Nucleic Acids

We have studied three other sets of Macromolecules:

Carbohydrates, lipids, & proteins

The 4th macromolecule used by organisms:Nucleic Acids

Two main types: DNA (deoxyribonucleic acid) - found in the nucleusRNA (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 nucleotidesRNA is a single strandDNA is a double strandBoth 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 SugarsDNA = deoxyribose RNA = ribose Difference is:Deoxyribose lacks an –OH at 2’ C. Note:

5th 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 1st 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 nucleotidesA  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

H2O

Nucleotide formation

Condensation reaction or Dehydration synthesis

Nucleotide nomenclature: "5'-monophosphate" suffix – phosphate group attached to 5’ Ce.g. "adenosine 5'-monophosphate". Prefix describes the base:

purines (double ring) end in –osine pyrimidines (single ring) end in –idine

e.g. thymine = thymidineadenine = adenosine

Ribose sugar = no additional prefixdeoxyribose + 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 ( PO43- is an acid).

“Diester" signifies the formation of two

ester linkages by each phosphate

H2O 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