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nucleic acids Flashcards

1
Q

general structure of a nucleotide

A
  • pentose sugar (ribose, deoxyribose)
  • phosphate
  • organic nitrogenous base
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2
Q

what is a polynucleotide?
and examples

A

many nucleotide monomers bonded into a chain
in a condensation reaction
e.g. DNA, RNA

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3
Q

what are the 5 nitrogenous bases

A

adenine
guanine
thymine
cytosine
uracil

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4
Q

what are the purines

A

adenine
guanine
- two rings

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5
Q

what are the pyrimidines

A

thymine
cytosine
uracil
- one ring

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6
Q

ATP structure

A
  • nitrogenous base adenine
  • ribose sugar
  • 3 phosphate groups
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7
Q

how is ATP formed?

A

in an endergonic reaction
ADP + Pi (inorganic phosphate) combine = ATP + water
energy to combine ADP + Pi comes from exergonic reactions (cell respiration)

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8
Q

how much energy is released when ATP is hydrolysed?and how?

A

30.6 kJ mol-1
- ATPase hydrolyses bond between 2nd+3rd phosphate
- reversible reaction
- made continuously as ATP can’t be stored in large quantities

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9
Q

why is ATP the universal energy currency in organisms?

A
  • it is a common energy source in reactions
  • found in all cells of all organisms
  • high energy bonds
  • energy released when bonds are hydrolysed
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10
Q

why is ATP better than glucose?

A
  • ATP hydrolysis = single reaction = immediate energy release
  • ATP requires 1 enzyme
  • ATP releases energy in small amounts, when and where its needed
  • ATP is the common energy source for many chemical reactions
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11
Q

what are the roles of ATP?

A

metabolic processes
active transport
movement
nerve transmission
secretion

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12
Q

role of ATP in metabolic processes

A

builds large, complex molecules

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13
Q

role of ATP in active transport

A

changes shape of carrier proteins
allows movement against conc gradient

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14
Q

role of ATP in movement

A

used for muscle contraction

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15
Q

role of ATP in nerve transmission

A

used in sodium-potassium pumps
transport across axon membrane

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16
Q

role of ATP in secretion

A

package into vesicles

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17
Q

DNA structure

A
  • 2 polynucleotide strands, wound in double helix
  • strands are antiparallel
  • 4 bases
  • pentose sugar deoxyribose
  • sugar + phosphate form backbone, protecting genetic info
  • stable, large = genetic info passed down generations
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18
Q

how are DNA polynucleotide strands antiparallel?

A

they run in opposite directions but lie parallel to each other
- one runs 5 prime to 3 prime end
- other runs 3 prime to 5 prime end

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19
Q

what is complementary base pairing

A

baes pair up, hydrogen bonds form between
- A + T = 2 hydrogen bonds
- G + C = 3 hydrogen bonds

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20
Q

RNA structure

A
  • single stranded polynucleotide
  • pentose sugar ribose
  • 4 bases (uracil not thymine)
    mRNA, tRNA, rRNA
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21
Q

function of messenger RNA

A
  • complementary copy of DNA genetic code in nucleus during transcription
    length relates to length of gene transcribed
    attaches to ribosome in cytoplasm
22
Q

ribosomal RNA function

A

form ribosomes

23
Q

transfer RNA structure and function

A
  • clover leaf shape
  • carries an amino acid at 3 prime end and an anticodon arm to attach to the mRNA
24
Q

DNA vs RNA

A

deoxyribose - ribose
double stranded - single stranded
A,T,G,C - A,U,G,C
long - short

25
what are the 2 functions of DNA?
replication: copying an original DNA molecule protein synthesis: sequence of bases determine amino acid sequence in proteins
26
stages of DNA replication
- DNA helicase breaks hydrogen bonds between bases in double helix - unwinds DNA, exposing unpaired bases - free nucleotides in nucleoplasm bind to complementary bases on unzipped strand (template strand) - DNA polymerase joins adjacent nucleotides together, forming phosphodiester bonds between sugar and phosphate in condensation reaction - 2 new DNA molecules formed (1 old, 1 new)
27
types of DNA replication
conservative semi-conservative dispersive
28
what is conservative DNA replication
parental strand remains new helix made
29
what is semi-conservative DNA replication
parental helix separates 2 strands act as templates
30
what is dispersive DNA replication
2 new helicases fragments from both parental strands
31
stages of the Meselson-Stahl experiment
- grow bacteria with heavy isotope (nitrogen 15) = heavy strand - remove heavy bacteria, add into light nitrogen isotope (N14). allow bacteria to divide. DNA contains 1 new (N14), 1 old (N15) strand = intermediate density - grow 1 more generation. 50% hybrid = intermediate density. 50% N14 = light density (spun in centrifuge)
32
what is the genetic code?
a linear, triplet, non-overlapping, degenerate, unambiguous, universal code for the production of polypeptides
33
how is the genetic code degenerate / redundant?
more than 1 triplet can encode each amino acid
34
how is the genetic code punctuated?
3 triplet codes don't code for amino acids they code for stop codons
35
how is the genetic code universal?
same triplets code for the same amino acids in all organisms
36
how is the genetic code non-overlapping?
each base only occurs in 1 triplet
37
feature of eukaryotic genes
discontinuous contain coding exons and non-coding introns RNA code too long = introns cut out of pre-mRNA by endonucleases = mRNA. leaves exons joined by ligases.
38
features of prokaryotic genes
continuous lack non-coding sequences mRNA directs synthesis
39
what are exons?
regions of DNA that contain the code for proteins present in final mRNA
40
what are introns?
regions of non-coding DNA removed from pre-mRNA
41
what is the triplet code?
amino acids are coded for by triplets of bases in DNA. DNA is transcribed to produce codons in mRNA, then translated to produce sequences of amino acids. - 20 amino acids - 4 times 4 times 4 = 64 = more than 20 = degenerate = different triplets code for the same amino acid
42
further modifications of polypeptides
- addition of carbohydrates (glycoprotein), lipids (lipoprotein), phosphate (phosphoprotein) - polypeptides combined (haemoglobin - folded, 4 polypeptide chains, 4 haem groups)
43
stages of protein synthesis
transcription movement of mRNA to ribosomes amino acid activation translation
44
stages of transcription
- DNA helicase unzips section of DNA (gene), breaks hydrogen bonds between complementary base pairs. exposes unpaired bases on template strand - RNA polymerase links to template (coding) DNA strand. attaches mRNA nucleotides to complementary base pairs (A+U, G+C) - DNA strand rewinds into helix behind RNA polymerase - continues until stop codon. RNA polymerase leaves DNA - newly made pre-mRNA leaves DNA. - post-transcriptional modification of pre-mRNA. removes introns, leaves exons = functional mRNA - mRNA leaves nucleus
45
stages of mRNA moving to ribosomes
mRNA leaves nucleus via nuclear pores into cytoplasm attaches to ribosome
46
stages of amino acid activation
enzymes attach amino acids to specific tRNA molecule needs ATP anticodon forms
47
stages of translation
- mRNA leaves nucleus, attaches to small sub unit of ribosome - large subunit of ribosome has 2 attachment sites for tRNA. ribosome holds mRNA and tRNA with attached amino acid. peptide bond forms between amino acids = polypeptide chain - ribosome binds to start codon on mRNA. tRNA binds to ribosome - ribosome moves along mRNA - continues until stop codon codon on mRNA determines tRNA with complementary base code carrying specific amino acid
48
what is the 1 gene 1 polypeptide hypothesis?
each gene is responsible for the synthesis of a single polypeptide
49
why not the 1 enzyme 1 polypeptide hypothesis?
not all proteins are enzymes
50
why not the 1 protein 1 polypeptide hypothesis?
some proteins are made of more than 1 polypeptide e.g. haemoglobin

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