Transcript Nucleic Acids

The nucleic acids
include the amazing
DNA molecule.
It is the source of
constancy and
variation among
species, and is the
foundation for the
unity and diversity of
all life on Earth.
Nucleic Acids
 Nucleic acids store and
transmit hereditary
information
 The amino acid sequence of a polypeptide is
programmed by a unit of inheritance called a gene
 Genes are made of DNA, a nucleic acid
Genes
• Are the units of inheritance
• Program the amino acid sequence of
polypeptides
• Are made of specific nucleotide sequences on
DNA
The
Roles
of
Nucleic
Acids
 There are two types of nucleic acids involved in
inheritance and protein synthesis
 Deoxyribonucleic acid (DNA)
 Ribonucleic acid (RNA)
 DNA
– Stores information for the synthesis of
specific proteins
– Found in the nucleus of cells
– Directs RNA synthesis (transcription)
– Directs protein synthesis through RNA

(translation)
RNA
– Single stranded nucleic acid which
carries the code for protein synthesis
– Found in nucleus, and outside of
nucleus in association with ribosomes
The Structure of Nucleic Acids
Nitrogenous bases
Pyrimidines
 Nucleic acids
 Exist as polymers called
polynucleotides
Thymine (T, in DNA)
Uracil (U, in RNA)
(C)
 Cytosine
Each
polynucleotide
5’ end
5’C
3’C
– Consists of monomers called
nucleotides
– Sugar + phosphate +
nitrogen base
O
Purines
Adenine (A)

O
O
Guanine (G)
Nucleotide monomers
Sugars
5’C
– Are made up of nucleosides (sugar +3’C
OH
base) and phosphate groups
– The portion of
a nucleotide without
Ribose (in RNA)
Deoxyribose (in DNA)
the phosphate group is called a
nucleoside
(c) Nucleoside components: sugars
O
3’ end
Nucleotide Monomers
 Nucleoside = nitrogenous base +
sugar
Adenine
 There
are twoGuanine
families of
Cytosine
Thymine
nitrogenous bases:
 Pyrimidines (cytosine, thymine, and
uracil) have a single six-membered
ring
 Purines (adenine and guanine)
have a six-membered
ring fused to
Deoxyribose
Ribose
a five-membered ring
• In DNA, the sugar is deoxyribose;
in RNA, the sugar is ribose
Uracil
Nucleotide Polymers
 Nucleotide polymers are linked
together to build a
polynucleotide
 Adjacent nucleotides are
joined by covalent bonds that
form between the –OH group
on the 3 carbon of one
nucleotide and the phosphate
on the 5 carbon on the next
 These links create a backbone
of sugar-phosphate units with
nitrogenous bases as
appendages
 The sequence of bases along a
DNA or mRNA polymer is
unique for each gene
DNA Double Helix
5
When guanine and cytosine bond, they 3
form triple hydrogen bonds
O
H-bonds
3
P
5
O
C
G
1
O
P
5
3
2
4
4
2
3
1
P
T
5
P
5
O
A
P
3
O
3
When thymine and adenine
bond, a double hydrogen
bond is formed
O
5
P
• Antiparallel nature: •
Sometimes called
complementary”
sugar/phosphate backbone
runs in opposite directions
• one strand runs 5’ to 3’, while
the other runs 3’ to 5’;
• One DNA molecule includes
many genes
Remember, the nucleotides
connect together at the
hydroxyl group of the 5’
carbon sugar (at the 3’ end)
Scientists can use DNA
and Proteins as Tape
Measures of Evolution
 Molecular comparisons
 Help biologists sort out the
evolutionary connections
among species
 How similar are the
sequences of nucleotides?
The closer the sequence, the
closer the relationship
 Remember, all life, from the
simplest prokaryote to the most
complex eukaryote, contains
the same four nitrogenous
bases.
It is simply the sequence of base-pairs, and amount of DNA that differs
from organism to organism!

Adenosine triphosphate is a common source of activation
energy for metabolic reactions.
ATP is essentially an RNA adenine (adenosine) nucleotide
with two additional phosphate groups.
The wavy lines between
these two phosphate groups
indicate high energy bonds.
When that last bond is
broken, and the ATP is
converted to ADP
(adenosine diphosphate),
energy is released, and can
be used to spur a reaction.
Conversely, a new ATP molecule can be built by combining ADP and a
phosphate through a process known as phosphorylation using energy
obtained from glucose.