9700_w15_qp_42
A paper of Biology, 9700
Questions:
10
Year:
2015
Paper:
4
Variant:
2
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1
The molecules listed below are all associated with respiration. ATP synthase glucose ATP NAD oxaloacetate pyruvate citrate oxygen From these molecules identify: a phosphorylated nucleotide a 3-carbon compound a coenzyme an enzyme A sample of tree sap, rich in sugars, was found to be contaminated with yeast. This sample was tested for the concentration of ethanol at regular intervals. The results are shown in . ethanol concentration / arbitrary units time / hours Calculate the percentage increase in ethanol concentration between 15 and 45 hours. Show your working. answer % Suggest why the concentration of ethanol decreased after 45 hours.
12. Energy and respiration  →  12.2. Respiration
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2
Gold ions (Au3+) are toxic to most microorganisms. However, the bacterium Delftia acidovorans is frequently found in sticky layers, called biofilms, that form on the surface of gold deposits. D. acidovorans produces a peptide synthase that catalyses the synthesis of a small peptide called delftibactin. When isolated, delftibactin can precipitate Au3+ ions as small particles of metallic gold. Delftibactin is a secondary metabolite. Name another example of a secondary metabolite and explain what is meant by the term. example explanation A mutant strain of D. acidovorans has been identified in which the gene coding for peptide synthase is inactive. The wild-type and mutant D. acidovorans were grown on agar plates and then flooded with gold chloride solution, which contains Au3+ ions. The appearance of such a plate after this treatment is shown in . mutant 'DFLGRYRUDQV wild-type 'DFLGRYRUDQV halo of small particles of gold With reference to , suggest how delftibactin protects D. acidovorans from toxic Au3+ ions. Wild-type and mutant D. acidovorans were grown in standardised conditions: • wild-type and mutant bacteria were grown in the absence of Au3+ ions • wild type and mutant bacteria were grown in the presence of Au3+ ions • mutant bacteria were grown in the presence of Au3+ ions and of delftibactin. The results are shown in . number of bacteria (log scale) in the absence of Au3+ ions wild-type bacteria mutant bacteria in the presence of Au3+ ions in the presence of Au3+ ions and delftibactin Key Explain whether or not the results shown in support the idea that delftibactin is protective. The secondary metabolite, delftibactin, could be used to remove the toxic Au3+ ions that are present in the waste produced by gold mining. Describe how delftibactin could be produced on a large scale.
17. Selection and evolution  →  17.2. Natural and artificial selection
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3
The blackcap, Sylvia atricapilla, is a small song bird. It is a summer visitor to parts of northern Europe, where it breeds. Many blackcaps spend the winter in southern Europe, particularly in Spain. As a result of many people putting out food for birds in their gardens, some birds can survive the winter in the UK. Scientists measured the genetic variation between blackcaps from two forest sites in Germany, 800 km apart. Both sites included birds that had overwintered in Spain and in the UK. The measurements were made shortly after the birds returned from their winter feeding grounds. Explain how DNA sequencing can be used to measure the genetic variation of birds. The measurements of genetic variation showed that: • birds that overwinter in the same country (Spain or the UK) shared many alleles, even though they were living 800 km apart in Germany in the summer • birds that overwintered in different countries (Spain or the UK) shared fewer alleles, even though they were living in the same forest in Germany in the summer • the genetic differences between the birds that overwinter in Spain suggest that they no longer breed with those that overwinter in the UK.
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
17. Selection and evolution  →  17.3. Evolution
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4
Bread wheat, Triticum aestivum, is a hexaploid that has developed from diploid wild grasses. Outline the process by which T. aestivum has developed from wild grasses. Wheat seeds begin to germinate when they are in warm conditions and can take up water. shows a germinating wheat seedling. root developing vascular bundles shoot apex coleoptile pericarp and testa aleurone layer endosperm scutellum seed The endosperm contains starch stores. There are also small quantities of sucrose stored in the aleurone layer. Water uptake stimulates the production of a plant growth regulator in the seed, which in turn activates the synthesis of enzymes in the aleurone layer. These enzymes hydrolyse starch to maltose and glucose. Name the plant growth regulator involved in the activation of the synthesis of the enzymes. An investigation was carried out into the role of a gene, TaSUT1, which codes for a sucrose transporter protein, in the germination of wheat seeds. • Wheat seeds were germinated and left to grow for 3, 7 or 10 days. • Samples of tissues from the roots, seeds and shoots of the seedlings were tested for the presence of mRNA transcribed from TaSUT1. • The extracted mRNA was mixed with a probe, and then placed on agarose gel across which a voltage was applied. The results are shown in . root seed days shoot Suggest why the researchers looked for mRNA transcribed from the TaSUT1 gene, rather than for the gene itself. Explain what the results in indicate about the sequence of activity of TaSUT1, from day 3 to day 10, in the root, seed and shoot of a seedling. TaSUT1 codes for the sucrose transporter protein, SUT. This protein transports only sucrose. To investigate where this protein was present in a germinating wheat seedling, a fluorescent antibody for SUT was added to sections of tissues from the seedling. Suggest how this enabled the researchers to determine the areas where SUT was located. Immediately after germination began, SUT was found in the membranes of cells in the aleurone layer. It was also determined that the most common sugar in the endosperm in the first hours after germination was sucrose. Explain how these results support the hypothesis that the first source of sugar for the embryo during germination is sucrose from the aleurone layer and not sugars produced by the hydrolysis of starch. SUT appeared in the developing phloem tissue within three days of the start of germination. Outline how sucrose is transported in phloem.
15. Control and coordination  →  15.2. Control and coordination in plants
2. Biological molecules  →  2.2. Carbohydrates and lipids
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
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5
Explain the meaning of the term biodiversity. The Javan gibbon, Hylobates moloch, is an endangered species. shows a female Javan gibbon with an infant. Javan gibbons live in fragmented patches of undisturbed forest in western Java, Indonesia. Habitat loss has reduced the population of wild gibbons to around 4500 individuals. Suggest why the separation of their habitat into small fragments, rather than a single large area, poses a threat to the long-term survival of this species. Several zoos in Java keep Javan gibbons, but few of these are involved in breeding programmes. Suggest how, other than through captive breeding programmes, zoos in Java could contribute to the conservation of the Javan gibbon.
18. Classification, biodiversity and conservation  →  18.3. Conservation
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6
Scorpions are predatory arthropods. They have a pair of grasping claws at the front of their bodies and a tail with a stinger. The stinger is used to inject venom into their prey to cause paralysis. shows a scorpion. Scorpion venom contains two active components: • a toxin that affects ion channels at synapses of the nervous system of their prey • an inhibitor of an enzyme found at these synapses. For each component of the venom, suggest and explain one way in which it may stop the correct functioning of the synapse. toxin inhibitor Scorpions stand very still on the sand. Moving prey will disturb grains of sand, and scorpions are able to detect this movement using sensory organs, known as slit hairs, at the tips of their legs. Some of the cells of a slit hair act as sensory receptors. State the role of a sensory receptor. When a slit hair is bent by the movement of the sand the potential difference across the cell surface membranes of the slit hair cells becomes more positive inside compared to the outside. State the name given to the initial change in potential difference that may lead to an action potential. Action potentials may then be sent by the cells in the slit hairs to the central nervous system (CNS) of the scorpion. Explain how the scorpion is able to distinguish between a small and a large movement of sand.
15. Control and coordination  →  15.1. Control and coordination in mammals
15. Control and coordination  →  15.2. Control and coordination in plants
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7
One way to estimate the rate of photosynthesis is to measure the rate of uptake of carbon dioxide. shows the relationship between light intensity and relative carbon dioxide uptake and production in a dicotyledonous plant. carbon dioxide uptake State two features of a dicotyledonous leaf that can affect the rate of photosynthesis. Explain the shape of the curve as light intensity increases from 0 to X. The uptake of radioactively-labelled carbon dioxide in chloroplasts was investigated. Three tubes, each containing different components of chloroplasts, were exposed to light. The results of the investigation are shown in Table 7.1. Table 7.1 tube contents uptake of radioactively- labelled carbon dioxide / counts per minute A stroma and grana 96 000 B stroma, ATP and reduced NADP 97 000 C stroma 4 000 Name the substance that combines with carbon dioxide in a chloroplast. Explain why the results in tube B are similar to those in tube A. Explain why the uptake in tube C was less than the uptake in tube B. Complete the following paragraph by using the most suitable words to fill in the gaps. In a photosystem, several hundred accessory pigment molecules surround a primary pigment molecule, called , in the membrane. The position of the primary pigment is also called the . Light energy is absorbed by the accessory pigments and passed on to the primary pigment. Electrons are excited to a higher energy level. They are emitted from the primary pigment and are captured by electron acceptors and eventually pass along the , producing ATP.
13. Photosynthesis  →  13.2. Investigation of limiting factors
13. Photosynthesis  →  13.1. Photosynthesis as an energy transfer process
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8
In shorthorn cattle, coat colour is controlled by a codominant pair of alleles. Coat colour can be red, white or roan, which is a mixture of red and white. The presence of horns is controlled by a separate pair of alleles. The allele coding for horns is recessive to the allele coding for hornless cattle. Choose suitable symbols for the following: allele for red coat colour allele for white coat colour allele for horns allele for no horns Using the symbols you have chosen, write down the genotypes of: white, hornless cattle roan, horned cattle Some fast-growing breeds of cattle have been produced by artificial selection. Outline the ways in which artificial selection differs from natural selection.
17. Selection and evolution  →  17.2. Natural and artificial selection
16. Inheritance  →  16.2. The roles of genes in determining the phenotype
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