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Biology > Topic 1B: More Biological Molecules > Flashcards

Topic 1B: More Biological Molecules Flashcards

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1
Q

What is the structure of a nucleotide?

A
  • Pentose sugar
  • Nitrogenous base
  • Phosphate group
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2
Q

What is the structure of a DNA nucleotide?

A
  • Deoxyribose
  • Nitrogenous base –> Adenine, Thymine, Cytosine, Guanine
  • Phosphate group
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3
Q

What is the structure of a RNA nucleotide?

A
  • Ribose
  • Nitrogenous base –> Adenine, Uracil, Cytosine, Guanine
  • Phosphate group
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4
Q

How do polynucleotides form?

A
  • Condensation reaction between the phosphate group of one nucleotide and the sugar of the next
  • Forms phosphodiester bonds to form the sugar-phosphate backbone
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5
Q

Which bases are pyrimidines and and how many rings do they have?

A
  • Cytosine, Thymine
  • 1 ring
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6
Q

Which bases are purines and how many rings do they have?

A
  • Adenine, Guanine
  • 2 rings
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7
Q

Which bases bond to which and with how many bonds?

A
  • A - T –> 2 bonds
  • C - G –> 3 bonds
  • All bonds = hydrogen bonds
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8
Q

How is DNA structured?

A
  • Complimentary base pairing between strands
  • Strands are antiparallel so the structure twists to a double helix shape
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9
Q

How is RNA different to DNA?

A
  • U not T
  • Single stranded
  • Much shorter
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10
Q

What is the model for DNA replication called and how does it work?

A
  • Semi-conservative model
  • Each daughter DNA has one parent strand and one new strand
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11
Q

How does DNA replication occur?

A
  • DNA helicase breaks H bonds between base pairs to separate the strands
  • Each strand acts as a template as free nucleotides move in to bond to a complimentary base
  • DNA polymerase forms phosphodiester bonds between the free nucleotides to make the sugar-phosphate backbone of the new complimentary strand
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12
Q

How does DNA polymerase work on each strand differently?

A
  • The active site of DNA polymerase is only complimentary to the 3’ end
  • As the strands are antiparallel the enzyme works in different directions on each
  • This makes a leading strand and a lagging strand
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13
Q

Which scientists did the investigation to give evidence for DNA replication as the semi-conservative model?

A

Meselson and Stahl

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14
Q

Which isotopes of nitrogen are used to give evidence in DNA replication?

A

14N and 15N

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15
Q

How does the experiment work to give evidence of DNA replication?

A
  • Bases = nitrogenous so takes in N in DNA replication
  • As different isotopes are used the DNA has differing masses
  • This can be found using a centrifuge to separate the strands by density
  • This provides evidence of semi-conservative DNA replication
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16
Q

Describe the generations of DNA replication in nitrogen isotopes

A
  • G0 = 100% 15N 15N –> all heavy –> all settle to the bottom
  • G1 = each strand is half new with lighter N and half is old with heavier N –> 100% 15N 14N –> all settles slightly further up
  • G2 = now 2 are fully lighter N and 2 are split –> 50% 15N 14N, 50% 14N 14N –> half settles further up than the other half
  • G3 = only 2 in 8 have half heavy –> 75% 14N 14N, 25% 15N 14N –> bigger settlement further up than a smaller one
17
Q

What about the structure of water makes it special?

A
  • It is a polar molecule
  • O side = slightly -ve
  • H side = slightly +ve
18
Q

What is hydrogen bonding?

A
  • The slightly -ve O attract the slightly +ve H of other water molecules
18
Q

How is water a metabolite?

A
  • Metabolic reactions usually involve condensation or hydrolysis –> water is an essential part of this
19
Q

How does high latent heat of vaporisation help water?

A
  • Takes lots of energy to break all the hydrogen bonds in water for it to evaporate
  • Useful for living organisms –> use water evaporation in sweat to cool down –> takes lots of energy with it with as minimal water loss as possible
20
Q

How does high specific heat capacity help water?

A
  • Hydrogen bonds between water molecules can absorb lots of energy
  • Water doesn’t have rapid temp changes –> stable living environment
  • Also water in an organism has a fairly constant temperature
21
Q

How is water a good solvent?

A
  • Many substances are ionic so have charged particles –> these are attracted to the polar ends of water so that they are totally surrounded by water molecules
22
Q

What is cohesion and how does this relate to water?

A
  • Cohesion = attraction between molecules of the same type
  • Water molecules are very cohesive because they are polar
  • Helps water to flow to transport substances
  • Has high surface tension –> sweat forms droplets + animals like pond skaters can ‘walk’ on water
23
Q

What is the structure of ATP?

A
  • Adenine base
  • Ribose sugar
  • 3 phosphate groups
  • Called a nucleotide derivative as it is a modified version of a nucleotide
24
Q

How is ATP produced?

A
  • When energy is released from glucose it is used to make ATP
25
Q

How is ATP used?

A
  • When energy is needed ATP is hydrolysed to ADP and Pi
  • The phosphate bond is broken releasing energy
  • Catalysed by ATP hydrolase
  • Can be coupled to an energy requiring reaction to be directly put to use
  • ATP can be resynthesised by ATP synthase
26
Q

What is the inorganic phosphate used for?

A
  • Can be added to another compound to make it more reactive –> phosphorylation
27
Q

What are inorganic ions and where are they usually found?

A
  • Charged atoms
  • Don’t usually contain carbon
  • Found in solution in cytoplasm and bodily fluids
28
Q

What are iron ions used for?

A
  • Fe 2+
  • Haemoglobin = 4 different polypeptides each with an iron ion in the centre
  • Fe 2+ binds to oxygen –> temporarily becomes Fe 3+ until the oxygen is released
29
Q

What do hydrogen ions do?

A
  • H +
  • pH is based on concentration of H+ ions and enzyme controlled reactions are affected by pH
30
Q

What do Sodium ions do?

A
  • Na +
  • Help glucose or amino acids to be transported into a cell by co transport
31
Q

What do phosphate ions do?

A
  • Po4 3-
  • When attached to another molecule they are a phosphate group
  • Phosphate groups are in DNA, RNA, ATP
  • In DNA + RNA they allow nucleotides to join to polynucleotides

Biology (16 decks)

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