Structure of Glucose and Fructose

Dhristi JEE 2022-24

Glucose vs Fructose

Glucose is defined as a monosaccharide and is found in all the primary carbohydrates such as in the table sugar starch. Glucose is also known as grape sugar or blood sugar, and it is represented as a six-membered ring that forms a pyranose ring structure. Glucose is aldohexose and is the primary and the most preferred energy source of the body. It is found in starch.


Fructose is defined as a monosaccharide and is found in fruits and vegetables. In fructose, the glycemic index is lower as compared to glucose. Compared to Glucose, the binding fructose to cellular protein is seven times faster. It is also referred to as D- fructose or fruit sugar and its functional group are known as ketone. Glucose is known to be primarily metabolized in the liver and is not found in starch.

 

Structure of Glucose

Glucose is defined as a group of carbohydrates, a simple sugar having a chemical formula C6H12O6. It is composed of six carbon atoms, including an aldehyde group. Thus, we can refer to this as aldohexose. It exists in two forms, which are either in the open-chain (acyclic) form or ring (cyclic) form. The major source of energy needed for living organisms is given as glucose. Algae and plants prepare glucose during the photosynthesis process with the help of water, carbon dioxide, and sunlight. It is naturally found in honey and fruits. The glycogenolysis process obtains glucose present in animals.


How to draw an Open-Chain Structure of the Glucose Molecule

The required steps to draw an acyclic form of glucose are:


Step 1: Draw six carbon atoms.


Step 2: Draw extended arms for all the carbon atoms.


Step 3: Draw a hydrogen atom to carbon bond in such a way that four will be on one side, one on the other side


Step 4: Fill up the rest of the spaces with an OH group. 


Step 5: Finally, complete both the ends with two single-bonded hydrogen bonds with one double-bonded carbon.


Dry fructose looks like a white coloured crystalline solid, which is odourless and sweet. Fructose is soluble in ether, in water, and also in alcohol.

 

Baeyer showed the open-chain structure of the glucose compound. However, these structures have faced difficulties in explaining why glucose fails to react with Schiff base, sodium bisulphate or the mutarotation process. Haworth introduced the cyclic structure of glucose that confirms the existence of alpha and beta forms of mutarotation, glucose, and more.

 

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Steps to draw the Ring Structure of a Glucose Molecule

Follow the below steps to draw a cyclic form of glucose.

 

Step 1: Firstly, construct a hexagon

 

Step 2: Then, draw carbon atoms at five consecutive edges.

 

Step 3: Thereafter, attach an oxygen atom at the left out edge.

 

Step 4: Now, attach the four carbon atoms with OH and H groups.

 

Step 5: Complete the entire structure by attaching the left out carbon atom to two hydrogen atoms, one carbon atom and OH group.

 

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Glucose Properties

Glucose Chemical Formula

C6H12O6

Glucose Molar mass

180.156 g/mol

IUPAC Name

D-Glucose

 

Fructose Ring Structure

Fructose is described as a monosaccharide which is given as a simple sugar having a chemical formula C6H12O6. It is also known as fruit sugar and was discovered in 1847 by a French chemist named Augustin-Pierre Dubrunfaut. It is composed of a 6-carbon polyhydroxy ketone.

 

Crystalline fructose takes place as a cyclic six-membered structure, which is delinquent to the stability of the internal hydrogen bonding and hemiketal. This form is known as D-fructopyranose. It primarily takes place in vine fruits, honey, most root vegetables, flowers, and berries. It can be obtained Commercially from maize, sugar beets, and sugar cane.

 

Open Chain Structure and Ring Structure of a Fructose Molecule

The cyclic structure of fructose is given below:

 

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The Fischer projections of D-fructose and L-fructose can be given as follows:

 

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Fructose Properties

Dry fructose appears as a white coloured crystalline solid, which is odourless and sweet. It is soluble in ether, water, and alcohol.

 

Properties of Fructose

Fructose Molar mass

180.156 g/mol

Fructose Formula

C6H12O6

Density

1.694 g/cm3

Fructose Chemical Formula

C6H12O6

Melting point

103°C

 

The Difference between the Glucose and Fructose Compounds

Known as constitutional isomers, which means that there is a difference in the bond connectivity. Glucose is an aldehyde, and fructose is a ketone. When they become cyclized by the formation of hemiketal/hemiacetal, glucose becomes a 6-ring sugar and on the other side, fructose becomes a five-ring sugar. Glucose is the most preferred form of energy of the body and every cell in the body is capable of metabolizing the glucose compound. AS far as Fructose is concerned, only the Liver is capable of metabolizing fructose. This is the reason why Fructose intake should be restricted.

 

D-Glucose Chemistry

In the glucose molecule, a hydrogen and oxygen atom group is bonded to the carbon atom. On the other side of the glucose molecule, there exists a double-bonded oxygen atom. Looking at the D-glucose’s Fisher model with the double-bonded oxygen atom, which is pointed down, the hydrogen and oxygen group present at the top of the atom points towards the right.

 

L-Glucose Chemistry

D-glucose and L-glucose are composed of similar atoms. The only difference between these two structures can be displayed using the Fisher model. In the Fisher model, unlike D-glucose, the hydrogen and oxygen group of atoms present in L-glucose points to the left. If these two specific molecules faced each other, they would look like a reflection of one another.

FAQs on Structure of Glucose and Fructose

1. Explain the Structure of Glucose.

Glucose is a group of carbohydrates, a simple sugar that has the chemical formula C6H12O6


Glucose is composed of six carbon atoms, including an aldehyde group. Glucose can be referred to as aldohexose. It exists in two forms, which are either in the open-chain (acyclic) form or the ring (cyclic) form. Glucose is considered a major source of energy that is needed for living organisms. 

2. Explain the Fructose Ring Structure.

Fructose is a monosaccharide which is a simple sugar that has a chemical formula C6H12O6. Fructose is also called fruit sugar and it was discovered in 1847 by a French chemist, Augustin-Pierre Dubrunfaut. Fructose is composed of a 6-carbon polyhydroxy ketone. The crystalline fructose takes place as a cyclic six-membered structure, that is delinquent to the stability of the internal hydrogen-bonding and hemiketal. Fructose can be obtained commercially from maize, sugar beets, and sugar cane.

3. Explain Glucose and Fructose?

Both the compounds Glucose and Fructose are given as simple sugars or monosaccharides. Both Glucose and Fructose can be said to be similar as they both contain the same amount of calories and they occur naturally in certain fruits as well as in some foods. They are both different in their chemical structures and in the way the human body digests and processes them.


Glucose is less fat producing as compared to Fructose. 

4. How to Draw the Ring Structure of a Glucose Molecule?

The required steps to draw the Ring Structure, or a cyclic form, of glucose, are:


Step 1: Firstly, construct a hexagon


Step 2: Draw carbon atoms at five consecutive edges.


Step 3: Attach an oxygen atom.


Step 4: Attach the four carbon atoms with OH and H groups.


Step 5: Finally, complete the entire structure by attaching the left out carbon atom to two hydrogen atoms, one carbon atom and the OH group.

5. Where are study materials available?

In Chemistry, the ‘Structure of Glucose and Fructose’ Chapter is as important a chapter as all the other chapters in Chemistry. It is necessary to be able to practice some of the important questions to be able to do well. The online portal, Vedantu.com offers important questions along with answers and other very helpful study material on the Structure of Glucose and Fructose, which have been formulated in a  well structured, and in an easy to understand manner. These study materials and solutions are all important and are very easily accessible from Vedantu.com and can be downloaded for free. 

6. Explain various types of glucose?

The d-isomer, d-glucose, which is also called dextrose, is commonly found in nature, but the l-glucose, l-isomer, is not found commonly in nature. Hydrolysis of carbohydrates like plant sugar (sucrose), dairy sugar (lactose), cellulose, maltose, glycogen is used to obtain glucose.

7. Where does glucose produce from?

The food we consume is produced either from sugar or glucose. The prevalent sources of glucose are given as carbohydrates, such as bread pasta, cereals. In our stomachs, these types of foods are split into sugar, and then they are absorbed into the bloodstream.

8. Why is Glucose a monosaccharide?

Monosaccharides (to explain clearly, mono- = “one;” sacchar- = “sugar”) are given as simple sugars, where glucose is the most prevalent compound.

9. What is the function of fructose?

Similar to glucose, fructose also provides energy cells. These cells process fructose to gain energy using a method known as aerobic breathing, which primarily involves burning fructose in the presence of oxygen to generate ATP, which is the molecule of cellular energy.

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