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AQA A Level Biology 2018 > More Biologial Molecules > Flashcards

More Biologial Molecules Flashcards

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1
Q

DNA …

A

Deoxyribonucleic acid

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2
Q

RNA …

A

Ribonucleic acid

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3
Q

What is DNA used for?

A

To store genetic information - it is all the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult.

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4
Q

What is RNA and what does it do?

HINT : RIBOSOMES

A

Similar in structure to DNA.

  • transfers genetic info from the DNA to the ribosomes. The ribosomes are in the “protein factories” and read the RNA to produce proteins via TRANSLATION.
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5
Q

What are Ribosomes made from?

A

RNA and Proteins.

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6
Q

What is a Nucleotide?

A

The monomer of DNA and RNA.
(DNA and RNA are polymers)

  • a type of biological molecule.
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7
Q

What are Nucleotides made up from? (3)

A
  • phosphate group / CIRCLE
  • pentose sugar ( a sugar with 5 carbon atoms) / PENTAGON
  • a nitrogen containing organic base / SQUARE
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8
Q

What is the pentose sugar in DNA nucleotide called?

A
  • Deoxyribose.
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9
Q

Each DNA nucleotide has the same sugar and phosphate group… what changes?

A

The base on each nucleotide can vary.

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10
Q

What are the 4 possible bases: (In a DNA nucleotide)

A
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
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11
Q

What is the pentose sugar in RNA nucleotide called?

A
  • Ribose sugar.
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12
Q

What are the 4 possible bases in an RNA nucleotide:

A
  • Adenine (A)
  • URACIL (U) (replaces the T)
  • Cytosine (C)
  • Guanine (G)
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13
Q

What is a Polynucleotide?

A

A polymer of nucleotides (Both DNA and RNA form this)

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14
Q

How do Nucleotides join up to form a polynucleotide?

A

Via a condensation reaction between the phosphate group of one nucleotide and the sugar of another.

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15
Q

What bond is formed?

A

Phosphodiester bond.

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16
Q

The chain of sugars and phosphate is is known as …

A

The sugar phosphate backbone.

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17
Q

What is DNA made up of?

A

Two polynucleotide chains in a double helix structure.

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18
Q

How does DNA form:

The bases can only…

A

1) two DNA polynucleotide strands join together by hydrogen bonding between the bases.
- bases can only join with one particular partner - COMPLIMENTARY BASE PAIRING.

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19
Q

Adenine always pairs with…

A

Adenine always pairs with Thymine.

A-T hydrogen bonding.

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20
Q

Cytosine always pairs with…

A

Cytosine always pairs with Guanine.

C-G hydrogen bonding.

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21
Q

There are always equal amounts of…

A

Adenine and Thymine in a DNA molecule and equal emotions of Cytosine and Guanine.

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22
Q

How many hydrogen bonds form between A and T?

Adenine and Thymine:

A

2

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23
Q

How many hydrogen bonds form between Cytosine and Guanine?

C and G:

A

3

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24
Q

How is the DNA double helix formed?

A

The two anitparallel (opposite directions) polynucleotide stands twist to form it.

There are hydrogen bonds between the bases which keeps the strands coiled together.

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25
Q

Why was DNA doubted in the 1800’s?

A

Because scientists thought it had too much of a simple chemical composition to carry the genetic code.

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26
Q

1953, what happened?

A

DNA was proven to be the carrier of the genetic code.

Waston and Crick observed the DOUBLE HELIX shape.

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27
Q

How is RNA made?

A

Just from a single polynucleotide chain - it is much shorter than most DNA polynucleotides.

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28
Q

How does DNA copy itself?

A

Via SEMI CONSERVATIVE REPLICATION.

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29
Q

Why is it called Semi Conservative Replication?

A

Because half of the strands in each new DNA molecule are from the original DNA molecule.

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30
Q

Why is it good that DNA is semi conservative?

A

Because there’s genetic continuity between generations of cells.

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31
Q

What’s the first step in Semi Conservative Replication?

A

The enzyme DNA HELICASE breaks hydrogen bonds between bases on the two polynucleotide DNA strands - two single strands.

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32
Q

What does each single strand act as?

A

A template for a new strand.

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33
Q

Complementary base pairing means that…

A

Free floating DNA nucelotides are attracted to their complementary exposed based on each organically template strand.

AT
CG

34
Q

What’s the second step of Semi Conservative Replication?

A

Condensation reactions join the Nucleotides of the new strands together - DNA POLYMERASE enzyme. H bonds form again.

35
Q

Each new DNA molecule ends containing…

A

One strand from the original DNA molecule and one new strand.

36
Q

What’s different about each end of a DNA strand?

A

One end is called the 3’ and the other is called the 5’ … these strands run in ANTIPARALLEL directions.

37
Q

Where can the DNA polymerase work?

A

On the 3’ end as the active site of the DNA polymerase is only complimentary to that side. It moves down the strand in a 3’ to 5’ direction

38
Q

The DNA polymerase working on one of the template strands moves in…

A

The opposite direction to the DNA polymerase working on the other template strand. Because it is ANTIPARALLEL.

39
Q

By who was Waston and Crick’s structure of DNA theory validated by?

A

MESELSON AND STAHL’s experiment.

40
Q

People were unsure whether…

A

DNA replication was semi-Conservative or conservative.

41
Q

What would happen if DNA replication was Conservative?

A

The original DNA strands would stay together and the new DNA molecules would contain two strands.

42
Q

How did MESELSON and STAHL show that DNA is replicated using the semi- Conservative method?

A

By using two isotopes of nitrogen ( DNA contains nitrogen , remember!)

  • HEAVY nitrogen (15 - N)
  • LIGHT nitrogen (14 - N)
43
Q

What happens in the first step of MESELSON and STAHL’s experiment?

A
  • two bacteria were grown - one in a nutrient broth containing the light nitrogen and one containing the heavy nitrogen.
44
Q

What happened as the bacteria reproduced?

A

They took up nitrogen from the broth to help make Nucleotides for new DNA - the nitrogen gradually became part of the bacteria’s DNA.

45
Q

What is the second step in MESELSON and STAHL’s experiment?

A

A sample of DNA was taken from each batch and spun in a centrifuge - DNA from heavy nitrogen settled lower down the centrifuge tube than the DNA from the light nitrogen bacteria.

46
Q

What is the third step in MESELSON and STAHL’s experiment?

A

The bacteria grown in the heavy nitrogen were taken out and put in broth containing only light nitrogen. Left for another round of DNA replication then another DNA sample was taken out and spun in the centrifuge.

47
Q

If the Replication was Conservative…

If the replication was Semi-Conservative…

A
  • Conservative = original heavy DNA would settle at the bottom and new light DNA would settle at the top.
  • Semi Conservative = the new bacterial DNA molecules would contain one strand of new DNA containing heavy and one light nitrogen.
48
Q

What was the actual result?

A

The DNA settled out in the middle showing that DNA molecules contained a mixture of heavy and light nitrogen - it replicated semi conservatively.

49
Q

What is respiration?

A

The process by which plant and animal cells release energy from glucose.

50
Q

But…

A

The cell can’t get energy directly from glucose so the energy released from glucose is used to make ATP.

51
Q

ATP is..

A

Adenosine Triphosphate.

  • one adenine , ribose sugar and 3 phosphate group.
52
Q

Why is ATP known as a nucleotide derivative?

A

Because it’s a modified form of a nucleotide.

53
Q

What happens once ATP is made?

A

It diffuses to the part of the cell that needs energy.

54
Q

Where is the energy in ATP formed?

A

In high energy bonds between the phosphate groups - released via hydrolysis.

55
Q

What happens when energy is needed by a cell?

A

ATP is broken down into ADP and P.

56
Q

A phosphate bond is broken and…

A

Energy is released - this is catalysed by the enzyme AYP hydrolase.

57
Q

ATP hydrolysis can be…

A

“Coupled” to other energy requiring reactions in the cell so the energy can be used to directly to make the coupled reaction happen.

58
Q

What can the released Inorganic Phosphate be put to use as?

A

It can be added to another compound (known as Phosphorylation) which often makes the compound note reactive.

59
Q

ATP can be re…

A

Re-synthesised in a condensation reaction between ADP and P - happens during respiration and photosynthesis.

60
Q

What catalyses the synthesis of ATP again?

A

The enzyme ATP synthase.

61
Q

Explain how the structure of DNA is related to its functions: (3)

A
  • many H bonds keep it stable.
  • alpha helix gives it a compact shape
  • long and large to store lots of genetic info
62
Q

What are Ions?

A

Atoms with an electric charge.

63
Q

What’s an ion with a positive charge called?

A

A Cation.

64
Q

What’s an ion with a negative charge called?

A

An anion.

65
Q

What is an INORGANIC ION?

A

One which doesn’t contain carbon.

66
Q

Where can we find inorganic ions?

A

In solution / in the cytoplasm of cells and in the body fluids of organisms.

67
Q

Each ion has…

A

A specific role - depending on its properties.

68
Q

What does an ion’s role determine?

A

Whether it’s found in high or low concentrations.

69
Q

What is Haemoglobin?

A

A large protein that carries oxygen around the body, in the red blood cells.

70
Q

Haemoglobin is made up of 4…

A

Different polypeptide chains.

71
Q

What does each polypeptide chain in Haemoglobin contain?

A

An iron ion in the centre - Fe (2+)

The ion is what binds to the oxygen so it’s a key component - when oxygen is bound, the iron ion becomes a Fe (3+) ion until oxygen is released.

72
Q

What’s the importance of H+ ions?

A

pH is based on the concentration of hydrogen ions present - the more = the lower the pH.

HYDROGEN IONS DETERMINE pH.

73
Q

What is the significance of Sodium ions? Na+

A

They help transport glucose and amino acids across membranes… known as co-transport.

74
Q

What is the significance of Phosphate Ions?

PO small 4 (3- charge)

A

It’s an essential component of DNA and ATP.

It’s the bonds between the phosphate groups that store energy in ATP and the phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides.

75
Q

Water is a M…

A

Metabolite - in loads of important metabolic reactions e.g. condensation and hydrolysis.

E.g. amino acids are joined by condensation and energy from ATP is released through hydrolysis.

76
Q

Is water a solvent?

A

Yes - substances can dissolve in it.

Because water is polar, the positive end of the water will be attracted to the negative ion and the negative end of a water molecule will be attracted to the positive ion - Ions will get totally surrounded by water molecules.

77
Q

How does water help temperature control? (specific heat capacity)

Why is this good?

A

The hydrogen bonds between water molecules can absorb a lot of energy so water has a high specific heat capacity.

Useful because it makes water a good habitat because temperature under water is likely to be stable = also keeps body temp stable.

78
Q

Water molecules are very C…

A

Cohesive - they stick together which helps water transport in plants as well as transport in other organisms.

Strong cohesion means that that water has a high surface tension when it comes into contact with air - this is why sweat forms droplets.

79
Q

Describe the structure of Water:

A

2 Hydrogen’s covalently bonded with Oxygen.

Contains Hydrogen Bonding.

80
Q

Why is water a polar molecule?

A

Because it has a partial negative charge on one side and a partial positive on the other.

81
Q

Is it easy to cause a change of state in a water molecule?

Why is this useful?

A

Takes a lot of energy to break the hydrogen bonds so water has a high latent heat of vaporisation - a lot of energy is used up when water evaporates .

  • useful because we can use water loss through evaporation to cool down (sweat) without losing too much water.
82
Q

Why is ice less dense than water?

A

Because when water freezes,

AQA A Level Biology 2018 (17 decks)

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