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Biology eduquas > nucleic acids > Flashcards

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
Q

what are the 2 functions of DNA?

A

replication: copying an original DNA molecule
protein synthesis: sequence of bases determine amino acid sequence in proteins

26
Q

stages of DNA replication

A
  • 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
Q

types of DNA replication

A

conservative
semi-conservative
dispersive

28
Q

what is conservative DNA replication

A

parental strand remains
new helix made

29
Q

what is semi-conservative DNA replication

A

parental helix separates
2 strands act as templates

30
Q

what is dispersive DNA replication

A

2 new helicases
fragments from both parental strands

31
Q

stages of the Meselson-Stahl experiment

A
  • 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
Q

what is the genetic code?

A

a linear, triplet, non-overlapping, degenerate, unambiguous, universal code for the production of polypeptides

33
Q

how is the genetic code degenerate / redundant?

A

more than 1 triplet can encode each amino acid

34
Q

how is the genetic code punctuated?

A

3 triplet codes don’t code for amino acids
they code for stop codons

35
Q

how is the genetic code universal?

A

same triplets code for the same amino acids in all organisms

36
Q

how is the genetic code non-overlapping?

A

each base only occurs in 1 triplet

37
Q

feature of eukaryotic genes

A

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
Q

features of prokaryotic genes

A

continuous
lack non-coding sequences
mRNA directs synthesis

39
Q

what are exons?

A

regions of DNA that contain the code for proteins
present in final mRNA

40
Q

what are introns?

A

regions of non-coding DNA
removed from pre-mRNA

41
Q

what is the triplet code?

A

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
Q

further modifications of polypeptides

A
  • addition of carbohydrates (glycoprotein), lipids (lipoprotein), phosphate (phosphoprotein)
  • polypeptides combined (haemoglobin - folded, 4 polypeptide chains, 4 haem groups)
43
Q

stages of protein synthesis

A

transcription
movement of mRNA to ribosomes
amino acid activation
translation

44
Q

stages of transcription

A
  • 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
Q

stages of mRNA moving to ribosomes

A

mRNA leaves nucleus via nuclear pores into cytoplasm
attaches to ribosome

46
Q

stages of amino acid activation

A

enzymes attach amino acids to specific tRNA molecule
needs ATP
anticodon forms

47
Q

stages of translation

A
  • 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
Q

what is the 1 gene 1 polypeptide hypothesis?

A

each gene is responsible for the synthesis of a single polypeptide

49
Q

why not the 1 enzyme 1 polypeptide hypothesis?

A

not all proteins are enzymes

50
Q

why not the 1 protein 1 polypeptide hypothesis?

A

some proteins are made of more than 1 polypeptide
e.g. haemoglobin

Biology eduquas (11 decks)

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