The Managing Director of a well-known company on Wall Street thrives on a diet of fruit jam, bread, pasta, and coffee. She exercises intermittently. One day she decides to go to her primary healthcare provider for a routine checkup. The healthcare provider recommends that she take the Benedict's test. Assume that the glucose levels of the patient are high.
• State the results that the test would indicate (specify the color of the solution).
• State the composition and the properties of the ketohexose derived from fruit jam.
• Describe the manner in which ketohexose acts as a reducing sugar in the test.
Well, Benedict's test detects reducing sugars (such as glucose). Benedict's reagent contains blue copper ions (Cu2+) which are reduced to copper (Cu+) in the presence of reducing sugars. These are precipitated as red copper(I) oxide which is insoluble in water.
The color of the solution would be red.
*** State the composition and the properties of the ketohexose derived from fruit jam. ***
I'm not exactly sure what answer this question wants. But anyway...
A ketohexose is a ketone-containing hexose (a six-carbon monosaccharide). In other words, it is a monosaccharide which has a 6 carbon backbone with a ketone group on C2.
Since they have three chiral centers, 8 (2^3 =8) different stereoisomers are possible.
*** Describe the manner in which ketohexose acts as a reducing sugar in the test. ***
When the hemi-acetal or ketal hydroxyl group is free, i.e. it is not locked, not linked to another (sugar) molecule, the aldehyde (or keto-) form (i.e. the chain-form) is available for reducing copper (II) ions. When a sugar is oxidized, its carbonyl group (i.e. aldehyde or ketone group) is converted to a carboxyl group.
To answer your question, let's break it down into three parts:
1. Results of the Benedict's test: The Benedict's test is used to detect the presence of reducing sugars, such as glucose, in a solution. When the Benedict's reagent (a blue solution containing copper sulfate) is heated with a solution containing a reducing sugar, it undergoes a chemical reaction. If the glucose levels of the patient are high, it means there is an excessive amount of glucose in their body. In the Benedict's test, a positive result for high glucose levels would be indicated by a color change from blue to green, yellow, orange, or red. The exact color would depend on the concentration of glucose present.
2. Composition and properties of the ketohexose derived from fruit jam: Fruit jam contains a type of sugar known as fructose, which is a ketohexose. Fructose has a chemical formula of C6H12O6 and belongs to the same family of sugars as glucose (a aldohexose). The main difference between the two is the functional group they have - glucose has an aldehyde group, and fructose has a ketone group. Fructose is naturally found in fruits and is a common sweetener used in many foods and beverages.
3. How ketohexose acts as a reducing sugar in the test: Ketohexoses, like fructose, can act as reducing sugars because they are capable of undergoing a chemical reaction with Benedict's reagent. In the presence of heat, the ketone group of fructose is oxidized by the copper ions in the Benedict's reagent. This oxidation causes a reduction in the copper ions, leading to a color change in the solution. The intensity of the color change indicates the concentration of the reducing sugar (glucose or fructose) present in the solution.
In summary, the Benedict's test would indicate high glucose levels in the patient if the test solution changes color from blue to green, yellow, orange, or red. Fruit jam contains fructose, a ketohexose, which acts as a reducing sugar in the test by undergoing oxidation in the presence of the Benedict's reagent.