A-level Biology > B2 Nucleic Acids > Flashcards

B2 Nucleic Acids Flashcards

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1
Q

What is DNA

A

codes for sequence of AA in primary structure of protein, which determines final 3D structure and function of protein.

essential that cells contain copy of this genetic code & it can be passed onto new cells without being damaged.

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2
Q

What is dna nucleotide monomer made up of

A

deoxyribose (pentose sugar)

nitrogenous base

1 phosphate group.

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3
Q

What’s polymer of nucleotides called

A

Polynucleotide

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4
Q

How is polynucleotide made

A

via condensation reaction

between deoxyribose sugar and phosphate group, creating phosphodiester bond.

Phosphodiester bonds (strong CBs) - help ensure genetic code not broken down

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5
Q

What is name of structure that holds polynucleotide (polymer) together

A

sugar-phosphate ‘backbone’

strong CBs between sugar & phosphate groups hold polymer together.

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6
Q

Where are HB in dna

A

between complementary base pairs.

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7
Q

number of HB between bases in DNA and why it’s important

A

A and T = 2 HBs

C and G = 3 HBs

important = help maintain order of genetic code when DNA replicates.

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8
Q

How structure relates to function in DNA

A

Stable structure - due to sugar-phosphate backbone (CBs) & double helix.

Double stranded - replication can occur using 1 strand as template.

Weak HBs - easy unzipping of 2 strands in double helix during replication.

Large molecule - carry lots of info

Complementary base pairing allows identical copies to be made.

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9
Q

What’s RNA made of

A

polymer of nucleotide formed of ribose, nitrogenous base and phosphate group.

bases = A G C U

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10
Q

How is rna different to dna (talk rna only)

A

RNA = base U instead of T

RNA is relatively short polynucleotide chain & single stranded.

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11
Q

function of RNA

A

copy & transfer genetic code from DNA in nucleus to ribosomes.

Some RNA is combined with proteins to create ribosomes.

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12
Q

What are 3 types of RNA

A

(Messenger) mRNA

(Transfer) tRNA

(Ribosomal) rRNA

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13
Q

What is mRNA

A

copy of gene from DNA

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14
Q

Where is mRNA created

A

in nucleus & then leaves nucleus to carry copy of genetic code of 1 gene to ribosome in cytoplasm.

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15
Q

Why is mRNA able to leave nucleus but DNA can’t

A

DNA too large

risk damage by enzymes - could destroying genetic code permanently.

mRNA much shorter (length of 1 gene, therefore leave nucleus)

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16
Q

Why is mRNA short lived

A

only needed temporarily to help create protein

by time any enzymes could break it down it would’ve already carried out its function.

mRNA is single stranded and every 3 bases in sequence code for specific amino acid, these 3 bases called codons.

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17
Q

Where is tRNA found

A

Only in cytoplasm

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18
Q

What’s rRNA

A

type of RNA that makes up bulk of ribosomes.

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19
Q

Describe shape of tRNA

A

single stranded

folded to create shape that looks like cloverleaf.

held place by HBs

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20
Q

What’s function of tRNA

A

function = to attach to 1 of 20 amino acids & transfer this AA to ribosome to create polypeptide chain.

Specific AAs attach to specific tRNA & determined by 3 bases found on tRNA which’re complementary to 3 bases on mRNA.

These are called anticodon, because they’re complementary to codon on mRNA.

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21
Q

Differences between DNA and RNA monomers

A

DNA - T
RNA - U

DNA - pentose sugar deoxyribose,
RNA - pentose sugar ribose.

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22
Q

Differences between polymers DNA & RNA

A

DNA - larger because it contains approx 23,000 genes (entire genome)

RNA - much shorter because only length of 1 gene

DNA - double stranded
RNA - single stranded

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23
Q

What does ATP stand for

A

Adenosine tri phosphate

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24
Q

What is ATP

A

immediate source of energy for biological processes

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25
What must metabolic reactions in cells have constant steady, supply of
ATP
26
What does ATP contain
3 inorganic phosphate groups Ribose sugar Adenine
27
Why are phosphate groups in ATP described as being inorganic
don’t contain any C atoms
28
What does ADP contain
Adenine Ribose 2 inorganic phosphate groups
29
What does AMP contain
Adenine Ribosome 1 inorganic phosphate group
30
What does adenosine contain
Adenine Ribose
31
In what process is ATP made
Respiration
32
What is ATP made from
ADP and Pi via condenstaion reaction using enzyme ATP synthase
33
What can ATP be hydrolysed into and using what enzyme
ADP and Pi ATP hydrolase
34
Equation for hydrolysis of ATP
ATP + water —> ADP + Pi + Energy
35
What type of molecule is ATP
phosphorylated macromolecule
36
How is energy released in hydrolysis of ATP
By breaking 1 of bond between Pi’s Small amount of energy released to surroundings
37
Why is ATP an immediate energy source
Only 1 bond has to be hydrolysed to release energy
38
Can ATP transfer energy to diff compounds
Yes Pi released during ATP hydrolysis can be bonded onto diff compounds to make them more reactive (Known as phosphorylation)
39
What is 1st ATP property in comparison to glucose
ATP release energy in small, manageable amount so no energy wasted (cells don’t overheat from wasted heat energy + less likely to run out of resources) Comparison to glucose = glucose release large amounts of energy that result in wasted energy
40
What is 2nd ATP property in comparison to glucose
It’s small and soluble to easily transport around cell ATP can move around cytoplasm with ease to provide energy for chem reactions in cells. ATP has this in common with glucose
41
What is 3rd ATP property in comparison to glucose
Only 1 bond’s hydrolysed to release energy -> which’s why energy release is immediate Glucose needs several bonds to break to release all its energy
42
What is 4th ATP property in comparison to glucose
transfer energy to another molecule by transferring 1 of Pi ATP enable phosphorylation, make other compounds more reactive Glucose can’t do this - doesn’t contain Pi
43
What is 5th ATP property in comparison to glucose
ATP can’t pass out cell - cell always has immediate supply of energy Glucose can leave cell - all cells have constant supply of ATP or ADP + Pi, but cell can run out of glucose
44
What bonds hold diff H2O together
HBs
45
Is water polar
Yes its dipolar
46
What are 5 key properties of H2O
Metabolite Solvent High heat capacity - buffers temp Large latent heat of vaporisation - provides cooling effect with loss of H2O through evaporation Strong cohesion between H2O - supports H2O columns + provides surface tension
47
Water is metabolite
in many reactions e.g. hydrolysis, photosynthesis and condensation reaction Because of this 90% blood plasma is water and cytoplasm is largely composed of H2O
48
Strong cohesion of water
H2O stick together by HBs H2O move up xylem in plants due to transpiration its continuous column of water - easier draw up column than individual molecules Cohesion provides surface tension to water enables small invertebrates to move & live on surface, providing them habitat away from predators in water.
49
Large latent heat of vaporisation of water
alot of energy required to convert water (l) to (g) due to HBs, as energy needed to break HBs between water molecules to turn into gas. advantage = water provides significant cooling effect. E.g., humans sweat release water onto skin. Large amounts of heat energy from skin transferred to water to evaporate it, & therefore removing alot of heat & cooling organism.
50
High specific heat capacity of water
alot of energy required to raise temp of water because some heat energy used to break HBs between water molecules. useful to organisms as means temp of water remains relatively stable, even if surrounding temp fluctuates significantly. Therefore, internal temp of plants and animals should remain relatively constant despite outside temp, as large proportion of organism is water. important so enzyme don’t denature or reduce in activity with temp fluctuations. Finally, provides stable enviro, in terms of temperature, for aquatic organisms.
51
Water is good solvent
many substances dissolve in it. Polar molecules dissolve readily in water due to water being dipolar. slight pos charge on H atoms will attract any neg ions solutes and the slight neg charge on the O atoms of water will attract any pos ions in solutes. These polar molecules are often described as hydrophilic, meaning they are attracted to water. Non-polar molecules, such as lipids, cannot dissolve in water and are therefore described as hydrophobic- they are repelled by water. The fact that so many essential polar substances dissolve in water enables them to be transported easily around animals and plants, either in the blood or xylem, to cells they are needed in inside of the organism.
52
Name of process of DNA replication
Semi-conservative replication
53
What must happen before cells divide by mitosis or meiosis
All DNA must replicate to provide copy for new cell
54
What is daughter DNA made of in semi-conservative replication
1 stand from parental DNA and 1 is newly synthesised
55
What are enzymes used in semi-conservative replication
DNA helicase DNA polymerase
56
What happens in semi-conservative replication
1) DNA helicase breaks HBs between complementary base pairs between strands in double helix - double helix unwinds 2) each of separated parental DNA strands act as template , free floating DNA nucleotides in nucleus are attracted to their complementary base pairs on template strands of parental DNA 3) DNA polymerase catalyses joining together of adjacent nucleotides by condensation reaction to form phosphodiester bond 4) 2 sets of daughter DNA contain 1 strand of parental DNA and 1 of newly synthesised strand.
57
Hypothesis of semi-conservative replication
Each replicated dna contains 1 of original DNA strands and 1 newly synthesised dna strand
58
Hypothesis about conservative replication
Original dna remains intact following dna replication adn 2 newly synthesised strands of dna join toghter
59
Define isotope
diff forms of element in which proton and electron number is same, but diff number of neutrons
60
Experiment background info for meselson and stahl
DNA bases are nitrogenous (contain nitrogen) N has 2 isotypes: 14N and I5N. I4N is lighter and I5N is heavier Bacteria take in N isotopes to make new DNA nucleotides.
61
Meselson and stahl
Bacteria take in nitrogen isotopes to make new DNA nucleotides. Therefore: Bacteria grown in medium containing 14N will have DNA which only contains this isotope and be lighter. Bacteria grown in a medium containing I5N will have DNA which only contains this isotope and be heavier. DNA samples can be spun in a centrifuge to confirm density.
62
Name pentose sugars in DNA & RNA
DNA = deoxyribose RNA = ribose
63
State role of DNA in living cells
Base sequence of genes codes for functional RNA & amino acid sequence of polypeptides Genetic info determines inherited characteristics = infuences structure & function of organisms
64
State role of RNA in living organisms
mRNA = complementary sequence to 1 gene from DNA with introns (non-coding regions) spliced out. Codons can be translated into polypeptide by ribosomes rRNA = component of ribosomes (along with proteins) tRNA = supplies complementary amino acid to mRNA codons during translation
65
How do polynucleotides form
Condensation reactions between nucleotides form strong phosphodiester bonds (sugar-phosphate backbone)
66
Which bases are purine and which are pyrimidine
A & G = 2-ring purine bases T & C & U = 1-ring pyrimidine bases
67
Relate structure of DNA to its functions
Sugar-phosphate backbone & many HBs = provide stability Long molecule = stores lots of info Helix = compact for storage in nucleus Base sequence of triplets = code for AAs Double-stranded = semi-conservative replication Complementary base pairing = accurate replication Weak HBs break = strands separate for replication
68
Describe structure of mRNA
Long ribose polynucleotide (shorter than DNA) U instead of T Single-stranded & linear (complementary base pairing) Codon sequence complementary to exons of 1 gene from 1 DNA strand
69
Relate structure of mRNA to its functions
Breaks down quickly = no excess polypeptide forms Ribosome move along strand & tRNA can bind to exposed bases Can be translated into specific polypeptide by ribosomes
70
Describe structure of tRNA
- Single strand of about 80 nucleotides - Folded into clover shape (some paired bases) - Anticodon on 1 end, amino acid binding site on other: a) anticodon binds to complementary mRNA codon b) amino acid corresponds to anticodon
71
Why did scientists initially doubt that DNA carried genetic code
Chemically simple molecule with few components
72
Why is DNA replication described as ‘semi-conservative’
Strands from original DNA molecule acts as a template New DNA molecule contains 1 old strand & 1 new strand
73
Outline process of semi-conservative DNA replication
1. DNA helicase breaks HBs between base pairs 2. Each strand acts as template 3. Free nucleotides from nuclear sap attach to exposed bases by complementary base pairing 4. DNA polymerase catalyses condensation reactions that join adjacent nucleotide on new strand 5. HBs reform
74
Describe meselson-stahl experiment
1. Bacteria grown in medium containing heavy isotope 15N for many gens 2. Some bacteria were moved to medium containing light isotope 14N. Samples were extracted after 1 & 2 cycles of DNA replication 3. Centrifugation formed pellet. Heavier DNA (bases made from 15N) settled closer to bottom of tube
75
How is ATP resynthesised in cells
ATP synthase catalyses condensation reactions between ADP + Pi During photosynthesis & respiration
76
Explain why ATP is suitable as ‘energy currency’ of cells
High energy bonds between phosphate groups Small amounts of energy released at time = less energy wasted as heat Single-step hydrolysis = energy available quickly Readily resynthesised
77
State 4 biologically important properties of water
Due to polarity & inter molecular HBs: - metabolite / solvent for chemical reactions in body - high specific heat capacity - high latent heat of vaporisation - cohesion between molecules
78
Explain why water is significant to living organisms
Solvent for polar molecules during metabolic reactions Enables organisms to avoid fluctuations in core temp Cohesion-tension of water molecules in transpiration stream
79
What are inorganic ions and where are they found in the body
Ions that don’t contain C atoms Found in cytoplasm & extracellular fluid May be in high or very low concs
80
Explain role of H+ in body
High conc of H+ = low (acidic) pH H+ interact with HBs & ionic bonds in tertiary structure of proteins, which can cause them to denature
81
Explain role of iron ions in body
Fe^2+ in porphyrin to form haem group in haemoglobin Haem group has binding site to transport 1 molecule of O2 around body in bloodstream 4 haem groups per haemoglobin molecule
82
Explain role of Na+ in body
Involved in co-transport for absorption of glucose & amino acids in lumen of gut Involved in propagation action potentials in neurons
83
Explain role of phosphate ions in body
Component of: - DNA - ATP - NADP - cAMP
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