Paper 2 PPQs Flashcards by daisy barlow

Exercise causes an increase in heart rate.
Describe the role of receptors and of the nervous system in this process (4 marks)

Chemoreceptors (in the carotid artery) detect a rise in CO2/carbonic acid concentration in blood OR detect a fall in blood pH
Send impulses to medulla oblongata.
Which sends more impulses to the SAN
Along the sympathetic nerve

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See question attached (3 marks)

There is less Malonyl-CoA
CPT1 transports more fatty acids into the mitochondria
Respiration of fatty acids provides ATP for exercise.

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Explain how using the SIT could reduce transmission of dengue (2 marks)

They compete with males to mate
So they do not reproduce

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Describe how the mark-release-recapture method could be used to determine the size of a mosquito population (4 marks)

Capture, mark and release.
Ensure mark is not toxic/ doesn’t increase chance of predation.
Leave time for the mosquitos to disperse before second sampling
Population= (number of individuals in 1st sample x number of individuals in second sample) / number of marked individuals recaptured

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Scientists compared the length of of time that trained and untrained mice could carry out prolonged exercise. The trained mice were able to exercise for longer. Explain why (3 marks)

Trained mice can carry out aerobic respiration for longer so more ATP can be produced.
This delays anaerobic respiration.
So no lactate produced.

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See image attached (2 marks)

Adult fibres peak at a higher mode of 50 micrometres whereas young fibres peak at a mode of 30micrometres.
The adult mice have a wider range of muscle fibres from 18-88micrometres, than the younger mice with a range of 14-47micrometres.

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A student placed chloroplasts in a suspension that had the same water potential as the chloroplasts before an experiment. Explain why it was important that these water potentials were the same (2 marks)

Prevents movement of water molecules into or out of the chloroplasts by osmosis
Chloroplasts do not burst or shrivel

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Explain why the student set up tube 1 (2 marks)
Explain the results in tube 3 (2 marks)

To show that light does not affect DCPIP
To show that chloroplasts are required
Reduction of DCPIP by electrons
From chlorophyll/light dependant reaction

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Explains the advantage of the student using the IC50 in this investigator (1 mark)

Cans compare different concentrations of chemicals/weedkiller
Can compare different chemicals/weedkillers
Provides a standard/reference point

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Explain how chemicals which inhibit the decolourisation of DCPIP could slow the growth of weeds. (2 marks)

Less ATP produced
Less NADPH produced
Less GP converted to TP

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Suggest one way in which an increase in the uptake of phosphate could increase plant growth (1 mark)

Used to produce DNA

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Suggest one way in which mycorrhiza fungi benefit from their association with plants (1 mark)

Receive carbohydrates produced by the plant

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Explain why an increase in shoot biomass can be taken as a measurement of net primary productivity (2 marks)

Represents the dry mass of carbon (because biomass is made from what’s left over after respiration.
So represents gross primary production - respiratory losses

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Give 2 reasons why pancreas transplants are not used for the treatment of type 2 diabetes (2 marks)

Their cells do not respond to insulin
Their pancreas still produces insulin
Better treated by changing diet/exercise

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Suggest how transcription factors can reprogrammed cells to form iPS cells (2 marks)

Attach to DNA/ promoter region
Stimulate/inhibit transcription

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Explain the role of reverse transcriptase in RT-PCR (1 mark)

Produces (c)DNA using (m)RNA

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Explain the role of DNA polymerase in RT-PCR (1 mark)

Joins adjacent nucleotides (by forming phosphodiester bonds)
To produce DNA

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Any DNA in the sample is hydrolysed by enzymes before the sample is added to the reaction mixture in RT-PCR. Explain why (2 marks)

To remove any DNA present
As otherwise it would be amplified

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Suggest one reason why DNA replication stops in the polymerase chain reaction (1 mark)

Limited number of primers/nucleotides

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Scientists have used RT-PCR to detect the presence of different RNA viruses in patients suffering from respiratory diseases. They produced a variety of primers. Explain why (2 marks)

Base sequences differ
Different complementary primers required

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Lord Howe island in the Tasman sea possesses two species of palm tree which have arisen via sympathies speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowing times of the two species are different. Using the information, suggest how these two species of palm tree arose by sympatric speciation (6 marks).

Occurs in the same population/in the same environment
Variation in the flowering times of the original population due to mutations.
Reproductive isolation
Different alleles passed on (in each reproductively isolated population)
Disruptive (natural) selection
Tow populations are separate species when they can no longer interbreed to produce fertile offspring.

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Explain how donepezil could improve communication between nerve cells (3 marks)

Less/no acetylcholine broken down
Acetylene choline attaches to receptors
Na+ enters to reach threshold for depolarisation

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Suggest an explain two reasons why there is a high frequency of the E280A mutation in Yaramul (2 marks)

It is an isolated town so inbreeding occurs
Allele is inherited from the common ancestor

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Explain why natural selection has not reduced the frequency of the E280A mutation in the population (2 marks)

AD develops late/age 49
Have already reproduced

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The age at which the E280A mutation is expressed to cause AD can vary. Suggest and explain one reason for this (2 marks)

Environmental factors/epistasis Methylation of DNA/acetylation of histones

Suggest an explanation for the results found in lines 19-21 by the scientists. (2 marks)

One person was homozygous dominant

Suggest why a DNA probe for the mutated triplet was not considered a suitable method for detection of the E280A mutation (2 marks)

Triplet/GCA is common so found in other places Would not know if it was the mutation/ produces false positives

Scientists found that in a choice chamber, insects moved for 94% of the time in the more humid side, compared to only 20% of the time in the drier side. The scientists concluded that reduced movement in the drier side was an adaptation that reduced water loss. Use your knowledge of gas exchange in insects to explain how this behaviour would reduce water loss in insects (2 marks)

Less respiration (for movement) so less gas exchange (in drier side) So spiracles open less so less water loss

Describe how a pacinian corpuscle produces a generator potential when stimulated (3 marks)

(Mechanical pressure applied) deforms the stretch-mediated sodium ion channels Sodium ions flow in Causing depolarisation

A student studying figure 4 concluded that as humidity increases, so does movement of the insects. Evaluate the student’s conclusion. (2 marks)

Data shows positive correlation Large sample size so is representative However overlaps in individual experiments for all humidities 70-90% humidity correct as movement only increases after 76% humidity

What does this data suggest about the control of heart rate by the parasympathetic and sympathetic nervous system in response to changes in arterial blood pressure? (3 marks)

ANY 3 FROM Parasympathetic greater effect than sympathetic (because the difference from the normal is greater when PSNS is inhibited) Parasympathetic keeps the heart rate lower Sympathetic keeps the heart rate higher Parasympathetic has a greater effect at high blood pressure (as difference from the normal for PSNS is greater at high blood pressures)

Explain what causes vision in the fovea to be in colour (1 mark)

DIFFERENT cone cells absorb DIFFERENT wavelengths of light

Explain the importance of reflex actions (3 marks)

Escape from predators Prevent burning Find food Find mating partners

User your knowledge of the structure of a neurone to explain why many neural toxins and poisons work at the synapse rather than along the length of the neurone (2 marks)

Myelination of the axon provides protection of the axon/length of neurone from toxins or poisons The synapse is unmyelinated so not protected from chemicals which affect the neural membrane

Describe how the resting potential is established in an axon by the movement of ions across the membrane (2 marks)

Na+/K+ pump actively transports K+ ions into the axon membrane and Na+ ions out of the axon membrane K+ diffuses out of axon in permanently open K+ channels

Sodium and potassium ions can only cross the axon membrane through proteins. Explain why (2 marks)

Because they cannot pass through the phospholipid bilayer Because they are charged and not lipid-soluble

When a neurone transmits a series of impulses, its are of oxygen consumption increases. Explain why (3 marks)

Na+/K+ pump requires energy in the form of ATP So more oxygen needed for aerobic respiration To produce more ATP to actively transport ions across the axon membrane

A myelinated axon conducts impulses faster than a non-myelinated axon. Explain this difference (3 marks)

Depolarisation only occurs at the nodes of ranvier (Action potentials appear to) jump from node to node/ saltatory conduction Action potential does not travel along the whole length of the axon

An effect of heat stress in plants is a decrease in the activity of the enzyme rubisco. A decrease in the activity of an enzyme means that the rate of reaction it catalyses becomes slower, which would limit the rate of photosynthesis. Explain why (2 marks)

Less carbon dioxide reacts with RuBP So less GP

Describe how alterations to tumour surpressor genes can lead to the development of tumours (3 marks)

Increased methylation of tumour suppressor genes Mutations to tumour suppressor genes Tumour suppressor genes are not transcribed OR Amino acid sequence altered Tumour suppressor genes are not transcribed

Explain why a log scale is used to record the growth in a typical population of cells (1 mark)

There is a large range in the number of cells

Describe how you would determine the mean percentage cover for beach grass on a sand dune (3 marks)

1. Method of randomly determining position (of quadrats) e.g. random numbers table/generator; 2. Large number/sample of quadrats; 3. Divide total percentage by number of quadrats/samples/readings;

The scientists concluded that the results shown in figure 5 were due to succession taking place. Use figure 5 to explain why the scientists reached this conclusion (4 marks)

1. Beach grass is the pioneer (species); 2. Pioneers/named species change the (abiotic) environment/habitat/conditions/factors; 4 2. Must convey idea of change being caused by a species 2. Accept example of change e.g. more humus 3. (So) less hostile for named species OR (So) more suitable for named species; 4. Conifer/hardwood trees represent climax community;

Assume climax community = established at 450 years Using evidence from figure 6, what can you conclude about the net primary productivity in the sand dunes that are older than 100 years (2marks)

NPP remains constant GPP and respiration constant

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons Explain how furosemide causes an increase in the volume of urine produced (3 marks)

Water potential of filtrate decreased Less water reabsorbed by osmosis from filtrate In the collecting duct

GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this inhibits postsynaptic neurones (3 marks)

Influx of Cl- means postsynaptic neurones becomes more negative/hyperpolarised Not enough sodium ions enter To reach threshold for depolarisation/action potential

What is meant by a genome? (1 mark)

All of the DNA in an organism/cell

Use the information provided to explain why the number of people showing LP would rapidly increase once selection for this condition had been established (2 marks)

It is a dominant allele Always expressed in phenotype

Lactase persistence is caused by a mutation in DNA. This mutation does not occur in the gene coding for lactase. Suggest and explain how this mutation causes LP. (2 marks) LP= continue producing lactase into adulthood

Mutation in promotor for transcription factor for gene Lactase gene continues to be transcribed

Red-green colour build people have green-sensitive cones but the photorecpetive pigment they contain does not function. People with red-green colourblindness are unable to distinguish between red and green and also other colours. Explain why (3 marks)

Green-sensitive pigment does not function 3 different types of pigment/cone Other colours due to stimulation of more than one pigment/cone

Use your knowledge of fast muscle fibres to explain why the time taken for phosphocreatine to be reformed increases as age increases (4 marks)

1. Fast muscle fibres used for rapid / brief / powerful / strong contractions; 2. Phosphocreatine used up rapidly during contraction / to make ATP; 3. (As people get older) slower metabolic rate / slower ATP production / slower respiration; 4. ATP used to reform phosphocreatine;

Which of the events A to F starts depolarisation? (1 mark)

Suggest two advantages of simple reflexes (2 marks)

1. Rapid 2. Protect against damage to body tissues; 3. Do not have to be learnt; 4. Help escape from predators; 5. Enable homeostatic control.

An axon, P, was found to conduct impulses much faster than other axons in the nerve pathway shown in the diagram. Suggest one feature of axon P that may make this the case and explain why. (2 marks)

Axon P is Myelinated So shows saltatory conduction/ impulses jump between nodes of ranvier

When a nerve impulse arrives at a synapse, it causes the release of neurotransmitter from vesicles in the presynaptic knob. Describe how (3 marks)

1. (Nerve impulse / depolarisation of membrane) causes Ca 2+ channel (proteins) to open; 2. Ca 2+ enter by (facilitated) diffusion; 3. Causes (synaptic) vesicles to FUSE!!!!!! with (presynaptic) membrane; Accept single reference to ions to cover 1 and 2 Penalise once for no reference to ions 1. Reject carrier proteins 3. Reject ref to release of vesicles 3. Ignore vesicles bind to membrane (but accept merge with)

1. Myosin head attaches to actin and bends / performs powerstroke; 2. (This) pulls mitochondria past / along the actin; 3. Other / next myosin head attaches to actin (and bends / performs powerstroke); 1. Accept change shape / change angle 2. Ignore pulls actin along 2. Ignore refs to cytoskeleon Accept plural or singular statements

Suggest one advantage of the movement of mitochondria towards the presynaptic membrane when a nerve impulse arrives at the synapse

Supply ATP To move vesicles/for active transport of ions/for myosin to move past actin OR Re-synthesis/reabsoprtion of neurotransmitter

What does the hardy Weinberg principle predict? (3 marks)

Frequency of alleles (of a particular gene) Will stay constant from one generation to the next Providing no mutation/no selection/population is large/meting at random/population genetically isolated/no migration

If white cats are deaf, will the hardy Weinberg principle hold true for white cats? Why? (2 marks)

No because white/deaf cats are unlikely to survive Will not pass on allele (for deafness/white fur) to next generation

Explain why both types of twins are used in twin studies (2 marks)

Identical twins show the genetic influence on a phenotype Non-identical twins show the environmental influence on a phenotype

The following data is given from the percentage of cases where both twins had developed schizophrenia for identical and non-identical twin pairs. Identical twins = 50% Non-identical twins = 15% What does the data suggest about the relative effects of genetic and environmental influences on the development of schizophrenia? (1 mark)

Genes play a greater role (as MZ concordance higher)

Explain the relationship shown by the graph (2 marks)

Intraspecific competition For food

Natural selection influences the number of eggs laid by birds. Explain why birds that lay fewer than 3 eggs per nest or more than 14 eggs per nest are at a selective disadvantage. (3 marks)

Large number of eggs/above 14 eggs, each individual young will receive less food Low number of eggs/below 3 eggs, higher mortality rates due to disease/ predators So in both cases low number of offspring reach maturity/survive so less likely to pass on alleles

What is allopatric speciation? (2 marks)

New species form From geographically isolated populations

There have been long periods over the last 700,000 years where the water level was much lower and Lake Malawi split up into many smaller lakes. Explain how speciation of chichlids may have occurred following the formation of separate, smaller lakes (4 marks)

In South America, there are several species of guinea pig. Explain how sympathies speciation may have occurred. (3 marks)

Explain how a non-rotating ATP synthase enzyme would cause both the lack of ATP synthesis and the significantly lower pH in the thylakoid lumen (4 marks)

The rotation/spinning of ATP synthase provides the energy to join ADP + Pi As the enzyme cannot rotate, no ATP is synthesised Protons continue to move into the thylakoid lumen by active transport/proton pumping As they cannot move through ATP synthase by facilitated diffusion, they accumulate in the thylakoid lumen, so causing a low/acidic pH

Describe how stimulation of a Pacinian corpuscle produces a generator potential (5 marks)

Stretch mediated sodium ion channels Deformation of sodium channels Sodium channels open Influx of Na+ by diffusion Causes depolarisation

Describe the myogenic stimulation of the heart and how the regular contraction of the atria and ventricles is coordinated. Do not include the autonomic nervous system in your answer (5 marks)

SAN releases wave of electrical activity So atria contract AVN passes electrical activity after a delay Purkyne tissue and bundle of His (transmit electrical activity) Ventricles contract (from the bottom upwards)

(3 marks)

Any 3 from: Significant with age, hyperthyroidism and high blood pressure Most significant risk with high blood pressure No significant risk with high LDL concentration For age/hyperthyroidism/high blood pressure reject the null hypothesis OR For LDL concentration accept the null hypothesis

(2 marks)

Increasing IAA concentration increases plasticity Increase in plasticity results in cell elongation

A technician produced the different concentrations of GA solution from astock 10–1 mol dm–3 concentration of GA. Describe how the technician produced the 10–3 mol dm–3 solution. (1 mark)

1:9 ratio of stock to distilled water THEN 1:9 ratio of 10^-1 solution to distilled water

Describe a suitable procedure the student could follow to investigate the effect of different concentrations of GA on the growth of stem segments. In your answer, you should include the variables that should be controlled in this investigation (5 marks)

1. Use distilled water Use different concentrations of GA Use 10 stem segments in each Petri dish 2. Measure length of stem segments at the start and at the end 3. Place in same volume of GA solution 4. Leave for same period of time 5. Same temperature 6. Same species of plant 7. Same age of plant 8. Same diameter of stem segments

Name the parts labelled A to D (2 marks)

A = mitochondrion B = presynaptic membrane C = synaptic vesicles D = synaptic cleft

Inhibitory synapses cause hyperpolarisation in postsynaptic neurones. Explain how this inhibits synaptic transmission. (2 marks)

Membrane/neurone/axon potential is below resting potential More sodium ions required to enter for depolarisation

(5 marks)

1. No/fewer calcium ions enter synaptic knob OR No/less calcium enter synaptic knob via calcium ion channels; 2. No/fewer synaptic vesicles move to/fuse with presynaptic membrane and no/less glutamate is released; 3. No/less glutamate diffuses across (synaptic cleft); 4. No/less (glutamate attaches) to receptors on the postsynaptic membrane; 5. No/fewer sodium ions enter (postsynaptic neurone) so no/ fewer impulses (sent to brain);

When a study requires patients to record the intensity of their pain, suggest two reasons why it is important to use a statistically valid scale (2 marks)

1. To ensure that the difference is significant OR Valid comparison 2. Pain is subjective

(2 marks)

P = capsule/lamellae (accept connective tissue) Q = axon R = myelin sheath/schwann cells

In this investigation, it is not possible for a student to react in less than 45ms. Suggest one explanation why a value of less than 45ms may be recorded (1 mark)

The student started to move her hand before the ruler was released Or The ruler did not fall vertically Or The ruler was stuck to her skin Or Student B held the ruler too high

In response to touch, nerve impulses can be transmitted at speeds of 76.2m s–1 Suggest three reasons why, in this investigation, the estimated speed of student A’s impulse transmission was less than 76.2 m s–1 (3 marks)

1. Synaptic transmission/neuromuscular junction transmission 2. Time for muscle contraction 3. Time taken for sodium ion channels to open 4. Student was distracted/not concentrating 5. Time taken for coordination/comprehension by the brain

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. (4 marks)

Fast fibres contract quickly whereas slow fibres contract slowly Or Fast fibres used for a short time whereas slow fibres used for a long time Fast fibres use anaerobic respiration Or Slow fibres use aerobic respiration Fast fibres produce ATP quickly Glycogen is a store of glucose (so enables quick production of ATP)

Describe the role of ATP in muscle contraction (2 marks)

To break actinomyosin bridges To move/bend the myosin head/arm Actin filaments are moved inwards For active transport of calcium ions into sarcoplasmic reticulum

Describe and explain how taking creatine supplements and carbohydrate loading can improve the performance of different types of muscle fibres during different types of exercise (5 marks)

In fruit flies, the genes for body colour and for wing development are not on the sex chromosomes. The allele for grey body colour, G, is dominant to the allele for black body colour, g. The allele for long wings, L, is dominant to the allele for short wings, l. A geneticist carried out a cross between fruit flies with grey bodies and long wings (heterozygous for both genes) and fruit flies with black bodies and short wings. The table below shows the results of this cross. Explain the results in the table above (3 marks)

Autosomal linkage No Gl and gL gametes produced OR No Ggll or ggLl offspring produced No crossing over occurred

Mutation is one cause of genetic variation in organisms. Give 3 other causes of genetic variation in organisms (3 marks)

Independent segregation Crossing over Random fusion of gametes

Give one piece of evidence from the diagram above to show that the allele for grey body colour is dominant (1 mark)

Parents 3 and 4 with grey bodies have offspring 9 with a black body (so 3 and 4 are carriers of the recessive allele for black body)

Explain one piece of evidence from the diagram above that the gene for body colour is not on the X chromosome (2 marks)

Mother 2 has male offspring 5 5 would receive a recessive allele from 2

(2 marks)

48%

In genetic crosses the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios. Suggest two reasons why (2 marks)

Lethal genotypes Small sample size Random fusion of gametes Linked genes Epistasis

Use the information provided to explain the results in table 1 (3 marks)

Autosomal linkage Produces fewer offspring that are tall and mottled or short and normal Crossing over occurred

In fruit flies, the genes for body colour and wing length are linked. Use your knowledge of gene linkage to explain these results (4 marks)

Two couples, couple A and couple B, had one or more children affected by a mitochondrial disease. The type of mitochondrial disease was different for each couple. None of the parents showed signs or symptoms of MD. • Couple A had four children who were all affected by an MD. • Couple B had four children and only one was affected by an MD. (b) Use the information in lines 5–9 and your knowledge of inheritance to suggest why: • all of couple A’s children had an MD • only one of couple B’s children had an MD. (4 marks)

A: mutation in mitochondrial DNA in mother So all children got affected mitochondria from mother During formation of mothers egg cells B: mutation occured in cell nucleus of both parents which produced recessive allele Both parents are heterozygous Expect 1 in 4 homozygous recessive so affected

(3 marks)

Less aerobic respiration so less ATP produced Less force due to fewer actin and myosin interactions in muscle Lactate produced in anaerobic respiration leads to muscle fatigue

Suggest how the change in the anticodon of a tRNA leads to MD (lines 10–13) (3 marks)

Change to tRNA leads to wrong amino acid being incorporated into protein; Tertiary structure (of protein) changed; Protein required for oxidative phosphorylation / the Krebs cycle, so less / no ATP made.

3 marks

(Large) number/variety of plant species/populations (More/different) habitats/niches (Greater) variety/types/sources of food

Nutrient recycling occurs rapidly on the group of tropical rainforests (lines 4-5) Explain how two abiotic factors in these rainforests enable the rapid rate of recycling (2 marks)

(Warm so) optimum temperature of enzymes involved in respiration/nitrification/ammonification Water/moisture for metabolic/enzyme reactions Optimum pH for enzymes/respiration/nitrification/ammonification

The recycling of nitrogen-containing compounds from dead organic matter sustains the growth of plants. Describe the roles of bacteria in this recycling (4 marks)

Proteins/amino acids/DNA into ammonium/ammonia By saprobionts Ammonium/ammonia into nitrites and then nitrates By nitrifying bacteria

Farming practices have prevented the natutral regeneration of rainforests by secondary succession Suggest two farming practices that prevent the natural regeneration of rainforests by secondary succession (2 marks)

Crop growth Animal farming/grazing Ploughing Weed killers/herbicides/pesticides Burning Building on land where rainforests previously were

1 mark

Ink and leaf pigments would mix OR With ink origin would be in different position

Describe the method the student used to separate the pigments after the solution of pigments had been applied to the origin. (2 marks)

Level of solvent below origin/line Remove/stop before solvent reaches top/end

1 mark

Oxygen is produced in the light dependant reaction The faster the rate of oxygen production, the faster the rate of the light dependant reaction

In each trial, the scientists collected oxygen for 15 minutes. Calculate the difference in the oxygen produced by the chloroplasts from mutant plants grown in low and high light intensities at a light intensity of 500 μmol photons m–2 s–1 (2 marks)

35-36 umol o2 mg-1 hour-1

The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants at all light intensities. Explain how these data support this suggestion (4 marks)

In natural ecosystems, most of the light falling on producers is not used in photosynthesis. Suggest two reasons why. (2 marks)

Light is reflected Light misses chlorophyll/chloroplasts Light is wrong wavelength CO2 concentration or temperature is a limiting factor

2 marks

1.3 x 10^8

A teacher studying these data with her students told her class that no definite conclusions could be drawn when comparing the mean values in the graph. Suggest why the teacher said this.

No error bars/SD To show if overlap occurs so difference is not significant

Atrazine binds to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain. When treated with atrazine, weeds have been shown to give off small amounts of heat. Suggest an explanation for this observation (1 mark)

Energy not released from high energy electrons (so temperature increases)

1 mark

Large range of numbers

3 marks

After 10 minutes, the tap attached to tube A was closed and the syringe was attached to tube B. Every minute, the syringe plunger was moved until the levels in the U-tube were the same. The reading on the syringe volume scale was then recorded. During the experiment, the coloured liquid in the tubing moved towards tube B. Explain what caused this. (3 marks)

Describe the advantage of the Bohr effect during intense exercise (3 marks)

Suggest one physiological change that would mean that the pCO2 of air breathed out would not increase during exercise. Explain how the physiological change would allow for the removal of the increase in the volume of carbon dioxide produced (2 marks)

GW1516 is a performance-enhancing drug. GW1516 activates AMPK and develops slow muscle fibres at rest. Use diagram above to justify why professional athletes are not allowed to take GW1516. Do not include details of chemiosmotic theory in your answer. (4 marks)

EPO is another performance-enhancing drug. It can increase the haematocrit (the percentage of red blood cells in blood). A heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscle via the coronary arteries. The overuse of EPO can increase the risk of a heart attack. Suggest how. (2 marks)

Causes blood to thicken Could block the coronary arteries OR Slow blood flow OR Cause clots

The normal haematocrit for human males is 47(±5)%. For professional male cyclists, the maximum haematocrit allowed is 50%. A student suggested that professional male cyclists should be allowed to use EPO until their haematocrit is 50%. Give two reasons why this suggestion is not valid. (2 marks)

The body temperature of the insects was largely determined by the temperature they were kept at. At each temperature, the scientists recorded rate of carbon dioxide release by individual insects over time. This rate depends upon spiracles opening or closing. Explain how you could determine the total amount of carbon dioxide secreted at 30 °C during the period of recording. (1 mark)

Determine area under the curve

Suggest an explanation for the effect of temperature on the rate of carbon dioxide release in insects as shown by the graphs (3 marks)

At the end of the investigation, the student noted the freshwater marsh plant had grown 268 mm in height, and now measured 387 mm. She calculated the rate of growth (R) to be 0.097 mm m–1 day–1 Use this information and, substituting height for biomass, use the equation to calculate the duration of the student’s investigation. Give your answer to the nearest full day. Show your working

12 days

Describe the role of saprobionts in the nitrogen cycle (2 marks)

One environmental issue arising from the use of fertilisers is eutrophication. Eutrophication can cause water to become cloudy. You are given samples of water from three different rivers. Describe how you would obtain a quantitative measurement of their cloudiness. (3 marks)

Use of colourimeter Measure the absorbence/transmission of light Example of how method can be standardised eg. Same volume of water, zeroing colourimeter, use same wavelength of light, shake the sample

The scientists concluded that the soil mixture experiment showed there were different communities of bacteria in soils A and B. What evidence from Figure 1 supports their conclusions? Give reasons for your answer. (3 marks)

This method allowed the scientists to estimate the expression of the amoA gene in each culture but not the growth of the bacterial population in each culture. Explain why. (4 marks)

The scientists set up their cultures in sterile glass bottles. Suggest one suitable method for sterilising the bottles and explain why it was necessary to sterilise them. (2 marks)

Boiling water/steam/autoclave/wash in disinfectant/wash in alcohol To remove/kill other bacteria/microorganisms that might break down ammonia

Scientists investigated changes in the use of artificial fertiliser in India between 1970 and 2005. They also investigated changes in the fertiliser response ratio. This ratio shows how many kg of grain are produced for each kg of fertiliser used. The graph shows their results in the form the scientists presented them. (A hectare is a unit of area commonly used in agriculture) Use the data in the graph above to evaluate the use of artificial fertilisers on grain-producing crops in India. (2 marks)

To kill any fungus/bacteria on the surface of seeds or in the soil So only the added fungus has any effect

Scientists investigated the effect of a mycorrhizal fungus on the growth of pea plants with a nitrate fertiliser or an ammonium fertiliser. The fertilisers were identical, except for nitrate or ammonium. The scientists took pea seeds and sterilised their surfaces. They planted the seeds in soil that had been heated to 85 °C for 2 days before use. The soil was sand that contained no mineral ions useful to the plants. The pea plants were divided into four groups, A, B, C and D. • Group A – heat-treated mycorrhizal fungus added, nitrate fertiliser • Group B – mycorrhizal fungus added, nitrate fertiliser • Group C – heat-treated mycorrhizal fungus added, ammonium fertiliser • Group D – mycorrhizal fungus added, ammonium fertiliser The heat-treated fungus had been heated to 120 °C for 1 hour. Explain how groups A and C act as controls. (2 marks)

So that effects of nitrate or ammonium alone could be seen So only the added fungus has any effect

What conclusions can be drawn from the data in the table about the following? The effects of the fungus on growth of the pea plants. The effects of nitrate fertiliser and ammonium fertiliser on growth of the pea plants. (4 marks)

The scientists determined the dry mass of the roots and shoots separately. Themreason for this was they were interested in the ratio of shoot to root growth of pea plants. It is the shoot of the pea plant that is harvested for commercial purposes. Explain why determination of dry mass was an appropriate method to use in this investigation. (2 marks)

Dry mass measures/determines increase in biological/organic material Water content varies

The scientists determined the dry mass of the roots and shoots separately. The reason for this was they were interested in the ratio of shoot to root growth of pea plants. It is the shoot of the pea plant that is harvested for commercial purposes. Which treatment gave the best results in commercial terms and why? (2 marks)

Fungus with nitrate-containing fertiliser gave largest shoot:root ratio And largest dry mass of shoot 6.09:1 compared with ammonium containing fertiliser 4.18:1 Any 2 points

Suggest one way in which insulin receptors may be abnormal (1 mark)

Have a different tertiary structure

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration (2 marks)

More insulin binds to receptors More glucose moves into cells by facilitated diffusion

Describe the role of glucagon in gluconeogenesis (2 marks)

Stimulates/activates enzymes Convert glycogen and amino acids to glucose

3 marks

IAA is produced in the shoot tip Diffuses into cells Cell elongation on one side of the shoot due to accumulation of IAA

2 marks

Taxis Find a mate, avoid competition, avoid predators

Suggest reasons their conclusions may not be valid (3 marks)

The retina of an owl has a high density of rod cells. Explain how this enables an owl to hunt its prey at night. Do not refer to rhodopsin in your answer. (3 marks)

High visual sensitivity Multiple rod cells connected to the same bipolar neurone Enough neurotransmitter to overcome threshold OR spatial summation to overcome threshold

Explain how a resting potential of -70mV is maintained in the sensory neurone (2 marks)

Axon membrane more permeable to K+ and less permeable to Na+ Na+ ions actively transported out and K+ ions in

Explain how applying pressure to the Pacinian corpuscle produces a change in membrane potential (3 marks)

Pressure causes deformation of lamellae in pacinian corpuscle Stretch mediated sodium ion channels open and Influx of Na+ ion to sensory neurone Greater pressure more channels open/ Na+ ions enter

Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower responses to stimuli. (2 marks)

No saltatory conduction More depolarisation over length/area of membranes

Give two safety precautions that should be followed when dissecting a heart (1 mark)

4 marks

Loss of nutrients into Lake Malawi has resulted in a decrease in some fish populations (lines 12–13). Explain why. (4 marks)

1 mark

Less chance of recapturing marked fish Unlikely that fish distribute evenly/randomly

Suggest and explain how digesting insects helps sundew to grow in soil with very low concentrations of some nutrients (2 marks)

Mark in pairs so 1 and 2 or 3 and 4

Describe how you would determine the mean percentage cover for beach grass on a sand dune. (3 marks)

Explain how a resting potential is maintained across the axon membrane in a neurone. (3 marks)

Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon. (3 marks)

A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV to 0 mV. Explain why. (3 marks)

Describe the sequence of events involved in transmission across a cholinergic synapse. Do not include details on the breakdown of acetylcholine in your answer. (5 marks)

Scientists investigated the effect of a decrease in pH on muscle contraction. The scientists did the investigation with four different preparations of isolated muscle tissue: A, B, C and D. A - mouse muscle fibres at typical pH of mouse muscle tissue (control 1). B - mouse muscle fibres at 0.5 pH units below typical pH. C - rabbit muscle fibres at typical pH of rabbit muscle tissue (control 2). D - rabbit muscle fibres at 0.5 pH units below typical pH. They measured the force of muscle contraction of the muscle fibres at 12 °C, 22°C and 32 °C The graph shows the results the scientists obtained for B and D compared with the appropriate control. (4 marks)

Their hypothesis is that an increase in the concentration of Pi prevents the release of calcium ions within muscle tissues. Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force of muscle contraction. (3 marks)

3 marks

During vigorous exercise, the pH of skeletal muscle tissue falls. This fall in pH leads to a reduction in the ability of calcium ions to stimulate muscle contraction. Suggest how. (3 marks)

Suggest an explanation for these results. (2 marks)

2 marks

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes. (3 marks)

Describe the role of glucagon in gluconeogenesis. Do not include the second messenger model in your answer (2 marks)

Activates/stimulates enzymes Glycerol/amino acids to glucose

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes (2 marks)

Diabetes can damage the nervous system. The response of the rats with diabetes is different from the response of the healthy rats. Use your knowledge of the control of heart rate by the nervous system to suggest an explanation for these results. (4 marks)

The non-homologous section of an X chromosome

Describe how ultrafiltration occurs in a glomerulus. (3 marks)

3 marks

2 marks

Affects water potential of blood So affects volume of urine produced

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons. Explain how furosemide causes an increase in the volume of urine produced. (3 marks)

3 marks

Guppies with large brains are better at identifying predators. The scientists found that only female guppies with large brains were attracted to male guppies bright in colour. Suggest and explain the advantage of this behaviour to the population of guppies (3 marks)

Guppies with large brains are better at identifying predators. The scientists found that only female guppies with large brains were attracted to male guppies bright in colour. Describe how the behaviour of female guppies could result in sympatric speciation (3 marks)

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the two species are different. Using this information, suggest how these two species of palm tree arose by sympatric speciation. (5 marks)

Suggest and explain two reasons why there is a high frequency of the E280A mutation in Yaramul (lines 13–15). (2 marks)

Explain why natural selection has not reduced the frequency of the E280A mutation in the population (lines 16–17). (2 marks)

To reduce the damage caused by insect pests, some farmers spray their fields of crop plants with pesticide. Many of these pesticides have been shown to cause environmental damage. Bt plants have been genetically modified to produce a toxin that kills insect pests. The use of Bt crop plants has led to a reduction in the use of pesticides. Scientists have found that some species of insect pest have become resistant to the toxin produced by the Bt crop plants. The figure below shows information about the use of Bt crops and the number of species of insect pest resistant to the Bt toxin in one country. (1 mark)

There was a time lag between the introduction of Bt crops and the appearance of the first insect species that was resistant to the Bt toxin. Explain why there was a time lag. (3 marks)

There are nine subspecies of giraffe. These subspecies evolved when populations of giraffe were separated for long time periods. Each subspecies has distinct coloured skin markings. Some biologists have suggested that up to six of these subspecies should be classified as different species. Explain how different subspecies of giraffe may have evolved from a common ancestor. Use information from the passage in your answer. (5 marks)

Mitochondrial DNA (mtDNA) is a small circular DNA molecule located in mitochondria. It is 16 569 nucleotides long and contains 37 genes and a control region. Sports scientists investigated whether a mutation in the control region of mtDNA in human males was related to an ability to exercise for longer. • The males in Group T had thymine at nucleotide position 16 519 • The males in Group C had a mutation resulting in cytosine at nucleotide position 16 519 A student concluded from Figure 1 and Figure 2 that training has a positive effect on VO2 max and CS activity. Evaluate the student’s conclusion. (3 marks)

Mitochondrial DNA (mtDNA) is a small circular DNA molecule located in mitochondria. It is 16 569 nucleotides long and contains 37 genes and a control region. Sports scientists investigated whether a mutation in the control region of mtDNA in human males was related to an ability to exercise for longer. • The males in Group T had thymine at nucleotide position 16 519 • The males in Group C had a mutation resulting in cytosine at nucleotide position 16 519 See image The mitochondrial DNA (mtDNA) control region is an area of mtDNA that is non-coding. This region stimulates the synthesis of both mtDNA and mitochondrial messenger RNA. Use this information to suggest two reasons why the mutation at nucleotide position 16 519 could lead to the differences seen in Figure 2. (2 marks)

Increased methylation of the promoter region of a tumour suppressor gene causes one type of human throat cancer. In this type of throat cancer, cancer cells are able to pass on the increased methylation to daughter cells. The methylation is caused by an enzyme called DNMT. Scientists have found that a chemical in green tea, called EGCG, is a competitive inhibitor of DNMT. EGCG enables daughter cells to produce messenger RNA (mRNA) from the tumour suppressor gene. Suggest how EGCG allows the production of mRNA in daughter cells. (3 marks)

Describe how alterations to tumour suppressor genes can lead to the development of tumours. (3 marks)

Using all the information provided, evaluate the use of the two types of RNAi in treating hepatitis B in humans. Do not refer in your answer to how RNAi reduces HBV replication. (5 marks)

3 marks

Myelodysplastic syndromes (MDS) are a group of malignant cancers. In MDS, the bone marrow does not produce healthy blood cells. Haematopoietic stem cell transplantation (HSCT) is one treatment for MDS. In HSCT, the patient receives stem cells from the bone marrow of a person who does not have MDS. Before the treatment starts, the patient’s faulty bone marrow is destroyed. For some patients, HSCT is an effective treatment for MDS. Explain how. (3 marks)

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of protein in their urine). The scientists carried out further work to investigate how the transplanted stem cells developed after transplantation. • The scientists transplanted stem cells from wild type male mice into AS female mice. • After 20 weeks, they found that the quantity of protein in the urine of these female mice had significantly decreased. • They examined cells from glomeruli in the female mice. Some of these cells contained a Y chromosome. Suggest how the transplanted stem cells reduce proteinuria. (2 marks)

In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group. Previously, the viruses infected only one species of frog. Suggest and explain how the viruses became able to infect other species of frog. (2 marks)

Name two techniques the scientists may have used when analysing viral DNA to determine that the viruses were closely related. (1 mark)

Determining the genome of the viruses could allow scientists to develop a vaccine. Explain how. (2 marks)

Describe how the B lymphocytes of a frog would respond to vaccination against Ranavirus. You can assume that the B lymphocytes of a frog respond in the same way as B lymphocytes of a human. Do not include details of the cellular response in your answer. (3 marks)

Plants transport sucrose from leaves to other tissues for growth and storage. SUT1 is a sucrose co-transporter protein. Scientists investigated whether the cells of tobacco plant leaves used SUT1 to transport sucrose to other tissues. (The scientists used a radioactively labelled DNA probe to show that the cells of tobacco plant leaves contained the SUT1 gene. Describe how they would do this. Do not include PCR in your answer. (4 marks)

What is a DNA probe? (2 marks)

Describe how the DNA is broken down into smaller fragments. (2 marks)

What is meant by a non-coding base sequence? (1 mark)

Mycobacterium tuberculosis causes tuberculosis. The DNA of M. tuberculosis contains a direct repeat (DR) region. The DR region consists of 43 different, non-coding base sequences called spacers. Each spacer is found in a specific place in the DR region. In different strains of M. tuberculosis, some of these spacers have been lost. Name the process by which these spacers have been lost (1 mark)

Deletion mutation

Doctors can use the method with DNA probes to identify the specific strain of M. tuberculosis infecting a patient. This is very important when there is an outbreak of a number of cases of tuberculosis in a city. Suggest and explain why it is important to be able to identify the specific strain of M. tuberculosis infecting a patient. (2 marks)

Microinjection of DNA into fertilised egg cells is a frequent method of producing transgenic fish. However, the insertion of the transferred gene into nuclear DNA may be delayed. Consequently, the offspring of transgenic fish may not possess the desired characteristic. Suggest and explain how delayed insertion of the GH gene could produce offspring of transgenic fish without the desired characteristic. (2 marks)

Suggest two features of the structure of different proteins that enable them to be separated by gel electrophoresis. (2 marks)

Any additional DNA in the PCR sample is hydrolysed by enzymes before the sample is added to the reaction mixture. Explain why. (2 marks)

Paper 2 PPQs Flashcards

(197 cards)