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A Level Biology OCR A > nucleotides and nucleic acids > Flashcards

nucleotides and nucleic acids Flashcards

chap 3

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1
Q

2 types of ribose? What’s the difference? What are they in?

A

Deoxyribose (DNA)
Ribose (RNA)
Deoxy- oxygen removed (in this case from C2)

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2
Q

What is a 1,4 glycosidic bond? In what reaction?

A

The bond between C1’ and C4’ in a disaccharide
Condensation reaction

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3
Q

Lactose

A

Galactose + glucose

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4
Q

Maltose

A

Glucose + glucose

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5
Q

Sucrose

A

Fructose + glucose

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6
Q

2 types of nucleic acids? Difference?

A

Deoxyribonucleic acid (one less oxygen on C2’)
Ribonucleic acid (one more oxygen on C2’)

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7
Q

3 types of RNA?

A

tRNA, mRNA, rRNA

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8
Q

Nucleotide structure (3)

A

PO4 ^2- phosphate group
Pentose sugar monosaccharide (ribose or deoxyribose)
Nitrogenous base (A,T,G,C)

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9
Q

What reaction makes a polynucleotide? Bonds? Between what?

A

-Condensation
-Phosphate group on C5’ forms a phosphodiester bond with hydroxyl group on C’3

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10
Q

What is a polynucleotide?

A

One DNA strand

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11
Q

Bonds between bases? What is the rule that bonds these bases?

A

Hydrogen bonds
Complementary base pairing

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12
Q

Purine structure? Egs?

A

Double ring
A,G

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13
Q

Pyrimidine structure? Egs?

A

Single ring
T,C,U

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14
Q

Anti parallel strands means?

A

2 strands run in opposite directions

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15
Q

Why is complementary base pairing important? (2)

A

-allows DNA to be copied and transcribed during protein synthesis
-maintains 2nm width of DNA

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16
Q

True or false- RNA is single stranded, unlike DNA

A

True

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17
Q

Alternating sugar and phosphate groups called?

A

Sugar phosphate backbone

18
Q

What is DNA replication? why must it be accurate?

A

making identical copies of DNA molecules
so daughter cells have exact copy of parental DNA

19
Q

4 steps of DNA replication
(1st enzyme, pairing from nucleus, 2nd enzyme, result)

A
  • helicase unwinds + unzips hydrogen bonds
  • Bases (from nucleus-abundant nucleotides) bind to bases on the strands
  • polymerase joins phosphodiester bonds, forming backbone
  • 2 identical DNA molecules
20
Q

Why is DNA replication called semi conservative?

A

1 strand og
1 strand new

21
Q

Where does the water molecule come from during the condensation reaction to make polynucleotides?

A

The OH- in the phosphate group on C5’ and the H from the hydroxyl group on C3’

22
Q

Genetic code- 4 adjectives + their meanings

A
  • triplet code
  • universal: genetic code applies to all organisms
  • degenerate: 1 amino acid can be made from lots of combos of diff codons
  • nonoverlapping: codons read ‘in frame’ (nucleotides don’t share codons)
23
Q

Transcription vs translation (process + location)

A

Transcription- copy gene into mRNA (nucleus)
Translation- decode mRNA into protein (cytoplasm)

24
Q

What is the ‘reading frame’? What is usually the start codon?

A

The arrangement of nucleotides into codons
ATG/AUG

25
Q

What are the 2 strands of DNA in transcription called? What are their functions?

A

Sense strand- coding strand
Antisense strand- template strand

26
Q

mRNA has the same codon sequence as which DNA strand?

A

sense

27
Q

tRNA has the same codon sequence as which DNA strand?

A

antisense

28
Q

What enzyme is used in TRANSCRIPTION to unwind DNA into sense and antisense strands? Which enzyme is this similar to?

A

RNA polymerase
(similar to DNA helicase)

29
Q

List 3 similarities between transcription and replication

HINT (bonds, enzyme, nucleotide)

A
  • both form hydrogen bonds
  • both use polymerase to form phosphodiester bonds between nucleotides
  • both require free nucleotides to pair bases
30
Q

List 3 differences between transcription and replication

HINT (product, enzyme, nucleotide)

A
  • transcription makes a single mRNA strand whereas replication makes 2 DNA molecules
  • transcription uses RNA polymerase whereas replication uses DNA polymerase
  • transcription uses A,U,G,C (ribonucleotides) whereas replication uses A,T,G,C (deoxyribonucleotides)
31
Q

Is mRNA single or double stranded?

A

Single

32
Q

What did the semi-conservative experiment prove and how?

A
  • that one DNA strand in replicated molecules was old and one was new
  • using heavy and light nitrogen to form the bases (before division: all heavy, 1st division: half heavy, 2nd division: all light, some a little bit heavy)
33
Q

Explain the process of translation in protein synthesis (6)

A
  • mRNA start codon binds to rRNA in ribosomes (in the rough ER)
  • a tRNA with a complementary anticodon and an amino acid binds to mRNA start codon
  • repeat with more tRNA so the first amino acid is transferred to the second amino acid via a peptide bond
  • catalysed by peptidyl transferase (in ribosome)
  • ribosome moves along mRNA, releasing tRNA, until a polypeptide is formed
34
Q

What does ATP stand for?

A

Adenosine triphosphate

35
Q

Adenosine Triphosphate structure vs Adenosine Diphosphate structure

A

TRI: 3 phosphate groups, ribose sugar, adenine
DI: 2 phosphate groups, ribose sugar, adenine

36
Q

How much energy does ATP release per hydrolysis? Endo or exo? Why?

A

30.6 KJmol-1
Exo bc energy change is pos so more energy is taken in breaking bonds

37
Q

What is the equation for ATP hydrolysis?

A

ATP + water–> P (inorganic) + ADP

38
Q

Properties and functions of ATP? (5)

A
  • Small- moves easily
  • Releases small amounts of energy- reduces waste
  • Unstable- phosphate easily removed, immediate energy source
  • Regenerated easily from ADP- constant energy supply
  • Water soluble- can dissolve in cytoplasm where chemical reactions occur
39
Q

5 steps to DNA extraction

HINT: each step involves one thing removing one part of the cell

A
  1. Grind sample= cell wall
  2. Mix detergent= cell surface membrane
  3. Salt= hydrogen bonds (so DNA does not dissolve in water)
  4. Protease= histones
  5. Alcohol= makes DNA a precipitate
40
Q

Names of strands in DNA replication vs transcription

A

Replication:
leading and lagging
Transcription:
sense and antisense

A Level Biology OCR A (8 decks)

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