Biomacromolecules Pt III: Nucleic Acids. Nucleic acids Linear polymers made up of monomers called...
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Transcript of Biomacromolecules Pt III: Nucleic Acids. Nucleic acids Linear polymers made up of monomers called...
Biomacromolecules
Pt III: Nucleic Acids
Nucleic acids
• Linear polymers made up of monomers called nucleotides.
• They are of critical importance to the cell because of their roles in the storage, transmission and expression of genetic information.
• They are essentially information molecules.
Two types of nucleic acid
• There are two major types of nucleic acid:– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)
• They differ in their chemical components and the role they play in the cell.
What are nucleotides?
• Each nucleotide is made up of three components:– A deoxyribose
sugar– A phosphate group
with a negative charge
– A nitrogen base
• Nucleotides are the monomers that make up nucleic acids.
Condensation reaction:
• The phosphate and sugar groups link via the condensation reaction.
• A water molecule is produced as a by-product.
Nitrogen bases
• Two families of nitrogen bases: the purines and pyrimidines.
• Purines – two ring structure– adenine (A) & guanine (G)
• Pyrimidines – single ring structure– cytosine (C), thymine (T) and uracil (U)– Uracil only found in RNA, it replaces thymine
which is only found in DNA.
Purines and Pyrimidines
MEMORY AID: PURLAGPURines are Larger,
Adenine and Guanine
Pairing between nitrogen bases• Bases contain many nitrogen
atoms and an oxygen functional group that are capable of forming hydrogen bonds between bases.
• Purines and pyrimidines have a complementary relationship – a purine always pairs with a pyrimidine.– A forms two hydrogen bonds with T
(or U)– G forms three hydrogen bonds with
C• This base pairing is a fundamental
property of nucleic acids and provides the mechanism for the coding of genetic information.
Ribonucleic Acid (RNA)
• Contains uracil instead of thymine.
Ribonucleic Acid (RNA)
• Multiple forms – all produced in the nucleus from a DNA template.– Messenger RNA (mRNA)– Transfer RNA (tRNA)– Ribosomal RNA (rRNA)
Deoxyribonucleic acid (DNA)
• Double stranded polynucleotides
• Two strands with complementary nitrogen base sequences pair to form a double helical structure.
• Base pairs are held together by hydrogen bonding.
• For base pairing to occur, the two strands run in opposite directions. We say the strands are antiparallel.
Memory Aids for DNA
• Atoms in DNA - PONCH– Phosphorous , Oxygen,
Nitrogen, Carbon, Hydrogen
• Nucleotide - t is for three parts– Base, sugar and phosphate.
• Difference between purines and pyrimidines – PURLAG– PURines are Larger, Adenine
and Guanine
• To remember pyrimidines – CUT– Smaller – have only one ring
so they have been CUT– Cytosine, uracil, thymine