Topic 1B - More biological molecules ARN * Flashcards
DNA and RNA DNA replication water ATP inorganic ions
1
Q
what does DNA stand for?
A
deoxyribonucleic acid
2
Q
what does DNA do?
A
its used to store genetic information
3
Q
what is genetic information?
A
all the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult
4
Q
what does RNA stand for?
A
ribonucleic acid - it has a similar structure to DNA
5
Q
What are RNAs main functions?
A
to transfer genetic information from the DNA to the ribosomes.
6
Q
what do ribosomes do?
A
they are the body’s ‘protein factories’ they read the RNA to make polypeptides in a process called translation
7
Q
what are ribosomes made of?
A
RNA and proteins
8
Q
what are nucleotides?
A
biological molecules, that are the monomers that make up DNA and RNA
9
Q
what are nucleotides made from?
A
a pentose sugar
a nitrogen-containing organic base
a phosphate group
each of which are joined via condensation reactions
the phosphate is joined to the 5’ prime end of the sugar (5th carbon)
10
Q
what is the pentose sugar in a DNA nucleotide called?
A
deoxyribose
11
Q
what is the organic base called in a DNA nucleotide?
A
can be either: adenine (A) thymine (T) cytosine (C) guanine (G)
12
Q
what is the pentose sugar in an RNA nucleotide called?
A
ribose
13
Q
what is the organic base called in an RNA nucleotide?
A
the same bases as in DNA but with Uracil (U) instead of thymine
14
Q
how are nucleotides joined together?
A
via condensation reaction between the phosphate group of 1 nucleotide and the 3’ end (3rd carbon) of the sugar of another. this forms a phosphodiester bond.
the chain of sugars and phosphates is known as the sugar-phosphate backbone
15
Q
how do DNA polynucleotide strands join together?
A
hydrogen bonding between complementary base pairings.
2 bonds between A-T
3 bonds between C-G
16
Q
what are complementary base pairings?
A
each base can only join with 1 particular partner
adenine - thymine
cytosine - guanine. there are always equal amounts of A and T and equal amounts C and G
17
Q
how is the DNA double-helix formed?
A
2 antiparallel (running in opposite directions) polynucleotide strands twist to form the DNA double-helix
18
Q
why did people doubt DNA carried the genetic code?
A
it had a relatively simple chemical composition. some thought genetic information must be carried by proteins which are more chemically varied
19
Q
when was the double-helix discovered?
A
1953, by Watson and Crick, this is also when DNA was shown to be the carrier of the genetic code
20
Q
what is RNA made from?
A
a single polynucleotide chain, its much shorter than most DNA polynucleotides
21
Q
what does DNA do to itself before cell division?
A
it copies itself so each new cell has the full amount of DNA
22
Q
what is semi-conservative replication?
A
half of the strands in each new DNA molecule are from the original DNA molecule. this means there is genetic continuity between generations of cells
23
Q
what is the first step of semi-conservative replication?
A
the enzyme DNA helicase breaks hydrogen bonds between bases on the 2 polynucleotide DNA strands.
this makes helix unwind to form 2 single strands
24
Q
what is the second step of semi-conservative replication?
A
each original strand acts as a template for a new strand.
complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand
25
what is the third step of semi-conservative replication?
condensation reactions join nucleotides of the new strands together - catalysed by the enzyme DNA polymerase
hydrogen bonds form between the bases on the original and new strands
26
what is the fourth step of semi-conservative replication?
each new DNA molecule contains 1 strand from the original DNA molecule and 1 new strand
27
what does antiparallel mean for DNA?
in a DNA helix, the strands run opposite to each other - they're antiparallel
28
what are the ends of DNA strands called?
the ends are slightly different in structure. one end is the 5' end the other is 3'
29
what is the active site of DNA polymerase complementary to?
it is only complementary to the 5’ end of the newly forming DNA strand. so the enzyme can only add nucleotides to the new strand starting at the 5’ end moving to the 3’ end
30
how does DNA polymerase move down each strand?
the new strand is made in a 5' to 3' direction and the template strand is made in a 3' to 5' direction.
because strands in helix are antiparallel, DNA polymerase working on 1 template strand moves in opposite direction to DNA polymerase on other template strand
31
how was the semi-conservative DNA replication theory proven?
Meselson and Stahl's experiment - using 2 different types of isotopes of nitrogen
32
what other theory's of DNA replication were there?
fully conservative model - original DNA strands stay together, and 2 new strands are made
dispersive model of replication - alternating bases stay in the strand then new bases come in, forming a sort of zig zag of new bases
33
How did Meselson and Stahl carry out their experiment?
1. bacteria grown in nutrient broth with heavy nitrogen, bacteria took up heavy nitrogen to make nucleotides for new DNA
2. sample of DNA taken and spun in centrifuge. heavy DNA settles at bottom
3. bacteria put in broth with light nitrogen, and left to replicate once, then another sample taken and spun in centrifuge
4. a new line forms higher up, as each helix has 1 strand of heavy DNA and one strand of light DNA
5. if left to replicate once more in light nitrogen broth and spun in centrifuge. the same line would be present for half and half DNA strands but another would also form even higher with helix's made of 2 strands of light nitrogen
34
what isotopes were used for Meselson and Stahl's experiment?
heavy nitrogen - 15N
| light nitrogen - 14N
35
how did Meselson and Stahl disprove the conservative method of DNA replication?
the 2nd centrifuge would show a line for the original heavy-heavy DNA and another line for the new light-light DNA
36
how did Meselson and Stahl disprove the dispersive method of DNA replication?
the second centrifuge would show a mix, the same as the semi- conservative, but the 3rd centrifuge would still only show one line as a new mix, with more light nucleotides, and every time it is spun a line appears further, and further up
37
how was Meselson and Stahl's experiment proved universal?
other scientists carried out their own experiments to show it was a universal method of DNA replication in all living things
38
how much of a cell's contents is water?
80%
39
what are the properties of water?
```
polar - good solvent
reactive - can be used in hydrolysis
high specific heat capacity
high latent heat of vaporisation
cohesive and adhesive
transparent
variable density
```
40
what is the importance of water being a metabolite?
its a metabolite in loads of important metabolic reactions, like condensation and hydrolysis
e.g. amino acids joined by condensation to make polypeptides
energy from ATP released through hydrolysis
41
how is water a good solvent?
positive and negative ions in ionic compounds more attracted to polar molecule than each other, this causes them to dissociate and dissolve
42
what is the importance of water having a high latent heat of vaporisation?
it helps with temperature control.
| living organisms can use water loss through evaporation to cool down without losing too much water e.g. sweat
43
what is the importance of water being very cohesive and adhesive in plants?
it helps water transport in plants
cohesion between water molecules and adhesion between water and the walls of the xylem allows continuous column of water to move up the xylem
44
what is a metabolic reaction?
a chemical reaction that happens in a living organism to keep the organism alive.
45
what is a metabolite?
a substance involved in a metabolic reaction
46
what makes water a polar molecule?
the electron in a hydrogen atom is shared with oxygen to form bonds, this leaves the other side of the hydrogen with a slight positive charge
the unshared electron on the oxygen give a slight negative charge.
47
what kind of bond happens between water molecule?
hydrogen bonding
| the slightly negatively charge oxygen atoms attract slightly positively-charged hydrogen atoms of other molecules
48
how is water involved in hydrolysis and condensation?
hydrolysis requires a molecule of water to break a bond
| condensation releases a molecule of water as a new bond is formed
49
what does it mean that water has a high latent heat of vaporisation?
it takes a lot of energy to break the hydrogen bonds between water molecules.
so a lot of energy is used
50
what does it mean that water has a high specific heat capacity?
lots of hydrogen bonds between water molecules can absorb a lot of energy
it takes a lot of energy to heat it up
water's SHC is 4184 J/Kg
51
why is water's high specific heat capacity important?
makes water a good temperature buffer
water doesn't experience rapid temperature changes
this makes water a good habitat because the temperature underwater is likely to be more stable than on land.
water inside organisms also has a stable temperature so internal body temperature can be kept constant
enzymes protected against denaturing
52
what does ionic mean?
they're made from 1 positively charged atom or molecule and 1 negatively charged atom or molecule. a lot of important substances in metabolic reactions are ionic
53
what happens when an ions and water interact?
positive end of a water molecule attracted to negative ion, and negative end to a positive ion, this means ions will get surrounded by water molecules, they'll dissolve
water's polarity makes it a useful solvent
54
what is cohesion?
the attraction between molecules of the same type. water molecules are very cohesive because they're polar, and hydrogen bonds can form between molecules
55
what does strong cohesion mean for water?
it helps it flow, making it great for transporting substances
has high surface tension, when it comes into contact with air
56
what's an example of water being good at transporting substances?
water travels in columns up the xylem in plants
57
what does water's high surface tension mean?
sweat forms droplets, which evaporate from the skin to cool an organism down.
pond skaters and some other insects can 'walk' on the surface of water so they can escape predators or find prey
58
how do living organism release energy?
from glucose in respiration, the energy released from glucose is used to make ATP
C6H12O6 + O2 --> CO2 +H2O + ATP
59
what does ATP stand for?
adenosine triphosphate
60
what is the structure of ATP?
its made from the nucleotide base adenine, combined with a ribose sugar and 3 phosphate groups
61
what is a nucleotide derivative?
a modified form of a nucleotide
| e.g. ATP
62
what does ATP do once it's been made?
it diffuses to the part of the cell that needs energy
63
how does ATP release energy?
the energy in ATP is stored in high energy bonds between the phosphate groups. it's released via hydrolysis reactions when a phosphate bond is broken
64
what is ATP broken down into?
ADP and Pi
65
what does ADP stand for?
adenosine diphosphate
66
what does Pi stand for?
inorganic phosphate
67
what is the hydrolysis of ATP catalysed by?
ATP hydrolase
68
how can the hydrolysis of ATP be used efficiently instead of the energy being lost as heat?
ATP hydrolysis can be coupled up to other energy-requiring reactions in the cell so the energy released can be used directly
69
what happens to the inorganic phosphate released in the hydrolysis of ATP?
it can be added to another compound (phosphorylation) which often make the compound more reactive
70
how can ATP be resynthesised?
in a condensation reaction between ADP and the Pi catalysed by the enzyme ATP synthase. this can happen during both respiration and photosynthesis
71
what is the reversible reaction for the hydrolysis / condensation of ATP?
condensation----->
| ADP + Pi ATP
72
what is the structure of ADP?
the nucleotide base adenine, a ribose sugar and 2 phosphates
73
what is an ion?
an atom (or group of atoms) that has an electric charge
74
what is a cation?
an ion with a positive chrge
75
what is an anion?
an ion with a negative charge
76
what is an inorganic ion?
one which doesn't contain carbon (but there are some exceptions)
77
where can inorganic ions be found?
in solution, in the cytoplasms of cells and in the body fluids of organisms
each ion has a specific role , depending on its properties. an ion's role determines whether it is found in high or low concentrations
78
what is the role of iron ions in the body?
to bind to oxygen in the haemoglobin.
| the Fe2+ temporarily becomes an Fe3+ ion, until oxygen is released
79
what is haemoglobin?
a large protein that carries oxygen around the body, in the red blood cells
80
what is haemoglobin made up of?
it's made up of 4 different polypeptide chains, each with an iron ion in the centre(Fe2+)
81
what is the role of hydrogen ions in the body?
pH is calculated based on the concentration of hydrogen ions in the environment. the more H+ present, the lower the pH. enzyme-controlled reactions are all affected by pH
82
what is the role of sodium ions in the body?
to co-transport glucose or amino acids into cells against their concentration gradients alongside Na+
83
what is the role of phosphate ions in the body?
bonds between phosphate groups store energy in ATP.
| the phosphate groups in DNA and RNA allow nucleotides to join up to form the polynucleotides
84
what are the useful structures of DNA?
```
phosphodiester backbone
long molecule
double helix structure
weak hydrogen bonds between base pairs
double stranded
base sequence
base stacking
```
85
how does DNA's phosphodiester backbone aid its function?
it protects the more chemically reactive bases inside the double helix, and prevents the organic bases from reacting with the environment
86
how does DNA being a long molecule aid its function?
it stores a lot of information
87
how does DNA's double helix structure aid its function?
it makes DNA compact
88
how does DNA's weak hydrogen bonds aid its function?
easily broken for DNA replication.
| more hydrogen bonds between cytosine and guanine so DNA with a higher proportion of C-G pairings are more stable
89
how does DNA being double stranded aid its function?
allows replication from template strands
90
how does DNA's base sequence aid its function?
allows information to be stored
91
how does DNA's base stacking aid its function?
these are additional forces between base pairs that hold the molecule together. this makes DNA more stable
92
what is energy used for in living organisms?
keeping body temperature steady
muscle contractions so animals can move
building large molecules from smaller ones
93
Why is ATP so useful?
releases energy in small, manageable amounts
broken down in 1 step reaction
phosphorylates to lower activation energy of biomolecules
rapidly reformed
ATP can't be moved from cell, can't be stored
ATP used for active transport / synthesis
soluble - most biological reactions take place in solution
94
how do carbohydrates and lipids differ to ATP as an energy source?
large quantities present as fat/glycogen
slower to form
energy released in larger less manageable amounts
many reactions required to release energy from glucose
can be stored
glycogen/fat insoluble
95
what are hydrogen bonds?
bonds that form between polar molecules containing hydrogen, they do not result in a permanent structure, and break and reform as water moves
96
why is it important that water is a good solvent?
minerals can be obtained by pond life e.g. phosphate for ATP
| chemical reactions happen faster in solution
97
what is specific heat capacity?
the energy required to increase 1 kg of a substance by 1*C
98
what is latent heat of vaporisation?
energy required to vaporise 1kg of water
99
how does water's variable density aid its function?
when water cools and forms ice, a lattice is formed, which makes the molecules more spread out, and ice is less dense
100
how does ice's light density aid its function?
floats on top of liquid water, insulating the water underneath, so the water below doesn't freeze and organisms don't freeze and can still move.
currents and nutrients can also still circulate in the water
101
how does water's transparency aid its function?
light can pass through so underwater plants can photosynthesise
