Biomolecules Definition
- Biomolecules are molecules that occur naturally in living organisms. Biomolecules include macromolecules like proteins, carbohydrates, lipids and nucleic acids.
- It also includes small molecules like primary and secondary metabolites and natural products.
- Biomolecules consists mainly of carbon and hydrogen with nitrogen, oxygen, sulphur, and phosphorus.
- Biomolecules are very large molecules of many atoms, which are covalently bound together.
Classes of Biomolecules
There are four major classes of
biomolecules:
i.
Carbohydrates
ii.
ii.
Lipids
iii.
iii.
Proteins
iv.
iv.
Nucleic acids
Carbohydrate
·
Carbohydrates
are good source of energy. Carbohydrates (polysaccharides) are long chains of
sugars.Monosaccharides are simple sugars that are composed of 3-7 carbon atoms.
·
They
have a free aldehyde or ketone group, which acts as reducing agents and are
known as reducing sugars. Disaccharides are made of two monosaccharides. The
bonds shared between two monosaccharides are the glycosidic bonds.
·
Monosaccharides
and disaccharides are sweet, crystalline and water soluble substances.
Polysaccharides are polymers of monosaccharides. They are un-sweet and complex
carbohydrates. They are insoluble in water and are not in crystalline form.
·
Example:
glucose, fructose, sucrose, maltose, starch, cellulose etc.
Lipids
·
Lipids
are composed of long hydrocarbon chains. Lipid molecules hold a large amount of
energy and are energy storage molecules. Lipids are generally esters of fatty
acids and are building blocks of biological membranes.
·
Most
of the lipids have a polar head and non-polar tail. Fatty acids can be unsaturated
and saturated fatty acids.
·
Lipids
present in biological membranes are of three classes based on the type of
hydrophilic head present:
·
Example
of lipids: oils, fats, phospholipids, glycolipids, etc.
Nucleic Acids
·
Nucleic
acids are organic compounds with heterocyclic rings.
·
Nucleic
acids are made of polymer of nucleotides. Nucleotides consist of nitrogenous
base, a pentose sugar and a phosphate group.
·
A
nucleoside is made of nitrogenous base attached to a pentose sugar.
·
The
nitrogenous bases are adenine, guanine, thyamine, cytosine and uracil.
Polymerized nucleotides form DNA and RNA which are genetic material
Proteins
·
Proteins
are heteropolymers of stings of amino acids. Amino acids are joined together by
the peptide bond which is formed in between the carboxyl group and amino group
of successive amino acids. Proteins are formed from 20 different amino acids,
depending on the number of amino acids and the sequence of amino acids.
·
There
are four levels of protein structure:
(i) Primary structure of Protein - Here
protein exist as long chain of amino acids arranged in a particular sequence.
They are non-functional proteins.
(ii) Secondary structure of
protein - The long chain of proteins are folded and arranged in a helix shape,
where the amino acids interact by the formation of hydrogen bonds. This
structure is called the pleated sheet.
Example: silk fibres.
(iii) Tertiary structure of
protein - Long polypeptide chains become more stabilizes by folding and
coiling, by the formation of ionic or hydrophobic bonds or disulphide bridges,
these results in the tertiary structure of protein.
(iv) Quaternary structure of
protein - When a protein is an assembly of more than one polypeptide or
subunits of its own, this is said to be the quaternary structure of protein.
Example: Haemoglobin, insulin.
Functions of Biomolecules
- Carbohydrates
provide the body with source of fuel and energy, it aids in proper functioning
of our brain, heart and nervous, digestive and immune system. Deficiency of
carbohydrates in the diet causes fatigue, poor mental function.
- Each
protein in the body has specific functions, some proteins provide structural
support, help in body movement, and also defense against germs and infections.
Proteins can be antibodies, hormonal, enzymes and contractile proteins.
- Lipids, the primary purpose of lipids in body are energy storage. Structural membranes are composed of lipids which form a barrier and controls flow of material in and out of the cell. Lipid hormones, like sterols, help in mediating communication between cells.
- Nucleic Acids are the DNA and RNA; they carry genetic information in the cell. They also help in synthesis of proteins, through the process of translation and transcription
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