Carbohydrates Classification

Definition of Biomolecules and Carbohydrates, Classification of carbohydrate,

BIOCHEMISTRY

Alok Bains

9/21/20234 min read

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brown and maroon textile pack lot

Biomolecules

Introduction and classification, carbohydrate,

Older terms for biochemistry are physiological chemistry, biological chemistry, or chemical biology.

  • · Biochemistry is the chemistry of biology.

  • · It is the study of biological processes at the cellular level and molecular level.

  • · It deals with the chemical nature and chemical behavior of active constituents in the living body.

  • · It is the discipline of science that analyze biological phenomena in term of chemistry.

Biomolecules: Organic molecules produced by the cells and act as structural and functional units of cells are called biomolecules. Biomolecules include carbohydrates, proteins, lipids, amino acids, fatty acids, glucose, enzymes, nucleic acids (DNA and RNA), hormones vitamins, etc.

Inorganic chemicals are also present in the cells such as water, minerals, and ions. However, they are not included in biochemicals because they do not participate in the complex processes of life. But they are essential for the cellular function.

Broadly biochemistry is divided into two parts. These are descriptive biochemistry and dynamic biochemistry.

  • · Descriptive Biochemistry: The study of qualitative and quantitative characters of biomolecules (constituents of living cells) is termed descriptive biochemistry.

  • · Dynamic Biochemistry: The study of the mechanism of action of biomolecules inside living cells is termed dynamic biochemistry.

CARBOHYDRATES

Carbohydrates are represented by general chemical formula (CH2O)n or Cn(H2O)n. The hydrogen and oxygen ratio in carbohydrates is the same as the hydrogen and oxygen ratio in water i.e. 2:1. But,  some carbohydrates do not have a 2:1 ratio of hydrogen and oxygen. eg. Rhamnose (C6H12O5), deoxyribose (C5H10O4). Some other compounds have a hydrogen: oxygen ratio same as water. But they are not carbohydrates. Examples are Lactic acid (C3H6O3), or acetic acid (C2H4O2).

“Carbohydrates are polyhydroxy aldehyde or polyhydroxy ketone or their derivatives. These derivatives yield either a  polyhydroxy aldehyde or a polyhydroxy ketone upon their hydrolysis”

Classification of Carbohydrates: There are two classes of carbohydrates.

  1. Small Carbohydrates

    • a. Monosaccharides:

      • i. Aldoses: Glyceraldehyde, Erythrose, Ribose. Glucose

      • ii. Ketoses: Dihydroxy acetone, Erythrulose, Ribulose, Fructose

    • b. Derived monosaccharides: Deoxy sugar, Amino sugar, Sugar alcohol, Sugar acid

    • c. Disaccharides:

    • d. Oligosaccharides: Trisaccharides, Tetrasaccharides, etc.

    • e. Polysaccharides: Glucon, Fructon, Xylon, Arban

  2. Complex carbohydrates (Large carbohydrates)

    • a. Homopolysaccharides: Starch, Cellulose, Glucan, Fructan, Xylan, Araban, Galactan

    • b. Heteropolysaccharides: Hyaluronic acid, Pectin, Peptidoglycan, Agar.

Definitions

  1. Monosaccharides: They consist of either a single polyhydroxy aldehyde or a single polyhydroxy ketone. They cannot be further hydrolyzed into another simpler component. Monosaccharides containing aldehyde functional groups are called Aldoses. Monosaccharides containing ketone functional groups are called ketoses. Monosaccharides are simple sugars with general chemical formula Cn(H2O)n or CnH2nOn. Monosaccharides are further subdivided into the following classes depending on the number of carbon atoms present in monosaccharide compounds. These are

    • i. Triose: It has three carbon atoms. General formula is C3H6O3. Example of triose containing aldehyde functional group (-CHO) i.e. Glycerose. Example of triose containing ketone functional (C=O). i. e. Dihydroxy acetone.

    • ii. Tetrose: It has four carbon atoms. General formula is C4H8O4. An example of tetrose containing an aldehyde functional group (-CHO) is Erythrose. An example of a tetrose-containing ketone functional group is Erythrulose.

    • iii. Pentose: It has five carbon atoms. The general formula is C5H10O5eg.of pentose containing aldehyde functional group (-CHO) is Ribose. An example of a pentose-containing ketone (C=O) functional group is Ribulose.

    • iv. Hexose: It has six carbon atoms. The general formula is C6H12O6 Example of Hexose containing an aldehyde functional group (-CHO) is Glucose. An example of a hexose-containing ketone (C=O) functional group is Fructose.

    • v. Heptose: It has seven carbon atoms. General formula is C7H14O7. An example of heptose containing aldehyde functional group (-CHO) is Glucoheptose. An example of a heptose-containing ketone functional group (=CO) is Sodoheptulose.

    Aldolases are more common in nature than ketoses (except fructose).

  2. Derived monosaccharides: There are various derivatives of monosaccharides. Such as deoxy sugar, amino sugar, sugar alcohol, sugar acid, etc. Ribose de-oxidation (removal of oxygen) produces deoxyribose. It is deoxy sugar. Glycerol and mannitol are examples of sugar alcohol. Ascorbic acid is considered a sugar acid. Glucosamine is an amino sugar.

  3. Disaccharides: It yields 2 molecules of monosaccharides upon its hydrolysis. eg. Sucrose, Maltose, Lactose, Cellobiose, Trechalose.

  4. Oligosaccharides: Oligosaccharides are formed by condensation of 3-10 monosaccharides. They are small carbohydrates considered as compound carbohydrates. Hydrolysis of oligosaccharides yields 2 to 10 molecules of monosaccharides. These monosaccharide molecules may be the same or different. Oligosaccharides are further subdivided depending upon the number of monosaccharides yields upon their hydrolysis.

    i. Trisaccharides: It yields 3 molecules of monosaccharides. eg. Raffinose, Rhamninose, Gentianose.

    ii. Tetrasaccharides: It yields four molecules of monosaccharides upon hydrolysis. eg. Stachyocose, Scorodose.

    iii. Pentasaccharides: It yields five molecules of monosaccharides upon hydrolysis. eg. Verbascose.

    iv. Other examples of oligosaccharides are hexasaccharides and Hepatosaccharides.

  5. Polysaccharides: Polysaccharides yield more than 10 molecules of monosaccharides upon hydrolysis. They are complex carbohydrates and are also called glycans. They are long-chain compounds with one reducing end (Right end of the chain) and one non-reducing end (left end of the chain). The general formula for polysaccharides (C6H10O5)X

Polysaccharides are further subdivided into two subclasses depending on their composition.

  • i.Homopolysaccharides: Homopolysaccharides produce one type of monosaccharide on hydrolysis. eg. Starch, Inulin, Cellulose, Pectin, etc. There are several types of homopolysaccharides depending upon the type of monosaccharides present in homopolysaccharides.

    • a. Glucan: It is made up of glucose.

    • b. Fructose: It is made up of fructose.

    • c. Xylan: It is made up of xylose.

    • d. Araban: It is made up of arabinose.

    • e. Galactan: It is made up of galactose.

  • ii.Heteropolysaccharides: Heteropolysaccharides produce two or more types of polysaccharides upon hydrolysis. eg. hyaluronic acid, Pectin, Peptidoglycan, Agar.

Condensation of more than 10 monosaccharides produces polysaccharides. This condensation develops the following properties in polysaccharides

  •  insoluble in water, no sweet taste,

  • decrease in its osmotic potential,

  • impermeable to the cell membrane and ideal to be stored in the cell as food

Author: Alok Bains