nucleic acids Flashcards

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1
Q

what elements do nucleic acids contain

A

carbon
hydrogen
oxygen
nitrogen
phosphorus

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2
Q

monomers of nucleic acids

A

nucleotides

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3
Q

what is a nucleotide made up of

A
  • pentose monosaccharide (5 C atoms)
  • phosphate group -PO42- (Inorganic, acidic, negatively charged)
  • nitrogenous base (organic molecule, 1 or 2 C rings and nitrogen)
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4
Q

how are nucleotides linked together

A
  • phosphodiester bonds in condensation reactions to form polynucleotides.
  • 5’ carbon on the pentose sugar on a nucleotide forms a covalent bond with the OH group of the 3’ carbon on the pentose sugar on an adjacent nucleotide.
  • forms a long, strong sugar-phosphate backbone with a base attached to each sugar
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5
Q

Pyramidines

A
  • the smaller bases
  • thymine, cytosine
  • single carbon ring structures
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6
Q

purines

A
  • the larger bases
  • adenine, guanine
  • double ring structures
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7
Q

difference between DNA and RNA

A
  • DNA contains deoxyribose sugar
  • RNA contains ribose sugar
  • deoxyribose has 1 less oxygen atom than ribose
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8
Q

what structure is DNA found in

A

double helix

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9
Q

why are the 2 strands of DNA said to be antiparallel

A
  • they run parallel to each other but in opposite directions
  • Each strand has a phosphate group (5’) at one end and a hydroxyl group (3’) at the other end.
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10
Q

complementary base pairing

A
  • adenine pairs with thymine with 2 hydrogen bonds
  • cytosine pairs with guanine with 3 hydrogen bonds
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11
Q

how is a constant distance maintained between DNA strands

A
  • complementary base pairing means that a small pyrimidine base is always paired with a large purine base
  • constant distance between backbones is contained
  • so polynucleotides are parallel
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12
Q

why is RNA shorter than DNA

A
  • the relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short mRNA molecule.
  • so each individual mRNA is shorter than the whole chromosome of DNA
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13
Q

RNA nucleotide

A
  • pentose sugar ribose
  • thymine base is replaced with uracil
  • uracil is a pyrimidine that forms 2 hydrogen bonds with adenine
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14
Q

how do RNA nucleotides form polymers

A
  • formation of phosphodiester bonds in condensation reactions (Same as DNA)
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15
Q

why can RNA leave the nucleus

A
  • RNA polymers are small enough to leave via nuclear pores and travel to the ribosomes through cytoplasm
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16
Q

what happens to RNA molecules after protein synthesis

A
  • RNA molecules are degraded in the cytoplasm
  • phosphodiester bonds are hydrolysed
  • RNA molecules are released and reused