past paper notes Flashcards
explain the role of auxin in cell elongation? /8
1) auxin binds to receptor
2) in cell surface membrane
3) auxin increases proton pump activity
4) more protons enter cell wall
5) cell wall becomes acidic
6) expansins activated
7) expansins breaks bonds between microfibrils
8) K+ enters the cell
9) water potential of cell decreases
more water enter cell by osmosis
10) turgor pressure
11) ref to acid growth hypothesis
Explain, using examples, how the environment may affect the phenotype of individual
organisms. /7
1) phenotype results from interaction of genotype and environment
2) environment may, limit / modify, expression of gene
3) continuous variation example ; e.g. size / mass / height
4) qualified ; e.g. because, food / nutrients / ions, missing or malnutrition occurs
5) environment may, trigger / switch on, gene ;
6) such as temperature and change in animal colour
7) or UV light and melanin production
8) environment effect usually greater on polygenes
9) environment may induce mutation (affecting phenotype) ;
Outline how a gene mutation may occur. /4
1) random/ spontaneous
2) change in sequence of base
3) base substitution
4) causes frameshift
State two reasons why people may have objections to the growth of insect-resistant GM
crops. /2
1) resistance may be transferred to wild plants
2) contamination of food marketed as organic
3) may kill, useful insects / pollinators
4) decrease in biodiversity
5) potential health risks of humans (eating GM crops)
6) insects may become resistant (to toxin)
Describe the properties of mtDNA that make it suitable for the study of evolution. /3
1) mutations occur at constant rate
2) mutations occur at faster rate than, nuclear / chromosomal, DNA ;
3) not protected by histone proteins ;
4) no enzymes to repair DNA mutations ;
5) many copies of mtDNA per cell ;
6) no mixing of DNA at fertilisation (as only inherited from mother)
or
circular DNA, so no crossing over
Explain how rice is adapted to grow with its roots submerged in water /5
1) arenchyma in roots and stem allows oxygen to diffuse to roots for aerobic respiration
2) high tolerance to ethanol
3) root cells produce ethanol dehydrogenase to break down ethanol in anaerobic respiration
4) some leaves trap air underwater due to ridges on leaves
Name the two enzymes present on the dip stick and outline the reaction catalysed by each
enzyme. /2
1) enzyme: glucose oxidase
reaction: glucose reacts
with glucose oxidase to
form hydrogen peroxide
and gluconic acid
2) enzyme: peroxidase
reaction: hydrogen
peroxide reacts with
peroxidase and
chromogen to form
coloured solution
Sea otters may spend up to five minutes under water while searching for food. During this
time, respiration in anaerobic conditions takes place.
When a sea otter first returns to the surface of the ocean, its breathing is faster and deeper
than normal.
Explain why its breathing is faster and deeper than normal. /3
1) as anaerobic respiration causes formation of lactate in muscles this causes oxygen debt
2) so more oxygen needed than normal
3) to break down lactate to pyruvate
4) and for rexoygenation of haemoglobin
Describe the proteins that are involved in the contraction of a sarcomere. /4
myosin is a fibrous protein with a globular head
actin is a globular protein
troponin and tropomyosin. tropomyosin
actin has binding site for myosin head
Outline the effects of mutant alleles on the phenotype in albinism and haemophilia. /7
albinism:
1) the TYR gene which
codes for the enzyme
tyrosinase is mutated.
it is caused by
recessive ellele.
2) results in absence of
melanin
3) causes skin burn, pale
skin and pink eyes and
blurry vision
haemophilia:
1) caused by recessive
allele
2) fatctor 8 is not
produced
3) sex linked as gene is
on X chromosome
4) this prevents blood
clotting
5) leads to excessive
bleeding
Describe how random sampling can be used to assess the distribution and abundance of
plants in an area. /6
1) area marked out as grid
2) coordinates obtained using random coordinate generator
3) quadrats used
4) quadrats placed at random coordinates
5) the size of quadrats should be same
6) count number within quadrat using blaun blanquet
7) repeat sampling
Suggest measures that could help to protect wild populations of grey wolves in
south-west Europe. /3
national parks
provide them with healthcare and food
can be used to raise awareness by educating others
ban hunting
Explain how the results of this technique would be used to confirm that phycoerythrin is
present in red algae and not present in a plant with green leaves. /3
calculate Rf value
compare Rf values of both pigments
find pigment present on chromatogram from red algae and absent from green leaves
identify pigments using reference point
Suggest why Venus fly trap plants need to capture insects. /1
poor mineral content in soil
Dogs have an exceptionally good sense of smell. They can detect molecules in the air with a
concentration of one part per trillion (1012).
(a) Olfactory receptor cells are the sensory receptors in the nasal cavity that respond to chemicals
in the air. They function in a similar way to the chemoreceptor cells in the taste buds of the
tongue.
Describe how olfactory receptor cells in the nasal cavity of dogs respond to chemicals to
generate an action potential. /5
chemicals binds to receptor cells
Na+ ions diffuse into cells via microvilli
membrane depolarised
receptor potential generated
voltage gated Ca2+ channels open and Ca2+ diffuses into cell
vesicles containing neurotransmitters move and fuse with cell membrane
exocytosis of neurotransmitters
neurotransmitters binds to receptor
receptor cells acts as transducer
Describe the methods used to conserve endangered plant species. /7
botanic gardens
can be used for research controlled growing conditions such as temperature, light intensity and CO2 concentration plants controlled so can be reintroduced back into wild store seeds seeds regularly checked for viability maintains genetic diversity seeds can be germinated prior to introduction back into natural habitat
Explain the term F1 generation. /2
first generation of offspring
it is cross between recessive homozygous chromosomes and dominant homozygous
chromosomes
offpsring will be heterozygous
Suggest two reasons why phenotypic ratios in the F2 generation do not always match
the expected ratios /2
linkage
environmental effects
mutations
Explain why improving milk yields in cattle by selective breeding can be more challenging
than improving yields of crops by selective breeding /3
takes longer time to mature
fewer offsprings per cross
ethical issues
cattle require more care
milk yield must be measured over period of time ;
difficulty in identifying suitable males for use in crosses
Describe the role of abscisic acid in stomatal closure. /4
abscisic acid binds to receptors
proton pumps are inhibited
opens Ca2+ channels
Ca2+ acts as second messenger
K+ diffuses out of guard cell
water potential of cell increases
water leaves cell by osmosis
cell becomes flaccid
Describe the role of aquaporins in osmoregulation./3
(aquaporins are) water channel (proteins) ;
(more) aquaporins increase (cell surface) membrane permeability (to water)
of collecting duct (cells)
allow water to, be reabsorbed / move into tissue fluid or blood ;
Explain what is meant by continuous variation and how it can be caused. /3
continuous variation has range of values
phenotypes are quantitative
polygenic/ controlled by many genes
different genes have an additive effect
environmental factors contribute to variation
Outline the steps required to prepare the genome of an individual so that the genome is ready
for analysis using a microarray chip. /3
extract DNA from cells
cut DNA into small fragments using restriction enzymes
denature to make single stranded DNA
tagged with fluorescent dye
Explain the need for a reduction division during meiosis. /4
meiosis produces gametes
gametes fuse to form zygote
zygote will have maternal and paternal chromosomes
gametes are haploid so zygote is diploid
prevents doubling of chromosome number
Describe the functions of the internal membranes of the chloroplast in photosynthesis /7
photosynthetic / named / primary / accessory, pigments to absorb light (energy) ;
photosystems / antenna complex and reaction centre / light harvesting structures ;
photoactivation / electrons excited / emission of electrons ;
electrons move along electron transport chain ;
(cyclic / non-cyclic) photophosphorylation / light-dependent stage ;
site of photolysis / location of oxygen-evolving complex ;
thylakoids stacked to form grana
gives large surface area ;
thylakoid space or lumen to, form proton gradient / have high concentration of protons ;
thylakoid membrane is (relatively) impermeable, to maintain the proton gradient
ATP synthase to make ATP;
chemiosmosis
Suggest reasons why more fish species than mammal species are endangered. /4
fish:
overfishing ;
(on water / at sea) difficult to enforce protective, laws / regulations
trophy hunting ;
climate change qualified ; e.g. increased ocean temperatures /
predatory species moving into new areas now water is warmer
pollution qualified ; e.g. plastics in the sea / oil spills / eutrophication
there are more species of fish than there are species of mammals ;
mammals:
more conservation projects for mammals
laws in place, banning hunting / protecting mammals
Describe the role of seed banks in the protection of endangered species. /7
seed banks collects seed
long term storage
storage to prevent germination
seeds are kept frozen
seeds are regularly checked for viability
seeds re stocked regularly
seeds maintain genetic diversity
can be used to increase number in future
maintains biodiversity
for research
Suggest why a microarray is suitable for identifying the function of the transcription factor. /3
transcription factors regulate expression of genes
microarray can detect expression of genes
by fluorescence between two samples
State two benefits to farmers of insect resistance in crops. /2
increase yield
increase quality of yield
no pesticides need to be used
State two reasons why people may have objections to the growth of insect-resistant GM
crops. /2
resistance may be transferred to wild plants
contamination of food marketed as organic
may kill, useful insects / pollinators
decrease in biodiversity
potential health risks of
humans (eating GM crops)
insects may become resistant (to toxin)
Suggest measures that could help to protect wild populations of grey wolves in
south-west Europe. /3
national parks
provide them with healthcare and food
can be used to raise awareness by educating others
ban hunting
Explain why it is important to the gene pool of Sumatran tigers to move tigers from one zoo to
another. /3
create genetic diversity among them
increases hytrozygosity
hybrid vigor
reduces inbreeding depression
reduces chances of harmful recessive alleles together
The AAV vector used was unable to replicate itself within the target cells.
Suggest why the researchers chose a vector that could not replicate. /2
To prevent virus from spreading into the body
to limit side effects
Suggest and explain three ways in which the tank environment may make the phenotype of
a captive fish different from a wild fish. /3
controlled conditions so phenotype less varied
more oxygen so larger
less space so smaller
Explain why ATP is needed in the first part of glycolysis. /2
ATP needed for phosphorylation of glucose
this activates glucose
Explain the social benefits of this example of gene editing. /3
increases yield
improves quality of food
more income for farmers
cheaper
spend less on pesticides
State the role of the enzyme cascade. /1
amplifies signal for faster response
Explain how very dry conditions cause CO2 concentration to become the main limiting
factor of photosynthesis in plants. /3
humidity causes stomata to close
due to water stress
ABA causes stomata to close to prevent water loss
Explain why the lumen of the afferent blood vessel needs to be wider than the lumen of the
efferent blood vessel. /2
to force out filterate from glomeruli into bowman’s capsule
small substances like glucose get pushed out but large substances like proteins cant
some reabsorbed back into blood at efferent blood vessel
Explain why the reaction that takes place at high temperatures in C3 plants reduces the
rate of photosynthesis. /2
oxygen combines with RuBP
so less oxygen will combine with RuBP
Explain why bioinformatics was used to compare these gene sequences and suggest a
conclusion that could be made from the percentage similarity data obtained. /2
why:
fast and accurate
more percentage similarity means more recent accestor
stroma has higher pH when H+ move out into thylakoid space
leads to increased H+ concentration in thylakoid space
then H+ diffuses back into stroma through ATP synthase
Describe the procedure of embryo transfer in a mammal such as a camel. /4
make male and and females camel mate
and remove embryo from mated female
select healthy embryo
may freeze embryo for later use
implant embryo in different female uterus
which is surrogate mother
Explain the relationship between the absorption spectrum of the main chloroplast pigments
in a species of plant and the action spectrum for photosynthesis for that species. /2
absorption spectrum shows absorption of wavelength of light by photosynthetic pigments
action spectrum shows the rate of photosynthesis
higher absorption gives higher photosynthesis
Name three molecules, other than coenzymes, that are found in the mitochondrial matrix
and explain their role in aerobic respiration. /3
pyruvate for links reaction
oxaloacetate to make citrate
citrate to make reduced NAD
enzymes to catalyse link reaction and krebs cycle
oxygen to accept protons
water as a solvent
DNA to make respiratory enzymes
Suggest and explain how Pi
is transported across the inner membrane of the
mitochondrion into the matrix. /2
Pi by facilitated diffusion
Pi and H+ move together
as H+ ions diffuse through ATP synthase
Suggest the advantages of linking ATP transport to ADP transport across the inner
membrane of the mitochondrion. /2
constant supply of ADP
so ATP can be continued to be made
Outline how vigorous, uniform varieties of maize were developed by selective breeding. /4
breed plants with desired characteristics
breed offspring for many generations
so plants get smaller this causes inbreeding depression
cross pollinate 2 inbred lines, this is hybridisation
gives hybrid vigour in offspring
F1 seeds have same genotype
Describe and explain the action of ADH on the cells of the collecting duct when the water
potential of the blood decreases. /5
detected by osmoreceptors in hypothalamus
pituitary gland releases ADH
ADH binds to receptors on collecting duct
g protein activated which activates adenyl cyclase
adenyl cyclase synthesises cAMP
cAMP causes protein kinase to be activated
so vesicles containing aquaporins fuse with cell surface membrane of collecting duct and makes it permeable
so water from collecting duct moves into blood by osmosis
Explain why calvin cycle is described as a cycle? /2
no start and end, point / molecules ;
all, molecules / intermediates, present all the time ;
ribulose bisphosphate / RuBP / 5C molecule, is regenerated
Give reasons why low genetic variation may decrease the long-term survival of a species. /3
less able able, to, adapt
little variation for selection to act on ;
few useful / beneficial, alleles ;
all / most, (could be) killed by same, disease / selection pressure ;
if due to small population size this decreases species survival chance
Outline the similarities in structure between a neuromuscular junction and a cholinergic
synapse. /4
Na+ enters post synaptic membrane
both have presynaptic and post synaptic membrane
have receptors for ACh
acetylcholine is vesicles
many mitochondria
synaptic cleft
Medicine is defined as the diagnosis, treatment and prevention of disease.
Outline the different ways in which genetic technology can be applied to medicine, with reference
to named diseases. /7
genetic engineering is treatment from GM bacteria
make insulin (drug for diabetes)
make factor VIII (drug for haemophilia) ;
make adenosine deaminase (drug for SCID) ;
genetic, screening / diagnosis / testing ;
(detect) BRCA1 / BRCA2 ;
(detect number of repeats / allele for) Huntington’s ;
(detect allele for) cystic fibrosis / CFTR ;
example of action if diagnosis positive ;
gene therapy ;
insert / add, normal allele into (named), cells / tissue (of person) ;
to treat, eye disease(s) / LCA / Leber’s congenital amaurosis ;
to treat SCID
Coenzymes are important in aerobic respiration.
Outline the roles of named coenzymes in aerobic respiration. /5
NAD and FAD
coenzymes are dehydrogenase enzymes
coenzymes get reduced in glycolysis, links reaction and krebs cycle by accepting proton
and then release hydrogen at oxidative phosphorylation at end of cristae
coenzyme A:
binds to acetyl
acetyl + 2C fragment + oxaloacetate = citrate
joins links reaction and krebs cycle
Describe two processes in the liver that are stimulated by glucagon. /2
glycogenolysis- it is the break down of glycose to glucose
gluconeogeneis- it is the amino acids/ lipids to glucose
Explain how different types of gene mutation can affect the phenotype and outline the effects
of the mutant alleles that cause Huntington’s disease on the phenotype of a person. /9
base substitution
does not have a significant effect on phenotype
base, insertion / deletion leads to, frame shift / described
has significant effect on phenotype
change in, primary structure / amino acid sequence / polypeptide made
change in, tertiary structure
loss of function in protein
premature) stop codon
Huntinton’s disease
mutant allele is dominant
dominant, allele has more repeats of base triplet CAG (than normal)
heterozygote will have disease
brain cells die more rapidly
involuntary movements
onset in middle age
greater number of CAG repeats affects, earlier onset / severity of disease
Tumours can form in the liver.
Explain how a liver tumour develops. /2
uncontrolled mitosis
abnormal mass of cells formed
no programmed cell death
mutation of oncogene
Describe and explain one characteristic of mtDNA that makes it more useful than using
nuclear DNA to provide evidence of evolution. /2
1) large quantities in the cell - so easier to extract
2) small genome size- so easier to locate specific section of DNA to test
3) mtDNA is a single copy of DNA- so only mutation causes it to change
4) inherited maternally- all mtDNA sections are shared between all members of family
5) faster molecular clock - more accurate time estimate
Explain why the production of memory cells prevents the gene therapy from working in
long-term chronic conditions such as cystic fibrosis. /3
repeat treatment causes rapid immune response
so target cells short lived
decrease in gene expression
With reference to the three types of vectors that are commonly used, discuss the challenges
in choosing appropriate vectors for use in gene therapy.
Do not include problems associated with an immune response in your answer. /4
liposomes: low ability to add gene into target cells
naked DNA: has to be injected into cells
low efficiency of cellular uptake
rapidly broken down
viruses: small packaging capacity
cause mutation in host DNA
(i) A region that contains voltage-gated channel proteins.
(i) A region that contains ligand-gated channel proteins
(i) pre synaptic membrane
(ii) post synaptic membrane
Outline the steps involved in the introduction of disease resistance to varieties of wheat. /5
select plant resistant to wheat
by exposing plants to disease to show resistance
breed selected plants with resistance
grow offsprings
select offspring with resistance and breed together
repeat for many generations
