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1
Q

Describe how a sample of chloroplasts could be isolates from leaves

A

Break open cells and filter
In cold, isotonic and buffered solution
Centrifuge and remove nuclei
Centrifuge at higher speeds chloroplasts settle out

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2
Q

Describe how acetylcoenzyme A is formed in the link reaction

A

Oxidation/hydrogen removed from pyruvate and carbon dioxide released
Addition of co enzyme A

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3
Q

Purification ponds only work efficiently when they are shallow and warm. Explain why

A

Sufficient light for photosynthesis
Warm leads to faster enzyme activity, so faster bacterial respiration and decomposition
So faster photoynthesis ( as respiration by bacteria produces CO2 used in photosynthesis)
Increased growth

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4
Q

Explain the advantage of having both algae and bacteria in a purification pond

A

Breakdown organic matter by enzymes from bacteria
Ammonia used by algae to make proteins
Algae photosynthesise
Bacterial respiration uses O2
Respiration allows for growth of bacteria

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5
Q

Explain why a statistical test should be applied to the data obtained in this investigation

A

To determine the probability of results being due to chance

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6
Q

Give 2 types of factors that cause PHENOTYPIC variation

A

Environment
Mutation/meiosis/alleles

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7
Q

What is Allopatric speciaton

A

New species form from different populations
In different areas/isolated populations

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8
Q

What is sympatric speciation

A

Formation of new species/reproductive isolation
From a population in the same area/ without geographical isolation

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9
Q

Describe one way which scientists could find out whether organisms from 2 diff populations belong to same species

A

Breed together
If fertile offspring then same species

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10
Q

Explain how sympatric speciation may have occured (in relation to question)

A

Mutation occurs

Correct e.g. of isolating mechanism
e.g.
temporal − different breeding seasons / feeding times /
ecological / behavioural − different courtship displays / different niches / habitats / feeding areas /
mechanical − mismatch of reproductive parts /
gamete incompatibility − sperm killed in female’s reproductive tract /
hybrid inviability / hybrid infertility;
Ignore references to “genetic isolation” or “reproductive isolation”
Different selection pressures operate / changes in allele frequency / divergence of gene

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11
Q

Explain the advantage of presenting the results as a ratio

A

•allows for comparison
• sample sizes may vary

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12
Q

Viruses infect only one species. Suggest and explain how the viruses became able to infect other species of frog

A

Mutation in Viral dna
Altered tertiary structure
Allows attachment proteins to bind to other species

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13
Q

Name techniques scientists use when analysing viral DNA to determine viruses were closely related

A

Genetic Dna fingerprinting
Gel electrophoresis
Dna sequencing
Polymerase chain reaction

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14
Q

Determining genome of viruses allows scientists to develop vaccine. How?

A

Scientists could identify proteins
Then identify potential antigens

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15
Q

Describe how B lymphocytes respond to vaccination against virus
Dont include cellular response

A

B cell divides by mitosis
To produce plasma cells which produce antibodies
B cells also produce memory cells

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16
Q

Genome

A

All the DNA in an organism

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17
Q

Explain why antibody binds to transcription factor

A

It has a specific binding site
Complementary to Transcription factor

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18
Q

Suggest how single stranded cDNA could prevent transcription of the question gene

A

Bind to promoter region

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19
Q

Describe roles of 2 enzymes used to insert DNA fragments into plasmids

A

DNA LIGASE
joins vector DNA and foreign DNA forming phosphodiester bonds

RESTRICTION endonuclease cut plasmid/ hydrolyse dna?

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20
Q

Suggest 2 features of the structure of different proteins that enable them to be separated by electrophoresis

A

Primary structure/tertiary structure
R groups

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21
Q

Dna probe

A

Short single stranded DNA with complementary base sequence to target DNA (radioactive labelled by a fluorescent molecule)

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22
Q

Fertillised egg cell (zygote) is made up of what and what else do they do

A

Totipotent stem cells
They divide rapidly by mitosis producing genetically identical daughter cells
Can also produce any type of body cells BECAUSE they translate part of their Dna

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23
Q

Which types of cells are vital for growth and repair of damaged tissues

A

Multipotent and unipotent (1) stem cells

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24
Q

Which types of cells are the only ones which can divide by mitosis

A

STEM CELLS

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25
Production of IPS
Laboratory grown pluripotent cells produced from human somatic cells using certain protein transcription factors. Not identical to pluripotent stem cells but capable of self renewal- providing limitless supply in medical research and removes ethical issues of using embryonic stem cells in medical research
26
Doninant characteristic rules
Affected offspring must have at least one affected parent Unaffected parents only have unaffected offspring If both parents are affected and produce an unaffected offspring, both parents must be heterozygous
27
Suggest how a mutation can spread
Founder effect/migration/interbreeding
28
DESCRIBE how alterations to tumour suppressor genes can lead to the development of tumours
Increased methylation Mutation in tumour suppressor genes Tumour suppressor genes are not transcribed/expressed Results in uncontrollable cell division
29
Explain advantage of growing plants in tissue culture
Will be clones and have desired characteristics
30
Suggest how these type of stem cells( related to the question) can cause harm
Might divide uncontrollably Leads to formation of a tumour/cancer
31
What does a large SD suggest (a very wide range)
Not much increase, no better than control
32
Describe method to find mean number of () per mm2
Measure diameter, calculate area Using micrometer eyepiece graticule Count number of () and calculate mean
33
Epigenetics
Heritable changes to gene function Without changes to the base sequence of DNA
34
Explain how increased methylation could lead to cancer
Methyl groups added to tumour suppressor gene Transcription of tumour suppressor gene is inhibited Leading to uncontrolled cell division
35
Give one way in which benign tumours differ from malignant tumours
Cells of benign tumours cannot spread to other parts of the body/metastasise Whereas cells of malignant tumours can
36
Codominant alleles
Both alleles expressed within the phenotype
37
Phenotype
Expression of its genetic constitution and its interaction with its environment
38
Explain why males are more likely than females to show a phenotype produced by a recessive allele carried on X chromosomes
Males have one allele Females need two recessive alleles must be homozygous recessive
39
Sex linked gene
Gene located on the X chromosome
40
Genes that are linked are on the same chromosome
41
Describe how behaviour can result in sympatric speciation If related to a question also talk about
Not geographically isolated Leads to reproductive isolation Separate gene pools Change in allelic frequencies Cannot breed to produce fertile offspring (Occurring in the same area) Mutations causes (whatever question gives e.g diff breeding times/ occupy diff habitat/courtship) Reproductive isolation
42
Gene pool
All the alleles in a population
43
Suggest one reason why DNA replication stops in the polymerase chain reaction
Limited number of nucleotides Dna polymerase also eventually denatures
44
Describe two ways in which both types of tumour may cause harm to the body
May damage organ concerned May cause blockage
45
Explain the link between sunbathing and skin cancer
Suns radiation contains ultra violet radiation Which causes mutation of genes which control cell division
46
Suggest why fair skinned people are at a greater risk if skin cancer than darker skinned people when bathinf
Fair skin has less melanin which protects against ultraviolet radiation
47
Suggest why people with a family of history of cancer are at a greater risk of cancer than those with no family history of cancer
Because cancer has genetic component + gene which gives predisposition to cause cancer
48
Describe how altered DNA may lead to cancer
Dna altered by mutation Mutation changes base sequence of gene controlling cell growth Change in primary structure producing non functional protein Tumour surpressor genes produce proteins that inhibit cell division Uncontrolled cell division leads to malignant tumour
49
Correlation coefficient
Allows to see correlation between two variables
50
Give two reasons why bacteria are able to use human DNA to produce human proteins
Genetic code is universal Translation is universal Transcription is universal
51
Suggest and explain one reason why bacteria might not produce every human protein
Bacteria cannot remove introns
52
Explain the purpose of a marker gene
Allows detection of genetically modified cells
53
Describe how this Dna could be screened for all known mutations in both genes
Use of PCR to amplify sample Use restriction endonuclease to cut DNA Separate DNA fragments using electrophoresis addition of DNA probe and binds Mutation identified by fluorescence/radioactivity
54
Describe how HIV is replicated once inside helper T cells
RNA converted into DNA using reverse transcriptase DNA inserted into helper tcell DNA transcribed into HIV mRNA HIV mRNA translated into HIV proteins
55
Give one example of using monoclonal antibodies in a medical treatment
Targets drugs
56
Describe role of antibodies in producing a positive result in an ELISA test
First antibody binds to antigen as they are complementary Second antibody with enzyme attached is added Second antibody attaches to antigen Substrate added and colour change
57
Explain how HIV affects production of antibodies when AIDS develops in a person
LESS antibody produces because HIV destroys Thelper cells So less B cells activated Less B cells divide by mitosis into plasma cells
58
Use your knowledge of antigen antibody complexes to suggest how monoclonal antibodies prevent [ } damaging other cells
Monoclonal antibody forms antigen-antibody complex so none of the [anti-antibody can bind watever in the question] can bind Monoclonal antibody does not damage the cell
59
Explain why antibody only damages specific cells
Has a specific tertiary structure Which is complementary to one antigen Antigen to this antibody only found on [specific cells in question]
60
Suggest practical method to test for memory cells
Inject vaccine Memory cells would product antibody faster/immune response is quicker
61
Suggest 2 advantages of simple reflex arcs
Rapid Protect against damage from body tissues Does not have to be learnt Help escape from predators Enable homeostatic control
62
Taxis
Moves towards or away from directional stimuli
63
Kinesis
Movement is random
64
Stimulus
Detectable change in environment. External (light intensity,temp,pressure) or internal(change in pH,glucose conc)
65
IAA in the shoots
Promotes cell elongation IAA synthesises in the shoot tips and diffuses into the growing regions Light causes movement of IAA from the light side to shaded side Higher conc of IAA on the shaded side Causes directional growth as there is greater cell elongation on shaded side Shaded side grows faster and causes shoot to bend towards the light
66
IAA in the roots
Inhibits cell elongation IAA synthesised in the root tips ans then diffuses into the growing regions Light causes movement of IAA from light side to shaded side and towards gravity Higher conc of IAA on the shaded side Cell elongation inhibited on shaded side Results in directional growth away from light and towards gravity
67
Simple reflex arc
Only involves 3 neurones
68
Synapses ensure that nerve impulses only travel in one direction How
Neurotransmitters only stored in the pre-synaptic neurone Neurotransmitter receptors only on post synaptic membrane
69
Features of axons that conduct impulses faster and why
Myelinated Show saltatory conduction/ jumping of nerve impulses Larger diameter so larger surface area of channel proteins Less resistance of flow of ions
70
Explain how a resting potential is maintained across the axon membrane in a neurone
Higher conc of potassium ions inside and higher conc of sodium ions inside Membrane more permeable to potassium ions Sodium ions actively transported out and potassium Ions in
71
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon
Myelinated axon provides electrical insulation and saltatory conduction Depolarisation only occurs at the nodes of ranvier However in non-myelinated axon depolarisation occurs along whole length of axon
72
Resting potential -70mv to 0mv after adding respiratory inhibitor Why
Respiratory inhibitor so no atp produced No active transport of ions No net movement of sodium and potassium ions
73
Types of stimuli eye receptors might respond to
Light Pressure Touch Temperature Chemicals Noise Smell
74
Student did not draw a line of best fit Why
Not possible to predict intermediate values No mean values
75
Student did not carry our repeats but was still able to carry our statistical test Why
Collected paired data
76
Channel proteins on presynaptic neurones are involved in reflex responses. Explain how
Allow calcium ions in At end of presynaptic neurone Causing the release of a neurotransmitter
77
After exercise some atp used to re-establish resting potential. Explain how
Sodium potassium pump Sodium out potassium in
78
Describe how the resting potential is established in an axon by the movement of ions across the membrane
Pump of sodium ions out Diffusion of potassium ions out of axon/little diffusion of sodium ions into axon
79
Sodium and potassium ions can only cross the axon membrane through proteins Why
Cannot pass through phospholipid bilayer Because not lipid soluble/charged
80
Production of action potential=depolarisation?
81
Damage to myelin sheath of neurones can lead to problems controlling contraction of muscles. Suggest why
Action potentials travel slower So muscles contract slower
82
What happens when calcium ion channel proteins close
Less diffusion of calcium ions into the synaptic knob of presynaptic neurone Synaptic vesiclss dont fuse with the presynaptic neurone membrane so dont release neurotransmitter So neurotransmitter doesn’t diffuse across the synapse and bind to receptor on post synaptic membrane No action potential No depolarisation as sodium ion channels do not open
83
Other than temperature give 2 factors that affect the speed of nerve impulses
Myelination Axon diamater
84
As a neurone transmits an impulse its rate of oxygen consumption increases Why
Atp required for active transport
85
Describe how a resting potential is maintained in a neurone
Active transport/pumping out of sodium ions Out of neurone Different permeabillity to sodium and potassium ions Membrane more permeable to potassium ions Diffusion of potassium ions out
86
Potential across the membrane is reversed when an action potential is produced. How
Sodium ion channel proteins open Sodium ions diffuse in
87
SYNAPSE: describe the events leading to the release of acetylcholine and binding to post synaptic membrane
Depolarisation of presynaptic membrane Calcium ion channel proteins open and calcium ions enter the synaptic knob via facilitated diffusion Calcium ions activate enzymes which cause synaptic vesicles to fuse with presynaptic membrane and release acetylcholine neurotransmitter Acetylcholine diffuses across the synaptic cleft Acetylcholine binds to receptors on post synaptic membrane Sodium ions enter leading to depolarisation
88
Binding of GABA causes chloride ions to enter post synaptic neurones Explain how this inhibits transmission of nerve impulses
Neurone becomes more negative More sodium ions required to reach threshold For action potential/depolarisation
89
Myelination affects rate of conduction of nerve impulse How
Depolarisation only at node of ranvier Fewer jumps
90
Describe how inhibition of acetylcholineesterase affects action of synpases
Acetylcholine not broken doen Sodium ions continue to enter
91
Refractory period
Limits number of impulses per second Period of time between threshold and resting membrane potential When maximum frequency reached, no further increase in information Time taken to restore resting potential
92
How is a control group treated
Given the thing that theyre tested in the question Otherwise treated exactly the same
93
Suggest how you could determine the dry mass of plant material
Heat at 100 degrees celcius Weigh and heat until no further change in mass
94
Advantage of using dry mass and not fresh mass to compare yield of plants
Water content variable Will not affect dry mass
95
Downsides of monoculture
Diseases and insects can spread from plant to plant quickly Reducing biodiversity through loss of niches reduction in variety of food sources
96
Why cant most organisms use atmospheric nitrogen gas
Chemically inert
97
Whats erosion
Once rock has been weakened and broken by weathering it can be moved to another place by ice wind or gravity
98
Phosphorus cycle
Phospholipids, RNA + DNA from dead organisms into phosphate ions Decomposed by saprobionts Phosphate ions also found in waste and remains e.g bones Phosphate ions transported by streams rivers and lakes Form sedimentary rock Weathering and erosion of rocks helps phosphate ions dissolve in ocean+lakes+soils Phosphate becomes ready for absorption by plans to incorporate into new biomass
99
How is the energy of light converted into chemical energy in LDR
Electrons excited Use of electron carriers Production of ATP
100
* if scientists conduct an experiment and increase variable but products/results stay the same, something else LF
101
Suitable units for measuring rate of photosynthesis
Co2 used Per unit of time
102
Why would reducing light intensity reduce oxygen released
Light intensity limiting factor Fewer electrons released from chlorophyll Less photolysis so less oxygen
103
Evaluate suggestion that increase in temp will not affect oxygen released
No affect because photolysis does not require an enzyme May affect because increased temperature increased respiration Respiration uses oxygen
104
Describe how NADP is reduced in the LDR
Electrons from chlorophyll
105
Aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration Why
Oxygen final electron acceptor Oxidative phosphorylation occurs in Aerobic respiration Anaerobic respiration only glycolysis no KC/LR
106
How pyruvate transported into the mitochondrial matrix
Actively
107
Natural vs agricultural ecosystems
Natural ecosystems recycle their inorganic ions but agricultural the crops are harvested/removed so less recycling of inorganic ions *nitrogen required to produce proteins and DNA foe growth so less growth
108
Environmental impact of using fertilisers
Reduced species diversity- plants which are adapted to souls with high in nitrate concentrations outcompete other species Environmental issues- in agricultural ecosystems crops are removed and less decomposition so less nitrate/phosphate returned to soil. *issue fixed with fertillisers Leaching- inorganic fertiliser sometimes leads to more ions being applied to the soil than taken up by the plants. The ions dissolve in the water and are washed from soil into streams rivers and lakes
109
What measurements required to calculate rate of CO2 production
Volume of CO2 given off From known area In a set time
110
Units for gross productivity
Unit of energy per area
111
How can net productivity show little increase
Net productivity= gross productivity - respiratory losses Increase in respiration Or Decrease in gross productivity
112
Reason for conserving woodlands
Conserving habitats/niches Increases biodiversity Tourism Reduces erosion/eutrophication

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