2. 3 Nucleotides And Nucleic Acid

Every organism reproduces within its life span. This is accomplished through cell divisions and is regulated by many kinds of protiens. The information forsynthesizing unique proteins is located in the nucleus of the cell. It is called the genetic code which is the "blue print" for producing specific sequences of the amino acids in proteins. Thus the genetic code can regulate chemical reaction going on in the cell.

Man’s queries into the nature of cells did not end with its discovery of general structures. In an attempt to understand the chemical make up and functional details of the cell he succeeded in discovering a substance called nucleic acid, made up of long chains of nucleotide units.

(A) Nucleotide

It is the structural unit of nucleic acid. Each nucleotide is composed of:

(1) Pentose sugar

(2) Phosphate group

(3) One of four nitrogen bases attached to the pentose sugar. A nucleotide without a phosphate group is a nucleoside.

(B) Nucleic acids

They are complex, large biomolecules formed of many units called nucleotides.

Nucleic acids are of two types :

(1) DNA - Deoxyribonucleic acid and, (2) RNA - Ribonucleic acid

The DNA of cells contains genetic information in a coded form, and is only present in the nucleus of the cellis formed from DNA, plus a few special organelles. RNA and is present in the cytoplasm and in the nucleus of the cell.

DNA and RNA differ from one another in their components. DNA contains the pentose sugar, deoxyribose, while RNA contains ribose.

There are also small differences in the types of nitrogen bases found in DNA and RNA. (The structure of DNA and its importance in the life of cells will be explained in the chapter "Genes and Molecular genetics" ,Chapter 7.)

Table of Contents

2.0 - Introduction
2.1 Structural Organization and Chemical Basis Of Life
2.2 Organic Compounds
2.3 Nucleotides and Nucleic Acid
2.4 Lipids

Chapter 3