Download Nucleotides and Nucleic Acids DNA and RNA

Nucleotides and Nucleic Acids
Lesson Learning Outcomes
Upon completion of this lecture, students should
be able to:
 understand the properties of nucleotides and
nucleic acids
 recognize DNA and RNA
Essential Question
 What are the structures of the
nucleotides?
 How are nucleotides joined together
to form nucleic acids?
 How is information stored in nucleic
acids?
 What are the biological functions of
nucleotides and nucleic acids?
Level of structure in nucleic acids
 In proteins – primary, secondary, tertiary and
quaternary
 Nucleic acids are viewed is the same way
 Primary structure: order of bases in polynucleotide
 Secondary structure: 3D conformation of the backbone
 Tertiary structure: supercoiling of the molecule
What are nucleic acids?
 Nucleic acids are large biological molecules, essential
for all known forms of life.
 Nucleic
acids,
which
include
DNA
(deoxyribonucleic acid) and RNA (ribonucleic acid), are
made from monomers known as nucleotides linked in a
chain through phosphodiester bonds.
 In biological systems, they serves as information-carrying
molecules or, in the case of some RNA molecules are
catalysts.
What are nucleotides?
 Nucleotides are organic molecules that serve as the
monomers, or subunits, of nucleic acids like DNA and
RNA.
 The building blocks of nucleic acids
 Nucleotides are composed of
 a nitrogenous base,
 a five-carbon sugar (ribose or deoxyribose),
 and at least one phosphate group.
What is the Structure and Chemistry of
Nitrogenous Bases?
 Pyrimidines
 Cytosine (DNA, RNA)
 Uracil (RNA)
 Thymine (DNA)
 Purines
 Adenine (DNA, RNA)
 Guanine (DNA, RNA)
DNA and RNA
DNA & RNA Differences?
Why is DNA 2'-deoxy and RNA is not?
 Vicinal -OH groups (2' and 3') in RNA make it more
susceptible to hydrolysis
 DNA, lacking 2'-OH is more stable
 This makes sense - the genetic material must be more
stable
 RNA is designed to be used and then broken down
What Are the Different Classes of Nucleic
Acids?
 DNA - one type, one purpose
 RNA - 3 (or 4) types, 3 (or 4) purposes
 ribosomal RNA - the basis of structure and function of
ribosomes
 messenger RNA - carries the message
 transfer RNA - carries the amino acids
Hydrolysis of Nucleic Acids
 RNA is resistant to dilute acid
 RNA is hydrolyzed by dilute base
 DNA is depurinated by dilute acid
 DNA is not susceptible to base
Functions of Nucleotides
 Nucleoside 5'-triphosphates are carriers of energy
 Bases serve as recognition units
 Cyclic nucleotides are signal molecules and regulators of




cellular metabolism and reproduction
ATP is central to energy metabolism
GTP drives protein synthesis
CTP drives lipid synthesis
UTP drives carbohydrate metabolism
How does nucleotide forms nucleic acids?
 Nucleotides join together through phosphodiester
linkages between the 5' and 3' carbon atoms to form
nucleic acids.
 The 3' -OH of the sugar group forms a bond with one
of the negatively charged oxygen of the phosphate
group attached to the 5' carbon of another sugar.
 When many of these nucleotide subunits combine, the
result is the large single-stranded polynucleotide or
nucleic acid, DNA
Nucleic acid polymers
 Polymers linked 3' to 5' by phosphodiester bridges
 Ribonucleic acid and deoxyribonucleic acid
 Know the shorthand notations
 Sequence is always read 5' to 3'

Eg: 5’-CTTAGATACGTTGCCAGG-3’
 In terms of genetic information, this corresponds to "N to C"
in proteins
The DNA Double Helix
 Stabilized by hydrogen bonds!
 "Base pairs" arise from hydrogen bonds
 Erwin Chargaff had the pairing data, but didn't
understand its implications
 Rosalind Franklin's X-ray fiber diffraction data
was crucial
 Francis Crick knew it was a helix
 James Watson figured out the H bonds
Structure of DNA
 Double helix – James Watson and Francis Crick (1953)