Nucleic acids, which include DNA and RNA, are polymers made of nucleotides comprised of a nitrogenous base, a pentose sugar, and a phosphate group. The structure includes purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil), with base pairing stabilized by hydrogen bonds. DNA and RNA differ in the sugar component, with DNA containing deoxyribose and RNA containing ribose, and the strands of DNA are anti-parallel with a backbone formed by phosphodiester linkages.

1. *

2. Nucleic Acids

3. Two types of Nucleic Acids

4. Nucleic Acids
-are made up of monomers
known as nucleotides.
-the nucleotides combine
with each other to form a
polynucleotide, DNA or RNA.

5. Nucleotide
-is made up of three
components: a nitrogenous base,
a pentose (five-carbon) sugar,
and a phosphate group.
-each nitrogenous base in a
nucleotide is attached to a sugar
molecule, which is attached to
one or more phosphate groups.

6. Nitrogenous bases:
-adenine (A)
-guanine (G)
-cytosine (C)
-thymine (T)
-uracil (U)

7. Nitrogenous bases:
Purines (ADENINE & GUANINE)
- primary structure is composed
of:
Pyrimidines (CYTOSINE, THYMINE & URACIL)
-primary structure is composed of:
-SINGLE

8. Complementary Base Pairs:
Adenine –Thymine (2-H bond)
Cytosine-Guanine (3-H bond)
(Base pairs are stabilized by hydrogen bonds)

9. Pentose sugar:
DNA -deoxyribose
-absence of OH group on 2-Carbon
RNA-ribose
-presence of OH group on 2-Carbon

10. RIBOSE & DEOXYRIBOSE STRUCTURE:
*The carbon atoms of the sugar molecule are numbered as 1’, 2’,3’ 4’,and 5’
(1’ is read as “one prime”)
*The phosphate residue is attached to the hydroxyl group of the 5’ carbon of one
sugar and the hydroxyl group of the 3’ carbon of the sugar of the next
nucleotide, which forms a 5’-3’ phosphodiester linkage.

11. 5’-3’ PHOSPHODIESTER LINKAGE:

12. DNA Strands are anti-parallel :
-3’ end of one strand faces 5’
end of the other strand.
-The sugar and phosphate of the
nucleotides form the backbone
of the structure, whereas the
nitrogenous bases are stacked
inside.