2024 bio a level q Flashcards
The ratio of saturated to unsaturated fatty acids in a cell-surface membrane
determines the extent of the membrane’s fluidity.
the scientists observed:
* an increase in the proportion of phospholipids in the phagocytes containing
unsaturated fatty acids
* more phagocytosis.
Suggest and explain why there was more phagocytosis.
more unsaturated fatty acids
more fluid
membrane more fluid
easy to engulf
Describe the processes of facilitated diffusion and active transport.
fd- movement of polar/charged molecules down a conc gradient using carrier/channel proteins
at- atp against gradient using carrier proteins
what are microvilli
large projections of a membrane
itamin A is a fat-soluble substance.
Micelles are involved in the process of vitamin A absorption.
Describe the process of vitamin A absorption into cells lining the ileum
combine/mix W bile salt
-make more soluble in water
- micelles breakdown close to cells.
- diffuses into illeum
Describe the appearance and behaviour of chromosomes during prophase and during
anaphase of mitosis
condense and become more visible
chromosomes on opposite sides
spindle fibres attached to them
Give three structural differences between an mRNA molecule and a tRNA molecule.
mrna- linear, codon, no amino binding site
trna- clover, anticodon, amino binding sit
- 2Suggest one change the scientists could make to both frog populations to increase
the number of mating calls
more sexually active females
8.1 Give two structural features of an aorta wall and explain how they are related to the
function of an aorta.
elastic stretches and recoils to maintain smooth blood pressure
muscle withstands high pressure
smooth endothelium reduces friction
10.2 Describe the role of organelles in the production and release of enzymes by
animal cells.
Do not include details of transcription in your answer.
dna in nucelus cpdes for enzyme/protein production
ribosome es produce enzyme/protein
rer modifies enzyme/protein
mitochondria produce atp
Golgi apparatus make/transport glyxoprotein
vesicle move protein to cell surface membrane
10.3 Describe the structure of ATP.
Outline how named enzymes break down and resynthesise ATP.
ribose adenine and 3 phophstaes
atp to adp + piby atp hydrolase in hydrolsss
adp+pi - atp by atp syhtase in condejnsatoin reaxtoon
mitotic index
number of cells in mitosis / number of cells In field of view
EE2 is contained in human contraceptive pills. Some EE2 is released in human urine
and collects in sewage. Untreated sewage pollutes the water in frog habitats.
Suggest and explain the effect EE2 pollution in frog habitats will have on
frog breeding.
less mating/breeding
fewer adverts ent cells so females not attracted
fewer mating cells as more males not sexually active
1.2 Following the release of acetylcholine into a neuromuscular junction, a muscle
contraction occurs.
Describe the sequence of events, following the release of acetylcholine, that leads to
stimulation of this contraction.
Do not include in your answer the events following the release of calcium ions in the
myofibril.
- Acetylcholine/neurotransmitter diffuses (across
synaptic cleft); - (Acetylcholine/neurotransmitter) attaches to
receptors on the sarcolemma; - Sodium ions enter leading to
depolarisation/action potential; - Calcium (ions) released by
endoplasmic/sarcoplasmic reticulum;
1.3 Inhibitory synapses cause hyperpolarisation in postsynaptic neurones.
Explain how this inhibits synaptic transmission.
- (Inside postsynaptic neurone/membrane/axon)
is more negative - More sodium ions (required to enter) for
depolarisation
2.3 Fast muscle fibres have a higher concentration of glycogen than slow muscle fibres.
Explain how the difference in glycogen concentration is related to the different
properties of these muscle fibres.
- Fast (fibres) contract quickly whereas
slow (fibres) contract slowly - Fast (fibres mainly) use anaerobic respiration
- Fast (fibres) produce ATP quickly
- Glycogen is a store of glucose
3.2 Give three environmental factors that should be controlled when measuring the rate
of photosynthesis in this investigation.
Do not include features of the plant in your answer.
- Intensity/brightness of light (at each wavelength)
- Carbon dioxide concentration
- Temperature
- Water
3.3 Describe how the products of the light-dependent reaction are used in the
light-independent reaction to produce triose phosphate.
- ATP and reduced NADP;
- ATP provides energy;
- GP reduced to triose phosphate;
4.1 In fruit flies, a gene for body colour has a dominant allele for grey body, G, and a
recessive allele for black body, g.
Explain how you would determine if the genotype of a grey fly is homozygous or
heterozygous for body colour.
- Cross with homozygous recessive (fly)
- Black offspring/flies then is heterozygous/G
4.2 In fruit flies, males are XY and females are XX.
A cross between a grey-bodied male fly and a black-bodied female fly produced some
black-bodied females. Explain how this shows that the gene for body colour is not
sex-linked.
(If sex-linked) grey/male fly would only have / pass
on grey/dominant allele
5.1 A weed is a plant growing where it is not wanted. Fat hen is a weed which grows in
some crop fields.
Describe how you could estimate the number of fat hen plants in a field.
- Use a grid
- Method of obtaining random
coordinates/numbers e.g.
calculator/computer/random numbers
table/generator; - Count number/frequency in a quadrat;
- Large sample and calculate mean
number (per quadrat); - Multiply mean number of plants per m2 by area
of field
5.2 In potato plant fields, fat hen plants can grow up to a height of 2 m and absorb large
quantities of nutrients from the soil.
Fat hen has a negative effect on the growth of potato plants.
Use the information provided to explain why.
In your answer, name the type of competition occurring between fat hen plants and
potato plants
- Interspecific (competition);
- Less/no light (for potato plant) so less/no
photosynthesis; - Less nitrates/nitrogen to produce
amino acids/protein/DNA/RNA/ATP
8.3 A technician produced the different concentrations of GA solution from a stock
10–1 mol dm–3 concentration of GA.
Describe how the technician produced the 10–3 mol dm–3 solution.
0.1 parts/cm3 of 10–1/stock/GA and/to 9.9 parts/cm3
of (distilled) water;
7.4 Describe how restriction endonuclease and DNA ligase are used to insert a gene into
a plasmid.
- Restriction endonucleases/enzymes cuts
plasmid - Ligase joins gene/DNA and plasmid
Read the following passage.
The wall gecko is a medium-sized lizard. In an isolated habitat of southern
Italy, the wall gecko shows phenotypic diversity. Scientists investigated
whether disruptive selection was leading to sympatric speciation in the
wall gecko.
Pale geckos live only on walls and are nocturnal (active at night). Dark geckos
live mainly on the dark trunks of olive trees and are diurnal (active during the
day). These diurnal geckos can change skin colour when occupying different
surfaces during the day.
Comparison of mitochondrial genes indicated that the diurnal geckos formed a
distinct genetic group. This comparison also confirmed that all the geckos in
the habitat were of the same species.
The scientists used the mark-release-recapture method to estimate the size of
the population of geckos in the habitat.
5
10
Use the information in the passage and your own knowledge to answer the
following questions.
1 0 . 1 The wall gecko shows phenotypic diversity (lines 1–2).
Suggest two factors that have resulted in this phenotypic diversit
1.Mutations/genotype/alleles;
2. Environment/habitat
3. Epigenetics;
4. Crossing over;
5. Independent segregation/assortment (of
homologous chromosomes);
6. Random fusion of gametes
