Introduction to Biomolecules and Its 4 Major Types

Biological molecules or Biomolecules are defined as those numerous biotic substances that are produced by cells and living organisms. These biological molecules (biomolecules) perform a vast array of functions along with having a wide range of sizes and structures. Carbohydrates, lipids, nucleic acids, and proteins these molecules which are classified as the four major types of Biomolecules.

Carbohydrates

They are the most abundant biomolecules (biomacromolecules) on the earth. They are commonly known as sugars because they have a sweet taste. Chemically all carbohydrates are polyhydroxy aldehyde and ketones. All cardboard rates are hydrates of carbon and they contain C, H, and O. The ratio of carbon and Oxygen will be 2:1. The classification of carbohydrates is in three major categories based on the number of monomer units and the degree of polymerization. They are as follows:

1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides

Monosaccharide

• Monosaccharides consist of a single polyhydroxy aldehyde ketone unit. 
• They are simple sugars, also colorless and crystalline solids and the solubility of monosaccharides is that they are freely soluble in water but are not soluble (insoluble) in non-polar solvents.
• The most abundant monosaccharide in nature is being D- glucose.

The further sub-classification of monosaccharides can be done on the basis of:

Types of functional group

• Aldoses: are monosaccharides with an aldehyde group.
• Ketoses: are monosaccharides containing a ketone group.

Number of the carbon atoms

The Number of carbon atoms present in a monosaccharide molecule is the basis of the system by which these sugar molecules are named, with the suffix -ose added. And the prefixes tri-,tetr-, pent-,and so forth indicates the number of carbon atom in the chain.

Oligosaccharides

• Disaccharides are the simplest and the most common oligosaccharides.
• Oligosaccharides containing three or more residues are relatively rare, occurring almost entirely in plants.
• A disaccharide consists of two monosaccharides joined by an O- glycosidic bond.
• The anomeric carbon atom of a monosaccharide and the oxygen atom of alcohol form a bond between each other which is called a glycosidic bond.

Polysaccharides

• Polysaccharides are ubiquitous in nature.
• They are also called glycans.
• They can be classified into two separate groups, based on their functions: structural and storage polysaccharides.
• Structural polysaccharides provide mechanical stability to cells, organs, and organisms.
• Storage polysaccharides as carbohydrate stores that release monosaccharides as required.
• There are two types of polysaccharides on the basis of a number of the monomeric units which can be-Homopolysaccharides (contain only a single type of monomeric unit) or Heteropolysaccharides (contain two or more different kinds of monomeric units).

Proteins

Amino acids are complex biomolecules containing carbon, hydrogen, oxygen, and nitrogen and serve as monomers (building blocks) of proteins. These complex biomolecules contain both an amino group and a carboxylic acid group. These amino acids residue form a peptide bond on linking of two or more amino acids and the product is called a dipeptide and tripeptide, respectively. Hence a peptide is a compound consisting of two or more amino acids.

Peptide chains of more than 12 and less than about 20 amino acid residues are usually referred to as oligopeptides. Peptides and polypeptides are mostly linear and branched polymers composed of amino acids linked together by a peptide bond. Peptide bonds are linkages formed between the alpha-amino group of one amino acid and the Alpha carboxyl group of another. This reaction is a dehydration reaction that is a water molecule is removed and the linked amino acid are referred to as amino acid reduce. Peptide bond formation is an endergonic process.

Nucleic Acid

Nucleic acid was first discovered by Friedrich Miecher from the nuclei of the pus cell from discarded surgical bandages and called it nuclein. They are the polymer of nucleotides, therefore, are also called polynucleotides.

There are two types of nucleic acid:

1. Ribonucleic acid (RNA)
2. Reoxyribonucleic acid (DNA)

Nucleotides

Nucleotides are the monomeric units of nucleic acids. They are phosphate esters of nucleosides and made up of three components:

1. A base that has a nitrogen atom.
2. A five-carbon sugar
3. An ion of phosphoric acid.

Nitrogenous bases

Nitrogenous bases are heterocyclic, planar, and relatively water-insoluble aromatic molecules. There are two general types of nitrogenous bases in both DNA and RNA, pyrimidines and purines.

Sugars

There are two types of nucleic acids in which  there are naturally occurring two types of pentose sugars:

Ribose and deoxyribose sugar. 

• Ribose sugar is found in RNA. It is a 5 carbon monosaccharide with the hydroxyl group-OH on each carbon.
• Deoxyribose sugar is found in DNA. It is a 5 carbon monosaccharide, lacking one oxygen atom at 2′ position. A Hydrogen atom (-H) has replaced the hydroxyl group (-OH) at the 2′ position of the ribose sugar.

Nucleoside

Sugar and nitrogenous base join to form a nucleoside. The bond between the sugar and the base is called the N-glycosidic bond. The nitrogenous base lies above the plane of the sugar when the structure is written in the standard orientation; that is, the configuration of the N-glycosidic linkage is beta.

Nucleotides

Phosphoric acid esters of nucleosides are called nucleotides, with the phosphate group attached at position C-5′. Hence a nucleotide can be called nucleoside-5′-phosphate. The nucleotides can have one, two, or three phosphate groups at the C-5′ position and are called nucleoside Monaphosphates, diphosphates, and triphosphates.

Lipids

Biological lipids are chemically diverse groups of organic complex biomolecules that are insoluble or poorly soluble in water. The solubility of lipids in nonpolar solvents such as ether, chloroform, or benzene is readily dissolvable. The hydrophilic nature of lipids is due to the predominance of hydrocarbon chains in their structures. Lipids are not polymers, like proteins, nucleic acids, and polysaccharides.

Functions:

• Lipids serve as a storage form of metabolic fuel
• They serve as a transport form of metabolic fuel.
• They provide the structural components of membranes.
• They have protective functions in bacteria, plants, insects, and vertebrates, serving as a part of the organism and the environment.

Fatty acids

Fatty acids are the simplest form of lipids and serve as constituents in a large number of complex form of lipids. The long-chain hydrocarbons (4 to 36 carbons long) with one carboxyl group are Fatty acids. There are two types of fatty acids saturated and unsaturated fatty acids. There is no double bond in the Saturated fatty acid. Examples of predominant saturated fatty acids are lauric,myristic, palmitic, and others. There is the presence of one or more double bonds in the Unsaturated fatty acids and are called monounsaturated or polyunsaturated respectively.

Triacylglycerol and Wax

Triacylglycerol is triesters of fatty acids and glycerol. They are composed of three fatty acids and a glycerol molecule. Triacylglycerol is of two types: simple and mixed type. Those containing a single kind of fatty acid are called simple triacylglycerol and those containing two or more different kinds of fatty acids are called mixed triacylglycerol. Triacylglycerol is nonpolar, hydrophobic in nature, and a major form of stored lipid.

Waxes

The typical esters of fatty acids and long-chain alcohols are Natural waxes. They are Formed by the stratification of long-chain fatty acids and high molecular weight monohydroxy alcohol. Waxes are biosynthesized by many plants and animals. The best-known animal wax is beeswax. Triacontanyl palmitate an ester of palmitic acid with alcohol triacontanol is the major component of beeswax.

Phospholipids

A phospholipid is constructed from four components: fatty acids, a platform to which the fatty acids are attached, phosphate, and alcohol attached to the phosphate. That’s why Phospholipid is called an amphipathic molecule. The platform on which phospholipids are built may be glycerol or sphingosine.

Glycolipids

Lipid-containing saccharide groups go under the general name of glycolipids. The glycosphingolipid is the most important type of glycolipid and constituted the third major class of membrane lipids. In Glycosphingolipid head group contains one or more sugars connected directly to the -OH at C-1 of the ceramide moiety (do not contain phosphate). It can be – 

• Cerebroside: have a single monosaccharide link to ceramide.
• Globoside: with oligosaccharide link to ceramide.
• Gangliosides: globoside that contains complex oligosaccharides as their polar head groups with one or more residence of N-acetyl neuraminic acid, a sialic acid.

Steroid

Steroids are complex derivatives of triterpenes. Each type of steroid is composed of four fused rings called steroids nucleus. A sterol is a class of steroids characterized by a hydroxyl group at C-3.  Cholesterol is an example of this sterol and an essential component in animal cell membranes. Cholesterol acts as a precursor for the biosynthesis of all steroid hormones and bile salts and it is usually stored within cells as the esters of a fatty acid.

Eicosanoid

Eicosanoids are a family of very important biological signaling molecules (biomolecules) that act as short-range messengers. It includes prostanoids and leukotrienes. It is known as eicosanoids because of their common origin from 20 carbons polyunsaturated fatty acids, eicosanoic acids, particularly arachidonic acid. Eicosanoids are potent hormones and act locally instead of being transported in the blood to act on cells of other tissues or organs.

Plasma Lipoproteins

Triacylglycerol, phospholipids, cholesterol, and cholesterol asters are transported in human plasma in association with proteins as Lipoproteins. Blood plasma contains a number of soluble lipoproteins, which are classified, according to their densities into five major types. These lipid-protein complexes function as a leopard transport system because isolated lipids are insoluble in blood. There are five basic types of lipoproteins in human blood: Chylomicrons, Very low-density lipoproteins, Intermediate density lipoproteins, Low-density lipoproteins, High-density lipoproteins.

REFERENCES

https://en.wikipedia.org/wiki/Biomolecule