Which carbohydrates give a reducing sugar after hydrolysis?

Asked By: Kali Altabella | Last Updated: 13th April, 2020
Category: healthy living nutrition
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The monosaccharides can be divided into two groups: the aldoses, which have an aldehyde group, and the ketoses, which have a ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars. The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars.

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Likewise, people ask, why is hydrolyzed sucrose a reducing sugar?

Hydrolysis is catalyzed by strong acids and certain enzymes. For example, when sucrose, a non-reducing sugar, is hydrolyzed the reducing sugars glucose and fructose are formed. Likewise, when starch is hydrolyzed, the reducing sugar glucose is produced.

Secondly, is lactose a reducing sugar? Lactose is composed of a molecule of galactose joined to a molecule of glucose by a β-1,4-glycosidic linkage. It is a reducing sugar that is found in milk.

In this way, what is the reducing end of a sugar?

In the instance of disaccharides, structures that possess one free unsubstituted anomeric carbon atom are reducing sugars. The end of the molecule containing the free anomeric carbon is called the reducing end, and the other end is called the nonreducing end.

Why does sucrose not react with Benedict's solution?

Because Sucrose (table sugar) contains two sugars (fructose and glucose) joined by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to alpha-hydroxy-ketone form. Sucrose is thus a non-reducing sugar which does not react with Benedict's reagent.

38 Related Question Answers Found

Is sucrose Dextrorotatory or Levorotatory?

Sucrose is dextrorotatory, but the resulting mixture of glucose and fructose is slightly levorotatory, because the levorotatory fructose has a greater molar rotation than the dextrorotatory glucose.

What happens when sucrose is hydrolyzed?

When sucrose is hydrolyzed it forms a 1:1 mixture of glucose and fructose. It is called invert sugar because the angle of the specific rotation of the plain polarized light changes from a positive to a negative value due to the presence of the optical isomers of the mixture of glucose and fructose sugars.

Is honey a reducing sugar?

A reducing sugar is a type of sugar with an aldehyde group. Reducing sugars on honey include mainly fructose and glucose. Significantly, sucrose is not a reducing sugar.

How do you test sugar quality?

  1. Talk water in a transparent/see-through glass.
  2. Dissolve around 10 grams of the sugar sample in it.
  3. If chalk adulterant is present, it will settle down at the bottom.

What makes a sugar reducing?


A reducing sugar is any sugar that is capable of acting as a reducing agent because it has a free aldehyde group or a free ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars. The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars.

Is sucrose reducing sugar?

Reducing sugars are sugars where the anomeric carbon has an OH group attached that can reduce other compounds. All monosaccharides such as glucose are reducing sugars. A disaccharide can be a reducing sugar or a non-reducing sugar. Maltose and lactose are reducing sugars, while sucrose is a non-reducing sugar.

What are the products formed when sucrose is hydrolyzed?

The products obtained on the hydrolysis of sucrose are glucose and fructose. Glucose is dextrorotatory and fructose is laevorotatory. Sucrose is dextrorotatory. The resulting solution after hydrolysis is laevorotatory.

How do you know what is being oxidized and reduced?

Identifying the Elements Oxidized and Reduced
  1. Assign oxidation numbers to all atoms in the equation.
  2. Compare oxidation numbers from the reactant side to the product side of the equation.
  3. The element oxidized is the one whose oxidation number increased.
  4. The element reduced is the one whose oxidation number decreased.

How do you identify a reducing agent?

A reducing agent is a substance that causes another substance to reduce. So to identify an oxidizing agent, simply look at the oxidation number of an atom before and after the reaction. If the oxidation number is greater in the product, then it lost electrons and the substance was oxidized.

Is starch a reducing sugar?


Glucose has a free aldehyde group which can be oxidized to the acidic groups. Hence, glucose is a reducing sugar. Starch and Cellulose are polysaccharides. The glucose in starch and cellulose does not contain a free aldehyde group and hence, starch and cellulose do not act as reducing sugars.

How does Benedict's test work?

A positive test with Benedict's reagent is shown by a color change from clear blue to a brick-red precipitate. The principle of Benedict's test is that when reducing sugars are heated in the presence of an alkali they are converted to powerful reducing species known as enediols.

What is Fehling's test?

Fehling's test is a chemical test to detect reducing sugars and aldehydes in a solution, devised by the German chemist Hermann Christian von Fehling (1812-1885). Methanal, being a strong reducing agent, also produces copper metal; ketones do not react.

What makes a good reducing agent?

Strong reducing agents easily lose (or donate) electrons. Good reducing agents tend to consist of atoms with a low electronegativity, the ability of an atom or molecule to attract bonding electrons, and species with relatively small ionization energies serve as good reducing agents too.

How can Fehling's test determine the reducing property of sugar?

Fehling's Test. In this test the presence of aldehydes but not ketones is detected by reduction of the deep blue solution of copper(II) to a red precipitate of insoluble copper oxide. The test is commonly used for reducing sugars but is known to be NOT specific for aldehydes.

Is Sucrose a monosaccharide?


Sucrose is common sugar. It is a disaccharide, a molecule composed of two monosaccharides: glucose and fructose. It has the molecular formula C12H22O11. For human consumption, sucrose is extracted and refined from either sugarcane or sugar beet.

Is water a non reducing sugar?

A nonreducing sugar is a carbohydrate that is not oxidized by a weak oxidizing agent (an oxidizing agent that oxidizes aldehydes but not alcohols, such as the Tollen's reagent) in basic aqueous solution. eg: sucrose, which contains neither a hemiacetal group nor a hemiketal group and, therefore, is stable in water.

Why is lactose a reducing sugar?

Because the aglycone is a hemiacetal, lactose undergoes mutarotation. For the same reason lactose is a reducing sugar. The free aldehyde formed by ring opening can react with Benedict's solution. Thus, a solution of lactose contains both the α and β anomer at the “reducing end” of the disaccharide.