Nucleic Acids And Protein Synthesis - Session 1

As we already know, DNA is a molecule that carries the genetic instructions of living organisms. These genetic instructions are used in the development, functioning, and reproduction of all known living organisms and many viruses. Have you ever wondered how this large amount of information is stored in DNA? To answer this question let us understand the structure of DNA.

DNA is similar to a polymer. A polymer is a large molecule composed of repeating subunits called monomers. DNA is made up of smaller units called nucleotides. These nucleotides are monomers of a DNA polymer.

Now we shall discuss the structure of a nucleotide. A nucleotide consists of three components. These are, a sugar molecule called deoxyribose, a phosphate group, and a nitrogenous base. The sugar molecule and phosphate group form the backbone of the DNA molecule. Meanwhile the nitrogenous base is attached to the sugar molecule.

Now let us understand these components of a nucleotide. We shall start with the sugar molecule. In DNA the sugar molecule is deoxyribose sugar. It is derived from ribose sugar. Deoxyribose sugar lacks a oxygen atom at carbon number two.

RNA stands for ribosenucleic acid. In nucleotide of RNA, ribose sugar is found instead of deoxyribose sugar. Unlike deoxyribose, an oxygen atom is seen at carbon number two in ribose sugar.

Next component of nucleotide is phosphate group. Phosphate group is attached to carbon number five of deoxyribose sugar. The nucleotide is linked with other nucleotide through this phosphate group. Both phosphate group and deoxyribose sugar make up the backbone of the DNA molecule.

The third component of nucleotide is nitrogenous base. Nitrogenous base is attached at carbon number one of deoxyribose sugar in DNA. There are a total of five types of nitrogenous bases. These are adenine, guanine, cytosine, thyamine and uracil. In DNA, adenine, guanine, cytosine, thymine are seen. Meanwhile in RNA, adenine, guanine, cytosine and uracil are seen.

As we know, ATP is the energy currency of the cell. Cells use energy in the form of ATP. The structure of ATP is also similar to nucleotide. It consists of a sugar molecule. Three phosphate groups are attached to sugar molecule. Adenine is also attached as nitrogenous base to the sugar molecule.

Nitrogenous bases can be categorized into two types. These are purines and pyrimidines. Purines are larger nitrogenous bases consisting of a double-ring structure. Adenine and guanine are called purines. Adenine and guanine have distinct chemical structures. They share the common feature of having two rings fused together.

Pyrimidines are smaller nitrogenous bases consisting of a single-ring structure. The three types of pyrimidines found in nucleic acids are cytosine, thymine, and uracil. Thymine is found only in DNA. While Uracil is found only in RNA. Cytosine and thymine have similar chemical structures, while uracil differs slightly.

Nucleotides are linked together through phosphodiester linkages. A phosphodiester linkage is a chemical bond that connects nucleotides in DNA molecule. It forms between the phosphate group of one nucleotide and the sugar molecule of another nucleotide.

A polynucleotide is a polymer made up of nucleotide monomers linked together by phosphodiester bonds. In DNA there are two polynucleotide chains. These polynucleotide chains are antiparallel to each other. The nitrogenous bases from each chain are connected through hydrogen bonds. Hydrogen bonds are relatively weak compared to covalent bonds. They are vital for maintaining the stability and integrity of the DNA molecule.

The hydrogen bonding patterns between the nitrogenous bases have a specific function. This hydrogen bonding keeps the two polynucleotide chains together. There are two hydrogen bonds between adenine and thymine. Meanwhile there are three hydrogen bonds between cytosine and guanine.

In DNA, adenine always pairs with thymine. Guanine always pairs with cytosine. This pairing scheme is called complementary base pairing. Adenine and thymine are complementary base pairs. Cytosine and Guanine are also complementary base pairs.

The DNA double helix is like a twisted ladder or a spiral staircase. It has a shape that twists in a clockwise direction. The double helix has a two nanometers consistent width throughout its length. The nitrogenous bases are positioned at the center of the double helix. Nitrogenous bases are like the steps of the ladder. The specific sequence of nitrogenous bases along the DNA molecule carries the genetic information. This specific sequence of the nitrogenous bases encodes the instructions for constructing and maintaining an organism.