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1B More Biological Molecules Flashcards

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1
Q

What is a hereditary molecule?

A

It is passed down through generations (i.e. DNA)

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2
Q

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

A

3.2 billion

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3
Q

Is DNA a stable molecule?

A

Yes - it is very stable

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4
Q

How are the two stands of DNA held together?

A

By hydrogen bonds between the nitrogenous bases

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5
Q

What is an advantage of the hydrogen bonds in DNA?

A

It allows the strands to separate easily during semiconservative replication

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6
Q

What does DNA being large allow?

A

Lots of info to be transferred

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7
Q

What is a function of the double helix structure of DNA?

A

It partly protects the genetic info carried by the bases

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8
Q

What does base pairing mean for DNA and RNA?

A

Makes the DNA and RNA sequences compatible, allowing RNA to transfer info from the DNA

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9
Q

Give three properties of DNA

A
  • Highly stable
  • Two strands held together by hydrogen bonds allows molecule to unzip during replication
  • A long molecule so can store lots of info
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10
Q

Who discovered DNA?

A

Watson and Crick

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11
Q

How is DNA replicated?

A

Semiconservatively

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12
Q

What makes up each part of the DNA?

A

Nucleotides

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13
Q

What are the parts of a nucleotide?

A
  • Phosphate group
  • Pentose sugar
  • Nitrogenous base
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14
Q

What is needed for the production of proteins?

A

Nucleic acids –> these proteins turn into other molecules

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15
Q

What is a nucleic acid?

A

A complex organic substance present in living cells

Whose molecules consist of many nucleotides linked in a long chain

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16
Q

What are the 5 nitrogenous bases?

A
  • Adenine
  • Cytosine
  • Guanine
  • Thymine
  • Uracil
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17
Q

Which nucleotides are found in DNA?

A
  • Adenine
  • Cytosine
  • Guanine
  • Thymine
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18
Q

Which nucleotides are found in RNA?

A
  • Adenine
  • Cytosine
  • Guanine
  • Uracil
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19
Q

Which reaction forms nucleotides?

A

Condensation

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20
Q

What do two nucleotides bond to form?

A

Dinucleotide

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21
Q

What do many nucleotides bond to form?

A

Polynucleotide

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22
Q

What is the pentose sugar in RNA?

A

Ribose

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23
Q

What is the pentose sugar in DNA?

A

Deoxyribose

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24
Q

What are the bonds between nucleotides called?

A

Phosphodiester bond

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25
Q

How many strands does RNA have?

A

One polynucleotide chain

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26
Q

What are the three types of RNA?

A
  • Transfer (tRNA)
  • Messenger (mRNA)
  • Ribosome (rRNA)
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27
Q

How many strands does DNA have?

A

A pair of extremely long polynucleotide chains

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28
Q

How are the bases in DNA bonded?

A

Hydrogen bonds

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29
Q

What is the role of the phosphodiester backbone

A

It’s relatively unreactive therefore protects the more reactive bases

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30
Q

What 2 factors make DNA more stable and suited to long term storage?

A
  • Hydrogen bonds holding complementary bases

- Phosphodiester backbone

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31
Q

How do the nitrogenous bases pair?

A

Thymine –> Adenine

Cytosine –> Guamine

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32
Q

What are the two prime ends of DNA?

A

3 end and 5 end

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33
Q

When DNA forms a double helix structure how do the DNA strands run in relation to each other?

A

The two strands run in opposite directions to each other
(one 5 prime end will be at the top of one and a 3 prime end at the top of another)

ANTI-PARALLEL

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34
Q

Explain how the organic bases in nucleotides help to stabilise the structure of DNA

A
  • They hydrogen bond between each complementary base hold the structure together
  • This closes the two strands of DNA which protects the molecule
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35
Q

Explain why some enzymes only work from end of the DNA?

A
  • The active site of DNA polymerase is only complementary to the 3 prime end
    Nucleotides are attached in the 5’ to 3’ end direction
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36
Q

Give 2 features of DNA that is important in the semi-conservative replication of DNA

A
  • The hydrogen bonds between nitrogenous bases make it easy for the two strands to peel apart
  • Complementary bases mean free nucleotides can be attached after
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37
Q

What are the two enzymes involved in semi-conservative replication?

A

DNA helicase

DNA polymerase

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38
Q

What is the function of DNA helicase?

A

Unzips the DNA via breaking the hydrogen bonds

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39
Q

What is the function of DNA polymerase?

A

Zips the chain together by forming hydrogen bonds

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40
Q

What does ATP stand for?

A

Adenosine Triphosphate

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41
Q

How is ATP produced?

A

The oxidation of glucose used to release energy which is used to produce ATP

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42
Q

What sort of molecule is ATP?

A

A phosphorylated macromolecule

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43
Q

What does phosphorylated refer to?

A

The attachment of a phosphoryl group

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44
Q

What are the 3 parts of ATP?

A
  • Adenine
  • Ribose
  • Phosphate
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45
Q

What is the adenine in ATP?

A

A nitrogenous base

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46
Q

What is the ribose in ATP?

A

A pentose sugar which acts as the backbone

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47
Q

What is the phosphate in ATP?

A

Chain of 3 phosphate groups

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48
Q

What are the two types of bonds in ATP?

A
  • Phosphate ester bond (between ribose sugar and phosphate molecule)
  • Phosphoanhydride bond (between the phosphate molecules)
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49
Q

What is ATP?

A

The immediate source of energy because a cell is incapable of releasing energy directly from glucose

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50
Q

Are mitochondria unicellular organisms

A

Yes

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51
Q

Where is the energy in ATP stored?

A

Available energy is stored in bonds between phosphate groups

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52
Q

What are the phosphate bonds in ATP like?

A
  • Unstable
  • Have a low activation energy
  • When they break they release a substantial amount of energy
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53
Q

When ATP is broken down what usually happens?

A

ADP + energy + inorganic phosphate

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54
Q

What is the formula for the breakdown of ATP?

A

ATP + H2O —–> ADP + Pi + E

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55
Q

What is ADP?

A

Adenosine diphosphate

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56
Q

What is the ATP breakdown reaction catalysed by?

A

ATP hydrolase

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57
Q

What sort of reaction is the breakdown of ATP?

A

A hydrolysis reaction as water is used

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58
Q

What can the hydrolysis of ATP be coupled to?

A

Energy requiring reactions in the cell

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59
Q

.

A

.

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60
Q

What can the the phosphate molecule be used to do in the coupling of ATP and another cellular reaction?

A

Can be used to phosphorylate other molecules in order to make it more reactive

61
Q

What can happen to ADP

A

It can be recycled back to ATP

62
Q

How is ADP recycled back to ATP?

A

Via respiration of glucose in the mitochondria or by photosynthesis in chloroplasts

63
Q

What sort of reaction is the recycling of ADP?

A

Water is released therefore it is a condensation reaction

64
Q

What is the catalyst of the synthesis of ATP?

A

The enzyme ATP synthase

65
Q

What is the breaking and remaking of ATP called?

A

Interconversion as each can be transferred back to each other

66
Q

Is ATP a good storage molecule?

A

No it is very unstable therefore it is not good for storage

67
Q

What type of energy is ATP?

A

Immediate energy for a cell

68
Q

Do cells store ATP?

A

No, they don’t need to store the energy because it can be rapidly reformed

69
Q

What % of mass in cells is made of water?

A

70%

70
Q

Is water a polar molecule?

A

Yes it has a positive and a negative end and it is polar sue to the bent shape of th molecule

71
Q

What charges do Oxygen and Hydrogen have that make it polar?

A

Oxygen - negative

Hydrogen - positive

72
Q

What sort of bond is in water?

A

Covalent

73
Q

When solutes are added to water, what may affect them?

A

The charge distribution in water

74
Q

How do water molecules bond?

A
  • Through hydrogen bonds with each other

- They bond due to their polarity

75
Q

Why does water have a higher boiling point than expected?

A

They hydrogen bonds between the molecules means more energy is needed to break the bonds of this small molecule

76
Q

What is water’s specific heat capacity like?

A

It is high - this acts as a buffer against rapid temperature change

77
Q

Why are aqueous environments relatively stable?

A

Due to water’s high specific heat capacity

78
Q

Why is the high latent heat of water good?

A

It makes it an excellent substance for cooling off by sweating as the water evapourates, cooling us

79
Q

Which properties of water make it easy for water to be drawn up xylem tubes?

A

Cohesion and surface tension

80
Q

What would happen if water wasn’t cohesive?

A

It would not hold together therefore the column of water would be unable to travel up the plant through the xylem tubes

81
Q

Water is an important metabolite

Why is this?

A

Many reactions are either condensation or hydrolysis reactions

82
Q

Water is a good solvent

Why is this?

A

A lot of important metabolic reactions are ionic

The dipolar nature of water means both +ive and -ive ions can dissolve in water

83
Q

Why is the dipolar nature of water useful?

A

It is good for facilitating reactions and allowing diffusion

84
Q

Why is water a temperature buffer?

A

The hydrogen bonds between water molecules absorb lots of energy –> So it has a high specific heat capacity

85
Q

What does cohesive mean?

A

Sticky - water is cohesive

86
Q

What is a good example of the cohesion of water

A

Water boatmen (water striders) can live on the surface of the water

87
Q

List 4 properties of water

A
  • Good solvent due to dipolar nature
  • Good metabolite
  • Good temp buffer
  • Cohesive
88
Q

Why do cells replicate their DNA and how do they do this?

A

For cell division, so each new cell has the full amount of DNA

Through semi-conservative replication

89
Q

Where does semi-conservative replication get its name from?

A

Half of the strands in each new DNA molecule are from the original DNA molecule

90
Q

What does semi-conservative replication mean for the continuity of the genetic code?

A

As one of the strand in the DNA is from the original molecule, this means there’s genetic continuity between generations of cells

91
Q

What are happens in each of the 4 stages in Semi-conservative replication?

A
  • DNA is unzipped
  • Base strands act as templates - free nucleotides attached
  • Condensation reaction joins the nucleotides together
  • Each strand contains half of the original strand
92
Q

What happens in the first stage of DNA replication?

A
  • DNA helicase breaks the hydrogen bonds between bases on each (polynucleotide) strand
  • Makes the helix unwind into two single strands
93
Q

What happens in the second stage of DNA replication?

A
  • Original strands act as templates for new free strands

- Complementary base pairing means free nucleotides are attached to complementary bases on each original template strand

94
Q

What happens in the third stage of DNA replication?

A
  • Condensation reactions join the nucleotides of the new strands together by DNA polymerase
  • Hydrogen bonds form between the bases on the original and new strands
95
Q

What happens in the fourth stage of DNA replication?

A

Each new DNA molecule contains one strand from the original DNA molecule and one new strand

96
Q

Which enzyme’s active site is complementary to the 3’ end?

A

DNA polymerase

97
Q

Which end can nucleotides only be added to?

A

The 3’ end

98
Q

Which direction does semi-conservative replication happen in?

A

From the 5’ end to the 3’ end

99
Q

Why do the DNA polymerases working on each strand move in opposite directions?

A

The strands are antiparallel - therefore the 3’ ends of each strand are at opposite ends of the chain

100
Q

Who provided evidence for Semi-Conservative Replication?

A

Meselson and Stahl

101
Q

Who came up with the theory of Semi-Conservative Replication?

A

Watson and Crick - they also discovered the structure of DNA

102
Q

Before Meselson and Stahl proved Semi-Conservative Replication, what were the two theories for replication?

A
  • Conservative

- Semi-Conservative

103
Q

If DNA replication was Conservative, what would DNA be like?

A

The original DNA strands would stay together and the new DNA molecules would contain 2 new strands

104
Q

What did Meselson and Stahl use to prove Semi-Conservative Replication?

A

Two isotopes of nitrogen (DNA contains nitrogen)

  • Heavy nitrogen (15N)
  • Light nitrogen (14N)
105
Q

What were the 6 stages of Meselson and Stahl’s Semi-Conservative Replication experiment?

A

1 - Initial DNA sample contains heavy or light nitrogen sample
2 - Light DNA settles higher in the centrifuge tube than heavy DNA
3 - Heavy nitrogen bacteria replicates in light nitrogen broth
4 - Conservative replication –> 6 - DNA with original heavy + light strand would stay in original places
5 - Semi-Conservative Replication –> 6 - DNA with a combo of heavy + light strands settle in the middle

106
Q

What was the first stage of Meselson and Stahl’s testing?

A
  • Two samples of bacteria grown in nutrient broths (one light one heavy nitrogen)
  • As the bacteria reproduced nitrogen taken from broth to make nucleotides for DNA
  • Nitrogen became part of bacteria’s DNA
107
Q

What was the second stage of Meselson and Stahl’s testing?

A
  • DNA sample taken from each batch + spun in centrifuge

- Heavy nitrogen DNA settled lower down centrifuge tube than light DNA as it’s heavier

108
Q

What was the third stage of Meselson and Stahl’s testing?

A
  • Bacteria grown in heavy nitrogen broth taken out - put in light nitrogen broth
  • Bacteria left for one round of DNA replication
  • Another DNA sample taken and spun in centrifuge
109
Q

What was the fourth stage of Meselson and Stahl’s testing?

A

If replication was Conservative:
- Original heavy DNA would still be together and settle at the bottom

  • New light DNA would settle at the top
110
Q

What was the fifth stage of Meselson and Stahl’s testing? (what they concluded)

A

If replication was Semi-Conservative:
- New bacterial molecules would contain one old heavy strand + one new light strand

  • DNA would settle between where light and heavy settle
111
Q

What was the sixth stage of Meselson and Stahl’s testing?

A

Results:
- DNA settled in the middle

  • Showed DNA contains a mixture of heavy and light nitrogen
  • Bacterial DNA had replicated semi-conservatively in the light nitrogen
112
Q

What was discovered by other scientists after Meselson and Stahl’s discovery?

A

That it was the universal method for DNA replication in all living things

113
Q

Why is water being a good temp buffer good for animals?

A

Means water doesn’t experience rapid temp change

  • -> makes water a good habitat as temp is stable
  • -> Water inside organisms stays at a fairly stable temp - helps maintain constant internal temp
114
Q

What is cohesion?

A

The attraction between molecules of the same type

115
Q

Why are water molecules cohesive?

A

They’re polar so they tend to stick together

116
Q

Why is strong cohesion of water good?

A

Helps water to flow - good for transporting substances

117
Q

Strong cohesion of water means what for water when it comes into contact with air?

A

Has high surface tension - this is why sweat forms droplets which evaporate from the skin

118
Q

Give an example of water being a good metabolite

A

Amino acids are joined by condensation reaction which needs water

119
Q

Why do we know that water has a high latent heat?

A

It takes a lot of energy (heat) to break the hydrogen bonds between water molecules

120
Q

What is one of RNA’s main functions?

A

To transfer genetic info from the DNA to the ribosomes

121
Q

What do ribosomes do in relation to DNA replication?

A

They are the body’s ‘protein factories’

Read RNA to make polypeptides in a process called translation

122
Q

What are ribosomes made from?

A
  • RNA

- Proteins

123
Q

Nucleotides join to form what?

A

Polynucleotides

124
Q

Name 2 polynucleotides

A
  • DNA

- RNA

125
Q

Which 2 parts of the nucleotides join to form DNA?

A

Phosphate group of one and the sugar of another

126
Q

What is the bond between the sugar and phosphate molecule called in DNA?

A

A Phosphodiester bond - phosphate group + two diester bonds

127
Q

What did scientists argue carried genetic code before DNA was discovered?

A

Proteins - they thought DNA was too simple when it was first observe, proteins are more chemically varied

128
Q

Why is ATP known as a nucleotide derivative?

A

Because it’s a modified form of a nucleotide

129
Q

Once ATP is made what does it do?

A

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

130
Q

How is energy released from ATP?

A

Via hydrolysis reactions

131
Q

What sort of reaction is the breakdown of ADP?

A

Hydrolysis - a phosphate bond is broken + energy is released

132
Q

What happens to the released inorganic phosphate from ATP?

A

It can be added to another compound which makes the compound more reactive

133
Q

What is the process of the released inorganic phosphate from ADP joining another compound called?

A

Phosphorylation

134
Q

When is ATP re-synthesised?

A

During respiration and photosynthesis

135
Q

All inorganic ions have what?

A

A charge

136
Q

What is an inorganic ion?

A

An ion which doesn’t contain carbon (there are a few exceptions)

137
Q

Give 4 examples of inorganic ions

A
  • Iron ions
  • Hydrogen ions
  • Sodium ions
  • Phosphate ions
138
Q

What are iron ions an important part of?

A

Haemoglobin

139
Q

What does Haemoglobin do?

A

Large protein that carries oxygen around the body, in the red blood cells

140
Q

What is haemoglobin made up of?

A

4 different polypeptide chains - each has an iron ion in the centre

141
Q

What is the role of iron ions in haemoglobin?

A

It’s the Fe2+ that binds to the oxygen in haemoglobin - a key component

142
Q

In haemoglobin, what happens to the iron ions when the oxygen are temporarily bonded to them?

A

They become Fe3+ for this time

143
Q

What do hydrogen ions determine?

A

pH

144
Q

pH is calculated based on what?

A

The conc. of hydrogen ions (H+) in the environment

145
Q

What is the role of sodium ions in transportation?

A

They help to transport glucose and amino acids across membranes

146
Q

How do sodium ions help co-transport?

A

A molecule of glucose or amino acid can be transported into a cell alongside sodium ions

147
Q

What are phosphate ions essential for?

A

They are an essential component of ATP and DNA

148
Q

When a phosphate ion is attached to another molecule, what is it known as?

A

A phosphate group

149
Q

Name 3 things that contain phosphate groups?

A

DNA, RNA and ATP

Biology A-level (20 decks)

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