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Biology A LEVEL > DNA/RNA and Water > Flashcards

DNA/RNA and Water Flashcards

1
Q

Who discovered the double helix structure of DNA?

A

James Watson and Francis Crick following the work of Rosalind Franklin

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2
Q

What did James Watson and Francis Crick discover about DNA?

A

-DNA comprised of a double stranded helix structure
-Containing a sugar phosphate backbone
-with nitrogen-containing organic base pairs in the centre

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3
Q

What is the name for a strand of DNA or RNA?

A

Polynucleotide made up from joined nucleotides

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4
Q

What are the two types of polynucleotides?

A

DNA and RNA

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5
Q

What are the 3 components nucleotides are made up from?

A

-Phosphate group
-Pentose sugar
-Organic base

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6
Q

What is the function of DNA?

A

Codes for the sequence of amino acids in the primary structure of a protein, which determines the final 3D structure and function of a protein

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7
Q

In a DNA nucleotide what 4 things can the organic base be?

A
  • adenine
  • thymine
  • cytosine
  • guanine
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8
Q

What is the pentose sugar for DNA?

A

Deoxyribose

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9
Q

What is the function of RNA?

A
  • Copy and transfer the genetic code from DNA in the nucleus to the ribosomes
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10
Q

In an RNA nucleotide what 4 things can the organic base be?

A
  • adenine
  • uracil
  • cytosine
  • guanine
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11
Q

What is the pentose sugar for RNA?

A

Ribose

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12
Q

What are the 3 types of RNA?

A
  1. mRNA (Messenger RNA)
  2. tRNA (Transfer RNA)
  3. rRNA (Ribosomal RNA)
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13
Q

What is the function of mRNA?

A

-Copies genetic information from DNA and carries it to the ribosome for protein synthesis.
-It provides the sequence of codons that determine the order of amino acids in the protein

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14
Q

What is the function of tRNA?

A

Carries amino acids to the ribosome and matches them to the mRNA sequence using anticodons during translation.

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15
Q

What is the function of rRNA?

A

Combines with proteins to form ribosomes, the site of protein synthesis.

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16
Q

Describe the structure of DNA:

A

-Bases on 2 antiparallel strands are joined together by hydrogen bonds
-Phosphodiester bonds joined via condensation reaction

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17
Q

What can be said about the bonds that join DNA strands?

A
  • hydrogen bonds occur between opposite nucleotides
  • phosphodiester bonds from between adjacent nucleotides
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18
Q

What is meant by antiparallel in DNA structure?

A
  • Two strands of DNA running opposite (5’ to 3’ and 3’ to 5’)
    -Critical for hydrogen bonding and DNA replication
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19
Q

What are the base pairings that make up DNA?

A

Adenine- Thymine
Cytosine- Guanine

They are complementary to one another

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20
Q

How is DNA made stable?

A

-Phosphodiester backbone protects chemically reactive bases within structure
-Many hydrogen bonds (3) between Cytosine and Guanine provides strength
-Base stacking

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21
Q

What is the sugar phosphate backbone?

A

A structure made only of sugars and phosphates

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22
Q

What is the structure of DNA (Exam technique)?

A

-Phosphodiester backbone
-Long molecule
-Double helix structure
-Weak hydrogen bonds joins base pairs
-Double stranded
-Base sequence
- Base stacking

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23
Q

How does the phosphodiester backbone aid the function of DNA?

A

Prevents organic bases reacting with environment

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24
Q

How does DNA being a long molecule aid its function?

A

Stores lots of genetic information

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25
Q

How does DNA being a double helix aid its function?

A

Makes DNA compact

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26
Q

Draw and label a DNA double helix:

A
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27
Q

How do the weak hydrogen bonds joining base pairs aid the function of DNA?

A

Easily broken for DNA replication

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28
Q

How does DNA being double stranded aid its function?

A

Allows replication from template strands

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29
Q

How does the base sequence of DNA aid its function?

A

Allows information to be stored

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30
Q

How does base stacking aid the function of DNA?

A

Arranges nitrogenous bases in parallel

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31
Q

What are the differences between DNA and RNA monomers?

A
  • DNA contains the base thymine, whereas RNA contains uracil
  • DNA contains the pentose sugar deoxyribose, whereas RNA contains ribose
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32
Q

What are the differences between DNA and RNA polymers?

A

-DNA is much larger because it contains the entire genome, whereas RNA is much shorter because it is only the length of one gene.
-DNA is double stranded, whereas RNA is single stranded.

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33
Q

Describe the process by which two nucleotides are joined together:

A

-Condensation reaction forming a phosphodiester bond
-Phosphate group of one nucleotide binds to the sugar of another
-Bond forms sugar phosphate backbone

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34
Q

What does DNA replication do?

A

forms free DNA nucleotides

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35
Q

When does DNA synthesis occur?

A

during the interphase of the cell cycle

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36
Q

What is the process of DNA replication called?

A

semi-conservative replication

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37
Q

What is meant by semi-conservative replication?

A

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

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38
Q

What is parental DNA?

A

name given to the original DNA that is going to be copied

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39
Q

Which enzymes are involved in DNA replication?

A

Helicase and Polymerase

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40
Q

What is the function of helicase?

A

-Breaks the hydrogen bonds between the complementary base pairs
-This causes the DNA double helix to unwind

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41
Q

How is DNA replicated?

A

1.Strands are separated/ Helicase breaks down hydrogen bonds
2.Both strands act as templates
3.Free floating DNA nucleotides within nucleus are attracted to complementary base pairs
4.Adjacent nucleotides joined together by condensation reaction
5. Two sets of daughter DNA contains one strand of parental DNA and one newly synthesised strand.

42
Q

What is the function of polymerase?

A

Catalyses the joining together of adjacent nucleotides

43
Q

What are the ways Watson and Crick hypothesised that DNA could replicate?

A

conservatively and non-conservatively

44
Q

What is meant by conservative replication?

A

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

45
Q

Who conducted an experiment proving that DNA replication must be semi-conservative?

A

Meselson and Stahl

46
Q

What are the two isotopes of Nitrogen?

A

Nitrogen 14
Nitrogen 15- heavier

47
Q

What does bacteria do relating to nitrogen isotopes?

A

Bacteria take them in to make new DNA nucleotides

48
Q

What can be said about bacteria, nitrogen and DNA?

A

-Bacteria grown in a medium containing 14N will have DNA which only contains this isotope and be lighter.
-Bacteria grown in a medium containing 15N will have DNA which only contains this isotope and be heavier.

49
Q

How can you confirm the density of DNA?

A

Spin it in a centrifuge where 15N will settle lower down as it is more dense

50
Q

What is stage 1 of the Meselson and Stahl experiment?

A

-Grow E-coli bacteria in medium that only contains 15N
-100% of 2 strands of DNA is 15N 15N

51
Q

What is stage 2 of the Meselson and Stahl experiment?

A

-Take all E-coli out of growth medium
-Bacteria left to grow in growth medium of only 14N
-Allow bacteria to undergo 1 cell division
-DNA sample in centrifuge shifts to higher position

52
Q

What is stage 3 of the Meselson and Stahl experiment?

A

-2 strands of DNA separates and acts as a template
-New DNA only contains 14N
-Ou of 4 double helixes, 2 are one strand 14N and one strand 15N whilst 2 are 2 strands 14N
-2 bands in centrifuge

53
Q

What is the centrifuge split into in stage 3 of Meselson and Stahl’s experiment?

A

50% of DNA is 14N 14N (higher up as it is lighter)
50% of DNA is 15N 14N

54
Q

What is stage 4 of the Meselson and Stahl experiment?

A

-Another round of cell division
-Bacteria growing in 14N medium
-Now got 8 double helixes after strands act as templates once again

55
Q

What is the centrifuge split into in stage 4 of Meselson and Stahl’s experiment?

A

75% of DNA is 14N 14N
25% of DNA is 15N 14N

56
Q

Drawn an image showing the results of conservative, dispersive and semi-conservative replication:

A
57
Q

What do Meselson and Stahl’s experimental results look like?

A
58
Q

Why was the experiment so good?

A

Clear experimental design, the use of innovative techniques, and its conclusive results

59
Q

What are the uses of energy in the body?

A

Active transport- glucose absorption
Muscle contraction
Protein synthesis- growth and repair
Phosphorylation- make molecules more reactive by lowering activation energy

60
Q

What form does the energy from respiration take?

A

nucleotide

61
Q

What does ATP stand for?

A

Adenosine Triphosphate

62
Q

What is the structure of ATP?

A
63
Q

Explain the structure of ATP and describe the role of each component:

A

-ATP is a nucleotide derivative
-Adenine: nitrogenous base
-Ribose
-Three inorganic phosphate groups responsible for energy storage and release

64
Q

Do ATP molecules ever join to make a polymer?

A

NO

65
Q

What is unstable in an ATP molecule?

A

The bonds between the outer phosphate groups

66
Q

What do the unstable bonds in an ATP molecule mean?

A

The bonds have a low activation energy

67
Q

How is a phosphate removed from an ATP molecule?

A

A single hydrolysis

68
Q

What is phosphorylation?

A

Phosphate forms bonds with other molecules which releases energy.

69
Q

What is the equation for ATP breakdown?

A
70
Q

Which enzyme catalyses the ATP breakdown reaction?

A

ATP hydrolase (ATPase)

71
Q

What does the Pi stand for in the ATP reaction?

A

Inorganic phosphate

72
Q

How is ATP synthesised?

A

The enzyme ATP synthase catalyses a condensation reaction to join a a phosphate to ADP to form ATP (phosphorylation)

73
Q

Where does energy come from?

A

Light- results in phosphorylation
Respiration- oxidative phosphorylation

74
Q

Describe how ATP releases energy and explain why ATP is considered an “immediate” source of energy for cells:

A

-ATP releases energy by hydrolysing the bond between the second and third phosphate groups
-This forms ADP and inorganic phosphate
-ATP is considered an immediate source of energy because only one bond needs to be hydrolysed, releasing energy quickly

75
Q

What are the Pros of ATP?

A

1.Releases energy in small amounts
2. Broken down in one step reaction
3. Phosphorylates to lower the activation energy needed for biological molecules to react
4. Rapidly reformed
5. Soluble in the cytoplasm

76
Q

What are the Cons of ATP?

A

ATP cannot be moved from cell to cell /stored because it is so reactive

77
Q

What type of energy store is ATP?

A

Short term (immediate energy source of a cell)

78
Q

ATP vs Carbs/Lipids:

A
79
Q

How is water formed?

A

2 hydrogens covalently bond to 1 oxygen atom

80
Q

What does water having a dipolar nature mean?

A

It has delta positive and delta negative regions

81
Q

How does water’s dipolar nature relate to its properties?

A

-Allows water molecules to form hydrogen bonds with each other
-Gives it high surface tension, high specific heat capacity and solubility

82
Q

What does water being a metabolite mean?

A

Involved in many biochemical reactions within organisms, either as a reactant or product.

83
Q

What are examples of water acting as a metabolite?

A

-In photosynthesis, water is split to provide electrons.
-In hydrolysis reactions, water is used to break bonds in molecules (digestion of carbohydrates or hydrolysis of glycogen)

84
Q

How are the electrons distributed in water?

A

Unevenly so water is a polar molecule

85
Q

Where do the hydrogen bonds form in water?

A

-Form between polar molecules containing hydrogen
-They do not result in a permanent structure, bonds break and reform as water molecules move around

86
Q

How does water interact with ionic compounds?

A

-Can dissolve ionic compounds by surrounding ions with its molecules ,oxygen attracts positive ions and hydrogen attracts negative ions.
-E.g NaCl

87
Q

What are the properties of water (good for cytoplasm):

A

-polarity means it can act as a good solvent (chemical reactions happen faster in solution)
-reactive, can be used in hydrolysis reactions

88
Q

What are the properties of water (Due to H bonds):

A

-high specific heat capacity
-high latent heat of vaporisation
-cohesive
-adhesive

Extra:
-Transparent
-Variable density

89
Q

How is water having a high specific heat capacity useful to organisms?

A

-Allows for homeostasis ensuring that enzyme-controlled reactions work at optimum.
-Stabilises aquatic environments, preventing drastic temperature changes that could be harmful to organisms living there.

90
Q

How is water having a high latent heat of vaporisation useful to organisms?

A
  • Cools organisms down when sweating as sweat evaporates
  • Transpirations helps cool plants down by removing excess heat as water evaporates
91
Q

What is cohesion in water?

A

Ability of water molecules to stick together, due to hydrogen bonds.

92
Q

How does cohesion contribute to the movement of water in plants?

A

Helps water form a continuous column in the xylem, facilitating its movement from the roots to the leaves via transpiration.

93
Q

Explain how water’s high heat capacity contributes to temperature stability in aquatic environments.

A

Water can absorb or release large amounts of heat without significantly changing its temperature, which stabilises aquatic environments.

94
Q

What are inorganic ions?

A
  • Iron
  • Calcium
  • Phosphate
  • Nitrate
  • Magnesium
  • Hydrogen
95
Q

What is the role of iron ion?

A
  • Fe2+
  • Involved in haemoglobin structure
  • Allows oxygen to bind and be transported
  • Plays key role in redox reactions
96
Q

What is the role of phosphate ions?

A
  • PO43
  • Involved in phospholipids, ATP, DNA/RNA
  • Involved in energy transfer and storage; structural role in bones and teeth
  • building block for cell membranes/ cells involved in energy transfer
97
Q

What is the role of Nitrate ions?

A
  • NO3
  • Uptaken by plants
  • Make nitrogen (source for plants) containing biomols eg amino acids
  • Nitrogen used in the synthesis of amino acids and proteins
  • essential for plant growth and development
98
Q

What is the role of Hydrogen ions?

A
  • H+
  • Involved in photosynthesis and respiration
  • determined the pH of solutions
99
Q

What is the role of Calcium ions?

A
  • Ca2+
  • Involved in muscle contraction, neurotransmission and blood clotting
100
Q

What is the role of Magnesium ions?

A
  • Mg2+
  • Involved in making chlorophyll
  • Essential for enzyme activation

Biology A LEVEL (9 decks)

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