Classification of Carbohydrates Biochemistry
Carbohydrates are a group of organic compounds that occur in living tissues and foods in the form of sugars, cellulose, and starch. The general formula of carbohydrates is \[CH_{2}O_{n}\]. Just as in water, the ratio of oxygen and hydrogen is fixed in carbohydrates, which is 2:1. It generally breaks down to release energy in humans and animals. Today, we are going to learn about the classification of carbohydrates and their structures.
Carbohydrates Classification
Given below is the classification of carbohydrates in biochemistry.
Types of Carbohydrates – Simple Carbohydrates
The basic type of carbohydrates is simple carbohydrates that are found in natural sugars present in fruits, vegetables, milk, and honey. These carbohydrates are much simpler to study since they have a less complex structure.
Simple carbohydrates consist of only units of monosaccharides, which is why they are the smallest and simplest of all the other types of carbohydrates. Their smaller size plays a vital role in metabolism and digestion in the gastrointestinal tract.
Types of Carbohydrates – Complex Carbohydrates
Complex carbohydrates are an essential source of energy for our body. They give us the sustained fuel that our body needs for carrying out day-to-day activities, for working out, and for even taking rest. Complex carbohydrates often comprise different units of monosaccharides bound together and provide us with long-lasting energy. The complex carbohydrates are classified depending on their hydrolysis behavior. They are divided into three groups as follows.
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
Monosaccharides are carbohydrates that cannot be hydrolyzed further for giving simpler units of either a polyhydroxy aldehyde or a ketone. If a monosaccharide consists of an aldehyde group, it is referred to as aldose and if it consists of a keto group then it is referred to as a ketose.
Disaccharides
After the process of hydrolysis, disaccharides tend to yield either two molecules of the same or the different monosaccharides.
Two units of monosaccharide are joined by an oxide linkage that is formed when there is the loss of water molecule, and this linkage is referred to as glycosidic linkage.
Sucrose is amongst the most common disaccharides that give both glucose and fructose on hydrolysis.
Maltose and lactose, often referred to as milk sugar, are also the two kinds of important disaccharides.
Maltose contains two α-D-glucose whereas lactose consists of two β-D-glucose that are connected through an oxide bond.
Polysaccharides
Polysaccharides consist of longer monosaccharide units that are joined together by glycosidic bonds.
Most of these polysaccharides act as storage for food, such as starch. Starch is known to be an important storage polysaccharide in plants.
Starch is a polymer of α glucose and has two components, that are amylose and amylopectin.
Cellulose is also an essential polysaccharide that is found mostly in plants.
It comprises β-D- glucose units that are joined by a glycosidic bond between the C1 of one glucose unit and the C4 of another glucose unit.
Structure of Carbohydrates
Carbohydrates have traditionally been characterized as compounds having the empirical formula \[Cn(H_{2}O)m\]. Glucose, fructose, and sucrose are popular sugars that suit this formula, however, currently, a carbohydrate is defined as a polyhydroxy aldehyde or polyhydroxy ketone with the traditional formula, a molecule closely similar to it, or oligomers or polymers of such molecules. Because they are water-soluble and difficult to crystallise, they need a different set of abilities to manipulate than traditional "natural products" like terpenes, steroids, and alkaloids.
A "monosaccharide" is a carbohydrate derivative with a single carbon chain; "disaccharide" and "trisaccharide" are compounds with two or three monosaccharide units linked together by acetal or ketal linkages. Larger aggregates with "a few" and "many" monosaccharide units are referred to as "oligosaccharide" and "polysaccharide," respectively. The divide between "few" and "many" appears to be drawn at roughly 10 units in current use.
By the middle of the nineteenth century, chemists in Europe, particularly in Germany, had discovered a variety of relatively pure carbohydrates such as sucrose, cotton cellulose, starch, glucose, fructose, mannose, and lactose. Emil Fischer produced phenylhydrazine for his University of Munich thesis in 1878. He also found in 1884 that carbohydrates produced crystalline phenylosazone when two phenyl hydrazines interacted with the aldehyde group and the carbon next to it.
Structure of Carbohydrates – Glucose
Glucose is amongst the most important monosaccharides. The two commonly used methods to prepare glucose are as follows.
From Sucrose: When sucrose is boiled with dilute acid in an alcohol solution, glucose and fructose are obtained.
From Starch: Glucose can also be obtained by the hydrolysis of starch and boiling it with dilute sulphuric acid, at a temperature of 393K, under high pressure.
Glucose is also known as dextrose and aldohexose and is plentiful on earth.
Structure of Carbohydrates – Fructose
Fructose is an essential ketohexose having a molecular formula \[C_{6}H_{12}O_{6}\]. It consists of a ketone functional group situated at carbon number 2 and contains six carbon atoms in the form of a straight chain. The ring member of fructose is analogous to the compound called Furan and is therefore termed furanose. The cyclic structure of fructose is as follows:
Conclusion
We are all surrounded Carbohydrates are a group of organic compounds that occur in living tissues and foods. The general formula of carbohydrates is \[CH_{2}O_{n}\]. Just as in water, the ratio of oxygen and hydrogen is fixed in carbohydrates, which is 2:1.
FAQs on Structure and Classification of Carbohydrates
1. Carbohydrates: What are they? What are their classifications?
Carbohydrates are polyhydroxy aldehydes or ketones, their polymers, or their simpler derivatives, according to chemistry. The word hydrates or carbohydrate comes from its fundamental formula, which has a carbon atom linked to oxygen and hydrogen in the same proportion as water.
Based on their architectures, they are divided into simple and complex carbohydrates. Depending on the hydrolysis process, complex carbohydrates are further split into monosaccharides, disaccharides, or polysaccharides. The majority of sugars' names end in -ose, indicating that they are carbohydrate-based. As a result, table sugar is commonly referred to as sucrose, principal blood sugar is referred to as glucose, and malt sugar is referred to as maltose.
2. Explain how carbohydrates are classified.
Carbohydrate classification is based on the hydrolysis process, which is as follows.
Monosaccharides: Monosaccharides are the most basic carbohydrate type that cannot be further hydrolyzed and contain the general formula \[(CH_{2}O)n\]. Monosaccharides include glucose and ribose, for example.
When disaccharides are hydrolyzed, they produce two units of the same or different monosaccharides.
Trisaccharides: When trisaccharides are hydrolyzed, they produce three molecules of the same or different monosaccharides.
Polysaccharides: Polysaccharides are carbohydrates that break down into a higher number of monosaccharides after being hydrolyzed. Because they don't have a sweet taste, they're also known as non-sugars.
3. What is the structure of carbohydrate glucose?
- One of the most significant monosaccharides is glucose.
- The following are the two most frequent methods for preparing glucose.
- Sucrose is converted to glucose and fructose when it is cooked with dilute acid in an alcohol solution.
- From Starch: Glucose can also be made by hydrolyzing starch and boiling it with weak sulphuric acid at 393 degrees Fahrenheit under high pressure.
- Glucose, commonly known as dextrose and aldohexose, is abundant on the planet.
4. What is the structure of carbohydrate fructose?
Fructose has the chemical formula \[C_{6}H_{12}O_{6}\] and is an essential ketohexose. It includes six carbon atoms in the shape of a straight chain and has a ketone functional group at carbon number
Furanose is the name given to the ring component of fructose, which is comparable to the chemical Furan.
The only naturally occurring ketohexose is fructose, popularly known as fruit sugar. It's also known as levulose because of its significantly levorotatory optical rotation.
Fructose is a ketonic monosaccharide with a simple structure. Monosaccharides are the basic building blocks of carbohydrates that can't be broken down any further. The functional group connected to the carbohydrate is used to classify them.
5. What is the difference between disaccharides and polysaccharides?
Disaccharides:
Disaccharides tend to give either two molecules of the same monosaccharide or two molecules of different monosaccharides after hydrolysis.
When a water molecule is lost, an oxide bond is produced between two monosaccharide units, and this linkage is referred to as glycosidic linkage.
Sucrose is one of the most common disaccharides, and when hydrolyzed, it yields both glucose and fructose.
Maltose and lactose, which is also known as milk sugar, are two types of essential disaccharides.
Maltose has two -D-glucose molecules, whereas lactose has two -D-glucose molecules joined by an oxide connection.
Polysaccharides:
Polysaccharides are made up of longer monosaccharide molecules linked by glycosidic linkages.
The majority of these polysaccharides serve as food storage, such as starch.
Starch is a carbohydrate that serves as a storage molecule in plants.
Amylose and amylopectin are two components of starch, which is a polymer of glucose.
Cellulose is found primarily in plants and is also an important polysaccharide.
It is made up of -D- glucose units linked by a glycosidic bond between the C1 of one glucose unit and the C4 of another.
