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module 2 > nucleic acids > Flashcards

nucleic acids Flashcards

1
Q

what are nucleotides?

A

the monomers from which nucleic acids, like DNA and RNA are formed

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2
Q

what are the 2 types of nitrogenous bases?

A

purines & pyrimidines

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3
Q

what are purines?

A

2 carbon ring structures (adenine & guanine)

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4
Q

what are pyrimidines?

A

1 carbon ring structure (cytosine, thymine & uracil)

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5
Q

what pentose sugar is in DNA?

A

deoxyribose

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6
Q

what pentose sugar is in RNA?

A

ribose

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7
Q

what are the 3 components of a nucleotide?

A

nitrogenous group, phosphate group & pentose sugar

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8
Q

what are the complimentary base pairs in DNA?

A

thymine & adenine
guanine & cytosine

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9
Q

what are the complimentary base pairs in RNA?

A

uracil & adenine
guanine & cytosine

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10
Q

why is it important that purine and pyrimidine bases are always complementary to each other?

A

to help maintain the order of the genetic code when DNA replicates

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11
Q

what reaction bonds nucleotides together?

A

condensation reaction

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12
Q

what bonds form between the nucleotide monomers?

A

phosphodiester bonds

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13
Q

when the nucleotide monomers bond together, what does this create, and what is it called?

A

a polymer called a polynucleotide

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14
Q

what type of bond is a phosphodiester bond?

A

a strong covalent bond

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15
Q

where does the phosphodiester bond form?

A

between the pentose sugar, and phosphate group of different nucleotides

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16
Q

what is the structure of ATP?

A

pentose sugar which is always ribose, nitrogenous base which is always adenine & three phosphate groups

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17
Q

what is the function of the phosphate groups in ATP

A

energy transfer

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18
Q

what is ATP used for?

A
  • essential for metabolism
  • immediate source of energy for biological processes
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19
Q

where is ATP made?

A

during respiration (mostly aerobic) via a condensation reaction, using the enzyme ATP synthase

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20
Q

what enzyme hydrolyses ATP?

A

ATP hydrolase

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21
Q

what happens when ATP is hydrolysed?

A
  • a small amount of energy is released
  • the inorganic phosphate group that has been released, can be bonded onto a different compound, which makes the compound it’s bonded to more reactive, this is called phosphorylation
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22
Q

what does DNA code for?

A

the sequence of amino acids in the primary structure of a protein

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23
Q

what does the primary structure of a protein determine?

A

the final 3D structure & function of a protein

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24
Q

what is the structure of DNA?

A

the polymers form a double helix made of 2 antiparallel strands, which are joined together by hydrogen bonds between the bases on the 2 different strands

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25
Q

why does DNA have a stable structure?

A

due to the sugar-phosphate backbone with covalent bonds, and the double helix structure

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26
Q

why is DNA double-stranded?

A

so that replication can occur using both strands as a template

27
Q

why are there weak hydrogen bonds between the complimentary bases?

A

it benefits DNA replication, because there is very little energy required to break the bonds & separate the 2 strands to use them both as a template

28
Q

why is DNA a large molecule?

A

so that it can carry lots of information

29
Q

why are there complimentary base pairs in DNA?

A

it allows identical copies to be made when DNA is replicated

30
Q

what are the 3 types of RNA?

A

mRNA (messenger), tRNA (transfer) & rRNA (ribosomal)

31
Q

what is the purpose of rRNA?

A

1 of the 2 components of ribosomes

32
Q

what is mRNA?

A

a copy of one gene from DNA

33
Q

what is the purpose of mRNA?

A

after it is created in the nucleus, it leaves via the nuclear pore to carry the copy of the genetic code of one gene to a ribosome in the cytoplasm (protein synthesis)

34
Q

why can mRNA leave the nucleus via the nuclear pore?

A

because it is much smaller than DNA

35
Q

why is mRNA much shorter than DNA?

A

because it is only a copy of one gene

36
Q

why is mRNA short-lived?

A

when it leaves the nucleus, and goes into the cytoplasm, it can become hydrolysed by enzymes in the cytoplasm

37
Q

why does DNA not leave the nucleus?

A

the genetic code would be at risk of being hydrolysed by the enzymes in the cytoplasm

38
Q

what is the structure of mRNA?

A

it is single-stranded

39
Q

what are codons?

A

they are a ‘set’ of 3 bases in mRNA

40
Q

what is the purpose of codons?

A

they code for one specific amino acid

41
Q

where is tRNA found?

A

in the cytoplasm

42
Q

what is the structure of tRNA?

A

single-stranded, but folded to create a cloverleaf shape, it is held in place by hydrogen bonds

43
Q

what is the function of tRNA?

A

to bring specific amino acid to the ribosome

44
Q

how is the structure of tRNA adapted to its function?

A

it has a specific shaped binding site which is determined by the 3 bases found on the tRNA (anticodon), this is complimentary to the 3 bases on mRNA (codon)

45
Q

why is DNA replication described as semi-conservative?

A

because in replication one strand is conserved, and one new strand is created

46
Q

what is a mutation?

A

when copying errors in DNA replication occur

47
Q

when does DNA replication occur?

A

during S-phase in interphase of the cell cycle

48
Q

why does the enzyme that catalyses DNA replication only attach to the 3’ end of the DNA?

A

it has a complimentary shape to only the 3’ end, not the 5’ end

49
Q

what are the 4 stages of DNA replication?

A
  1. DNA helicase breaks down the hydrogen bonds between the complementary bases of the 2 DNA polymers, this causes the double helix to unwind and the 2 strands to separate
  2. these 2 strands then act as templates for DNA replication
  3. free-floating DNA nucleotides (which come from the nucleus) align opposite their complimentary base on the template strand of DNA. Hydrogen bonds then form between the base pairs of the new strand and the old strand
  4. DNA polymerase joins the adjacent DNA nucleotides together, which forms a phosphodiester bond between these nucleotides to create a new polymer chain of DNA
50
Q

what are the 3 features of the genetic code?

A

degenerate, universal & non-overlapping

51
Q

what does it mean that the genetic code is degenerate?

A

amino acids are coded for by more than one triplet of bases

52
Q

what does it mean that the genetic code is universal?

A

the same triplet of bases codes for the same amino acid in all organisms

53
Q

what does it mean that the genetic code is non-overlapping?

A

each base is only part of one triplet of bases that codes for one amino acid, each codon or triplet bases is read as a discrete unit

54
Q

what is an advantage of the genetic code being degenerate?

A

even if a gene mutation occurs, which changes one of the bases in a triplet, it might mean that it still codes for the same amino acid, and the mutation therefore has no impact on the final sequence of amino acids in the polypeptide chain, and therefore the protein’s shape & function

55
Q

what is an advantage of the genetic code being universal?

A

the same triplet of bases codes for the same amino acid in all organisms

56
Q

what is an advantage of the genetic code being non-overlapping?

A

each base is only part of one triplet of bases that codes for one amino acid, each codon, or triplet of bases, is read as a discrete unit, this means that if there was a mutation, this would only effect one codon which would reduce the overall impact

57
Q

what are the 2 stages of protein synthesis?

A

transcription & translation

58
Q

what is transcription?

A

where the DNA sequence for one gene is copied into mRNA

59
Q

what is translation?

A

where the mRNA joins with a ribosome (made of protein and rRNA), and a corresponding tRNA molecule brings the specific amino acid the codon codes for

60
Q

what are introns?

A

sequences of bases in a gene that do not code for amino acids, they get removed (spliced) out of mRNA molecules after transcription

61
Q

what are exons?

A

sequences of bases in a gene that code for a sequence of amino acids

62
Q

what is the process of transcription?

A
  1. DNA helicase breaks the hydrogen bonds between the bases in the 2 strands of DNA
  2. this causes the DNA helix to unwind and one strand acts as a template
  3. free mRNA nucleotides align opposite exposed complimentary DNA bases
  4. the enzyme RNA polymerase joins together the adjacent RNA nucleotides, forming phosphodiester bonds, to create a new mRNA polymer chain
  5. once one gene is copied, the mRNA is modified and then leaves the nucleus through the nuclear envelope pores
63
Q

what is the process of translation?

A
  1. once the modified mRNA has left the nucleus, it attaches to the small subunit of the ribosome at the start codon
  2. the tRNA molecule with the complimentary anticodon to the start codon aligns opposite the mRNA which is held in place by the ribosome, the ribosome can hold 2 tRNA molecules at a time
  3. the 2 amino acids that have been delivered by the tRNA molecule are joined together via a peptide bond which is catalysed by an enzyme using ATP
  4. the ribosome will move along the mRNA molecule to the next codon and another complimentary tRNA will attach to the next codon on the mRNA
  5. this continues until the ribosome reaches the stop codon at the end of the mRNA molecule causing the ribosome to detach and ends translation
  6. the polypeptide chain is now created and will enter the golgi for folding and modification

module 2 (6 decks)

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