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Biology > Nucleic acids > Flashcards

Nucleic acids Flashcards

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1
Q

structure of a nucleotide

A

nitrogenous base (rectangle), phosphate group (circle), pentose sugar (pentagon)

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2
Q

what elements do nucleotides contain?

A

carbon, hydrogen, oxygen, nitrogen, phosphorus

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3
Q

pentose sugar in DNA and RNA

A

DNA - deoxyribose (one less oxygen atom on bottom right carbon)
RNA - ribose

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4
Q

4 bases in DNA

A

adenine, guanine, cytosine, thymine

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5
Q

which 2 bases in DNA have double ring structure and what is the name for them?

A

adenine and guanine - purines

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6
Q

which 2 bases are pyramidines?

A

cytosine and thymine - single ring structure

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7
Q

4 bases in RNA

A

adenine, guanine, cytosine, uracil

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8
Q

how are polynucleotides formed?

A

phosphate group at carbon 5 of pentose sugar forms covalent bond with hydroxyl group of carbon 3 of another nucleotide
- condensation reaction

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9
Q

what is the bond between 2 nucleotides?

A

phosphodiester bond

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10
Q

structure of DNA

A
  • 2 polynucleotide strands held together by hydrogen bonds between complementary bases on opposite strands
  • 2 polynucleotide strands are anti-parallel - run in opposite directions
  • sugar-phosphate backbone on outside with bases in the centre
  • distance between 2 strands is constant the whole way down
  • 2 strands form double helix
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11
Q

how many bonds are formed between guanine and cytosine?

A

3 hydrogen bonds

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12
Q

how many bonds are formed between thymine and adenine?

A

2 hydrogen bonds

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13
Q

differences between RNA and DNA

A
  • DNA found in chromosomes in nucleus, RNA found in cytoplasm
  • DNA is extremely long, RNA is relatively short
  • 2 polynucleotide strands in double helix, RNA has only 1 polynucleotide strand
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14
Q

Stages of DNA replication

A
  • DNA helicase attaches to DNA molecule causing H bonds between bases to break
  • 2 polynucleotides separate
  • free nucleotides line up with complementary base on DNA strands
  • free activated nucleotides held in place by hydrogen bonds between bases
  • DNA polymerase moves down molecule and catalyses formation of phosphodiester bonds between activated nucleotides - condensation reaction
  • when phosphodiester bonds form activated nucelotides lose their extra 2 phosphate groups
  • as the 2 phophate groups leave, it provides energy for the reaction
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15
Q

difference between normal nucleotide activated nucelotide

A

activated nucleotide contains 3 phosphate groups, normal nucleotide contains 1

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16
Q

why is it called semi-conservative replication

A
  • one old strand and one new strand
17
Q

what is a mutation?

A

an incorrect base is inserted into the growing polynucleotide strand during replication changing the DNA sequence
- random

18
Q

differences between DNA in eukaryotes and prokaryotes

A
  • prokaryotes - circular DNA no free ends, relatively short, not bound to histones
  • eukaryotes - linear DNA with 2 ends, much longer, tightly wrapped around histones forming chromosomes
19
Q

transcription

A
  • DNA helicase breaks H bonds between 2 strands of DNA
  • complementary free nucleotides form H bonds with bases on exposed nucleotides of one strand
  • RNA polymerase moves along template strand and joins RNA nucleotides forming phophodiester bonds
  • enzymes move down DNA until they reach the end of the gene
  • strand of mRNA formed
  • thymine is replaced by uracil
  • once mRNA has synthesised, RNA polymerase detaches from DNA and DNA goes back to double helix structure
  • mRNA moves out of nucleus through nuclear pore
  • prokaryotic cells - mRNA, in eukaryotic cells - pre-mRNA is spliced to get mRNA
20
Q

genome

A

all the genes in a cell

21
Q

how are mRNA nucleotides read?

A

as a series of triplets - the genetic code

22
Q

why is the genetic code degenerate?

A

most amino acids have more than one triplet coding for them

23
Q

what does it mean by the triplet code is non-overlapping?

A

no base is read more than once

24
Q

what does it mean by the genetic code is universal?

A

same triplets encode the same amino acids in most organisms on earth

25
Q

translation

A
  • once mRNA moved from nucleus to cytoplasm, a subunit of a ribosome binds to mRNA at start codon
  • tRNA molecule with complementary anti-codon to start codon attaches by H bonds between complementary base pairs on anti-codon
  • second tRNA molecule attaches with complementary anticodon for second codon on mRNA
  • peptide bond forms between 2 amino acids on tRNA’s using ATP - catalysed by enzyme peptidyl transferase (part of ribosomal RNA molecule)
  • ribosome moves to next codon and forms peptide bond to next amino acid, first tRNA molecule released
  • ribosome continues moving down mRNA forming polypeptide until it reaches a stop codon and is polypeptide chain is released
  • multiple ribosomes can be translating one polypeptide chain at once
26
Q

what is a codon?

A

each triplet in mRNA sequence

27
Q

what is special about a tRNA anticodon?

A

it’s complementary for the mRNA codon for each specific amino acid

28
Q

what does tRNA do?

A

a specific amino acid attaches to their attachment site and brings it to the ribosome for translation

29
Q

ATP structure

A

3 phosphate groups, ribose, adenine
(ATP is a nucleotide)
- adenine and ribose - adenosine

30
Q

how is energy released from ATP?

A
  • not a lot of energy is required to break bond holding last phosphate in place
  • breaking bond requires water molecule - hydrolysis
  • lots of energy is released when it’s broken
31
Q

hydrolysis of ATP equation

A

ATP + water —-ATPase—-> ADP + Pi (inorganic phosphate - not attached to carbon molecule) + energy

32
Q

processes using ATP

A
  • active transport, muscle contraction, formation of proteins etc.
33
Q

how are ADP and phosphate recycled back to ATP?

A

respiration in plant and animal cells
photosynthesis in plant cells
- phosphorylation reaction - catalysed by ATP synthase
- water released - condensation reaction

Biology (16 decks)

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