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AQA A level Biology > Nucleic acids > Flashcards

Nucleic acids Flashcards

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1
Q

Is RNA a polymer

A

Yes

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2
Q

What is the monomer of RNA

A

A nucleotide

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3
Q

What are the 3 components of the nucleotide that makes up RNA

A
  • Ribose (pentose sugar)
  • A nitrogenous base (A,G,C,U)
  • A phosphate group
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4
Q

Name 4 differences between RNA and DNA

A
  • RNA contains ribose instead of deoxyribose in DNA
  • RNA has the base uracil whereas DNA has thymine
  • RNA is single stranded whereas DNA is double
  • RNA polymer is a relatively short polynucleotide chain whereas DNA is long
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5
Q

What are the functions of RNA

A
  • Copy and transfer the genetic code from DNA in the nucleus to the ribosomes
  • Some RNA also combines with proteins to create ribosomes
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6
Q

What are the 3 types of RNA

A
  • mRNA (messenger)
    -tRNA (transfer)
    -rRNA (ribosomal)
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7
Q

What is mRNA

A

A copy of a gene from DNA

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8
Q

Where is mRNA created

A

In the nucleus

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9
Q

Why is mRNA created instead of just having DNA

A

Because DNA is too large to leave the nucleus whereas mRNA is much smaller because it’s only the length of one gene therefore can fit through the nuclear pores

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10
Q

Why is mRNA short lived

A

Because once the genetic material has left the nucleus it has a risk of being exposed to enzymes which can hydrolyse the polymers

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11
Q

How many bases on mRNA code for one specific amino acid

A

3

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12
Q

What is the name of the 3 bases that code for an amino acid

A

A codon

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13
Q

Where is tRNA found

A

In the cytoplasm

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14
Q

Is tRNA single or double stranded

A

Single

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15
Q

What is the shape of mRNA

A

A straight line

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16
Q

What is the shape of tRNA

A

Folds in on itself to create a shape that looks like a cloverleaf

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17
Q

What type of bonds hold the cloverleaf shape of a tRNA molecule

A

Hydrogen bonds

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18
Q

What is the function of tRNA

A

To transfer amino acids

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19
Q

At the top of the tRNA molecule there are 3 exposed bases, what is the name for these bases

A

The amino acid attachment site

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20
Q

What is the function of rRNA

A

Combines with protein to make ribosomes

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21
Q

Differences between the DNA and RNA monomers (x2)

A
  • DNA contains the base thymine whereas RNA contains uracil instead
  • DNA contains the pentose sugar deoxyribose, whereas RNA contains the pentose sugar ribose
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22
Q

What is the function of DNA

A
  • Carries genetic code for protein synthesis
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23
Q

What is the name of the monomer making up nucleic acid

A

Nucleotides

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24
Q

What is the name of the polymer made from nucleotides

A

Polynucleotides

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25
Q

What reaction joins nucleotides together to form a polynucleotide

A

A condensation reaction

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26
Q

What is the name of the bond when nucleotides join together via a condensation reaction

A

phosphodiester bond

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27
Q

How many polynucleotides make up DNA

A

2

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28
Q

How many polynucleotides make up RNA

A

1

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29
Q

What are the 3 main components of a nucleotide

A
  • Phosphate group
  • Pentose sugar
  • Nitrogen-containing base
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30
Q

In DNA, what is the name of the pentose sugar

A

Deoxyribose

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31
Q

In DNA, what are the names of the 4 possible nitrogen-containing bases

A
  • Adenine
  • Thymine
  • Cytosine
  • Guanine
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32
Q

In RNA, what is the name of the pentose sugar

A

Ribose

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33
Q

In RNA, what are the names of the 4 possible nitrogen-containing bases

A
  • Adenine
  • Cytosine
  • Guanine
  • Uracil
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34
Q

What is the proper name for ATP

A

Adenosine triphosphate
(must remember the osine)

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35
Q

What is the name of the pentose sugar in ATP

A

Ribose

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36
Q

What is the name of the nitrogen-containing base in ATP

A

Adenine

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37
Q

In ATP what is the name of the phosphate group

A

Triphosphate group

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38
Q

What type of structure do purine nitrogenous bases have

A

Double ring

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39
Q

What are the 2 nitrogenous bases that are purine bases

A
  • Adenine
  • Guanine
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40
Q

What type of structure do pyrimidine, nitrogenous bases have

A

Single ring structure

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41
Q

What are the 3 nitrogenous bases that have pyrimidine structures

A
  • Thymine
  • Cytosine
  • Uracil
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42
Q

What type of nitrogenous base is bigger, purine bases or pyrimidine bases

A

Purine bases are bigger

43
Q

How many hydrogen bonds does the purine base adenine make

A

2 hydrogen bonds

44
Q

How many hydrogen bonds does the purine base guanine make

A

3 hydrogen bonds

45
Q

In DNA, what is the ratio of purine bases to pyrimidine bases

A

1:1

46
Q

What is the name of the structure of DNA

A

Double helix

47
Q

DNA has a sugar-phosphate backbone, what is it’s role in overall DNA function

A

Gives strength to DNA molecule

48
Q

DNA is composed of 2 chains held together by weak hydrogen bonds, what is this features relation to the overall function

A

The chains can be separated for transcription (protein synthesis) and replication

49
Q

DNA has a coiled structure why is this useful

A

Protects the hydrogen bonds therefore reducing corruption of genetic code

50
Q

DNA contains many weak hydrogen bonds what benefit does this have

A

Make DNA a stable molecule

51
Q

DNA is a long molecule, what impact does this have on the role of DNA

A

It can store a lot of genetic information (genes)

52
Q

Where is DNA found

A

Nucleus

53
Q

Where is RNA found

A
  • Nucleus
  • Cytoplasm
54
Q

What forms from the hydrolysis of ATP

A

ADP and Pi

55
Q

What is the enzyme that catalyses the hydrolysis of ATP

A

ATP hydrolase

56
Q

Is the hydrolysis of ATP an exergonic or endergonic reaction

A

Exergonic reaction

57
Q

What molecules are required to synthesise ATP

A

ADP and Pi

58
Q

What is the name of the enzyme that catalyses the synthesis of ATP

A

ATP synthase

59
Q

Is the synthesis of ATP endergonic or exergonic

A

Endergonic reaction

60
Q

What is the function of ATP

A

An immediate source of energy for biological processes

61
Q

Why is it essential that cells have a constant, steady supply of ATP

A

So the can under go all the chemical reactions in the cell

62
Q

What process makes ATP

A

Respiration

63
Q

Why is ATP described as an immediate source of energy

A

Because only one bond has to be hydrolysed to release energy - so very rapid

64
Q

Why is ATP releasing small, manageable amount of energy better than the energy released from glucose

A
  • Less energy is wasted
  • Stops cells from overheating since a lot of waste energy is released in the form of heat
  • Glucose would release large amounts of energy
65
Q

Why is ATP being a small and soluble molecule beneficial

A

It can easily be transported around the cell

66
Q

How many bonds in ATP need to be broken/ hydrolysed to release energy, and why is this better than glucose

A

Only 1 bond needs to be hydrolysed, so is an immediate energy release, whereas glucose would need several bonds to be hydrolysed to release all its energy

67
Q

What does phosphorylation mean in terms of ATP

A

The inorganic phosphate group can be bonded to new molecule and make that molecule more reactive

68
Q

Why is ATP not being able to pass out of the cell a benefit

A

So the cell always has an immediate supply of energy whereas glucose can run out

69
Q

When does DNA replication occur in the cell cycle

A

Before cell division

70
Q

What is the name of the process of DNA replication

A

Semi-conservative replication

71
Q

What does semi-conservative replication mean

A

In the daughter DNA one strand is from the parental DNA and one strand is newly synthesised

72
Q

What are the 2 complementary base pairs

A
  • Adenine and thymine
  • Cytosine and guanine
73
Q

What are the names of the 2 key enzymes involved in semi-conservative replication

A
  • DNA helicase
  • DNA polymerase
74
Q

What is the role of DNA helicase

A

This enzyme breaks the hydrogen bonds between complementary base pairs between the 2 strands within a double helix

75
Q

What is the first step needed to start the DNA replication process

A

The DNA double helix needs to unwind using the enzyme DNA helicase by breaking the hydrogen bonds

76
Q

Once the double helix of DNA has separated what do the 2 parental strands now act as

A

A template

77
Q

Once the 2 strands of DNA have been separated, what does the free floating DNA nucleotides within the nucleus do

A

They are attracted to their complementary base pairs on the template strands of the parental DNA - but these nucleotides are not attached together yet so still monomers

78
Q

Once the free floating nucleotides that are attracted to the template DNA strand align adjacent to one another, what enzyme catalyses the joining of these adjacent nucleotides

A

DNA polymerase

79
Q

What is the function of DNA polymerase

A

To join together adjacent nucleotides

80
Q

What are the names of the DNA replication theories

A
  • Conservative
  • Semi-conservative
  • Dispersive
81
Q

Explain what the theory semi-conservative replication of DNA is

A

Each replicated DNA molecule contains one of the original DNA strands and one newly synthesised DNA strand

Conservative one entire original strand

82
Q

Explain what is meant by conservative DNA replication

A

The original DNA remains intact following DNA replication and the two newly synthesised strands of DNA join together

83
Q

What are the names of the men who conducted the experiment proving semi-conservative DNA replication

A
  • Meselson
  • Stahl
84
Q

When Meselson and Stahl carried out their experiment on DNA replication what were the 2 different isotopes of nitrogen that were used, and which is the lighter one

A
  • Nitrogen-14, lighter
  • Nitrogen-15, heavier
85
Q

What bacteria did Meselson and Stahl use in their experiment

A

Ecoli

86
Q

In the first generation of bacterial growth in the Meselson and Stahl experiment, what medium was the ecoli grown in and how was this proven

A

Grown in nitrogen-15 medium and once placed in a centrifuge the DNA accumulated at the bottom of the tube

87
Q

After the Ecoli had replicated in the nitrogen-15 medium, what did Meselson and Stahl do next

A

They took the Ecoli out of the nitrgoen-15 medium and placed it in a nitrogen-14 medium

88
Q

In the first generation of Ecoli, placed in the nitrgon-14 medium, what happens when the DNA is centrifuged

A

There is only one band but it’s higher up the tube compared to the Ecoli that only contained nitrogen-15

89
Q

In the 2nd generation of ecoli DNA replication, what happens to the DNA when centrifuged

A

2 bands are formed
- one in the middle of the tube - 50% DNA is nitrogen-15 and nitrogen-14
- One at the top of the tube- 50% DNA is nitogen-14 and nitrogen-14

90
Q

In the 3rd generation of ecoli DNA replication, what happens to the DNA when centrifuged, what are the %

A

2 bands form
- one in the middle- 25% DNA is N-15 and N-14
- one thicker band at the top- 75% DNA is N-14 and N-14

91
Q

Name the type of bond between complementary base pairs

A

Hydrogen bonds

92
Q

Name the type of bond between adjacent nucleotides in a DNA strand

A

Phosphodiester bonds

93
Q

Describe the structure of DNA (5 marks)

A
  • Polymer of nucleotides
  • Each nucleotide formed from deoxyribose, a phosphate group, and an organic base
  • Phosphodiester bonds
  • Double helix held by hydrogen bonds
  • Hydrogen bonds between adenine, thymine and cytosine, guanine
94
Q

Describe how a phosphodiester bond is formed between 2 nucleotides within a DNA molecule (2 marks)

A
  • Condensation reaction
  • Between phosphate and deoxyribose
  • Catalysed by DNA polymerase
95
Q

Name the protein associated with DNA in a chromosome

A

HIstone

96
Q

Describe how the separation of the 2 DNA strands in semi-conservative DNA replication (2 marks)

A
  • DNA helicase
  • Breaks hydrogen bonds between base pairs / breaks hydrogen bonds between polynucleotide strands
97
Q

Describe the role of DNA polymerase in the semi-conservative replication of DNA (2 marks)

A
  • Joins adjacent DNA nucleotides
  • Catalyses condensation reactions
  • Phosphodiester bonds
98
Q

Name the 2 scientists who proposed models of the chemical structure of DNA and of DNA replication

A

Watson and Crick

99
Q

Give 2 features of DNA and explain how each one is important in the semi-conservative replication of DNA ( 2 marks)

A
  • Weak hydrogen bonds between bases allow 2 strands to separate
  • 2 strands, so both can act as templates
  • Complementary base pairing allows accurate replication
100
Q

Describe the role of 2 names enzymes in the process of semi-conservative replication of DNA (3 marks)

A
  • DNA helicase causes breaking of hydrogen bonds between DNA strands
  • DNA polymerase joins the DNA nucleotides
  • Forming phosphodiester bonds
101
Q

Describe the function of DNA helicase

A

Breaking hydrogen bonds between bases

102
Q

Describe the function of DNA polymerase

A

Joins adjacent nucleotides / forms. phosphodiester bonds

103
Q

Contrast the structures of ATP and a nucleotide found in DNA to give 2 differences (2 marks)

A
  • ATP has ribose and DNA nucleotides has deoxyribose
  • ATP has 3 phosphate groups and DNA nucleotide has 1 phosphate group
  • ATP- base always adenine and in DNA nucleotide base can be different

AQA A level Biology (32 decks)

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