biochem - 2 - nucleotides, nucleic acids, and nucleic acid structure

Nucleotides, Nucleic Acids, Nucleic Acid Structure

list the components of DNA and RNA and their abbreviations

• adenine (A)

• thymine (T)

• guanine (G)

• cytosine (C)

• uracil (U)

what are the two structural categories of bases?

• purines: fused five-membered and six-membered ring (A, G)

• pyrimidines: single six-membered ring (C, T, U)

what are the components of DNA?

• adenine (A)

• guanine (G)

• thymine (T)

• cytosine (C)

what are the components of RNA?

• uracil (U)

• guanine (G)

• thymine (T)

• cytosine (C)

what makes up a nucleoside?

• base (A, G, C, T, U)

• sugar

what two sugars are in nucleosides?

• ribose

• deoxyribose

what are the two categories of nucleosides?

• ribonucelosides: adenosine, uridine, cytidine, guanosine

• deoxyribonucleosides: deoxyadenosine, deoxythymidine, deoxycytidine, deoxyguanosine

what makes up a nucelotide?

• 1-3 phosphate groups

• nucleoside (sugar and a base)

what are the categories of nucleotides?

• ribonucleotides (monophosphates)

  • adenosine 5’-monophosphate (AMP)

  • uridine 5’-monophosphate (UMP)

  • guanosine 5’-monophosphate (GMP)

  • cytidine 5’-monophosphate (CMP)

• deoxyribonucelotides (monophosphates)

  • dAMP, dTMP, dGMP, dCMP

• diphosphates

  • ADP, UDP, GDP, CDP

  • dADP, dTDP, dGDP, dCDP

• triphosphates

  • ATP, UTP, GTP, CTP;

  • dATP, dTTP, dGTP, dCTP

define nucleic acid

linear polymers of nucelotides (polynucleotides) linked 3’ to 5’ by phosphodiester bridges

• the sequence of bases is always read from the 5’ to the 3’ end

describe the structure of DNA

• double helix

• held together by hydrogen bonds between base pairs

• makes up the chromosomes which encode the protiens and RNAs of a cell

what are the two fundamental differences between DNA and RNA?

• DNA contains deoxyribose instead of ribose

• DNA contains thymine instead of uracil

what are the four types of RNA?

• messenger RNA (mRNA): carries the “message” encoded in genes to the ribosomes, where this information is translated into polypeptide chains

• ribosomal RNA (rRNA): major component (65%) of ribosomes, the sites of protein synthesis

• transfer RNA (tRNA): carries amino acids to the ribosomes, where they are assembled into a polypeptide chain

• small nuclear RNAs (snRNAs): involved in processing of eukaryotic gene transcipts into mature messenger RNA

describe the primary, secondary, and tertiary structure of DNA and RNA

• primary structure: linear sequence of bases along a DNA or RNA strand

  • 5’-ATGAAACAAATGTTT-3’

• secondary structure: formation of double helix by specific base pairing

  • A:T (or A:U) and G:C

• tertiary structure:

  • for eukaryotic cells: organization of DNA into chromosomes by interactions with histone proteins and nonhistone proteins

  • for prokaryotic cells: supercoiling of circular chromosomal DNA molecules such as:

    • E. coli chromosome

    • plasmid DNA molecules

    • mini-chromosomes of organelles including mitochondria

when does DNA form supercoils?

circular DNA or linear DNA with fixed ends form supercoils if the two strands of the double helix are underwound (negative supercoils) or overwound (positive supercoils)