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AS level Biology > Section 1 - Nucleic Acid > Flashcards

Section 1 - Nucleic Acid Flashcards

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1
Q

Give two examples of Nuclei Acids

A
  • Ribonucleic acid (RNA)
  • Deoxyribonucleic acid (DNA)
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2
Q

What makes DNA so distinguishable?

A
  • Its double helix structure
  • Meaning the material can pass on the features of organisms from one generation to the next.
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3
Q

What does DNA do?

A

Carries genetic information.

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4
Q

What are the components of nucleotides?

A
  • A pentose sugar (5 carbon atoms)
  • A phosphate group
  • A nitrogen-containing organic base.
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5
Q

State the different nitrogenous bases

A
  • Cytosine C
  • Thymine T
  • Uracil U
  • Adenine A
  • Guanine G
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6
Q

What reaction joins the components of nucleic acids?

A

Condensation Reactions - To form a single nucleotide.

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7
Q

Explain the reaction between two mononucleotides

A

May be joined as a result of a condensation reaction between the deoxyribose sugar of one mononucleotide and the other phosphate group of another.

A phosphodiester bond is formed.

This new structure is called a dinucleotide.

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8
Q

What is the name given to two mononucleotides that have been bonded?

A

Dinucleotide

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9
Q

State the name of the bond formed between two mononucleotides

A

Phosphodiester

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10
Q

What nitrogenous bases are in DNA?

A

Adenine Thymine Guanine Cytosine

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11
Q

What nitrogenous bases are in RNA?

A

Adenine Uracil Guanine Cytosine

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12
Q

What is the name given to a long chain of nucleic acids?

A

Polynucleotides

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13
Q

Explain the structure of Ribonucleic acids

A

RNA

  • Polymer made up of nucleotides
  • A single relativity short polynucleotide chain
  • The pentose sugar is always Ribose
  • Organic bases are A G C U
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14
Q

What does RNA do?

A
  • Transfers genetic information from DNA to the ribosomes.
  • These ribosomes are made up of proteins and another type of RNA.
  • A third type of RNA is involved in protein synthesis.
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15
Q

What pentose sugar is in RNA?

A

Ribose

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16
Q

In what year was DNA discovered?

A

1953

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17
Q

How was DNA discovered?

A

An x-ray diffraction patterns of DNA by Rosalind Franklin.

Opening the door to many more major developments in biology

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18
Q

What pentose sugar is in DNA?

A

Deoxyribose

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19
Q

Explain the structure of DNA

A
  • The pentose sugar is deoxyribose
  • The organic bases are GC TA
  • Made of two strands of nucleotides
  • Each of the strands is very long and joined by hydrogen bonds
  • The phosphate and deoxyribose molecules alternate to form the uprights and organic bases pair together to form the rungs of ‘ladder’.
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20
Q

What bonds are formed between the strands of DNA?

A

Hydrogen Bonds

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21
Q

What holds together two strands of DNA?

A

The hydrogen bonds - Each strand is attracted to each other by these bonds.

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22
Q

What varies between DNA species?

A

The ratio of A+T and G+C varies from species to species.

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23
Q

Explain the double helix structure

A
  • Ladder-like arrangement
  • Two polynucleotide chains being twisted.
  • The uprights of phosphate and deoxyribose wind around one another to form a double helix.
  • They form the structural backbone of the DNA molecule.
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24
Q

Why is DNA a stable molecule?

A
    • The phosphodiester backbone unreactive protecting those insides
    • Hydrogen bonds link the organic base pairs forming bridges (rungs)
      • CG - 3 Hydrogen bonds
      • AT - 2 hydrogen bonds
    • Base stacking is another interactive force between the base pairs that hold molecules together.
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25
Q

What can make DNA a more stable molecule?

A

The higher proportion of C-G pairings

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26
Q

What is the function of DNA?

A

The hereditary material responsible for passing genetic information from cell to cell and generation to generation.

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27
Q

How many base pairs are there in the DNA of a typical mammalian cell?

A

Around 3.2 billion

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28
Q

What causes genetic diversity within living organisms?

A

The almost infinite variety of sequences of bases along the length of a DNA molecule.

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29
Q

How are DNA molecules adapted to its function?

A
    • A very stable structure
    • strands joined with hydrogen bonds, allowing separation during DNA replication and protein synthesis.
    • An extremely large molecule and carries an immense amount of genetic information
    • Having base pairs within the helical cylinder of the deoxyribose-phosphate backbone protects from being corrupted by outside chemical and physical forces
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30
Q

What is DNA transferred as?

A

mRNA

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31
Q

What shape is given to the deoxyribose-phosphate backbone of DNA?

A

Helical Cylinder

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32
Q

What does the function of DNA depend on?

A

The sequence of base pairs that it possesses. This sequence if important to everything it does and indeed to life itself.

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33
Q

Explain experiments that give evidence that DNA was the material that had provided the bacteria with the genetic information needed to make a virus.

A
    • viruses infect bacteria
    • Virus made of protein and DNA, one or the other must possess the instructions that the bacteria use to make new viruses
    • The protein and DNA in the viruses labelled with a different radioactive element.
    • One sample of bacteria was infected by viruses with radioactive protein while another sample was infected by viruses with radioactive DNA
    • In a later stage, the viruses and bacteria in both samples were separated from one another
    • Only the sample with bacteria that had been infected by viruses labelled with radioactive DNA showed signs of radioactivity.
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34
Q

How can you link bacterium, DNA and viruses?

A

DNA can be passed from one bacterium to another by viruses.

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35
Q

What is attached to the 3’ carbon atom in a nuclei acid?

A

A hydroxyl group

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36
Q

What is attached to the 5’ carbon atom in a nuclei acid?

A

A phosphate group

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37
Q

What two carbon atoms should you know in nuclei acids?

A

3’ - 3-prime

5’ - 5-prime

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38
Q

Explain the carbon arrangement in a double stands of DNA

A

One strand runs in the 5’ to 3’ direction while the other runs the opposite 3’ to 5’ direction

Antiparallel

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39
Q

Which way are nucleic acids synthesised?

A

in vivo The 5’ to 3’ direction

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40
Q

Why can nucleic acids only be synthesised in one direction?

A

5’ to 3’ direction Enzyme DNA polymerase that assembles nucleotides into a DNA molecule can only attach nucleotides to the hydroxyl (OH) group on the 3 carbon molecule.

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41
Q

State the two main stages of cell division

A
  • Nuclear division
  • Cytokinesis
42
Q

What is nuclear division?

A

The process by which the nucleus divides.

There are two types of nuclear division mitosis and meiosis.

43
Q

What does the DNA before nuclear division? Why?

A

DNA must be replicated.

To ensure that all the daughter cells have the genetic information to produce the enzymes and other proteins that they need.

44
Q

What are the requirements for semi-conservative replication?

A
    • The four types of nucleotide,
  • strands of the DNA act as a template for the attachment of these nucleotides
    • The enzyme DNA polymerase
    • source of chemical energy to drive the process.
45
Q

State a type of enzyme DNA which must be present in Semi- Conservative replication

A

Polymerase

46
Q

Explain the process of semi-conservative replication

A
  • enzyme DNA helicase breaks the hydrogen bonds
  • double helix structure separates into its two strands and unwinds
  • Each exposed polynucleotide strand acts as a template to which complementary free nucleotides bind by specific base pairing
  • Nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase
  • New DNA molecules contain one of the original DNA strands.
47
Q

What two hypothesises did Watson and Crick come up with?

A

The conservative model

The semi-conservative model

48
Q

Explain the conservative model

A
  • original DNA molecule remained intact
  • separate daughter DNA copy built up from new molecules of deoxyribose, phosphate and organic bases.
  • one would be made of entirely new material while the other would be entirely original material
49
Q

Explain the semi-conservative model

A
  • original DNA molecule split into two separate strands
  • each of which replicated its mirror image
  • one strand of new material and one strand of original material.
50
Q

Which scientist experimented with proving the DNA models?

A

Meselsohn Stahl

51
Q

What did Meselsohn and Stahl base their work on?

A
    • All bases in DNA contain nitrogen
  • Nitrogen has two forms: the lighter nitrogen 14N and isotope 15N which is heavier
  • bacteria will incorporate nitrogen from their growing medium into any new DNA that they make.
52
Q

State the lighter Nitogen

A

14N

53
Q

State the heavier isotope of Nitrogen

A

15N

54
Q

Explain the method Meselsohn and Stahl used

A
    • Labelled the original DNA grown on 15N medium
  • Transferred the bacteria to a medium of 14N for a single generation to allow it to replicate once.
  • The mass of each ‘new’ DNA molecule would depend upon which method of replication had taken place.
  • centrifuged the extracted DNA in a special solution to differentiate
  • The lighter the DNA the nearer the top of the centrifuge tube it was collected
  • hypothesis was correct.
55
Q

What did Meselsohn and Stahl conclude?

A

Bacteria grown on 14N lighter

Bacteria grown on 15N heavier

56
Q

What did Meselsohn and Stahl experiment determine?

A

determine which hypothesis was correct to determine the nature of DNA replication.

Semi conservative

57
Q

Where does initial energy come from?

A

The sun

58
Q

What is the main energy source inside a cell?

A

adenosine triphosphate

59
Q

What does ATP stand for?

A

adenosine triphosphate

60
Q

State the parts of ATP

A

Adenine

Ribose - Pentose sugar

Phosphates - A chain of three phosphate groups

61
Q

How many phosphate groups are in a ATP?

A

A chain of three phosphate groups.

62
Q

What is ATP?

A

A nucleotide - Main energy source inside cells

63
Q

How does ATP store energy?

A
    • The bonds between these three phosphate groups are unstable and so have low activation energy,
  • When break release of energy.
  • This is a hydrolysis reaction as water is added to ATP to convert to ADP.
  • This is catalysed by the enzyme ATP hydrolase (ATPase)
64
Q

State the equation of the reaction with ATP as a main energy group

A

ATP (Adenosine triphosphate) + H2O (Water) -> ADP (Adenosine diphosphate) + Pi (inorganic phosphate) + E (Energy)

65
Q

What does ADP stand for?

A

Adenosine diphosphate

66
Q

What substances are produced when ATP reacts with water?

A

Adenosine diphosphate

Inorganic phosphate

Energy

67
Q

What reacts with ATP to create energy?

A

Water

68
Q

What type of reaction does ATP use to make energy?

A

Hydrolysis reaction - As water is used Reversible reaction

69
Q

State the enzyme used to catalyse the ATP reaction to create energy

A

ATP hydrolase (ATPase)

70
Q

What enzyme catalyses the reverse reaction to create ATP?

A

ATP synnthase

71
Q

What type of reaction is used to create ATP?

A

Condensation Reaction

As water is removed in this process.

72
Q

What three ways can you add a phosphate molecule to ADP?

A
    • In chlorophyll-containing plant cells during photosynthesis (photophosphorylation)
    • In plants and animal cells during respiration (oxidative phosphorylation)
    • In plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation)
73
Q

What is photophosphorylation?

A

The process of adding a phosphate molecule to ADP. In chlorophyll-containing plant cells during photosynthesis

74
Q

What is oxidative phosphorylation?

A

The process of adding a phosphate molecule to ADP. In plants and animal cells during respiration

75
Q

What is substrate-level phosphorylation?

A

The process of adding a phosphate molecule to ADP. In plant and animal cells when phosphate groups are transferred from donor molecules to ADP

76
Q

Why is ATP not a good long-term energy store?

A

Immediate energy source of a cell

  • The instability of its phosphate bonds

Cells do not store large quantities of ATP but rather just maintain a few seconds’ supply.

77
Q

Give two reasons why ATP is a better immediate energy source than glucose

A
  • releases less energy than each glucose molecule.
  • more manageable quantities
  • the hydrolysis of ATP to ADP is a single reaction that releases immediate energy.
  • The breakdown of glucose is a long series of reactions and therefore the energy release takes longer.
78
Q

Where is ATP made?

A

It cannot be stored and so is continuously made within the mitochondria of cells that need it.

79
Q

State two examples of cells that possess many large mitochondria

A
  • Muscle fibres - For movement
  • The epithelium of the small intestine - active transport
80
Q

what is the most abundant liquid on Earth?

A

Water

81
Q

Explain how water is a dipolar molecule

A

Made up of two atoms of hydrogen and one of oxygen. It has no overall charge. The water molecule has both positive and negative poles and therefore is described as dipolar.

82
Q

How can you describe a water molecule?

A

Dipolar

83
Q

Explain the bonding of water molecules

A
  • The different poles attract - This is called the hydrogen bond. - Each bond it fairly weak but together they form important forces that cause the water molecules to stick together giving water its unusual properties.
84
Q

Why does it take a lot of heat to separate the bonds in water molecules?

A

High latent heat capsity

85
Q

What state would water be at without hydrogen bonds?

A

Vapour

86
Q

Why does water act as a buffer against temperature variation?

A

more energy to heat - specific heat capacity is very high.

aquatic environment a temperature-stable one. - buffers against sudden temperature changes especially in terrestrial environment.

87
Q

What is the latent heat of vaporisation in water?

A

A lot of energy to evaporate 1 gram of water.

88
Q

State an effective means to cool mammals body

A

Sweating

The evaporation of water as body heat is used to evaporate the water.

89
Q

What is cohesion?

A

The tendency of molecules to stick together.

90
Q

Explain water in terms of cohension

A

With hydrogen bonding allows water to be pulled up through a tube such as a xylem vessel in plants

91
Q

What happens when water molecules meet the air?

A

They tend to be pulled back into the body of water rather than escaping from it.

92
Q

What is surface tension?

A

Meaning that the water surface acts like a skin and is strong enough to support small organisms such as pond skater.

93
Q

What proportion of jellyfish is made up of water?

A

98%

94
Q

What proportion of mammals is made up of water?

A

Typically 65%

95
Q

Explain how water is used in metabolism

A
  • Water is used to break down many complex molecules by hydrolysis, eg. Proteins to amino acids.

Water is also produced in condensation reactions.

96
Q

Explain how water is used as a solvent

A

Water readily dissolves other substances:

  • oxygen and carbon dioxide
  • ammonia and urea
  • Inorganic ions
  • small hydrophilic molecules such as amino acids, monosaccharides and ATP
  • Enzymes, whose reactions take place in solution
97
Q

Explain some important features of water

A
    • Its evaporation cools organisms
    • It is not easily compressed and therefore provides support,
    • It is transparent and therefore aquatic plants can be photosynthesise also light rays can penetrate the jelly-like fluid that fills the eye and so reach the retina
98
Q

Where are inorganic ions found?

A

Found in organisms cytoplasm of cells and in body fluids and as well as part of larger molecules.

They may be in concentrations that range from very high to very low.

99
Q

What helps determine the pH of solutions?

A

Hydrogen ions

100
Q

What ions are important in the transport of glucose and amino acids across the plasma membranes?

A

Sodium

101
Q

How does ATP make enzyme-catalysed reactions take place more readily?

A
  • -ATP provides phosphate group that can attach to molecule.
  • -Makes molecule more reactive, lowering its activation energy.
  • -Enzymes work by lowering activation energy so has less to do and catalyses more readily.

AS level Biology (11 decks)

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