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An example of a positive Seliwanoff’s test. Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. If a sugar contains an aldehyde group, it is an aldose. This test relies on the principle that, when heated, ketoses are more rapidly dehydrated than ...
Fructose, an example of a ketose. The ketone group is the double-bonded oxygen. In organic chemistry, a ketose is a monosaccharide containing one ketone (>C=O) group per molecule. [1] [2] The simplest ketose is dihydroxyacetone ((CH 2 OH) 2 C=O), which has only three carbon atoms. It is the only ketose with no optical activity.
A positive result of Benedict's test is indicated by a color change from clear blue to brick-red with a precipitate. Generally, Benedict's test detects the presence of aldehyde groups, alpha-hydroxy-ketones , and hemiacetals , including those that occur in certain ketoses .
Ketones may be distinguished from aldehydes by giving a negative result with Tollens' reagent or with Fehling's solution. Methyl ketones give positive results for the iodoform test. [7] Ketones also give positive results when treated with m-dinitrobenzene in presence of dilute sodium hydroxide to give violet coloration.
Ketosis is a metabolic state characterized by elevated levels of ketone bodies in the blood or urine. Physiological ketosis is a normal response to low glucose availability. . In physiological ketosis, ketones in the blood are elevated above baseline levels, but the body's acid–base homeostasis is maintain
Fehling's test can be used as a generic test for monosaccharides and other reducing sugars (e.g., maltose). It will give a positive result for aldose monosaccharides (due to the oxidisable aldehyde group) but also for ketose monosaccharides, as they are converted to aldoses by the base in the reagent, and then give a positive result. [9]
The diastase negative slide will show a magenta staining where glycogen is present within a section of tissue. The slide that has been treated with diastase will lack any positive PAS staining in those locations on the slide PAS staining is also used for staining cellulose. One example would be looking for implanted medical devices composed of ...
Barfoed's test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu 2 O), which forms a brick-red precipitate. [1] [2] RCHO + 2Cu 2+ + 2H 2 O → RCOOH + Cu 2 O↓ + 4H + (Disaccharides may also react, but the reaction is much slower.)