nucleic acids 1. what are nucleic acids? used for: storing genetic information assembly instructions...
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WHAT ARE NUCLEIC ACIDS?• Used for:
• Storing genetic information• Assembly instructions for protein
synthesis• Energy molecule (ATP – adenosine
triphosphate)
• Two major nucleic acid polymers:• DNA: deoxyribonucleic acid
• RNA: ribonucleic acid
The distribution of nucleic acids in the eukaryotic cell Two types of Nucleic Acid: DNA and RNA
DNA is found in the nucleus with small amounts in mitochondria and chloroplasts
RNA is found throughout the cell
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NUCLEIC ACIDS
DNA RNA
- Located in the nucleus
- Located mostly in the cytoplasm
- Double-stranded, double helix structure
- Single-stranded structure
- Stable molecule - Less stable molecule
NUCLEIC ACID STRUCTURE
Nucleic acids are polynucleotides
Many nucleotides
Their building blocks are nucleotides
Nucleotides: nitrogenous base + 5 carbon pentose (sugar) + phosphate
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NUCLEOTIDES• Monomer of nucleic acids• Three components:
1. Phosphate2. Pentose sugar3. Nitrogenous base
Nucleotides
Nucleic acids consist of nucleotides that have a sugar, nitrogen base, and phosphate
nucleoside 7
Sugar
Base
PO4
SUGAR
Ribose or Deoxyribose
BASEPURINES PYRIMIDINES
Adenine (A)Guanine(G)
Cytocine (C)Thymine (T)Uracil (U)
Nitrogen-Containing Bases
N
N
N
N
H
NH2
N
N
O
CH3
O
H
H
N
N
N
N
O
H
NH2
H
N
N
NH2
CH3
O
H
N
N
O
CH3
O
H
H
adenine (A) thymine (T)
guanine (G) cytosine (C) uracil (U)
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Purines Pyrimidines
Nucleotides in DNA and RNA
DNAdAMP Deoxyadenosine monophosphatedGMP Deoxyguanosine monophosphatedCMP Deoxycytidine monophosphatedTMP Deoxythymidine monophosphate
RNAAMP adenosine monophosphateGMP guanosine monophosphateCMP cytidine monophosphateUMP uridine monophosphate
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Nucleosides in DNA
Nucleosides are the precursors to nucleotides; they are not phosphorylated
Base Sugar NucleosideAdenine (A) Deoxyribose AdenosineGuanine (G) Deoxyribose GuanosineCytosine (C) Deoxyribose CytidineThymine (T) Deoxyribose Thymidine**T is only found in DNA**
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Nucleosides in RNA
Base Sugar Nucleoside
Adenine (A) ribose Adenosine
Guanine (G) ribose Guanosine
Cytosine (C) ribose Cytidine
Uracil (U) ribose Uridine
**U is only found in RNA**
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Structure of Nucleic Acids
Polymers of four nucleotides Linked by alternating sugar-phosphate
bonds RNA: ribose and A, G, C, U DNA: deoxyribose and A,G,C,T
nucleotide nucleotide nucleotide nucleotide
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P sugar
base
P sugar
base
P sugar
base
P sugar
base
Nucleic Acid Structure
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O
N
N
NH2
O
CH2OP
O
O-
O-
OH
O
N
N
NH2
CH2OP
O
O-
OH
O
N
N
AMP
CMP
3
5
3,5-phosphodiester bond
Nucleic Acid Structure
Covalent bond between the phosphate group of 1 nucleotide and the hydroxyl group on the carbon three of the sugar on the adjacent nucleotide
PHOSPHODIESTER BOND• Phosphodiester bond formed between
nucleotides:• Pentose sugar (-OH group)
• Phosphate group
‘BACKBONE’ OF DNA• Linking nucleotides produces a
single strand of DNA
• Phosphate + deoxyribose =
backbone
COMPLIMENTARY BASE PAIRING
• Nitrogenous bases are joined through Hydrogen bonding
• Complimentary base pairs:
• Adenine + Thymine
• 2 H bonds• Cytosine +
Guanine• 3 H bonds
ANTI-PARALLEL STRANDS• Complimentary base
pairing results in double-stranded DNA
• Both DNA strands run anti-parallel to each
other (oriented in opposite directions)
One strand is 5’ 3’ while the other is 3’
5’
Structure of Nucleic Acids
DNA contains two strands of nucleotides Each strand of DNA has a free
phosphate group at one end and a free sugar at the other end
DNA takes on a helix structure, like a spiral stair case
Bases are always paired as A–T and G-C
RNA is single stranded but it still coils into a helix
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Double Helix of DNA
The sister strands of the DNA molecule run in opposite directions (antiparallel) Purine with Pyrimidine
The sister strands are complementary but not identical
The bases are joined by hydrogen bonds, individually weak but collectively strong
A-T is joined by two hydrogen bonds G-C is joined by three hydrogen bonds
Checkpoint
Write the complementary base sequence for the matching strand in the following DNA section:
-A-G-T-C-C-A-A-T-G-C-
• • • • • • • • • •
• • • • • • • • • •
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