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biology > 2.1.3: nucleotides and nucleic acids > Flashcards

2.1.3: nucleotides and nucleic acids Flashcards

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
how is atp recyclable?
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
how does dna replicate itself?
- 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
what is dna polymerase?
the enzyme used to form the new sugar-phosphate backbones. can only move in one direction
28
what is dna helicase?
breaks the hydrogen bonds between the bases in a dna double helix
29
what are the consequences of mutations?
could lead to genetic conditions and help organisms to adopt better to their environment
30
who did the experiments to prove the theory of semi-conservative replication?
meselson and stahl
31
what is a gene?
a short section of dna that codes for a specific protein
32
what is mrna?
- messenger rna -single polynucleotide strand - carries genetic code as a messenger to ribosomes - made in the nucleus during transcription
33
what is trna?
- 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
what is rrna?
- 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
how many amino acids are there?
20
36
what are 3 adjacent bases called?
codons
37
how do anticodons on trna and codons on mrna linked?
they are both complementary
38
what is meant by a triplet code?
each amino acid is coded for by a sequence of 3 bases
39
what happens during transcription?
- 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
what happens during translation?
- 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
what does dna helicase do?
unwinds the double helix by breaking the hydrogen bonds between the 2 dna strands
42
what does dna polymerase do?
joins the sugar-phosphate backbone of the new mrna molecule being made until it is complete
43
what are the features of the genetic code?
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
what is a start and a stop codon?
- stop codon = it indicates when that particular polypeptide is complete - start codon = indicates the start of a polypeptide
45
what is the method for the dna extraction from a strawberry?
- 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
what does the extraction buffer contain and why in the dna extraction experiment?
- 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 (18 decks)

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