[Chemistry Class Notes] on Structure of Glucose and Fructose Pdf for Exam

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

 

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

 

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-gluco
se points to the left. If these two specific molecules faced each other, they would look like a reflection of one another.