1B More Biological Molecules Flashcards
1
Q
What is a hereditary molecule?
A
It is passed down through generations (i.e. DNA)
2
Q
How many base pairs is in the DNA of a typical mammalian cell?
A
3.2 billion
3
Q
Is DNA a stable molecule?
A
Yes - it is very stable
4
Q
How are the two stands of DNA held together?
A
By hydrogen bonds between the nitrogenous bases
5
Q
What is an advantage of the hydrogen bonds in DNA?
A
It allows the strands to separate easily during semiconservative replication
6
Q
What does DNA being large allow?
A
Lots of info to be transferred
7
Q
What is a function of the double helix structure of DNA?
A
It partly protects the genetic info carried by the bases
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
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
10
Q
Who discovered DNA?
A
Watson and Crick
11
Q
How is DNA replicated?
A
Semiconservatively
12
Q
What makes up each part of the DNA?
A
Nucleotides
13
Q
What are the parts of a nucleotide?
A
- Phosphate group
- Pentose sugar
- Nitrogenous base
14
Q
What is needed for the production of proteins?
A
Nucleic acids –> these proteins turn into other molecules
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
16
Q
What are the 5 nitrogenous bases?
A
- Adenine
- Cytosine
- Guanine
- Thymine
- Uracil
17
Q
Which nucleotides are found in DNA?
A
- Adenine
- Cytosine
- Guanine
- Thymine
18
Q
Which nucleotides are found in RNA?
A
- Adenine
- Cytosine
- Guanine
- Uracil
19
Q
Which reaction forms nucleotides?
A
Condensation
20
Q
What do two nucleotides bond to form?
A
Dinucleotide
21
Q
What do many nucleotides bond to form?
A
Polynucleotide
22
Q
What is the pentose sugar in RNA?
A
Ribose
23
Q
What is the pentose sugar in DNA?
A
Deoxyribose
24
Q
What are the bonds between nucleotides called?
A
Phosphodiester bond
25
How many strands does RNA have?
One polynucleotide chain
26
What are the three types of RNA?
- Transfer (tRNA)
- Messenger (mRNA)
- Ribosome (rRNA)
27
How many strands does DNA have?
A pair of extremely long polynucleotide chains
28
How are the bases in DNA bonded?
Hydrogen bonds
29
What is the role of the phosphodiester backbone
It's relatively unreactive therefore protects the more reactive bases
30
What 2 factors make DNA more stable and suited to long term storage?
- Hydrogen bonds holding complementary bases
| - Phosphodiester backbone
31
How do the nitrogenous bases pair?
Thymine --> Adenine
| Cytosine --> Guamine
32
What are the two prime ends of DNA?
3 end and 5 end
33
When DNA forms a double helix structure how do the DNA strands run in relation to each other?
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
34
Explain how the organic bases in nucleotides help to stabilise the structure of DNA
- They hydrogen bond between each complementary base hold the structure together
- This closes the two strands of DNA which protects the molecule
35
Explain why some enzymes only work from end of the DNA?
- The active site of DNA polymerase is only complementary to the 3 prime end
Nucleotides are attached in the 5' to 3' end direction
36
Give 2 features of DNA that is important in the semi-conservative replication of DNA
- 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
37
What are the two enzymes involved in semi-conservative replication?
DNA helicase
| DNA polymerase
38
What is the function of DNA helicase?
Unzips the DNA via breaking the hydrogen bonds
39
What is the function of DNA polymerase?
Zips the chain together by forming hydrogen bonds
40
What does ATP stand for?
Adenosine Triphosphate
41
How is ATP produced?
The oxidation of glucose used to release energy which is used to produce ATP
42
What sort of molecule is ATP?
A phosphorylated macromolecule
43
What does phosphorylated refer to?
The attachment of a phosphoryl group
44
What are the 3 parts of ATP?
- Adenine
- Ribose
- Phosphate
45
What is the adenine in ATP?
A nitrogenous base
46
What is the ribose in ATP?
A pentose sugar which acts as the backbone
47
What is the phosphate in ATP?
Chain of 3 phosphate groups
48
What are the two types of bonds in ATP?
- Phosphate ester bond (between ribose sugar and phosphate molecule)
- Phosphoanhydride bond (between the phosphate molecules)
49
What is ATP?
The immediate source of energy because a cell is incapable of releasing energy directly from glucose
50
Are mitochondria unicellular organisms
Yes
51
Where is the energy in ATP stored?
Available energy is stored in bonds between phosphate groups
52
What are the phosphate bonds in ATP like?
- Unstable
- Have a low activation energy
- When they break they release a substantial amount of energy
53
When ATP is broken down what usually happens?
ADP + energy + inorganic phosphate
54
What is the formula for the breakdown of ATP?
ATP + H2O -----> ADP + Pi + E
55
What is ADP?
Adenosine diphosphate
56
What is the ATP breakdown reaction catalysed by?
ATP hydrolase
57
What sort of reaction is the breakdown of ATP?
A hydrolysis reaction as water is used
58
What can the hydrolysis of ATP be coupled to?
Energy requiring reactions in the cell
59
.
.
60
What can the the phosphate molecule be used to do in the coupling of ATP and another cellular reaction?
Can be used to phosphorylate other molecules in order to make it more reactive
61
What can happen to ADP
It can be recycled back to ATP
62
How is ADP recycled back to ATP?
Via respiration of glucose in the mitochondria or by photosynthesis in chloroplasts
63
What sort of reaction is the recycling of ADP?
Water is released therefore it is a condensation reaction
64
What is the catalyst of the synthesis of ATP?
The enzyme ATP synthase
65
What is the breaking and remaking of ATP called?
Interconversion as each can be transferred back to each other
66
Is ATP a good storage molecule?
No it is very unstable therefore it is not good for storage
67
What type of energy is ATP?
Immediate energy for a cell
68
Do cells store ATP?
No, they don't need to store the energy because it can be rapidly reformed
69
What % of mass in cells is made of water?
70%
70
Is water a polar molecule?
Yes it has a positive and a negative end and it is polar sue to the bent shape of th molecule
71
What charges do Oxygen and Hydrogen have that make it polar?
Oxygen - negative
| Hydrogen - positive
72
What sort of bond is in water?
Covalent
73
When solutes are added to water, what may affect them?
The charge distribution in water
74
How do water molecules bond?
- Through hydrogen bonds with each other
| - They bond due to their polarity
75
Why does water have a higher boiling point than expected?
They hydrogen bonds between the molecules means more energy is needed to break the bonds of this small molecule
76
What is water's specific heat capacity like?
It is high - this acts as a buffer against rapid temperature change
77
Why are aqueous environments relatively stable?
Due to water's high specific heat capacity
78
Why is the high latent heat of water good?
It makes it an excellent substance for cooling off by sweating as the water evapourates, cooling us
79
Which properties of water make it easy for water to be drawn up xylem tubes?
Cohesion and surface tension
80
What would happen if water wasn't cohesive?
It would not hold together therefore the column of water would be unable to travel up the plant through the xylem tubes
81
Water is an important metabolite
Why is this?
Many reactions are either condensation or hydrolysis reactions
82
Water is a good solvent
Why is this?
A lot of important metabolic reactions are ionic
The dipolar nature of water means both +ive and -ive ions can dissolve in water
83
Why is the dipolar nature of water useful?
It is good for facilitating reactions and allowing diffusion
84
Why is water a temperature buffer?
The hydrogen bonds between water molecules absorb lots of energy --> So it has a high specific heat capacity
85
What does cohesive mean?
Sticky - water is cohesive
86
What is a good example of the cohesion of water
Water boatmen (water striders) can live on the surface of the water
87
List 4 properties of water
- Good solvent due to dipolar nature
- Good metabolite
- Good temp buffer
- Cohesive
88
Why do cells replicate their DNA and how do they do this?
For cell division, so each new cell has the full amount of DNA
Through semi-conservative replication
89
Where does semi-conservative replication get its name from?
Half of the strands in each new DNA molecule are from the original DNA molecule
90
What does semi-conservative replication mean for the continuity of the genetic code?
As one of the strand in the DNA is from the original molecule, this means there's genetic continuity between generations of cells
91
What are happens in each of the 4 stages in Semi-conservative replication?
- 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
What happens in the first stage of DNA replication?
- DNA helicase breaks the hydrogen bonds between bases on each (polynucleotide) strand
- Makes the helix unwind into two single strands
93
What happens in the second stage of DNA replication?
- 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
What happens in the third stage of DNA replication?
- 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
What happens in the fourth stage of DNA replication?
Each new DNA molecule contains one strand from the original DNA molecule and one new strand
96
Which enzyme's active site is complementary to the 3' end?
DNA polymerase
97
Which end can nucleotides only be added to?
The 3' end
98
Which direction does semi-conservative replication happen in?
From the 5' end to the 3' end
99
Why do the DNA polymerases working on each strand move in opposite directions?
The strands are antiparallel - therefore the 3' ends of each strand are at opposite ends of the chain
100
Who provided evidence for Semi-Conservative Replication?
Meselson and Stahl
101
Who came up with the theory of Semi-Conservative Replication?
Watson and Crick - they also discovered the structure of DNA
102
Before Meselson and Stahl proved Semi-Conservative Replication, what were the two theories for replication?
- Conservative
| - Semi-Conservative
103
If DNA replication was Conservative, what would DNA be like?
The original DNA strands would stay together and the new DNA molecules would contain 2 new strands
104
What did Meselson and Stahl use to prove Semi-Conservative Replication?
Two isotopes of nitrogen (DNA contains nitrogen)
- Heavy nitrogen (15N)
- Light nitrogen (14N)
105
What were the 6 stages of Meselson and Stahl's Semi-Conservative Replication experiment?
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
What was the first stage of Meselson and Stahl's testing?
- 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
What was the second stage of Meselson and Stahl's testing?
- 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
What was the third stage of Meselson and Stahl's testing?
- 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
What was the fourth stage of Meselson and Stahl's testing?
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
What was the fifth stage of Meselson and Stahl's testing? (what they concluded)
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
What was the sixth stage of Meselson and Stahl's testing?
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
What was discovered by other scientists after Meselson and Stahl's discovery?
That it was the universal method for DNA replication in all living things
113
Why is water being a good temp buffer good for animals?
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
What is cohesion?
The attraction between molecules of the same type
115
Why are water molecules cohesive?
They're polar so they tend to stick together
116
Why is strong cohesion of water good?
Helps water to flow - good for transporting substances
117
Strong cohesion of water means what for water when it comes into contact with air?
Has high surface tension - this is why sweat forms droplets which evaporate from the skin
118
Give an example of water being a good metabolite
Amino acids are joined by condensation reaction which needs water
119
Why do we know that water has a high latent heat?
It takes a lot of energy (heat) to break the hydrogen bonds between water molecules
120
What is one of RNA's main functions?
To transfer genetic info from the DNA to the ribosomes
121
What do ribosomes do in relation to DNA replication?
They are the body's 'protein factories'
Read RNA to make polypeptides in a process called translation
122
What are ribosomes made from?
- RNA
| - Proteins
123
Nucleotides join to form what?
Polynucleotides
124
Name 2 polynucleotides
- DNA
| - RNA
125
Which 2 parts of the nucleotides join to form DNA?
Phosphate group of one and the sugar of another
126
What is the bond between the sugar and phosphate molecule called in DNA?
A Phosphodiester bond - phosphate group + two diester bonds
127
What did scientists argue carried genetic code before DNA was discovered?
Proteins - they thought DNA was too simple when it was first observe, proteins are more chemically varied
128
Why is ATP known as a nucleotide derivative?
Because it's a modified form of a nucleotide
129
Once ATP is made what does it do?
It diffuses to the part of the cell that needs the energy
130
How is energy released from ATP?
Via hydrolysis reactions
131
What sort of reaction is the breakdown of ADP?
Hydrolysis - a phosphate bond is broken + energy is released
132
What happens to the released inorganic phosphate from ATP?
It can be added to another compound which makes the compound more reactive
133
What is the process of the released inorganic phosphate from ADP joining another compound called?
Phosphorylation
134
When is ATP re-synthesised?
During respiration and photosynthesis
135
All inorganic ions have what?
A charge
136
What is an inorganic ion?
An ion which doesn't contain carbon (there are a few exceptions)
137
Give 4 examples of inorganic ions
- Iron ions
- Hydrogen ions
- Sodium ions
- Phosphate ions
138
What are iron ions an important part of?
Haemoglobin
139
What does Haemoglobin do?
Large protein that carries oxygen around the body, in the red blood cells
140
What is haemoglobin made up of?
4 different polypeptide chains - each has an iron ion in the centre
141
What is the role of iron ions in haemoglobin?
It's the Fe2+ that binds to the oxygen in haemoglobin - a key component
142
In haemoglobin, what happens to the iron ions when the oxygen are temporarily bonded to them?
They become Fe3+ for this time
143
What do hydrogen ions determine?
pH
144
pH is calculated based on what?
The conc. of hydrogen ions (H+) in the environment
145
What is the role of sodium ions in transportation?
They help to transport glucose and amino acids across membranes
146
How do sodium ions help co-transport?
A molecule of glucose or amino acid can be transported into a cell alongside sodium ions
147
What are phosphate ions essential for?
They are an essential component of ATP and DNA
148
When a phosphate ion is attached to another molecule, what is it known as?
A phosphate group
149
Name 3 things that contain phosphate groups?
DNA, RNA and ATP
