9700_m23_qp_12
A paper of Biology, 9700
Questions:
40
Year:
2023
Paper:
1
Variant:
2
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2
A student calibrated an eyepiece graticule using a stage micrometer.  Each division of the stage micrometer was 0.01 mm.  With a 10 magnification objective lens, 10 eyepiece graticule units matched 10 divisions on the stage micrometer. The same microscope was used with a 40, instead of a 10, magnification objective lens to measure the diameter of an alveolus. The diameter of the alveolus was found to be 96 eyepiece graticule units. The eyepiece lens was not changed. What is the best estimate for the diameter of the alveolus?
1. Cell structure  →  1.1. The microscope in cell studies
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7
To estimate the concentration of glucose in an unknown solution, equal volumes of a range of known concentrations of glucose were each mixed with the same excess volume of Benedict’s solution. After mixing, the solutions were placed in a thermostatically controlled water-bath at 90 C for three minutes. The unknown solution was then treated in the same way and the colours of the known and unknown solutions compared. What is the independent variable in this procedure?
2. Biological molecules  →  2.1. Testing for biological molecules
14. Homeostasis  →  14.1. Homeostasis in mammals
13. Photosynthesis  →  13.2. Investigation of limiting factors
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16
A scientist investigated the rate of breakdown of hydrogen peroxide. Four experiments were carried out using different mixtures.  substrate only  substrate + enzyme  substrate + enzyme + competitive inhibitor  substrate + enzyme + non-competitive inhibitor The results are sketched in the graph. rate of breakdown of hydrogen peroxide substrate concentration Which row shows the correct lines for two of the experimental mixtures?
3. Enzymes  →  3.2. Factors that affect enzyme action
3. Enzymes  →  3.1. Mode of action of enzymes
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20
The estimated total number of red blood cells in the human body is 2.5  1013. It is estimated that, each day, 2.5  1011 red blood cells are removed from the circulation and are replaced by stem cells in the bone marrow. Which percentage of the total number of red blood cells is replaced each day?
8. Transport in mammals  →  8.1. The circulatory system
5. The mitotic cell cycle  →  5.1. Replication and division of nuclei and cells
8. Transport in mammals  →  8.2. Transport of oxygen and carbon dioxide
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23
The PDx1 protein is found in a wide range of animal species where it is regarded as essential for normal metabolism. In sand rats, the gene coding for the PDx1 protein has a much lower proportion of A and T nucleotides than PDx1 genes from other animals. Finding the complete DNA sequence of the PDx1 gene in sand rats has been difficult. Sequencing involves splitting off nucleotides one at a time from single-stranded DNA. What could account for the difficulty in finding the DNA sequence of the PDx1 gene in sand rats?
6. Nucleic acids and protein synthesis  →  6.2. Protein synthesis
6. Nucleic acids and protein synthesis  →  6.1. Structure of nucleic acids and replication of DNA
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28
Cellulose, lignin and suberin are components of various plant cell walls. Descriptions of these cell wall components are listed. a component of the Casparian strip redirects water into the symplast pathway a hydrophobic component of cell walls water interacts with this molecule in the apoplast pathway Which row correctly matches three of the descriptions with cell wall components?
2. Biological molecules  →  2.2. Carbohydrates and lipids
7. Transport in plants  →  7.2. Transport mechanisms
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