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biology > 2.1.3: nucleotides and nucleic acids > Flashcards

2.1.3: nucleotides and nucleic acids Flashcards

1
Q

what does dna mean?

A

deoxyribonucleuic acid

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2
Q

what does rna stand for?

A

ribonucleuic acid

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3
Q

what monomers are dna and rna polymers made from?

A

nucleotides

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4
Q

what is the role of dna?

A

stores genetic material and codes for traits

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5
Q

what is the role of rna?

A

to transfer genetic material and synthesise proteins

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6
Q

what components make up nucleotides?

A

a phosphate group, a pentose sugar and a nitrogenous base

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7
Q

what are the components of the nucleotides that make up dna?

A

a phosphate group, a deoxyribose pentose sugar and either an adenine, guanine, thymine or cytosine base

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8
Q

what are the components of the nucleotides that make up rna?

A

a phosphate group, a ribose pentose sugar and either a adenine, guanine, uracil and cytosine base

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9
Q

how many strands are dna and rna?

A

dna is double stranded and rna is single stranded

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10
Q

what are the sugars that make up dna and rna?

A

dna is deoxyribose and rna is ribose

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11
Q

what are the lengths of dna and rna?

A

dna is usually long and rna is short

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12
Q

what is the structure of dna?

A

2 polynucleotide strands joined together to form a double helix which is antiparallel

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13
Q

what are the 5 nitrogenous bases?

A

adenine, guanine, cytosine, thymine and uracil

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14
Q

what are the 2 main categories the nitrogenous bases fall into?

A

purines and pyrimidines

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15
Q

which bases are purines?

A

adenine and guanine

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16
Q

which bases are pyrimidines?

A

cytosine, thymine and uracil

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17
Q

what is the structure of a purine?

A

double ringed

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18
Q

what is the structure of a pyrimidine?

A

single ringed

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19
Q

via which reaction do nucleotides join?

A

by a condensation reaction

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20
Q

when multiple nucleotides join via a condensation reaction, what are they called?

A

polynucleotides (2 are called dinucleotides)

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21
Q

between what in nucleotides do phosphodiester bonds occur?

A

between phosphate groups of one nucleotide and a sugar in the other nucleotide

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22
Q

what is 3’ to 5’?

A

3’ = the hydroxyl group at the third carbon 5’ = the phosphate group at the fifth carbon showing the direction of one of the strands in the double helix

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23
Q

in a double helix, what bonds join between the 2 strands to make this shape?

A

hydrogen bonds

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24
Q

what is meant by complementary base pairing?

A

adenine always pairs with thymine and cytosine always bonds with guanine. a small pyrimidine always pairs with a large purine

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25
Q

how many hydrogen bonds are between adenine and thymine?

A

2 hydrogen bonds

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26
Q

how many hydrogen bonds are between guanine and cytosine?

A

3 hydrogen bonds

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27
Q

what does antiparallel mean?

A

one strand runs in a 5’ to 3’ direction while the other runs in a 3’ to 5’ direction (essentially upside down)

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28
Q

why is dna being in a helix good for its function?

A

compact

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29
Q

why is dna being a large molecule good for its function?

A

stores a lot of information

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30
Q

why are the weak hydrogen bonds between base pairs in dna good for its function?

A

can be easily broken for reaction to take place and for replication to occur

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31
Q

what is the process by which dna replicates?

A

through semi-conservative replication

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32
Q

other than dna and rna, what other molecules have a structure based on nucleotides?

A

atp and adp

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33
Q

what does atp mean?

A

adenosine tri-phosphate

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34
Q

what is the role of atp?

A

the universal energy currency in all living cells

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35
Q

why do cells require energy?

A

synthesis (like proteins), transport (like active transport) and movement (like muscle contraction)

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36
Q

what are the components of the nucleotides that make atp?

A

three phosphate groups, a ribose pentose sugar and an adenine base

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37
Q

via what reaction is atp broken down?

A

hydrolysis reaction

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38
Q

what is the equation for the break down of atp?

A

atp + water > adp + inorganic phosphate + energy

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39
Q

what does adp stand for?

A

adenosine di-phosphate

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40
Q

how and where is adp made in cells?

A

atp synthesis occurs in the membrane of the mitochondria produced by enzyme atp synthase, which converts adp and phosphates to atp

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41
Q

is atp stable and what are the consequences?

A

not very stable so it is not an energy store but an immediate energy source

42
Q

how does the structure of an atp molecule make it a good energy source?

A

can be broken down easily because it is unstable by the three adjacent negative charges in its phosphate tail, so releasing energy when needed

43
Q

true or false: atp can be recycled?

A

true

44
Q

how is atp recyclable?

A

hydrolysis means energy is used up by cells (atp) and makes pi and adp. this then converts back to condensation reaction as atp is regenerated by cell respiration

45
Q

why does dna replicate itself?

A

allows the transfer of genetic material from one generation to another and for cell division for growth, repair and replacement

46
Q

how does dna replicate itself?

A

the 2 strands of the double helix are separated by dna helicase which temporarily breaks the hydrogen bonds between the bases. the “free” nucleotides in the nucleus will line up next to the bases by complementary base pairings. new hydrogen bonds form and the new sugar-phosphate back bones are formed by phosphodiester bonds, done by dna polymerase

47
Q

what is dna polymerase?

A

the enzyme used to form the new sugar-phosphate backbones. can only move in one direction

48
Q

what is dna helicase?

A

breaks the hydrogen bonds between the bases in a dna double helix

49
Q

why is it called semi-conservative dna replication?

A

when a new double stranded molecule is formed, one strand will be from the original template molecule and the other will be newly synthesised

50
Q

what does the fact that dna polymerase only works in one direction mean?

A

that one strand is continuously replicated (leading strand). the other strand has to be copied in sections as it unwinds (lagging strand)

51
Q

what is an error called in dna?

A

a mutation

52
Q

what are the consequences of mutations?

A

could lead to genetic conditions and help organisms to adopt better to their environment

53
Q

who did the experiments to prove the theory of semi-conservative replication?

A

meselson and stahl

54
Q

what is a gene?

A

a short section of dna that codes for a specific protein

55
Q

what are the 3 types of rna?

A

mrna, trna and rrna

56
Q

what does mrna stand for?

A

messenger rna

57
Q

what does trna stand for?

A

transfer rna

58
Q

what does rrna stand for?

A

ribosomal rna

59
Q

what is the structure of mrna?

A

a single poly nucleotide strand

60
Q

where is mrna made and how?

A

in the nucleus during transcription

61
Q

what is the role of mrna?

A

carries genetic code from the nucleus to the cytoplasm

62
Q

why is mrna called a messenger?

A

because it carries the genetic code as a message to the ribosomes

63
Q

what is the structure of trna?

A

a single polynucleotide strand that is folded into a clover shape. hydrogen bonds between the specific base pairs holds this shape. they also have an amino acid binding site at the other end

64
Q

in mrna, what are 3 adjacent bases called?

A

codons

65
Q

in trna, what are the specific sequence of 3 bases at one end called?

A

anticodon

66
Q

what is the role of trna?

A

involved in translation where it carries the amino acids, that are used to make proteins, to the ribosomes

67
Q

where is trna found?

A

the cytoplasm

68
Q

why is trna called transfer rna?

A

transfers amino acids to the ribosomes to make proteins

69
Q

how do anticodons on trna and codons on mrna linked?

A

they are both complementary

70
Q

how many types of amino acids are there?

A

20

71
Q

what is the structure of rrna?

A

forms the 2 subunits in the ribosome

72
Q

what does rrna do?

A

helps catalyse the formation of peptide bonds between amino acids

73
Q

why is rrna called ribosomal dna?

A

it makes up ribosomes

74
Q

what kind of code is the genetic code?

A

a triplet code

75
Q

what is meant by a triplet code?

A

each amino acid is coded for by a sequence of 3 bases

76
Q

where are proteins made?

A

ribosomes

77
Q

what are the 2 stages of proteins synthesis?

A

transcription and translation

78
Q

where does transcription occur?

A

in the nucleus

79
Q

what happens during transcription?

A
  • the dna double helix unzips and unwinds at gene required by breaking hydrogen bonds between bases (dna helicase)
  • splits into 2 strands (sense = 5’ to 3’ and contains code for protein) and anit-sense = 3’ to 5’)
  • free rna nucleotides join the complementary base pairning
  • phosphodiester bonds form between the rna nucleotides by the enzyme dna polymerase
  • rna nucleotides detach from the template strand forming mrna
  • the dna rezips and rewinds using dna ligase
80
Q

what does dna helicase do?

A

unwinds the double helix by breaking the hydrogen bonds between the 2 dna strands

81
Q

what does dna polymerase do?

A

joins the sugar-phosphate backbone of the new mrna molecule being made until it is complete

82
Q

what are introns?

A

the sections of dna between the genes

83
Q

what do introns do?

A

don’t code for any amino acids. they are copied from the dna, producing pre-mrna. they are cut out of the mrna before it leaves the nucleus

84
Q

why is the mrna capped?

A

prevent it from being damaged in the cytoplasm

85
Q

what does a codon code for?

A

one amino acid

86
Q

what happens during translation?

A
  • mrna moves out of the nuclear pore and attaches to ribosome in cytplasm
  • trna molecule with complementary base pairing, carrying an amino acid
  • second trna molecule attaches to next codon on mrna by coplementary base pairing as well
  • rrna catalyses the formation of the peptide bond between the 2 amino acids attached to the trna molecules (condensation)
  • the first empty trna molecule moves away, leaving its amino acid binds to the first two. the second trna molecule moves away
  • process repeats until it reaches a stop codon
  • chain moves away from the ribosome and translation is complete
  • ribosome moves across the mrna chain
87
Q

what are the things you need to know about the nature of the genetic code?

A

the code is degenerate, non-over-lapping and is universal

88
Q

what does the code being genetic being degenerate mean?

A

a single acid may be coded for by more than one codon

89
Q

what is a stop codon?

A

it indicates when that particular polypeptide is complete

90
Q

what is a start codon?

A

indicates the start of a polypeptide

91
Q

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

A

means that base triplets do not share their bases, each triplet is distinct from the next

92
Q

what does it mean by the genetic code being universal?

A

all species use the same 4 bases (adenine, guanine, thymine and cytosine) and each base sequence codes for the same amino acid in all species

93
Q

what is the longevity of dna?

A

long-lived stable molecule

94
Q

what is the longevity of rna?

A

short-lived, not as stable breaks down after a while

95
Q

how does protein synthesis happen in dna in prokaryotes?

A

transcription dna > mrna (no intron) and no splicing

96
Q

how does protein synthesis happen in dna in eukaryotes?

A

dna > premrna > mrna and introns are removed (splicing)

97
Q

what is the method for the dna extraction from a strawberry?

A

crush the strawberry with 20cm of extraction buffer. strain this into a beaker using a tea strainer and a muslin then add 1cm of protease enzyme to the filtrate and pour this into a boiling tube. gently add 5cm ice cold ethanol and tip the boiling tube to 45 degrees and slowly run the ethanol down the side. let it sit for 5 minutes then scoop the white precipitate off the top of the filtrate with an inoculating loop

98
Q

what does the extraction buffer contain?

A

detergent and salt r

99
Q

why is the strawberry crushed before extraction?

A

to break down the cell walls of the strawberry

100
Q

why does the buffer solution contain detergent?

A

disrupt the phospholipid bilayer of the cell and nuclear membranes

101
Q

why does the buffer solution contain salt?

A

neutralises the the charge of the phosphate groups and therefore reduced the solubility of the dna in water

102
Q

why is protease solution added to the strawberry filtrate?

A

it digests the histones, leaving just the dna behind

biology (10 decks)

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