Nucleic Acids

We have studied three other sets of Macromolecules: Carbohydrates, lipids, & proteins The 4 th macromolecule used by organisms: Nucleic Acids

Two main types: DNA (deoxyribonucleic acid) - found in the nucleus RNA (ribonucleic acid) – found all over the cell DNA functions: Store genetic information “blueprint” Transfer genetic blueprint to other generations Controls many cellular functions RNA functions: Carries genetic information out of nucleus Builds proteins

Both types are polymers The monomers are nucleotides RNA is a single strand DNA is a double strand Both have a helix structure

The basic unit for DNA and RNA is a “nucleotide” Composed of 3 parts: 1. a nitrogenous base (1 of 5 types) 2. a pentose sugar (1 of 2 types) 3. a phosphate

Pentose Sugars DNA = deoxyribose RNA = ribose Difference is: Deoxyribose lacks an –OH at 2’ C. Note: 5 th C sticks up from ring

C atoms numbered for orientation: “Primes" distinguish them from atoms of nitrogenous bases. We will be referring to this number system a lot! Particularly note the 5’ and 3’ carbons 1’-C –OH group is in a beta (  ) configuration

Nitrogenous bases of nucleotides Ring structures of N & C Plus side chains Double rings are purines Single rings are pyrimidines 5 types provide variety in nucleic acids Note where the carbonyl groups & amines are located

2 purine and 3 pyrimidine bases. Thymine is only in DNA Uracil is only in RNA (but similar to thymine)

Purines start at upper left Nitrogen Then move counterclockwise on 1 st ring, clockwise on 2nd Pyrimidines start at bottom, central Nitrogen and move clockwise Sugars start at far right Carbon and move clockwise Carbon numbering comparison:

Nucleosides and nucleotides A nucleoside forms by combining a nitrogenous base (A,T,C or G) with a pentose sugar. Purine bases:  glycosidic bond is N-9 of base and C-1' of the pentose. Pyrimidine bases:  glycosidic bond is N-1 of base and C-1' of the pentose.

Nucleotide formation -OH group on 5’ carbon H atom on phosphate OH group

H2OH2O Nucleotide formation Condensation reaction or Dehydration synthesis

Nucleotide nomenclature: "5'-monophosphate" suffix – phosphate group attached to 5’ C e.g. "adenosine 5'-monophosphate". Prefix describes the base: purines (double ring) end in –osine pyrimidines (single ring) end in –idine e.g.thymine = thymidine adenine = adenosine Ribose sugar = no additional prefix deoxyribose + adenine = deoxyadenosine Come on! Let it roll off the tongue!

Deoxyadenosine 5' monophosphate Deoxythymidine 5 ' monophosphate

Names of the Eight Nucleotides found in DNA and RNA.

Artificial nucleotides in treating fast growing cancers: 5-Fluorouracil Tumor cells utilize uracil for DNA synthesis more efficiently than normal cells. Fluorinated pyrimidine inhibits DNA synthesis.

Nucleotide monomers are linked using "phosphodiester bonds" between the 3' C of one sugar to the 5' C of another.

An ester (-O-) is a condensation reaction product of an alcohol (sugars are "polyalcohols") and an acid ( PO 4 3- is an acid). “Diester" signifies the formation of two ester linkages by each phosphate H 2 O is a byproduct

The phosphate groups link to the sugars at the 3' and 5' carbons. This is the sugar-phosphate “backbone” of long nucleic acids - held together by covalent bonds

Bases are perpendicular to the axis like the steps of a staircase