2. DEFINITION
Nucleic acids are biopolymers, or small
biomolecules, essential to all known
forms of life. They are composed of
monomers, which are nucleotides made
of three components: a 5-carbon sugar, a
phosphate group and a nitrogenous base.
If the sugar is a simple ribose, the
polymer is RNA (ribonucleic acid); if the
sugar is derived from ribose as
deoxyribose, the polymer is
DNA(deoxyribonucleic acid).
3. TYPES OF NUCLEIC ACID
1)RNA: May be found in nucleus but
mainly occurs in cytoplasm carry out
protein synthesis work.
2) DNA: Occurs in nucleus as well as cell
organelles like chloroplast and
mitochondria.
4. TYPES OF RNA
• Transfer RNA (t-RNA)
• Messenger RNA (m-RNA)
• Ribosomal RNA (r-RNA)
5. TRANSFER RNA (T-RNA)
A transfer RNA is an adaptor molecule
composed of RNA, typically 76 to 90
nucleotides in length, that serves as
the physical link between the mRNA
and the amino acid sequence of
proteins.
6. MESSENGER RNA (m-RNA)
Messenger RNA (mRNA) is a large family
of RNA molecules that convey genetic
information from DNA to the ribosome,
where they specify the amino acid
sequence of the protein products of
gene expression.
7. RIBOSOMAL RNA (r-RNA)
Ribosomal ribonucleic acid (rRNA) is
the RNA component of the ribosome,
and is essential for protein synthesis
in all living organisms. It constitutes
the predominant material within the
ribosome, which is approximately 60%
rRNA and 40% protein by weight, or
3/5 of ribosome mass.
8. STRUCTURE OF NUCLEOTIDE
The structure of DNA is dependent on only 4 different nucleotides
All nucleotides are 2 ring structures composed of:
5-carbon sugar : b-D-ribose (RNA)
b-D-deoxyribose (DNA)
Base: Purine
Pyrimidine
Phosphate group: A nucleotide WITHOUT a phosphate group is a
NUCLEOSIDE
9. Nucleotide Structure - 1
Sugars
RIBOSE: Ribose is a carbohydrate with the formula C5H10O5;
specifically, it is a pentose monosaccharide (simple sugar) with
linear form H−(C=O)−(CHOH)4−H, which has all the hydroxyl
groups on the same side in the Fischer projection.
Generic Ribose Structure Ribose
10. DEOXYRIBOSE: Deoxyribose, or more precisely 2-deoxyribose,
is a monosaccharide with idealized formula
H−(C=O)−(CH2)−(CHOH)3−H. Its name indicates that it is a
deoxy sugar, meaning that it is derived from the sugar ribose
by loss of an oxygen atom.
Generic Ribose Structure Deoxyribose
11. BASES
PURINE: A purine is a heterocyclic aromatic
organic compound that consists of a pyrimidine
ring fused to an imidazole ring.
Adenine
Guanine
12. PYRIMIDINES: Pyrimidine is an aromatic heterocyclic organic
compound similar to pyridine. One of the three diazines (six-membered
heterocyclics with two nitrogen atoms in the ring), it has the nitrogen
atoms at positions 1 and 3 in the ring. The other diazines are pyrazine
(nitrogen atoms at the 1 and 4 positions) and pyridazine (nitrogen
atoms at the 1 and 2 positions). In nucleic acids, three types of
nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and
uracil (U).
Thymine
Cytosine
13. Thymine is found ONLY in DNA.
In RNA, thymine is replaced by uracil
Uracil and Thymine are structurally similar
Uracil
14. PHOSPHATE GROUPS
Phosphate groups are what makes a nucleoside a
nucleotide.
Phosphate groups are essential for nucleotide
polymerization.
Basic structure:
P
O
O
O
O X
15. Number of phosphate groups determines nomenclature
Monophosphate
e.g. AMP
Free = inorganic
phosphate (Pi)
Diphosphate
e.g. ADP
Free = Pyro-
phosphate (PPi)
Triphosphate
e.g. ATP
No Free form exists
16. DOUBLE HELIX
First determined by Watson & Crick in 1953
Most energy favorable conformation for double
stranded DNA to form Shape and size is
uniform for all life (i.e. DNA is identical)
Without anti-parallel base pairing this
conformation could not exist
Structure consists of “major” grooves and
“minor” grooves Major grooves are critical for
binding proteins that regulate DNA function.
18. PROPERTIES OF NUCLEIC ACID
• Nucleic acids (deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA) are extremely long polymers made
up of phosphate-sugar-nitrogenous base (nucleotide)
units.
• The bases found in DNA are adenine and guanine (both
purines) and cystidine and thymine (both pyrimidines).
• Thymine is replaced by uracil in RNA.
• The nucleotides are linked by 3' to 5' phosphodiester
bonds.
• A phosphate group on the 5' position of the sugar residue
becomes linked to the 3' hydroxyl group of the preceding
sugar group on the chain as the long polymer is
synthesized.
19. FUNCTIONS OF NUCLEIC ACIDS:
1) Transmission of hereditary Characters (DNA)
2) Synthesis of Proteins (RNA)
DNA: Store house of genetic information control protein
synthesis in cell. Direct synthesis of RNA.
RNA: Direct synthesis of specific proteins.
m-RNA: To take genetic massage from RNA
t- RNA: Transfer the activated amino acids to the site of
protein synthesis.
r-RNA: Function not clearly understood. Mostly present in
ribosomes and responsible for stability of m-RNA.-
