Biomolecules

Biomolecules are organic molecules that are crucial components of living organisms. They are involved in the structure, function, and regulation of the body's cells, tissues, and organs.

1.0What are Biomolecules?

A biomolecule definition involves any molecule produced by living organisms, with most being organic molecules. The primary groups of biomolecules are carbohydrates, amino acids, proteins, nucleic acids (DNA and RNA), and lipids. These substances, crucial for life, are typically found within and synthesized by living organisms, and many are polymers. A polymer is a compound composed of multiple repeating units, known as monomers or protomers, linked together through polymerization processes.

Most biomolecules in chemistry are organic compounds characterized by covalent bonding of carbon atoms to other elements, predominantly involving carbon-carbon (C-C) and carbon-hydrogen (C-H) bonds. The primary elements that make up these molecules include carbon, hydrogen, oxygen, and nitrogen. In this article we will discuss the most important types of Biomolecules and biomolecules examples.

2.0Carbohydrate

Carbohydrates are a major class of biomolecules that play a variety of essential roles in both the structure and function of living organisms. They are primarily composed of carbon (C), hydrogen (H), and oxygen (O). General formula of carbohydrate can be written as C_x (H₂O)_y

Here, x = y or x ≠ y

Hence these are called, Hydrates of carbon

For example- x = y = 6

Glucose → C₆ (H₂O)₆

Glucose → Molecular Formula (C₆H₁₂O₆)

Carbohydrates, also known as saccharides (derived from the Greek word "saccharon" meaning sugar), can be classified based on their behavior upon hydrolysis:

1. Monosaccharides:

Monosaccharides are the simplest form of carbohydrates, consisting of single sugar molecules.

They cannot be further hydrolyzed into simpler sugars.

Monosaccharides are the basic building blocks of more complex carbohydrates and serve as the primary source of energy for cellular processes.

Examples include glucose, fructose, and galactose.

2. Oligosaccharides:

Oligosaccharides are composed of a small number of monosaccharide units, typically 2 to 10, linked together by glycosidic bonds.

Upon hydrolysis, oligosaccharides break down into individual monosaccharide units.

They are found in various natural sources such as legumes, beans, and some vegetables.

Examples include disaccharides like sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose).

3. Polysaccharides:

Polysaccharides are complex carbohydrates consisting of long chains of monosaccharide units, sometimes containing hundreds to thousands of sugar residues.

They serve diverse functions in living organisms, including energy storage, structural support, and cell recognition.

Polysaccharides are hydrolyzed into their constituent monosaccharides under appropriate conditions.

Examples include starch (energy storage in plants), glycogen (energy storage in animals), cellulose (structural component of plant cell walls), and chitin (found in the exoskeletons of arthropods and cell walls of fungi).

3.0Proteins and Amino Acids

The term "protein" originates from the Greek word "proteios," which translates to primary or of prime importance. Proteins are fundamental molecules in living organisms, essential for various biological functions.

Amino Acids

Amino acids, the building blocks of proteins, contain amino (–NH₂) and carboxyl (–COOH) functional groups. They are characterized by the presence of both an amino group and a carboxyl group attached to the same carbon atom, known as the α-carbon. When proteins are hydrolyzed, they break down into their constituent amino acids. While amino acids can contain other functional groups, those that are derived from proteins are primarily α-amino acids.

Classification of α-Amino Acids:

α-Amino acids can be classified into three main categories based on the properties of their side chains:

1. Acidic Amino Acids:

Acidic amino acids possess a carboxyl group in their side chain, rendering them acidic in nature.

Examples include: Aspartic acid (Asp), Glutamic acid (Glu)

2. Basic Amino Acids:

Basic amino acids carry a positively charged amino group in their side chain at physiological pH.

Examples include: Lysine (Lys or K), Arginine (Arg or R), Histidine (His or H)

3. Neutral Amino Acids:

Neutral amino acids have side chains that are neither acidic nor basic at physiological pH.

They can be further categorized based on the properties of their side chains, such as polar, nonpolar, aromatic, etc.

Examples include:

Structure of Proteins

Proteins are intricate molecules, serving essential roles in various biological processes. They are composed of chains of α-amino acids linked together by peptide bonds or peptide linkages.

Peptide Bond Formation

Chemically, a peptide bond is an amide linkage formed between the carboxyl (-COOH) group of one amino acid and the amino (-NH2) group of another. When two amino acid molecules react, the amino group of one amino acid combines with the carboxyl group of the other, resulting in the elimination of a water molecule. This process is called condensation or dehydration synthesis. The resulting bond is a peptide bond (-CO-NH-), which joins the α-carbons of adjacent amino acids.

Polypeptide Chains

The repetitive formation of peptide bonds between successive amino acids results in the formation of a polypeptide chain. These chains can vary in length and sequence, giving rise to the diverse structures and functions of proteins.

Primary Structure

The primary structure of a protein refers to the linear sequence of amino acids in the polypeptide chain. It is determined by the specific order of amino acids linked together by peptide bonds. The sequence of amino acids is encoded by the genetic information stored in DNA.

Secondary Structure

The secondary structure of a protein arises from interactions between amino acids that are close in the primary sequence. Common secondary structures include α-helices and β-sheets, stabilized by hydrogen bonds between backbone atoms.

Tertiary Structure

The tertiary structure of a protein refers to the overall three-dimensional arrangement of the polypeptide chain. It is dictated by interactions between amino acid side chains, including hydrogen bonds, disulfide bonds, hydrophobic interactions, and electrostatic interactions.

Quaternary Structure

In some cases, proteins consist of multiple polypeptide chains that come together to form a functional protein complex. The arrangement of these subunits is referred to as the quaternary structure.

4.0Vitamins

Vitamins are essential organic compounds that are required in small amounts in the diet to support various biological functions necessary for optimal growth and health maintenance in organisms.

1.  Fat soluble vitamins : A, D, E and K

2.  Water soluble vitamins : B and C

5.0Nucleic Acids

Nucleic acids are complex biomolecules that play essential roles in the storage, transmission, and expression of genetic information in living organisms. They are polymers made up of repeating units called nucleotides. 

Structure of Nucleic Acids

Nucleic acids, the carriers of genetic information in living organisms, consist of nucleotides, which are the building blocks of these molecules.

• Nucleoside: A nucleoside is formed by the attachment of a nitrogenous base to the 1' position of a sugar molecule. The carbons in the sugar molecule are numbered as 1', 2', 3', etc., to distinguish them from the atoms in the base. Nucleosides serve as the basic units for the construction of nucleotides.
• Nucleotide: When a nucleoside is linked to a phosphoric acid group at the 5'-position of the sugar moiety, it forms a nucleotide. The addition of the phosphate group gives the nucleotide its characteristic structure and functionality. Nucleotides are the fundamental building blocks of nucleic acids, such as DNA and RNA.

Types of Nucleic Acids

Nucleic acids are primarily categorized into two types:

Deoxyribonucleic Acid (DNA):

• DNA serves as the repository of genetic information in living organisms.
• It is a double-stranded helical molecule composed of nucleotides.
• Each nucleotide consists of a sugar molecule (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
• The sequence of these nitrogenous bases encodes the genetic instructions for the development, functioning, and reproduction of organisms.

Ribonucleic Acid (RNA):

• RNA plays various crucial roles in protein synthesis, gene regulation, and other cellular processes.
• Unlike DNA, RNA is typically single-stranded, although it can fold into complex secondary and tertiary structures.
• Similar to DNA, RNA is composed of nucleotides, each containing a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), uracil (U), cytosine (C), and guanine (G).
• RNA molecules are involved in translating the genetic information stored in DNA into functional proteins through the process of transcription and translation.