- Slides: 5
Nucleic Acids • Nucleic acids are polynucleotide. They are two types: DNA and RNA. • I. Deoxyribonucleic acid (DNA): • DNA (Deoxyribonucleic acid) is a molecule composed of two chains (made of nucleotides) that coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and ribonucleic acid (RNA) alongside proteins, lipids and many viruses. are nucleic complex DNA acids; carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life.
• The two DNA strands are also known as polynucleotides since they are composed of simpler monomeric units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases (cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugarphosphate backbone. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA.
Structure of nucleotides: • A. Nucleotides: are intracellular molecules formed of: Base+ Sugar + Phosphate. • (Base I Sugar I Phosphate) • B. Nucleosides: are formed only of: nitrogenous bases and sugars. (Base I Sugar) • C. Bases: The nitrogenous bases are either pyrimidines or purines. • 1. Pyrimidine bases: • a) They contain pyrimidine ring. There are 3 pyrimidines enter in the structure of nucleotides and nucleic acids. These are uracil, thymine and cytosine.
• 2. Purine bases: • a) Adenine and guanine are the 2 purines which enter in the structure e of nucleic acids (DNA and RNA).