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biology M2 > Nucleotides and nucleic acids > Flashcards

Nucleotides and nucleic acids Flashcards

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1
Q

what 3 components structure a nucleotide

A

a phosphate group, a pentose sugar and an organic base

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2
Q

what are 2 polymers of nucleotides

A

DNA and RNA

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3
Q

what is the structure of ATP (adenosine triphosphate)

A

one molecule of adenine, one ribose sugar and 3 phosphate groups

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4
Q

what are the components of a DNA nucleotide

A

a deoxyribose sugar, a phosphate group and one of the 4 organic bases (adenine, guanine, cytosine or thymine)

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5
Q

what is the structure of a DNA molecule

A

double stranded that twists into a double helix, the 2 strands are anti-parallel and therefore run in opposite directions, that 2 sugar - phosphate backbones are held in place by pairs of complimentary bases joined by hydrogen bonds

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6
Q

what are the components of a RNA nucleotide

A

a ribose sugar, a phosphate group and one of the organic bases (adenine,guanine,cytosine or uracil)

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7
Q

what is the structure of a RNA nucleotide

A

a relatively short molecule and single-stranded

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8
Q

what bond is formed between 2 nucleotides due to a condensation reaction

A

phosphodiester bond/ester bond

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9
Q

what is a phosphodiester bond

A

a phosphate group and 2 ester bonds

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10
Q

what reaction breaks the phosphodiester bond

A

hydrolysis

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11
Q

what 2 organic bases are purines

A

adenine and guanine

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12
Q

what 2 organic bases are pyrimidines

A

cytosine and thymine

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13
Q

how many hydrogen bonds from between the complimentary base pairs

A

cytosine+guanine=3 hydrogen bonds
adenine+thymine=2 hydrogen bonds

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14
Q

what is the first stage of DNA replication

A

DNA helicase breaks the hydrogen bonds between the 2 polynucleotide DNA strands, the helix unzips to form 2 single strands

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15
Q

what is the second stage of DNA replication

A

each original strand acts as a template for a new strand , free-floating DNA nucleotides join to the exposed bases on each original template strand by complimentary base pairing

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16
Q

what is the third stage of DNA replication

A

the nucleotides of the new strand are joined together by DNA polymerase, forming the sugar-phospahte backbone, hydrogen bonds form between the bases on the original and new strand, this twists to form a double-helix

17
Q

what is the fourth stage of DNA replication

A

each new DNA molecule contains one strand from the original DNA molecule and one new strand

18
Q

what is semi-conservative replication

A

half of the strands from each molecule are from the original piece of DNA

19
Q

what is the first stage of transcription

A

DNA helicase breaks the hydrogen bonds which unzips and unwinds the section of DNA that contains the gene

20
Q

what are the 2 strands called and used for after being seperated by DNA helicase

A

one of the strands is a sense strand which contains the code for the protein to be synthesised it runes from 5’ to 3’, the anti-sense strand is a complimentary copy that doesn’t code for a protein and acts as a template strand

21
Q

what is the second stage of transcription

A

RNA polymerase moves along the DNA template strand and attaches free nucleotides to their complimentary bases on the DNA, phosphodiester bonds are formed

22
Q

what is the third stage of transcription

A

RNA polymerase continues making a strand of mRNA until a stop codon is reached

23
Q

what happens to the mRNA after it is produced through transcription

A

the mRNA detaches from the DNA template and leaves the nucleus via a nuclear pore, the DNA double helix reforms, mRNA then travels to a ribosome for translation

24
Q

what is splicing

A

when mature mRNA is formed by the introns (non-coding regions of genes) being removed from the pre - RNA molecule, and the exons (coding regions) joining together.

25
Q

what is the first stage of translation

A

rRNA (ribosomal RNA) makes up the ribosome that moves along the mRNA strand, and one end of the mRNA attaches to the ribosome

26
Q

what is the second stage of translation

A

a tRNA (transfer RNA) with a complimentary anticodon, carrying a specific amino acid moves to the ribosome and pairs with the first mRNA codon

27
Q

what is the third stage of translation

A

the ribosome moves along the mRNA to the next codon and again pairs up with a complementary tRNA, to bring the two amino acid-carrying tRNAs together

28
Q

what is the fourth stage of translation

A

energy released from ATP is used to form a peptide bond between the amino acids bought to the ribosome by tRNA

29
Q

what is the fifth stage of translation

A

the ribosome moves to the third mRNA codon, releasing the first tRNA and pairing up a third (only space for 2 tRNA at a time)

30
Q

what is the sixth stage of translation

A

this continues until the ribosome reaches a stop codon, then the polypeptide is complete and the mRNA and tRNAs are released from the ribosome

31
Q

the tRNA molecules released from the ribosome can’t be reused
true or false?

A

false
they can be reused

32
Q

what does it mean that the genetic code is non-overlapping

A

each base triplet is read in sequence,seperate from the triplet before it and after it and the base triplets don’t share their bases

33
Q

what does it mean that the genetic code is universal

A

the same base triplets code for the same amino acid in all living organisms/things

34
Q

what does it mean that the genetic code is degenerate

A

more combinations of base triplets than amino acids (20 amino acids but 64 possible base triplets), some amino acids are coded for by more than one base triplets

35
Q

what is the method for DNA purification

A

1- use a fruit or vegetable e.g. strawberries and break up the cells e.g. through use of a blender
2- make up a solution of detergent (dilute washing-up liquid), salt (sodium chloride) and distilled water
3- add broken cells to a beaker containing detergent solution, incubate the beaker in a water bath at 60 degrees for 15 minutes
4- once incubated put beaker in an ice bath to cool the mixture down, when its cooled filter the mixture e.g. pass through a mesh
5- add protease enzymes to the filtered mixture
6- slowly dribble some ice cold ethanol at a 45 degree angle to the solution, so it forms a layer on top of the DNA-detergent mixture
7- once left for a few minutes, the DNA will form a white precipitate (solid) which can be removed using a glass rod

36
Q

how is the detergent solution suited to make the method work

A

detergent- breaks down the cell membranes
salt- binds to the DNA and causes it to clump together
temperature- the temperature of the water bath should stop enzymes in the cells from working properly and breaking down the DNA

37
Q

how does the protease enzymes work

A

these will break down (hydrolyse) some proteins in the mixture

38
Q

what does adding the ethanol do to the DNA

A

causes it to precipitate

biology M2 (6 decks)

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