nucleic acids

nucleic acids have two main functions:

• pass information between generation (molecule of heredity in all living organisms)

• code for protein products and serve as templates for replication.

dna

• passes heredity information between generations of cells

• codes for making RNA during transcription

rna

• codes for making proteins during translation

• three types involved in protein synthesis: mRna, rRna, tRna

nucleic acids are polymers

• nucleic acids are chains of nucleotide combined in condensation reactions

• the nucleotide in the “monomer” of the nucleic acid “polymer”

parts of nucleotide:

• adenine, thymine, guanine, and cytosine, and uracil

• a five carbon “pentose” sugar (ribose in rna and deoxyribose in dna)

• negatively charged phosphate group

pentose sugars

• ribose and deoxyribose are pentose sugars

• five carbons

• four carbons plus oxygen atom form a ring shaped like a pentagon

• carbons are numbered O' to 5' in the sugar molecule, moving clockwise

DNA and RNA have “backbone”

• phosphate - sugar - phosphate

• the backbone provides structural support and stability to the nucleotides in their specific sequence

the backbone is formed when nucleotides combine in a…

using phosphodiester bonds during a condensation reaction

• two molecules combine to form a single molecule

• A water molecule is lost in the process

directionality

• the 5’ phosphate group on one nucleotide bonds with the 3’ carbon on the pentose of the next nucleotide

• 5’ phosphate

• 3’ pentose

• this directionality is important for DNA replication and transcription

dna backbone

• has two sugar phosphate backbones

• they run antiparallel to each other

• twist together in a helical shape

rna backbone

• has one sugar-phosphate backbone

• can twist and bind to itself

nitrogenous bases:

all five nitrogenous bases contain nitrogen atoms:

• A, T, G, C, U

classification of bases

based on the number of chemical rings in their structure:

• Purines: double rings = guanine and adenine

• Pyrimidines: single ring = cytosine, thymine, uracil

the genetic code

• the order in which different nucleotide are arranged serves as a code

• in the genetic code, a group of 3 nucleic acid bases signifies an amino acid

genes

• a gene is a specific sequence of nitrogenous bases in DNA nucleotides

• genes code for the making in a protein

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