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biology > 2.1.3: nucleotides and nucleic acids > Flashcards

2.1.3: nucleotides and nucleic acids Flashcards

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1
Q

what do dna stand for and do?

A
  • deoxyribonucleuic acid
  • stores genetic material and codes for traits
  • double stranded (polynucleotides) and long
  • double helix = antiparallel
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2
Q

what do rna stand for and do?

A
  • ribonucleic acid
  • to transfer genetic material and synthesise proteins
  • single stranded and short
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3
Q

what components make up nucleotides?

A
  • phosphate group
  • pentose sugar
  • nitrogenous base
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4
Q

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

A
  • phosphate group
  • deoxyribose pentose sugar
  • an adenine, guanine, thymine or cytosine basebase
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5
Q

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

A
  • phosphate group
  • ribose pentose sugar
  • either an adenine, guanine, uracil and cytosine base
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6
Q

which bases are purines?

A

adenine and guanine

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7
Q

which bases are pyrimidines?

A

cytosine, thymine and uracil

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8
Q

what is the structure of a purine?

A

double ringed

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9
Q

what is the structure of a pyrimidine?

A

single ringed

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10
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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11
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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12
Q

what bond occurs between 2 bases?

A

hydrogen bonds

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13
Q

what is complementary base pairing?

A
  • adenine pairs with thymine
  • cytosine pairs with guanine
  • pyrimidine pairs with purine
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14
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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15
Q

how is dna good for its function?

A
  • helix = compact
  • large = stores a lot of information
  • hydrogen bonds can be easily broken for replication
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16
Q

what does atp stand for?

A

adenosine tri-phosphate

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17
Q

what is the role of atp?

A

the universal energy currency in all living cells

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18
Q

why do cells require energy?

A

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

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19
Q

what are the components of the nucleotides that make atp?

A

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

20
Q

what is the equation for the break down of atp?

A

atp + water > adp + inorganic phosphate + energy

21
Q

what does adp stand for?

A

adenosine di-phosphate

22
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

23
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

24
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

25
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

26
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
27
Q

what is dna polymerase?

A

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

28
Q

what is dna helicase?

A

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

29
Q

what are the consequences of mutations?

A

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

30
Q

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

A

meselson and stahl

31
Q

what is a gene?

A

a short section of dna that codes for a specific protein

32
Q

what is mrna?

A
  • messenger rna
    -single polynucleotide strand
  • carries genetic code as a messenger to ribosomes
  • made in the nucleus during transcription
33
Q

what is trna?

A
  • transfer rna
  • single polynucleotide strand, folded into clover shape. have an amino acid binding site at the end
  • used in translation (carries the amino acids to the ribosomes)
  • found in the cytoplasm
34
Q

what is rrna?

A
  • ribosomal rna
  • forms the 2 subunits in the ribosome
  • helps catalyse the formation of peptide bonds between amino acids
  • it makes up the genetic code
35
Q

how many amino acids are there?

A

20

36
Q

what are 3 adjacent bases called?

A

codons

37
Q

how do anticodons on trna and codons on mrna linked?

A

they are both complementary

38
Q

what is meant by a triplet code?

A

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

39
Q

what happens during transcription?

A
  • in the nucleus
  • 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
40
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
41
Q

what does dna helicase do?

A

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

42
Q

what does dna polymerase do?

A

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

43
Q

what are the features of the genetic code?

A

the code is degenerate (a single acid may be coded for by more than one codon), non-over-lapping (means that base triplets do not share their bases) and is universal (all species use the same 4 bases)

44
Q

what is a start and a stop codon?

A
  • stop codon = it indicates when that particular polypeptide is complete
  • start codon = indicates the start of a polypeptide
45
Q

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

A
  • crush the strawberry (to break down the cell walls) with 20cm of extraction buffer
  • strain this into a beaker using a tea strainer and a muslin
  • add 1cm of protease (digests histones and leaves behind the dna) 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
46
Q

what does the extraction buffer contain and why in the dna extraction experiment?

A
  • salt = neutralises the the charge of the phosphate groups = reduces the solubility of the dna in water
  • detergent = disrupt the phospholipid bilayer of the cell and nuclear membranes

biology (10 decks)

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