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A level OCR Biology > Nucleotides and Nucleic Acid > Flashcards

Nucleotides and Nucleic Acid Flashcards

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1
Q

What abilities do nucleic acids have?

A
  • The ability to carry out instructions

- The ability to be copied

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2
Q

DNA and RNA are …; the individual … are the … that build up the …

A
  • polymers
  • nucleotides
  • monomers
  • polynucleotides
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3
Q

What does DNA stand for?

A

deoxyribonucleic acid

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4
Q

What does RNA stand for?

A

ribonucleic acid

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5
Q

What are nucleotides made up of?

A

Three smaller components:

  • Nitrogen-containing base
  • Pentose sugar (it has 5 carbon atoms)
  • Phosphate group
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6
Q

List the bases found in DNA

A
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
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7
Q

List the bases found in RNA

A
  • Adenine (A)
  • Uracil (U)
  • Cytosine (C)
  • Guanine (G)
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8
Q

What are the base pairings in DNA?

A

A - T

C - G

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9
Q

What are the base pairings in RNA?

A

A - U

C - G

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10
Q

What bases are purines?

A

A and G

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11
Q

Are purines larger or smaller than pyrimidines

A

Larger

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12
Q

What ring structure do purines have?

A

Double ring structure (Carbon and Nitrogen atoms)

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13
Q

What bases are pyrimidines?

A

T, U and C

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14
Q

What ring structure do pyrimidines have?

A

Single ring structure (Carbon and Nitrogen atoms)

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15
Q

How many hydrogen bonds are in base pairings in DNA?

A

A - T has two hydrogen bonds

C - G has three hydrogen bonds

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16
Q

What reaction are nucleotides linked by?

A

Condensation reaction

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17
Q

What is the polymer of nucleotides known as?

A

Polynucleotide

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18
Q

Alternating … and … groups join

A

Sugars

Phosphate group

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19
Q

What type of bond is formed at the 5th carbon of the pentose layer with the OH group 3 carbon of adjoining nucleotides?

A

Phosphodiester bond

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20
Q

What reaction are the phosphodiester bonds broken by?

A

Hydrolysis

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21
Q

What does the hydrolysis of phosphodiester bonds release?

A

Individual nucleotides

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22
Q

DNA strands are said to be antiparallel, which means

A

The DNA strands are side-by-side run in opposite directions

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23
Q

What type of bond is in between bases in DNA?

A

Hydrogen bonds

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24
Q

What is the fact that hydrogen bonds can be broken relatively easily important for?

A

Protein synthesis

DNA replication

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25
Q

What does tRNA do?

A

Brings amino acids to the ribosome

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26
Q

What does mRNA do?

A

Allows the transfer of genetic information from the nucleus to a ribosome

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27
Q

What does rRNA do?

A

Responsible for translation, they read the order of the amino acids and link the amino acids together

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28
Q

How do RNA nucleotides bond (is it the same as DNA)?

A

Bond in the same way as DNA - phosphodiester bonds formed in condensation reactions

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29
Q

What is the difference between RNA and DNA?

A

Deoxyribose has one less oxygen atom than ribose

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30
Q

When a cell divides, what must the daughter cell receive?

A

An exact copy of the genetic material from the parent cell

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31
Q

For the daughter cell to receive an exact copy of the genetic material, what must happen?

A

The DNA in the parent cell must first be replicated

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32
Q

How is DNA replicated?

A
  • DNA Helicase is responsible for unwinding DNA and allows strands to separate by breaking hydrogen bonds
  • Complementary base pairing occurs as free nucleotides in the nucleoplasm are attracted to the complementary bases on the two sugar-phosphate backbones
  • Once in place, the activated nucleotides are joined together by DNA polymerase using strong covalent bonds, forming the sugar-phosphate backbone
  • The result is that there is two DNA molecules, each with one newly synthesised strand of DNA and one strand from the original DNA
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33
Q

What is the lagging strand in DNA replication?

A

DNA polymerase is moving away from the replication fork. As DNA polymerase is moving away from helicase it must constantly return to copy newly separated stretches of DNA. This means that the lagging strand is copied as a series of short fragments (Okazaki fragments)

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34
Q

What are the short fragments called on the lagging strand?

A

Okazaki fragments

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35
Q

Why is there a lagging strand when copying DNA?

A

Helicase is moving in the opposite direction so unzipped parts of DNA is now being copied but DNA polymerase has to wait to copy them

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36
Q

What is the process of semi-conservative replication?

A
  • Replication starts at a specific sequence on the DNA molecule, which is called the origin of replication
  • DNA helicase unwinds and unzips the DNA molecule, breaking the hydrogen bonds that join the base pairs, and forms two separate strands of DNA
  • The new DNA molecules are built up from the four nucleotides (A, C, G, T) that are abundant in the nucleoplasm.
  • These nucleotides attach themselves to the bases on the old strands by complementary base pairing
  • DNA polymerase joins the new nucleotides to each other by strong covalent bonds, forming the new sugar-phosphate backbone
  • The two new DNA molecules are identical to the old molecule, and each has one strand of DNA from the original DNA molecule
37
Q

How are mutations caused?

A

Sequences of bases are not always matched correctly, such errors are random and spontaneous, which leads to a change in the DNA sequence called a mutation

38
Q

What is the sequence of bases on DNA called?

A

A code

39
Q

What is meant by ‘the code is universal’

A

It is used in all organisms

40
Q

How are the four bases read?

A

In triplets (codons)

41
Q

Are triplets overlapping?

A

No, they are non-overlapping

42
Q

How many possible base triplets are there?

A

64

A combination of 4 letters in groups of 3, gives 64 possible base triplets

43
Q

What do the 64 codons code for?

A

The 20 amino acids

44
Q

Why is the DNA code called degenerate?

A

More than one triplet will code for each amino acid

45
Q

What gives rise to the huge variety of proteins?

A

Combinations of the 20 amino acids

46
Q

What amino acid do all polypeptides start with?

A

Methionine

47
Q

What is the conservative hypothesis?

A

The complete parent DNA molecule acts as a template for the new daughter molecule, which is assembled from new nucleotides. The parent molecule is unchanged

48
Q

What is the semi-conservative hypothesis?

A

The parent DNA molecule separates into its two component strands, each of which acts as a template for the formation of a new, complementary strand. The two daughter molecules, therefore, contain half the parent DNA and half new DNA

49
Q

How did Meselson and Stahl in 1958, prove the semi-conservative hypothesis?

A
  • They grew E. coli with different isotopes of nitrogen
  • Bacteria were exposed to N15, for several generations until it was exposed to a lighter N14
  • Scientists could then distinguish between the different DNA densities by centrifuging them
50
Q

What did Meselson and Stahl know before they proved the semi-conservative hypothesis?

A
  • All the bases in DNA contain nitrogen
  • Nitrogen bases have two forms: Heavy (N15) and Light (N14)
  • Bacteria will incorporate nitrogen from their growing medium into any new DNA they make
51
Q

What is the function of DNA?

A
  • To code for proteins

- Not all of the DNA molecule code for proteins, the functional parts that do are called genes

52
Q

What is the function of RNA?

A
  • Different genes are instructions to build different proteins
  • The DNA that contains the genes can’t leave the nucleus, so a copy of the gene must be made, which is mRNA, a type of nucleic acid
53
Q

How is RNA structured differently to DNA?

A
  • Uracil instead of thymine
  • Ribose instead of deoxyribose
  • Single strand
54
Q

Where is transcription done in eukaryotes?

A

In the nucleus

55
Q

Is DNA directly involved in transcription and why?

A

Yes, it is being matched with complementary RNA bases

56
Q

Is RNA involved in transcription, and why?

A

Only mRNA, as it makes a template for protein synthesis through translation

57
Q

Where is translation done?

A

On a ribosome (in the cytoplasm in eukaryotes)

58
Q

Is DNA directly involved in translation and why?

A

No, as it stays in the nucleus

59
Q

Is RNA involved in translation and what does it do?

A

tRNA and rRNA are involved, they make a sequence of amino acids

60
Q

What are the similarities between DNA and RNA

A
  • Both are nucleic acids

- Both contain the bases: guanine, cytosine, adenine

61
Q

What are the features of DNA?

A
  • Only found in the nucleus of eukaryotes cells, except during mitosis, where the nucleus is temporarily disassembled
  • Arranged as a double helix
  • Has the base thymine
    Has the sugar deoxyribose
62
Q

What are the features of RNA?

A
  • Can travel out of the nucleus to a ribosome in eukaryotes
  • Single-stranded
  • Has the base uracil
  • Has the sugar ribose
63
Q

What the three types of RNA?

A
  • messenger RNA (mRNA)
  • transfer RNA (tRNA)
  • ribosomal RNA (rRNA)
64
Q

Define energy

A

The ability to do work

65
Q

What is energy needed for?

A
  • Metabolism/catabolism
  • Movement
  • Active transport
  • Maintenance, repair and division of cells
  • Production of substances
  • Maintenance of body temperature
  • Nerve impulse conduction
66
Q

When is light energy converted into chemical energy in plants?

A

During photosynthesis

67
Q

What energy is converted into ATP and during when?

A

Chemical energy from photosynthesis (in the form of organic molecules) is converted into ATP during respiration

68
Q

What is ATP used for?

A

Used by cells to perform useful work

69
Q

What does ATP stand for?

A

adenosine triphosphate

70
Q

What is ATP made up of?

A
  • Adenine (base)
  • Ribose (sugar)
  • Three phosphate groups
71
Q

What are the 3 phosphate groups joined together by?

A

2 high energy bonds

72
Q

How does ATP release a large amount of energy?

A

It can be hydrolysed to break a bond

73
Q

What catalyses the hydrolysis of ATP to ADP?

A

The enzyme ATPase

74
Q

What is the equation for the hydrolysis of ATP?

A

ATP + H2O –> ADP + P1 (+ energy = 30KJmol-1)

75
Q

How can ATP be reformed from ADP + P1?

A

In phosphorylation

76
Q

What type of reaction is phosphorylation?

A

Condensation reaction as water is released

77
Q

Is the energy released from the splitting of ATP into ADP is released as large, unmanageable bursts?

A

No, it is released in small, manageable bursts

78
Q

What is are the advantages of the hydrolysis of ATP to ADP rather than the breakdown of glucose?

A
  • The energy released from the splitting of ATP into ADP is released as small, manageable bursts
  • The hydrolysis of ATP to ADP is a single reaction, whereas the breakdown of glucose requires a long series of reactions
79
Q

What are the disadvantages of the hydrolysis of ATP to ADP?

A
  • Instability of bonds means ATP isn’t good for long term storage of energy
  • Instability means cells do not store large amounts of it, so the production of ATP needs to be constantly occurring in all living cells
80
Q

What are the roles of ATP?

A
  • ATP is an immediate energy source. It is made when required by reforming from ADP +P1. It is only stored for a matter of seconds
  • Less energy produced than glucose, so more manageable
  • ATP to ADP is a single reaction so it is very quick
81
Q

What is ATP a source of energy for?

A
  • Metabolic reactions
  • Active transport
  • Movement
  • Secretion
  • Activation of molecules
82
Q

Which of the following bonds occur in a molecule of DNA?

a. Ionic
b. Hydrogen
c. Phosphodiester
d. Covalent

A. All of the above
B. None of the above
C. b, c and d
D. b and c

A

C

83
Q

Complete the following passage with the most appropriate terms from the list below
anti-parallel B-pleated sheet Covalent Double helix
Hydrogen Parallel Polypeptide Ribose Sugar-phosphate

DNA is found in the nucleus. The molecule is twisted into a 1 2. in which each of the strands are 3. It has two 4 backbones attached to one another by complementary bases. These bases pair in the centre of the molecule by means of 5 bonds.

A 
1 Double helix
2 Polypeptide
3 Anti-parallel
4 Sugar-phosphate
5 Hydrogen
84
Q

State the components of a DNA nucleotide

A

Deoxyribose sugar
Phosphate group
Nitrogenous bases

85
Q

Describe how the structure of RNA differs from that of DNA

A

RNA has the sugar ribose, instead of deoxyribose
RNA has the base uracil instead of thymine
RNA is single-stranded

86
Q

State what a gene codes for

A

A sequence of amino acids

Protein

87
Q

Suggest how changing the sequence of DNA nucleotides could affect the final product the DNA codes for

A

The mutation may change how the bonds interact in a protein, so it doesn’t fold into its’ specific shape so it has a different function

88
Q

Suggest why DNA is not able to leave the nucleus

A

Too large to fit through the nuclear pores

89
Q

Explain why the mRNA molecule is shorter than a DNA molecule

A

Only the exons/coding parts of the DNA is included in the mRNA, so the non-coding parts of DNA are not included
DNA has more genes

A level OCR Biology (7 decks)

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