SBI4U biochemistry unit, nucleic acids

1. NUCLEIC ACIDS

2. 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

3. 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

4. NUCLEOTIDES
• Monomer of nucleic acids
• Three components:
1. Phosphate
2. Pentose sugar
3. Nitrogenous base

5. NUCLEOSIDE

6. PENTOSE SUGAR

7. NITROGENOUS BASES
Purines
Pyrimidines
RNA DNA

8. PHOSPHODIESTER BOND
• Phosphodiester bond formed between
nucleotides:
• Pentose sugar (-OH group)
• Phosphate group

9. ‘BACKBONE’ OF DNA
• Linking nucleotides
produces a single
strand of DNA
• Phosphate +
deoxyribose =
backbone

10. COMPLIMENTARY BASE PAIRING
• Nitrogenous bases
are joined through
Hydrogen bonding
• Complimentary
base pairs:
• Adenine +
Thymine
• 2 H bonds
• Cytosine +
Guanine
• 3 H bonds

11. 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’

12. COMPLIMENTARY BASE PAIRING
• The 2 anti-parallel strands coil together to
form a double helix.

13. DOUBLE HELIX

14. OVERVIEW