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Biology > 2.3-the only calm one (DNA) > Flashcards

2.3-the only calm one (DNA) Flashcards

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1
Q

what is a nucleotide?

A

phosphate esters of pentose sugars

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2
Q

what are the functions of nucleotides?

A

1) form monomers of nucleic acids
2) become ADP and ADP, and through this help regulate many metabolic pathways.
3) may be components of many coenzymes

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3
Q

what are the purines?

A

adenine or guanine: two rings

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4
Q

what are the pyramidines?

A

thymine or cytosine: one rings

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5
Q

what is the bond between the sugar residue and the phosphate group ?

A

covalent bond formed by condensation reaction- phosphodiester bond.

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6
Q

how many h-bonds between adenine and thymine?

A

2

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7
Q

how many h-bonds between guanine and cytosine?

A

3

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8
Q

how is dna organised in eukaryotic cells?

A
  • majority of DNA content in nucleus
  • histone proteins and chromatin
  • loop of dna, without histones, inside mitochondria and chloroplasts.
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9
Q

how is dna organised in prokaryotic cells?

A
  • DNA in a loop within cytoplasm

- no histones-“naked”

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10
Q

how is dna organised in viruses?

A

loop of naked DNA

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11
Q

what does dna polymerase do in dna replication?

A

catalyses addition of new nucleotide bases using DNA strands as templates

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12
Q

what direction does dna polymerase work?

A

moves 3’ to 5’

forms 5’ to 3’

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13
Q

what supplies energy to make phosphodiester bonds in dna replication?

A

hydrolysis of activated nucleotides to release the extra phosphate groups

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14
Q

how does DNA in prokaryotes, mitochondria, and chloroplasts replicate?

A

semi-conservatively:

bubble sprouts from the loop and unwinds and unzips, the complementary nucleotides join to the exposed nucleotides.

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15
Q

what does gyrase do?

A

untwists the double helix

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16
Q

what does dna helicase do?

A

breaks h-bonds between nucleotide bases

17
Q

how is rna structurally different from dna?

A
  • sugar molecule is ribose not deoxyribose
  • U instead of T
  • single stranded
  • shorter than dna
  • 3 forms
18
Q

what are the three forms of rna?

A

mRNA
tRNA
rRNA

19
Q

what are 4 examples of protein shape allowing them to carry out their function?

A

1) shape of active site of enzyme
2) shape of antibody complementary to antigen
3) receptor on cell membrane complementary to shape of cell-signalling molecule
4) ion-channel protein must be hydrophyllic on the inside and lipophyllic on the outside

20
Q

what is the nature of the genetic code?

A

universal
degenerate
non-overlapping

21
Q

why is the genetic code universal?

A

in almost all living organisms the same triplet of DNA codes for the same amino acid.

22
Q

why is the genetic code degenerate?

A

for almost all amino acids there is more than one base triplet

23
Q

what is the effect of the genetic code being degenerate?

A

reduces the effect of point mutations, as a change in one base of the triplet could produce another base for the same amino acid.

24
Q

why is the genetic code non-overlapping?

A

read starting from a fixed point in groups of threes- if a base is added or deleted it causes a frame shift, as every base triplet after that, and hence every amino acid coded for, is changed.

25
Q

what is the template strand?

A

the strand that rna works from

26
Q

what is the coding strand?

A

the strand the rna is making a copy of

27
Q

what is needed for polypeptide synthesis?

A

energy, in the form of ATP

28
Q

what are the important macromolecules that make up the structure of living organisms?

A

DNA, proteins, carbs, lipids

29
Q

what is the 5’ end of the DNA molecule?

A

where the phosphate group is attached to the 5th C atom of the deoxyribose sugar

30
Q

what is the 3’ end of the DNA molecule?

A

where the phosphate group is attached to the 3rd C atom of the deoxyribose sugar

31
Q

what is a gene?

A

a length of dna that codes for a polypeptide or a length of RNA involved in regulating gene expression

32
Q

how many molecules of dna does each chromosome contain?

A

1

33
Q

protein accounts for what percent of an organisms dry mass?

A

75

34
Q

WHAT DOES TRNA AND MRNA DO

A

THEY BIND! ANTICODONS BIND TO CODONS

35
Q

WHY IS DNA REPLICATION SEMI CONSERVATIVE FOR 2 MARKS

A

MAINTAINS HALF OF ORIGINAL DNA

ORIGINAL STRAND ACTS AS TEMPLATE FOR NEW STRAND

36
Q

WHAT’S THE IMPORTANCE OF COMPLEMENTARY BASE PAIRING IN DNA REPLICATION

A

CORRECT ORDER OF BASES
REDUCES OCCURENCE OF MUTATIONS
ALLOWS REFORMATION OF H BONDS

37
Q

HOW MANY POLYNUCLEOTIDE STRANDS ARE FOUND IN A TRNA MOLECULE

A

1

38
Q

HOW MANY BP ARE THERE IN 1 FULL TURN OF THE DNA DPIBLE HELIX

A

10

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