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PEARSON EDEXCEL MERGED QUESTION PAPER AND MARK SCHEME FOR JUNE 20249BN0/03 Paper Biology A (Salters Nuffield) AdvancedPAPER 3: General and Practical Applications in Biology
Typology: Exams
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Morning (Time: 2 hours) 9BN0/
Paper reference
Biology A (Salters Nuffield)
PAPER 3: General and Practical Applications in Biology
2
Answer ALL questions.
Write your answers in the spaces provided.
1 One of the first plant species to colonise some habitats is thale cress (Arabidopsis thaliana).
The plant hormone IAA (auxin) is produced in the growing tips of plants such as thale cress.
(Source: Nigel Cattlin / Alamy Stock Photo)
(a) State what is meant by the term colonisation of a habitat. (1)
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(b) One role of IAA is to stimulate the phototropic response of shoots.
Describe how IAA causes a phototropic response in the shoots of a plant. (3)
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(c) Another role of IAA is to stimulate the growth of lateral roots.
The diagram shows the roots of thale cress.
lateral roots
main root
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One type of receptor for IAA is coded for by the tir1 gene.
Scientists have investigated the effect of IAA on the growth of lateral roots in thale cress.
Plants homozygous for a normal tir1 gene and plants homozygous for a mutation in the tir1 gene were used in this investigation.
The plants were treated with different concentrations of IAA.
The mean number of lateral roots produced per mm of main root was recorded.
The graph shows the results of this investigation.
IAA concentration / μmol dm –
Mean number of lateral roots per mm
Key
Thale cress homozygous for:
normal tir1 gene
mutant tir1 gene
(i) Explain why the scientists used plants homozygous for the normal and the mutant tir1 gene in this investigation. (2)
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(ii) Calculate the percentage decrease in mean number of lateral roots for thale cress with the mutant tir1 gene compared to thale cress with the normal tir1 gene at 1.00 μmol dm –3^ of IAA. (1)
Answer .............................................................. %
(iii) Deduce the effect of the mutation in the tir1 gene on the response of thale cress to IAA. (2)
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(Total for Question 1 = 9 marks)
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2 Pathogenic bacteria can become resistant to antibiotics.
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen that is resistant to many antibiotics.
Licochalcone A is a chemical isolated from the liquorice plant.
The antibacterial properties of licochalcone A have been investigated.
The diagram shows the effect of licochalcone A on a bacterial lawn prepared using MRSA.
80 μg
10 μg 20 μg
40 μg
Magnification ×
(a) Complete the table using information from the diagram. (2)
Mass of licochalcone A / μg
Diameter of clear zone / mm
Area of clear zone / mm^2
10 14.5 165
20 16.5 214
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(b) The bacteria used in this investigation are pathogenic.
Describe how filter paper discs containing licochalcone A can be safely placed on the bacterial lawn. (3)
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(c) Explain how an anomalous result could be identified for this investigation. (2)
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(Total for Question 2 = 7 marks)
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3 Photosynthesis takes place in chloroplasts.
(a) The light-dependent processes in photosynthesis can be investigated using the Hill reaction.
The graph shows the effect of three different herbicides, A, B and C, on inhibition of the Hill reaction in isolated chloroplasts.
Concentration of herbicide / nmol dm–
Percentage inhibition of the Hill reaction (%)
Key Herbicide A Herbicide B Herbicide C
(i) State the location of the light-dependent reactions in chloroplasts. (1)
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(ii) Calculate the gradient of the slope for herbicide A at 50% inhibition of the Hill reaction.
Give your answer to two significant figures. (2)
Answer ............................................................................................................................
(iii) Describe the role of chlorophyll in the light-dependent reactions of photosynthesis. (2)
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(b) Describe the role of RUBISCO in the light-independent reactions of photosynthesis. (3)
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(Total for Question 3 = 8 marks)
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4 The photographs show two large marine animals, the great white shark and the humpback whale.
(Source: Sergey Uryadnikov/Shutterstock) (Source: Mircea Costina / Alamy Stock Photo)
Great white shark Humpback whale
A typical adult great white shark has a mass of approximately 600 kg. Adult humpback whales have a mass of approximately 140 000 kg.
The diagram shows the trophic levels for two marine communities, one that includes the great white shark and one that includes the humpback whale.
Tertiary consumer e.g. great white shark
Secondary consumer e.g. fish
Primary consumer e.g. zooplankton
Primary producer e.g. phytoplankton
Secondary consumer e.g. humpback whale
Primary consumer e.g. krill
Primary producer e.g. phytoplankton
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(a) Explain why an area of ocean can support a greater biomass of humpback whales than of great white sharks. (3)
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(b) Phytoplankton are photosynthetic unicellular microorganisms.
Phytoplankton are primary producers in aquatic ecosystems.
(i) State the relationship between gross primary productivity and net primary productivity. (1)
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(ii) The concentration of oxygen in water (dissolved oxygen) can be measured using an oxygen probe.
Explain how an oxygen probe could be used to estimate the effect of temperature on the gross primary productivity (GPP) of phytoplankton. (4)
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(c) Copepods are a group of zooplankton, small animals that feed on phytoplankton.
In an experiment, the production of carbon dioxide and the uptake of oxygen by copepods was measured at 14 °C and at 17 °C.
The results of the experiment are shown in the graph.
Uptake of O 2 per individual / μm 3 hour –
CO 2 produced per individual / μm^3 hour –
Key 17 °C 14 °C
(i) Determine the mean ratio of carbon dioxide produced to oxygen consumed at 17 °C. (1)
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(ii) Deduce two conclusions from the results of this experiment. (2)
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(Total for Question 4 = 11 marks)
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5 Human immune deficiency virus (HIV) can cause acquired immune deficiency syndrome (AIDS).
(a) The diagram shows an HIV virus particle.
capsid
lipid membrane
protease
reverse transcriptase
viral RNA genome
proteins of host cell
gp
(i) State the role of gp120 in the life cycle of the HIV virus. (1)
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(ii) Give a reason why there are proteins from the host cell in the lipid membrane surrounding the virus particle. (1)
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(b) During viral replication, virus mRNA molecules are translated into a virus polyprotein called gag. A polyprotein is a chain of smaller proteins.
This polyprotein is then split into individual proteins by the HIV protease.
The diagram shows the individual proteins produced from the polyprotein by HIV protease.
matrix protein capsid protein SP1 nucleocapsid SP2 p
matrix protein capsid protein SP1 nucleocapsid SP2 p
gag polyprotein
individual proteins
Key site targeted by HIV protease
Deduce how HIV protease can split the gag polyprotein into individual proteins. (3)
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(c) HIV protease inhibitors are used in drugs to treat HIV infection.
In some individuals, the HIV has developed resistance to protease inhibitors.
The graph shows the effect of polyprotein concentration on the initial rate of reaction of normal HIV protease and inhibitor-resistant HIV protease.
Polyprotein concentration / μmol dm–
Initial rate of reaction / μmol dm –3^ s –
normal HIV protease
inhibitor-resistant HIV protease
(i) Calculate the initial rate of reaction in the inhibitor-resistant HIV protease for a polyprotein concentration of 7 μmol dm –3. (2)
Answer ..............................................................
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(ii) Explain the importance of enzyme and substrate concentrations when comparing the initial rates of reaction of different enzymes. (3)
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(Total for Question 5 = 10 marks)
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6 The drug MDMA (ecstasy) can cause damage to the brain.
(a) This damage can cause changes in behaviour. This drug affects serotonin synapses.
(i) Explain how MDMA changes the rate of transmission of nerve impulses across serotonin synapses. (4)
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(ii) The effect of MDMA on the behaviour of mice has been investigated.
Mice were provided with access to two buttons, an MDMA button and a control button.
When they pressed the MDMA button they received a dose of MDMA. When they pressed the control button they received a dose of salt solution.
The buttons were activated for one three-hour period each day.
The graph shows the results of this experiment.
Day
Number of button presses in 3 hours
MDMA button
Control button
Determine the effect of MDMA on the number of button presses made by these mice. (3)
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(b) MDMA is responsible for swelling of the brain resulting in death in some people.
The diagram shows how MDMA can cause brain swelling and death in some people.
Retention of water in the body
Fall in blood solute concentration
Swelling of the brain cells
Constriction of blood vessels in the brain
Death
Brain cells regulate their volume using active transport of sodium ions.
(i) State what is meant by active transport. (2)
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(ii) Explain how the active transport of sodium ions can regulate brain cell volume. (3)
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(iii) Explain why swelling of the brain cells will result in vasoconstriction. (2)
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(iv) Explain why vasoconstriction will result in the death of brain cells. (2)
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(Total for Question 6 = 16 marks)
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*** 7** Sports injuries can be treated to reduce pain caused by muscle cramp.
Ice massage, ice pack and cold-water immersion are three different types of treatment.
The compound action potential (CAP) is a measure of the sum of all action potentials in a muscle.
In one investigation, the effects of these treatments on the CAP in a leg muscle were investigated.
The diagram shows the latency, duration and amplitude for a CAP.
stimulus
time
latency duration
amplitude