Glucose Chemical Formula: Carbohydrates are the nutritional category of sugars and the molecules that our body breaks down to make simple sugars. Depending upon the complexity of the structure, carbohydrates are categorised as simple sugars and complex sugars. Glucose is a simple carbohydrate that acts as an important source of energy in living beings.

A glucose molecule is formed of six carbon atoms and an aldehyde group. It is a monosaccharide with having a chemical formula \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) Glucose is the most important carbohydrate in plants and animals as the cells use it as a source of energy in photosynthesis and respiration. It also acts as a main source of fuel for the brain. A glucose molecule exists in two isomeric forms: \({\rm{D}}\)- Glucose, and \({\rm{L}}\)-Glucose. Glucose is found in foods that are rich in carbohydrates such as fruits, honey, sugars, etc. It is the major source of sugar circulating in the bloodstream of higher animals. This article will go through the structure, properties, and uses of glucose in detail.

Chemical Formula and Structure of Glucose

The term ‘glucose’ is derived from the Greek word ‘glykys’ that means ‘sweet.’ They are simple sugars. The chemical formula of glucose is \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) It is also known as ‘aldohexose’ because it contains six carbon atoms and an aldehyde group. The glucose molecule can exist in two forms: open-chain (acyclic) and ring (cyclic).

The cyclisation of the glucose molecule is the result of the intramolecular reaction between the aldehyde carbon atom and the \({\rm{C}} – 5\) hydroxyl group to form a hemiacetal. Both cyclic and acyclic forms exist in equilibrium, and at a \({\rm{pH}}\) of \(7,\) the cyclic one is the predominant one. Glucose is also referred to as glucopyranose because the ring contains five carbon atoms and one oxygen atom, which resembles the structure of pyran. In its cyclic form, each carbon is linked to a hydroxyl side group, and the fifth carbon atom links to the sixth carbon atom outside the ring, forming a \({\rm{C}}{{\rm{H}}_2}{\rm{OH}}\) group.

Evidence that deduced the Structure of Glucose

• 1. The formation of n-hexane when \({\rm{HI}}\) is heated for a long time with glucose indicates that all the six carbon atoms are present in a straight chain.
• 2. The presence of the carbonyl group in glucose was proved by the formation of oxime when glucose reacts with hydroxylamine and cyanohydrins on the addition of hydrogen cyanide to it.
• 3. Oxidation of Glucose with a mild oxidising agent like bromine water to a carboxylic acid that contains six carbon atoms indicates that the carbonyl group is present in the form of the aldehyde group.
• 4. Acetylation of Glucose with acetic acid gives glucose pentaacetate. This confirms the presence of \( – {\rm{OH}}\) groups.
• 5. The presence of primary alcohol in glucose is indicated by the formation of a dicarboxylic acid and saccharic acid on oxidation with nitric acid.

Isomers of Glucose

Glucose has \(4\) chiral carbon centres, so it will give \({2^4} = 16\) optical stereoisomers. Based on its stereoisomerism, glucose is divided into two types, \({\rm{L}}\)-Glucose and \({\rm{D}}\)-Glucose. This can be understood as: in the Fischer projection model, if we put the most oxidised carbon at the top, then the \( – {\rm{OH}}\) group at the bottom of the chiral carbon pointing towards the right is ‘\({\rm{D}}\)-Glucose’ and the \( – {\rm{OH}}\) group at the bottom of the chiral carbon pointing towards the left is ‘\({\rm{L}}\)-Glucose.’ Some other important carbohydrates include \({\rm{D}}\)-glucose (Glu), \({\rm{D}}\)-galactose (Gal), and \({\rm{D}}\)-mannose (Man). All these eight isomers (including glucose itself), i.e., among the two groups of \(16\) stereoisomers, all are diastereoisomers.

Anomers

When the glucose cyclises into the hemiacetal ring, an additional asymmetric centre at \({\rm{C}} – 1\) is generated, this carbon is known as the anomeric carbon atom, and the two ring structures formed, which are known as anomers, can be named as \({\rm{\alpha }} – {\rm{D}} – \)Glucopyranose and \({\rm{\beta }} – {\rm{D}} – \)Glucopyranose. Structurally, they differ in the orientation of the hydroxyl group linked to \({\rm{C}} – 1\) in the ring. The key difference between \({\rm{\alpha }}\) and \({\rm{\beta }}\) glucose is that, in alpha glucose, the hydroxyl group \(\left( { – {\rm{OH}}} \right),\) present on the first carbon atom of the molecule is on the opposite side as that of the \({\rm{C}}{{\rm{H}}_2}{\rm{OH}}\) group while in beta glucose, the hydroxyl group \(\left( { – {\rm{OH}}} \right)\) is present on the first carbon, that is present on the same side of the \({\rm{C}}{{\rm{H}}_2}{\rm{OH}}\) group.

Properties of Glucose

The properties of glucose are explained below:

Chemical Formula	\({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}\)
Molar Mass	\(180.16\,{\rm{gmo}}{{\rm{l}}^{ – 1}}\)
Density	\(1.54\,{\rm{gc}}{{\rm{m}}^{ – 3}}\)
Melting Point	\(146\,^\circ {\rm{C}}\)
Taste	Sweet taste
Solubility	Soluble in water and acetic acid.

Production of Glucose in the Living Organisms

• 1. Photosynthesis – Plants produce glucose as their food in the presence of carbon dioxide, water, and sunlight. This is the major source of energy in plants as well as oxygen in the environment. The chemical reaction involved in photosynthesis is:
• \(6\,{\rm{C}}{{\rm{O}}_2} + 6\,{{\rm{H}}_2}{\rm{O}} \to {{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6} + 6\,{{\rm{O}}_2}\)
• 2. Glycogenolysis – In animals, glycogen, the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into simple glucose molecules to provide immediate energy and to maintain blood glucose levels during fasting.

Uses of Glucose

• 1. Glucose is an important ingredient in maintaining energy levels in the body. Cells in our body require a definite amount of glucose to function properly. Red blood cells convert glucose into energy. The neurons present in the brain need a continuous supply of glucose to carry out different processes such as thinking, remembering, and learning. Hence, the brain requires the maximum amount of glucose among all the organs of the body.
• 2. Hypoglycemia (low blood sugar) is mostly experienced by diabetic people. Glucose helps to bring back the normal sugar level in the blood.
• 3. Glucose is an instant source of energy. Thus, athletes take glucose while performing vigorous physical activities to avoid fatigue.
• 4. Glucose is used as a first-line treatment of ‘Hyperkalemia’ that causes an increased potassium level in the body.

Summary

The chemical formula of glucose is \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) A glucose molecule is also known as aldohexose; it is made up of six carbon atoms and an aldehyde group. It is a monosaccharide. Based on stereoisomerism, glucose is divided into two types, \({\rm{L}}\)-Glucose and \({\rm{D}}\)-Glucose. Glucose is the main type of sugar present in the blood and is the major energy source for the body. We get glucose from the foods we eat, especially carbohydrates. Blood is responsible for carrying glucose to the different cells. Glucose levels in the blood are controlled by the hormone ‘Insulin’ in the body. Plants produce glucose as their food from carbon dioxide, water, and sunlight by photosynthesis. In an animal’s body, glucose is produced by glycogenolysis. Hence, it can be concluded that glucose is a very important chemical substance needed for our survival.

FAQs on Glucose Chemical Formula

Q.1. What do you notice with the chemical formula of glucose?
Ans: The chemical formula of glucose is \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) It shows that the glucose molecule is made up of six carbon atoms and an aldehyde group; hence it is also known as an aldohexose. It is a monosaccharide.

Q.2. What are three facts about glucose?
Ans: The three facts about glucose are:
(i) It is the major source of energy in the body of living organisms.
(ii) Glucose is a type of carbohydrate (sugars). Hence it tastes sweet.
(iii) Increased blood glucose levels can cause Diabetes.

Q.3. How do you calculate glucose levels?
Ans: Blood glucose level is calculated by Glucose Infusion Rate (GIR) in (mg/kg-min). It is calculated by using the formula:
\({\rm{GIR}} = \frac{{{\rm{Infusion}}\,{\rm{Rate}}\left( {\frac{{{\rm{mL}}}}{{{\rm{hr}}}}} \right) \times {\rm{Dextrose}}\,\,{\rm{concentration}}\,\left( {\frac{{\rm{g}}}{{{\rm{dL}}}}} \right) \times 1000\left( {\frac{{{\rm{mg}}}}{{\rm{g}}}} \right)}}{{{\rm{Weight}}\left( {{\rm{Kg}}} \right) \times 60\left( {\frac{{{\rm{min}}}}{{{\rm{hr}}}}} \right) \times 100\left( {\frac{{{\rm{mL}}}}{{{\rm{dL}}}}} \right)}}\)

Q.4. What is the glucose chemical formula and structure?
Ans: The chemical formula of glucose is \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) It contains six carbon atoms in the straight-chain along with an aldehyde group. Hydroxyl groups are also present in it. Its structure is given below:

Q.5. How do you write the chemical formula for glucose?
Ans: Glucose is also known as an aldohexose. Its chemical formula is \({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}.\) It is the main source of energy in the body.

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