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
