Nucleic acids: Definition, Classification, Functions

 Nucleic acids

Nucleic acids are a polynucleotides consisting of repeated units of mononucleotides.

Definition

Nucleic acids are the polymers of nucleotides. A nucleotide is a nucleoside containing phosphate group. A nucleoside is made up of a purine or pyrimidine nitrogenous base linked to a pentose sugar.


Classification : 

Nucleic acids are classified into

1. Deoxyribonucleic acids (DNA)

The most important consistuent of chromosome and exist as double stranded helix. The nitogenous bases present are adenine, guanine, cytosine and thymine and the pentose sugar is deoxyribose.

2. Ribonucleic acids (RNA)

RNA is a polymer of purine and pyrimidine ribonucleotides linked together by 3’, 5’ phosphodiester bridges. The nitrogenous bases are adenine, guanine, cytosine and uracil and the pentose sugar is ribose.

Types of RNA - There are 3 main classes of RNA molecules exist in all prokaryotic and eukaryotic organisms - They are messenger RNA (mRNA).

transfer RNA (t RNA)

ribosomal RNA (r RNA)

 

Functions of DNA

·           DNA serves as genetic material in cells.

·           DNA provides information inherited by the daughter cells and is also a source of information for the synthesis of proteins and it produces mRNA essential for protein biosynthesis.

 

Functions of RNA

·           It primarily functions in the cytoplasm of the cell as template for the synthesis of protein.

·           It carries genetic information from DNA to the site of protein biosynthesis.

·           It is an essential component of ribosome

·           Some RNA has enzymatic activity

·           It serves as genetic material for viruses such as tobacco mosaic virus, polio virus etc.

Comments

Post a Comment

Popular posts from this blog

Cell Membrane and its Functions

Image
  Cell Membrane The cell is enveloped and thus separated from its surroundings by a thin wall contains a rigid framework of polysaccharide chains crosslinked with short peptide chains. Its outer surface is coated with lipopolysaccharide. Cell membrane is also called as plasma membrane (or) plasma lemma. The pili, not found in all bacteria have extensions of the cell wall. The cell membrane contains about 45% lipid and 55% protein. The cell membrane or plasma membrane have an average thickness of 75A°. The principal lipids are phospholipids, sphingolipids and cholesterol. An important feature of these lipids is they are composed of hydrophobic (water - insoluble) hydrocarbon sections and hydrophilic (water soluble) units. The latter include charged units (eg. phosphate or amino groups) and uncharged units (eg. hexose). In water, such compounds orient themselves in such a way that only the hydrophilic section is exposed to water. The hydrophobic components of individual molecules ten...
Read more

Types of Living cells

Image
  Types of cells Two general types are recognised in nature. They are prokaryotic and eukaryotic cells. Prokaryotic cells Prokaryotes were the first cells to arise in biological evolution. They are very small and simple having only a single membrane. The cell membrane, is usually surrounded by a rigid cell wall. They are devoid of nucleus and membranous organelles such as mitochondria and endoplasmic reticulum etc. (Fig. 1.1). Eukaryotic cells Eukaryotic cells are presumably derived from prokaryotes. They are much larger and much more complex than prokaryotic cells (Fig. 1.2). They have nucleus and membrane bound subcellular organelles. Many of their metabolic reactions are segregated within structural compartments. The significant differences between prokaryotic and enkaryotic cells are: The eukaryotic cell structure is composed of (i) cell membrane, (ii) nucleus (iii) mitochondria (iv) endoplasmic reticulum (v) golgi apparatus (vi) ribosomes (vii) lysosomes and others. These spec...
Read more

Sub cellular Organelles

Image
  Sub cellular Organelles   Cell Membrane The cell is enveloped and thus separated from its surroundings by a thin wall contains a rigid framework of polysaccharide chains crosslinked with short peptide chains. Its outer surface is coated with lipopolysaccharide. Cell membrane is also called as plasma membrane (or) plasma lemma. The pili, not found in all bacteria have extensions of the cell wall. The cell membrane contains about 45% lipid and 55% protein. The cell membrane or plasma membrane have an average thickness of 75A°. The principal lipids are phospholipids, sphingolipids and cholesterol. An important feature of these lipids is they are composed of hydrophobic (water - insoluble) hydrocarbon sections and hydrophilic (water soluble) units. The latter include charged units (eg. phosphate or amino groups) and uncharged units (eg. hexose). In water, such compounds orient themselves in such a way that only the hydrophilic section is exposed to water. The hydrophobic compone...
Read more