NUCLEIC ACIDS

There are two kinds of nucleic acids. One is called DNA�from deoxyribonucleic acid. The other is called RNA�from ribonucleic acid.

The Structure of DNA and RNA

      The general structure of a nucleic acid molecule is that of a very long chain of repeating units. The backbone of the chain consists of two alternating chemical units. One unit is a

5-carbon sugar (deoxyribose in DNA, ribose in RNA). The other is the phosphate group, P0₄.

Attached to the sugar groups along one side of the chain, there are chemical groups called bases. In DNA, there are only four different bases that may be attached to the chain. They are adenine, thymine, cytosine, and guanine.

adenine is always bonded to a thymine. A cytosine is always bonded to a guanine.

The entire molecule is coiled into the form called a double helix.

      An RNA molecule is similar in chemical composition to DNA, but it has certain differences. The RNA molecule con�sists of only one chain, or strand, of bases. The sugar in RNA is ribose, not deoxyribose. And the base thymine is replaced by uracil. RNA is involved in protein synthesis. And there  are three types of RNA ; mRNA, tRNA, and rRNA.

Evaluation: Ask some questions to control if they understand

1.List the factors that effect enzyme action?

2.Name the types of nucleic acids 

3.Explain the structure of DNA

4. compaire the DNA and RNA structures

5. Campaire the functions of DNA and RNA

Homework: Read about the structure of nucleic acid and Draw the madel of DNA and RNA .   

Discussion:  students understood the all concepts of structure and functions of nucleic acids. The recommended  period  was enough.