Transcript Wednesday Sept 22, 2010 Bio 111 Dr. Ellen Yerger

Reminder-four classes of large biomolecules
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Carbohydrates/polysaccharides
Lipids
Proteins/polypeptides
Nucleic acids/polynucleotides
DNA
Two
Types
Nucleic
Acid
1 Synthesis of
mRNA
Function:
Information
Storage
And
Control
mRNA
NUCLEUS
CYTOPLASM
mRNA
DNA
and
RNA
2 Movement of
mRNA into
cytoplasm
Ribosome
3 Synthesis
of protein
Polypeptide
Amino
acids
Components of nucleic acids
• Nucleic acids are polymers
• Nucleotides are the monomers
• Each nucleotide consists of a base, a sugar and
a phosphate
• But the base plus the sugar without the
phosphate is called a nucleoside
• Bases are purines (Pu) or pyrimidines (Pyr)
• Sugars are either ribose or 2-deoxyribose
Phosphodiester Bond
• Links nucleotides
together
• Sugar and
phosphate
involved
• This example is a
3’-5’ bond
• Gives two distinct
ends
5 end
Sugar-phosphate backbone
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous
base
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Purines
5C
1C
5C
3C
Phosphate
group
3C
Sugar
(pentose)
Guanine (G)
Adenine (A)
(b) Nucleotide
Sugars
3 end
(a) Polynucleotide, or nucleic acid
Deoxyribose (in DNA)
(c) Nucleoside components
Ribose (in RNA)
RNA Structure
• Individual chains in cells
• Aka “single-stranded”: ssRNA
• Chains generally from 505000 nucleotides
• Distributed throughout the
cell
RNA molecules fold up on themselves
5’
3’
• Secondary
structure refers
to folding pattern
• Confers unique
shape
• Primary structure
is the 5’ to 3’
sequence of
bases
DNA structure-different from RNA
• Two molecules interact to form double strand
Important features of the double helix
• Antiparallel
strands
• Bases on the
inside
• Chain held
together by
hydrogen
bonds
• Watson-Crick
base pairs
AT and GC are the Watson-Crick
base pairs
Complementary
DNA Structure
• Almost always double
helix
• Aka “doublestranded”: dsDNA
• Not as flexible as RNA
• Chains can be very
long 120,000,000
nucleotides
• Distributed
throughout the cell
• Sequestered
Individual nucleotides
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Mononucleotides
Have different functions
Energy carriers
Help with enzyme reactions as cofactors
Signalling