Download Nucleic Acids

Most Biomacromolecules are Polymers....
A polymer is a long molecule consisting of many small repeating subunits
called monomers.
These polymers are
built by condensation
reactions
3 of the 4 classes of life’s organic molecules are polymers:
• Carbohydrates
• Proteins
• Nucleic acids
Biomacromolecules: Features
Biomacromolecules
Biomacromolecules are very large molecules that play an essential role in the
structure and function of cells.
Biomacromolecule Sub-units
Bond Formed by
Condensation
Cellular Functions
Lipids
Lipids are not
polymers
Fatty Acids & Glycerol
Ester linkage
Energy storage,
phospholipids, signalling
molecules
Complex
carbohydrates
Polysaccharides
Simple sugar monomers
Monosaccharides
Glycosidic linkage
Energy storage, structral
components (eg. cellulose)
Nucleic Acids
Polynucleotides
Nucleotide monomers
Phosphodiester
linkage
Genetic material
Proteins
Polypeptides
Amino Acid monomers
Peptide linkage
Diverse roles; control and
regulation, transport,
receptors, structural
components
Biomacromolecules: Features
Nucleic Acids
Nucleic acids store genetic
information
There are two main types
• Deoxyribonucleic Acid (DNA)
• Ribonucleic Acid (RNA)
DNA is hereditary and directs its
own replication
DNA also directs synthesis of
messenger RNA (mRNA)
mRNA, in turn, controls protein
synthesis in ribosomes
Biomacromolecules: Nucleic Acids
Nucleotides
Nucleotides are the monomers that make up nucleic acids.
A nucleotide has three distinct components;
1. 5 carbon sugar
• ribose in RNA
• deoxyribose in DNA
2. negatively charged phosphate group
3. nitrogenous base
• Adenine (both)
• Thymine (DNA only)
• Guanine (both)
• Cytsosine (both)
• Uracil (RNA only- takes the place of Thymine)
Nucleic Acids: Nucleotides
Nucleoside Components in Detail
Nucleoside is a term that refers only to the
variable components of a nucleotide;
• the sugars
• nitrogenous bases
Note the structural differences
•
•
Pyrimidines have a 6 carbon ring
Purines have a 5 and a 6 carbon ring
•
•
Ribose sugars have a 2' and 3' OH group
Deoxyribose sugars have lost an oxygen
from their 2' OH group
Nucleotides: Nucleoside Components
Hang On- What the Hell is Prime'?
“Prime” was hinted at with carbohydrates....but it has greater significance with
regards to nucleic acids.
In molecular biology, the
prime is used to denote the
positions of carbon on a ring.
If I refer to carbon number 3,
I say “3-prime carbon” or
write “3' C”.
glucose
Biochemical Nomenclature: Prime
Nucleic Acids are Polynucleotides
A nucleic acid, or polynucleotide, is
formed by the joining together of
nucleotides by condensation
polymerisation.
H2O
The type of covalent bond
formed here is called a
phosphodiester linkage
Nucleic Acids: Polynucleotides
Nucleic Acids are Polynucleotides
We say that these
nucleotides are assembling
in a 5' to 3' direction.
Is this DNA or RNA?
Polynucleotides: Assembly
Nucleic Acids are Polynucleotides
Polynucleotides: Assembly
DNA Structure
The DNA molecule has two
complementary strands of
polynucleotides spiralling about an
imaginary axis.
The strands are antiparallel- they run
in opposite 5' to 3' directions
Hydrogen bonds form between
complementary nitrogenous bases
called base pairs (bp).
Remember!
A
T
G
C
Base pairs
Nucleic Acids: Deoxyribonucleic Acid
From DNA to mRNA
The amino acid sequence of a protein is determined by the nucleotide
sequences of the gene that encodes it.
The sequence of nucleotides in the DNA of a gene is transcribed into the
equivalent sequence in messenger RNA.
In RNA, Thymine is replaced with Uracil.
Each group of three, called a triplet
codon, stands for a specific amino acid.
This same genetic code is used by
virtually all organisms on the planet.
The mRNA codons provide
instructions for protein
assembly.
From DNA to RNA: Transcription
From RNA to Proteins
Messenger RNA (mRNA) carries an amino acid sequence to a ribosome.
Ribosomes are complexes of protein and ribosomal RNA (rRNA).
They move along the mRNA in a 5' to 3' direction translating the triplet codons.
Transfer RNA (tRNA)
uses an anticodon to
fetch the required
amino acids.
Together the ribosome
synthesises the protein
one amino acid at a
time.
RNA to Proteins: Translation
A Broader Perspective
Each somatic cell in the human body has
• 46 chromosomes
• over a metre of DNA
• more than 3 billion base pairs
The functional components encoded for by DNA are called genes.
The total set of genes for an organism is called the genome, the study of
which is called genomics.
DNA is passed from parent to offspring.
• Nucleotide sequences can be assessed to establish kinship.
• Two closely related species are more similiar in DNA than distantly
related species
Nucleic Acids