Nucleic acid

1. AP Biology
Topic: Nucleic acid chemistry
By
Dr. Zablon Kerima
Lecturer
Dept. Biochemistry
Kampala International
University -Tanzania

2. AP Biology
 Nucleic acids are molecules that store information for
cellular growth and reproduction
 There are two types of nucleic acids:
- deoxyribonucleic acid (DNA) and ribonucleic acid
(RNA)
 These are polymers consisting of long chains of
monomers called nucleotides
 A nucleotide consists of a nitrogenous base, a pentose
sugar and a phosphate group:

3. AP Biology
Nucleic Acids
 Function:
 store & transmit genetic information
 Types:
 RNA (ribonucleic acid) (rRNA, mRNA, tRNA)
 DNA (deoxyribonucleic acid)
 Structure:
 monomers = nucleotides…..?
 Polymers = polynucleotides (DNA, RNA)

4. AP Biology
Nucleotides
Phosphate
Pentose
Sugar
Nitrogenous
Base

5. AP Biology

6. AP Biology
Nucleotides
 3 parts
 nitrogen base (C-N ring)
 pentose sugar (5C)
 ribose in RNA
 deoxyribose in DNA
 phosphate (PO4) group

7. AP Biology
Nucleotide structure 1 - Pentose Sugars
 There are two related pentose sugars:
- RNA contains ribose
- DNA contains deoxyribose
 The sugars have their carbon atoms numbered with
primes to distinguish them from the nitrogen bases

8. AP Biology
Sugars
O
HOCH2
5’
1’
4’
3’ 2’
O
HOCH2
OH
OH
OH
O
HOCH2
OH
H
OH
Ribose
Deoxyribose
Generic Ribose
Structure
N.B. Carbons are given numberings as a
prime

9. AP Biology
Based on McMurry, Organic Chemistry, Chapter
28, 6th edition, (c) 2003
9
Nucleotide Structure - 2
Bases: Purine and Pyrimidine
 Pyrimidine contains two pyridine-like nitrogens in a
six-membered aromatic ring (single ring)
 Purine has 4 N’s in a fused-ring structure. Three
are basic like pyridine-like and one is like that in
pyrrole (double rings)

10. AP Biology
Nitrogen Bases
 The nitrogen bases in nucleotides consist of two general
types:
- purines: adenine (A) and guanine (G)
- pyrimidines: cytosine (C), thymine (T) and Uracil (U)

11. AP Biology

12. AP Biology
Bases - Pyrimidines
N
N
5
6
1
2
3
4
Uracil
NH
N
O
U
O
H
Thymine is found ONLY in DNA.
In RNA, thymine is replaced by uracil
Uracil and Thymine are structurally similar

13. AP Biology
Nucleotide Structure - 3
Phosphate Groups
Phosphate groups are what makes a nucleoside a
nucleotide……???
Phosphate groups are essential for nucleotide
polymerization
P
O
O
O
O X
Basic structure:
Free = inorganic
phosphate (Pi)

14. AP Biology
Nucleotide : Base-Sugar-PO4
2-
P
O
O
O
O
N
N
5
6
1
2
3
4
O
C
5’
1’
4’
3’ 2’
OH
Monophosphate

15. AP Biology
Phosphate groups
are what makes a
nucleoside a
nucleotide

16. AP Biology
AMP, ADP and ATP
 Additional phosphate groups can be added to the
nucleoside 5’-monophosphates to form diphosphates
and triphosphates
 ATP is the major energy source for cellular activity

17. AP Biology
Nucleosides and Nucleotides
 A nucleoside consists of a nitrogen base linked by
a glycosidic bond to C1’ of a ribose or
deoxyribose
 Nucleosides are named by changing the nitrogen
base ending to -osine for purines and –idine for
pyrimidines
 A nucleotide is a nucleoside that forms a
phosphate ester with the C5’ OH group of ribose
or deoxyribose
 Nucleotides are named using the name of the
nucleoside followed by 5’-monophosphate

18. AP Biology
Names of Nucleosides and Nucleotides

19. AP Biology

20. AP Biology
RNA & DNA
 RNA
 single nucleotide chain
 DNA
 double nucleotide chain
 N bases bond in pairs
across chains
 spiraled in a double helix

21. AP Biology
Building the polymer

22. AP Biology
Nucleic polymer
 Backbone
 sugar to PO4 bond
 new base added to sugar of previous base
 polymer grows in one direction
 N bases hang off the
sugar-phosphate backbone
Dangling bases?
Why is this important?

23. AP Biology
Nucleic acids
 Structure / monomer
 nucleotide
 Function
 information storage
& transfer
 Examples
 DNA, RNA

24. AP Biology
DNA molecule
 Double helix
 H bonds between bases join
the 2 strands
 Adenine:: Thymine
 (A-T)
 Cytosine:: Guanine
 (C-G)
 RNA
oA-U (Uracil)
oG-C

25. AP Biology
Information polymer
 Function
 series of bases encodes information
 like the letters of a book
 stored information is passed
from parent to offspring
 need to copy accurately
 stored information = genes
 genetic information
Passing on information?
Why is this important?

26. AP Biology
A
A
A
A
T
C
G
C
G
T
G
C
T

27. AP Biology
ATP
 Adenosine triphosphate
 Adenosine
 Composed of adenine and ribose
 Triphosphate
 3 phosphate groups attached to
each other and the ribose
 ATP = High energy molecule
-supplies energy for muscle contraction and
nerve impulses
 ADP = Lower energy molecule (diphosphate)
+
+

28. AP Biology
What are the complementary
base pairs for DNA?
A. A-T and G-U
B. A-T and G-C
C. A-U and G-C
D. A-T and C-U
A
-
T
a
n
d
G
-
U
A
-
T
a
n
d
G
-
C
A
-
U
a
n
d
G
-
C
A
-
T
a
n
d
C
-
U
0%
10%
5%
86%

29. AP Biology
What is one difference between
DNA and RNA?
A. DNA has uracil and
RNA does not
B. RNA is single
stranded and DNA
is double stranded
C. DNA has 4 bases
and RNA has 5
D. DNA has a ribose
sugar and RNA
does not
D
N
A
h
a
s
u
r
a
c
i
l
a
n
d
R
N
A
.
.
.
R
N
A
i
s
s
i
n
g
l
e
s
t
r
a
n
d
e
d
a
.
.
D
N
A
h
a
s
4
b
a
s
e
s
a
n
d
R
N
.
.
.
D
N
A
h
a
s
a
r
i
b
o
s
e
s
u
g
a
r
a
.
.
5% 5%
10%
81%

30. AP Biology
What are the 3 parts of a
nucleotide?
A. 5 C sugar, carbon base,
carboxyl group
B. 3 C sugar, nitrogen base,
phosphate group
C. 5 C sugar, nitrogen base,
phosphate group
D. 5 C sugar, nitrogen base,
hydroxyl group
5
C
s
u
g
a
r
,
c
a
r
b
o
n
b
a
s
e
,
.
.
.
3
C
s
u
g
a
r
,
n
i
t
r
o
g
e
n
b
a
s
e
.
.
.
5
C
s
u
g
a
r
,
n
i
t
r
o
g
e
n
b
a
s
e
.
.
.
5
C
s
u
g
a
r
,
n
i
t
r
o
g
e
n
b
a
s
e
,
.
.
.
10%
5%
80%
5%

31. AP Biology
Which of the following supplies cellular
energy for muscle contractions and nerve
impulses?
A. DNA
B. RNA
C. ATP
D. ABC
D
N
A
R
N
A
A
T
P
A
B
C
0% 0%
95%
5%

32. AP Biology
Proteins
 Structure / monomer
 amino acids
 levels of structure
 Primary
 Secondary
 Tertiery
 Quaternary
 Function
 enzymes u defense
 transport u structure
 signals u receptors
 Examples
 digestive enzymes, membrane channels, insulin
hormone, actin and myosin, antibodies, collagen
peptide bond