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Biology Module 2 > 2.3 Nucleic Acids and Nucelotides > Flashcards

2.3 Nucleic Acids and Nucelotides Flashcards

Nucleotides and Nucleic Acids

1
Q

what is a nucleotide

A

a type of biological molecule made of:
- a pentose sugar ( 5 carbon atoms)
- a nitrogenous (containing nitrogen) base
- a phosphate groups

  • make up nucleic acids
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2
Q

what elements do all nucleotides contain

A

C, H, O, N, P

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3
Q

examples of nucleotides

A
  • monomers that make up DNA and RNA (store genetic information to grow and develop, make proteins from DNA instructions)
  • ADP and ATP (store and transport energy in cells)
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4
Q

what is a DNA nucleotide made of

A
  • PENTOSE SUGAR: deoxyribose (same)
  • PHOSPHATE GROUP (same)
  • NITROGENOUS BASE: adenine, thymine, cytosine, guanine
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5
Q

categorise the DNA bases

A

purine base:
- contains two carbon-nitrogen rings
- A and G
pyrimidine base:
- contains one carbon-nitrogen ring
- smaller
- T and C

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6
Q

what do a bunch of DNA nucleotides make up

A
  • a polynucleotide chain
  • two present in a DNA molcule
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7
Q

what is RNA made of

A

ribonucleic acid:
- PENTOSE SUGAR: ribose
- PHOSPHATE GROUP
- NITROGENOUS BASE: A, U, C, G (uracil, not thymine)

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8
Q

what do a bunch of RNA nucleotides make up

A
  • a SINGLE polynucleotide chain
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9
Q

what is a phosphorylated nucleotide and what are examples

A
  • a nucleotide with one or more phosphate groups added to it
  • ADP (adenosine diphosphate) and ATP (adenosine triphosphate)
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10
Q

similarities and
differences between ADP and ATP

A
  • both contain base adenine, pentose sugar ribose
  • ADP = 2 phosphate groups
  • ATP = 3 phosphate groups
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11
Q

how does ATP provide energy for chemical reactions in cells

A

ADP + P ===> ATP (condensation)

  • ATP is synthesised from a reaction between ADP and an inorganic phosphate
  • USES energy from an energy releasing reaction ( breakdown of glucose in respiration)
    -ADP is phosphorylated to form ATP and a phosphate bond is formed, which STORES ENERGY
  • when energy is needed by a cell, ATP ===> ADP + P (hydrolysis)
  • energy is RELEASED from the phosphate bond and used by cell
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12
Q

what are the properties of ATP which help with its function

A
  • small: can move easily in and out of cells
  • water soluble: can react in aqueous environments
  • contains intermediate energy bonds between phosphates: enough for reactions, not enough to be wasted
  • releases energy in small amounts: none wasted as heat, but enough for most cellular reactions
  • easily regenerated: can be recharged with energy
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13
Q

how does each nucleotide join to form a strand

A
  • condensation reaction between phosphate group of one nucleotide and sugar of another
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14
Q

what bond is formed between nucleotides

A

phosphodiester bond
- consists of phosphate group and two ester bonds

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15
Q

what is the chain of sugars and phosphates in a DNA molecule called

A

the sugar-phosphate backbone

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16
Q

how can polynucleotides be broken down

A

hydrolysis reaction
(to break the phosphodiester bond)

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17
Q

how do the two polynucleotide chains join together

A
  • form a double helix
  • two polynucleotide strands join by HYDROGEN bonding
  • the strands run antiparallel (opposite directions) and twist to form the DNA double helix
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18
Q

how does hydrogen bonding occur in the polynucleotide chain

A

between a purine (AG) and a pyrimidine (TC)
- two hydrogen bonds between A and T and 3 hydrogen bonds between C and G

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19
Q

what is complementary base pairing

A
  • each base can only join with a particular partner
20
Q

how do you purify DNA

A
  • precipitation reaction
    1) break up cells in the sample (e.g. blender/pestle and mortar)
    2) make a solution of salt, detergent and distilled water
    3) add cells into beaker with solution
    4) incubate in water bath at 60 degrees for 15 minutes
    5) once incubated, put beaker in ice bath and cool down
    6) filter mixture once cooled and transfer into cool boiling tube
    7) add protease enzymes into mixture
    8) slowly dribble cold ethanol down side of tube, so that it forms a layer on top of mixture
    9) leave for few minutes, and should see DNA form a white precipitate , which can be removed using glass rod
21
Q

give reasons for each step in DNA purification

A

detergent= breaks down cell membranes

salt= binds to DNA and causes it to clump together, as breaks bonds between DNA and water molecules, so less soluble

temperature= stop enzymes in cell from working properly and breaking down DNA

protease enzyme = breaks down some proteins in mixture, like those bound to DNA (use RNase to break down any RNA in mixture

ethanol= precipitate the DNA

22
Q

when and why does DNA replicate itself

A
  • before cell division
  • each new cell has full amount of DNA
23
Q

explain how DNA replicates

A

1) -DNA HELICASE breaks down the hydrogen bonds between the two polynucleotide DNA strands
-the helix unzips to form 2 single strands
2) each original strand acts as a template for a new strand.
-free-floating DNA nucleotides join to the exposed branches on each original template strand by complementary base pairing
3) - nucleotides of the new strand join together by DNA polymerase
- forms a sugar-phosphate backbone
- Hydrogen bonds form between the bases of the new and original strand.
- strands twist to form a double helix

24
Q

why is DNA replication referred to as semi-conservative

A
  • each new DNA molecule contains one strand from the original DNA molecule and one new strand
    -1/2 strands are original
25
Q

why does DNA replication have to be really accurate

A
  • to make sure the genetic information is conserved (stays the same) each time the DNA in a cell is replicated
26
Q

how can you describe the nature of mutations

A
  • random
  • spontaneous
27
Q

what is a mutation

A

any change to the DNA base sequence

28
Q

what can mutations do

A
  • alter the sequence of amino acids in a protein
  • causes an abnormal protein to be produced
  • might function better than normal protein, or not work at all
29
Q

what is a gene

A

a sequence of DNA nucleotides that code for a polypeptide (protein)

30
Q

how does DNA code for different proteins

A
  • order of nucleotide bases in a gene determines the order of amino acids, which determines what protein is made
  • the sequence of bases is used as a template during protein synthesis
31
Q

how many bases code for 1 amino acid

A
  • 3 DNA bases
  • base triplet
  • codon
32
Q

brief difference outlying differences between transcription and translation

A

transcription: section of DNA is copied into mRNA to leave the nucleus and travel outside of cell to ribosomes

translation: mRNA leaving nucleus to ribosome where it can be used to synthesise a protein

33
Q

what are the three types of RNA

A

mRNA (messenger)
tRNA (transfer)
rRNA (ribosomal)

34
Q

outline mRNA

A
  • made in the nucleus
  • 3 adjacent bases are called codon
  • carries genetic code from DNA in nucleus to cytoplasm, where its used to make a protein
35
Q

outline tRNA

A
  • found in the cytoplasm
  • has amino acid binding site at one end
  • has sequence of 3 bases on other end called anticodon
  • carries the amino acids that are used to make proteins to the ribosomes during translation
36
Q

outline rRNA

A
  • forms the two subunits in a ribosome (along with proteins)
  • helps to catalyse the formation of peptide bonds between the amino acids (when ribosome moves along the mRNA strand)
37
Q

what is the genetic code

A
  • the sequence of of base triplets (codons) in DNA or mRNA, which codes for a specific amino acid
38
Q

what are the 3 qualities of the genetic code

A
  • non-overlapping
  • degenerate
  • universal
39
Q

why is the genetic code non-overlapping

A
  • each base triplet is read in sequence, separate from the triplet before and after it (the triplets don’t share their bases)
40
Q

why is the genetic code degenerate

A
  • there are more combinations of triplets than there are amino acids (20 amino acids vs 64 combinations)
  • some amino acids are coded for by more than one base triplet
  • tyrosine = UAU or UAC
41
Q

why is the genetic code universal

A
  • the same specific base triplets code for the same amino acids in all living things
  • tyrosine = UAU in all living organisms
42
Q

what are start and stop signals/ codons

A
  • triplets used to tell the cell when to start or stop the production of protein
  • found at beginning and end of a gene
  • UAG = stop signal
43
Q

what else is the DNA template strand called

A

the antisense strand
- carries the complementary bases so that RNA will have same sequence as sense strand

44
Q

what is the process of transcription

A

1) the DNA double helix unzips and unwinds at gene required by breaking hydrogen bonds between bases, by DNA helicase
2) splits into two strands, (sense= 5’ to 3’ and contains code for protein) and (anti-sense= 3’ to 5’)
3) free RNA nucleotides join the template strand by complementary base pairing
4) phosphodiester bonds form between the RNA nucleotides by the enzyme RNA polymerase
5) RNA nucleotides detach from the template strand, forming mRNA
6) the DNA rezips and rewinds using DNA ligase

45
Q

explain how the DNA code is edited

A

-introns removed (non-coding sections)
- exons are kept (coding sections)
- through use of enzyme

46
Q

explain structure of tRNA

A
  • has anti-codon attached to bottom
  • has amino acid at the top
47
Q

explain process of translation

A

1) mRNA moves out of nuclear pore and attaches to ribosome in cytoplasm
2) tRNA molecule with complimentary anticodon to start codon attaches to the mRNA by complimentary base pairing, carrying an amino acid
3) second tRNA molecule attaches to next codon on mRNA by complimentary base pairing as well
4) rRNA catalyses the formation of the peptide bond between the two amino acids attached to the tRNA molecules (condensation)
5) the first empty tRNA molecule moves away, leaving its amino acid behind
6) third tRNA molecule binds to the next codon on mRNA, and its amino acid binds to the first two
- second tRNA molecule moves away
7) process repeats until it reaches a stop codon
8) chain moves away from the ribosome and translation is complete

  • ribosome moves across the mRNA chain

Biology Module 2 (6 decks)

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