do not react with Tollens reagent.
Why did the potato juice test negative in the benedict's reagent test?
The potato juice likely tested negative in the Benedict's reagent test because it does not contain reducing sugars, such as glucose or fructose, which are necessary to form a positive reaction with Benedict's reagent. Potatoes primarily consist of starch, a polysaccharide that is not a reducing sugar, explaining the negative test result.
What is a good conclusion of the benedicts test?
A good conclusion of the Benedict's test would be to state whether the test result was positive or negative for reducing sugars. Positive result would indicate the presence of reducing sugars, while a negative result would suggest their absence. This information can be important for further analysis or identification of certain carbohydrates.
Explain the chemical mechanism for detecting indole in a bacterial culture?
Indole is extracted from the medium and into the reagent layer (Kovac's) by the acidified butyl alcohol component and forms a complex with the p-dimethylaminobenzaldehyde, yielding the cherry red color seen when the culture is indole positive.
Effect of formaldehyde to schiff's reagent?
Formaldehyde reacts with Schiff's reagent to produce a colorless complex, inhibiting its ability to detect aldehydes or ketones in tissues. This can interfere with the staining process in histology studies, preventing accurate visualization of certain cellular components.
An unknown sample is tested with both biuret reagent and benedicts reagent both test result in a blue color what has been learned and why are these called negative results?
That the unknown sample is not a monosaccharide and is does not contain peptide bonds (is not a protein). This is because they both produced negative results because Biuret tests positive in solutions that contain peptide bonds and will turn a violet color. Benedict reagent reacts to monosaccharides and will turn green-reddish orange when a monosaccharide is present. Neither of these things happened so the results are negative.
