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CH112 > nucleic acids part 1 > Flashcards

nucleic acids part 1 Flashcards

1
Q

what are nucleic acids involved in ?

A

organisation , maintenance and regulation of cellular functions

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2
Q

how is information stored in DNA ?

A

through the base pair sequence

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3
Q

what are genes hereditary to

A

they are hereditary to chromosomes

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4
Q

is the complexity of DNA directly proportional to its length ?

A

no , just because DNA is large in length this does not indicate complexity

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5
Q

whats the 3 processes involved in genetic information transfer ?

A

DNA replication , transcription and translation

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6
Q

what is the central dogma of molecular biology ?

A

DNA replication , transcription , RNA , translation , Protein

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7
Q

how do reteroviruses store their genetic information ?

A

in RNA rather than DNA , this causes problems as the host cell doesn’t recognise RNA

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8
Q

how does a reterovirus overcome host cell not recognising RNA ?

A

it uses an enzyme called reverse transcriptase to convert RNA to DNA

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9
Q

whats an example of a reterovirus ?

A

HIV which becomes aids

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10
Q

what are nucleic acids biopolymers of ?

A

nucleotides

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11
Q

whats the difference between nuclotides and nucleosides ?

A

a nucleotide has a phosphodiester bond present while the nucleoside is just the sugar and base with no phosphodiester link instead OH on carbon 3

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12
Q

what is the sugar phosphate DNA backbone ?

A

2-deoxy-D-ribose rings ( no OH carbon 2 ) that are joined by 3’ to 5’ phosphodiester linkages

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13
Q

what holds the bases together and what does this form ?

A

hydrogen bonds that form between a purine and pyrimidine base and an antiparallel double helix forms

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14
Q

what is the sugar phosphate RNA backbone ?

A

D-ribose rings that are linked by 3’ to 5’ phosphodiester linkages

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15
Q

whats the difference structurally between DNA and RNA

A

RNA has a OH , hydroxyl, group on the 2’ position of the ribose ring.

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16
Q

whats the 2 groups that the 4 bases are divided into?

A

purines and pyrimidines

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17
Q

describe pyrimidines

A

this is a 6 membered ring with 2 nitrogens at carbon 1 and 3 position.

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18
Q

bases that are pyrimidens ?

A

Cytosine and thymine

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19
Q

describe purines

A

this is when a 5 membered ring and a 6 membered ring are fused together

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20
Q

bases that are purines ?

A

guanine and adenine

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21
Q

structurally what is different with uracil and what does this cause ?

A

it is missing a methyl group at C5 which makes the molecule smaller.

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22
Q

what is the glycosidic linkage ?

A

this is when the nucleotide bases are connected to ribose sugar by c-n bond that replaces the N-H.

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23
Q

are nucleosides found in DNA and RNA ?

A

no just DNA as it is missing the phosphate group.

24
Q

how do you name a nucleotide ?

A

based on the position of the phosphate

25
Q

what is an oligonucleotide ?

A

this is a short single strand of DNA that is made up of nucleotides ( contains phosphate)

26
Q

how come nucleotides can be describes as heterocyclic ?

A

This is due to them having nitrogen present in their rings

27
Q

what do the nitrogen atoms act as in the rings ?

A

nucleophiles

28
Q

equation for pKA ?

A

-logka

29
Q

what does Pka value measure ?

A

the position of equilibrium

30
Q

what does a large pkA value indicate ?

A

that the equilibrium lies to the left and that the base is strong

31
Q

what does a smaller Pka value indicate ?

A

that the equilibrium lies to the right

32
Q

Ka equation ?

A

[reactants]

33
Q

is pyrrole a weak or strong base and why ?

A

it is a weak base as the lone pair of electrons aren’t free to move as they are involved in pi bonding

34
Q

what is a nucleophile ?

A

this is a molecule that is negatively charged or contains lone pair of electrons , it is attracted to positive charged (electrophiles)

35
Q

what are many carcinogenic chemicals , nucleophilic or elctrophilic ?

A

electrophilic as they react with the nucleophilic nitrogen in the bases.

36
Q

what is tautomerisation ?

A

this is the transfer of a hydrogen atom from one place to another within the same molecule

37
Q

whats the 2 structures called before and after the hydrogen has been transferred

A

tautomers

38
Q

what are good examples of tautomerisation ?

A

nucleotide bases

39
Q

what occurs if small amounts of less stable tautomers of DNA occur ?

A

this can result in serious consequences in cell replication

40
Q

what is a hydrogen bond ?

A

An electrostatic attraction between a hydrogen atom and a lone pair of electrons

41
Q

what’s normally the elements that are attracted to hydrogen and why

A

nitrogen or oxygen as they are highly electronegative

42
Q

what is an intramolecular interaction ?

A

within the same molecule

43
Q

what is an intermolecular interaction ?

A

between 2 different molecules

44
Q

what functional groups are classed as hydrogen bond donors ?

A

OH and NH

45
Q

what functional groups are classified as hydrogen bond acceptors

A

functional groups with lone pairs

46
Q

based on a molecule having angular structure or linear which is stronger ?

A

the linear

47
Q

when is the hydrogen described as being complementary ?

A

is the HBD and HBA line up correctly

48
Q

what causes a change in the hydrogen bonding ?

A

tautomerisation of the carbonyl group or amino groups and HBD become HBA and vice versa

49
Q

what can this lead to ?

A

incorrect base pairing which will alter the DNA sequence and could result in a mutation

50
Q

how is the error rate of DNA decreased ?

A

due to the presence of proof reading enzymes that remove tautomerisation base mismatches

51
Q

how do phosphate esters differ to organic esters ?

A

in phosphate esters it is possible to replace all 3 hydroxyl groups (oh) to alkoxy groups (OR)

52
Q

how does phosphodiester hydrolysis occur ?

A

in water with an acid or base catalyst

53
Q

are phosphate esters stable or not and what does this mean ?

A

they are relatively stable so the hydrolysis will require harsh condtions

54
Q

how is the hydrolysis of RNA and DNA different and why ?

A

RNA is less stable due to the presence of the OH group at 2’ of the ribose ring.

55
Q

why does sugar base cleavage occur and what is produced ?

A

because the sugar base link ( glycosidic) is unstable to acid hydrolysis , especially the purines and abasic DNA is produced ( sugar separate from base)

CH112 (14 decks)

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