1. Biomacromolecules Pt III: Nucleic Acids

2. 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.

3. 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.

4. 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.

5. Condensation reaction: The phosphate and sugar groups link via the condensation reaction. A water molecule is produced as a by-product.

6. 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.

7. Purines and Pyrimidines MEMORY AID: PURLAG PURines are Larger, Adenine and Guanine

8. 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.

9. Ribonucleic Acid (RNA) Contains uracil instead of thymine.

10. Ribonucleic Acid (RNA) Multiple forms – all produced in the nucleus from a DNA template. –Messenger RNA (mRNA) –Transfer RNA (tRNA) –Ribosomal RNA (rRNA)

11. 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.

12. 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