May/June 2022

A student used a stage micrometer scale to calibrate an eyepiece graticule. The diagram shows the student’s combined view of the stage micrometer scale and the eyepiece graticule. The divisions on the stage micrometer scale are $0.1\,\text{mm}$ apart. After removing the stage micrometer scale, the student examined a slide containing blood cells. Because the same lenses were kept in place, the magnification did not change. Using the eyepiece graticule, the student measured the diameter of one of the white blood cells on the slide and found it to be $8$ eyepiece units. What is the correct diameter of this white blood cell in micrometers?

The microscope in cell studies

A polypeptide has a definite number of amino acids, $n$. What number of peptide bonds are found in this polypeptide?

Proteins

Which statement is the correct one?

Cells as the basic units of living organisms

A student carried out colorimetry to follow the hydrolysis of a protein by a protease enzyme. Biuret solution was used by the student to find the protein concentration in the hydrolysis reaction. The student then made a calibration curve from known protein concentrations. Which diagram shows the calibration curve?

Mode of action of enzymes

To investigate how the rate of an enzyme-controlled reaction changes as substrate concentration increases, a student carried out an experiment. The student repeated the investigation after introducing a fixed amount of a reversible competitive inhibitor. Which row shows the effect of a reversible competitive inhibitor on enzyme activity?

Mode of action of enzymes

The diagram illustrates a liposome. Liposomes may be used to carry therapeutic drugs into cells of the body to help treat conditions such as cancer. Which row identifies the property of a drug that could be transported in the parts of the liposome labelled 1 and 2?

Fluid mosaic membranes

Several processes that take place in cells are listed. 1 endocytosis of water into cells 2 exocytosis of enzymes from cells 3 facilitated diffusion of glucose into red blood cells 4 phagocytosis of dead cells by macrophages Which of these processes require ATP?

Movement into and out of cells

The graph illustrates how the concentration of a solute within a cell varies. Which process accounts for this change in concentration? 1 Diffusion 2 Endocytosis 3 Exocytosis 4 Osmosis

Movement into and out of cells

The indicator cresol red turns from red to yellow in acid. Four agar blocks that contained cresol red were cut into different sizes, measured in millimetres. The blocks were then placed in acid. All the other variables were kept the same. The time needed for each block to become completely yellow was noted. Which of the four blocks turned completely yellow the fastest?

Movement into and out of cells

Which processes involve mitosis? 1 the production of cloned T-lymphocytes 2 the restoration of cell structures through protein synthesis 3 the development of multicellular organisms from one cell 4 a unicellular eukaryote's reproduction

Replication and division of nuclei and cells

Which events in the list belong to the cell cycle? 1 interphase 2 prophase 3 cytokinesis

Replication and division of nuclei and cells

Four students were told to pair each function with the correct appearance of certain cell structures in an animal cell. The functions were numbered as follows: 1 mRNA passes through to the ribosome; 2 produces the mitotic spindle during cell division; 3 packaging of hydrolytic enzymes that will remain in the cell. The appearances were given the letters: V membranes which enclose an internal cavity; W spherical structures with no membrane; X a double membrane with pores between them; Y cylindrical structures with no membrane; Z membrane-bound sacs arranged as a flattened stack. Which student made the correct match between the numbered function and the appearance of the cell structure?

Cells as the basic units of living organisms

Telomerase is an enzyme which attaches nucleotides to telomeres. Which of the following statements about telomerase is correct?

Replication and division of nuclei and cells

The photomicrograph displays cells that are in different phases of mitosis. A student made four claims about the photomicrograph. 1 Cell P is in anaphase. 2 Spindle fibres are being formed in cell Q. 3 The amount of DNA in cell R is equal to that in cell T. 4 The correct sequence of the stages is S → R → T → P → Q. Which claims are correct?

Chromosome behaviour in mitosis

Bacterial cells whose DNA contains only the ‘heavy’ isotope of nitrogen ($^{15}\text{N}$) are then permitted to divide for three generations in a culture medium that contains the normal isotope of nitrogen ($^{14}\text{N}$). What percentage of the DNA molecules formed have strands containing the heavy isotope of nitrogen?

Replication and division of nuclei and cells

A circular bacterial DNA molecule contains 2 600 150 base pairs. Adenine accounts for 26% of the bases. How many cytosine bases are present in the DNA molecule?

Structure of nucleic acids and replication of DNA

Which statement about the structure of DNA is correct?

Structure of nucleic acids and replication of DNA

A student drew a diagram to illustrate the process of transcription. Which section of the diagram indicates the non-transcribed strand?

Proteins

In which row is the movement of water in a root described correctly?

Movement into and out of cells

The table gives some data about the uptake and transport of water and mineral ions in plants. From the information provided, which factors influence the uptake and movement of water or mineral ions in plants?

Movement into and out of cells

What changes happen to the water potential and to the volume of solution in the phloem sieve tube when sucrose is transferred from a photosynthesising leaf into the phloem sieve tube?

Movement into and out of cells

A student produced the following statements about a possible mechanism for loading sucrose from a source. Which statements are correct?

Movement into and out of cells

Which size range would encompass most prokaryotic cells?

Cells as the basic units of living organisms

The diagram illustrates a transverse section of an artery. Which tissues are found in layer X?

The circulatory system

What does systolic blood pressure mean?

The circulatory system

The diagram illustrates how pressure in the left side of the heart and the aorta changes with time. The duration of this cardiac cycle is $0.6\,\text{s}$. Points 1, 2, 3 and 4 show the moments when the atrioventricular valves and semilunar valves open or close. What is the total length of time in one cardiac cycle for which the atrioventricular valves and the semilunar valves are both closed together?

The microscope in cell studies

Which reactions occur in the capillaries that surround an alveolus?

Movement into and out of cells

Which statement describes why the chloride shift is important in red blood cells (RBC)?

Movement into and out of cells

The photomicrographs present a transverse section of the lining of a part of the respiratory system. Which of the following statements about the photomicrographs are correct?

The microscope in cell studies

The surface tension in the liquid film lining the alveoli tends to draw the walls inwards, so the alveoli could collapse. Which statements could account for how this is prevented?

Carbohydrates and lipids

What action will slow down the speed at which bacteria develop resistance to antibiotics?

Antibiotics

T-lymphocytes contain a protein called PD-1 on their cell membrane. Some cancer cells carry a receptor molecule on their cell membrane that attaches to PD-1 and switches off the T-lymphocyte. A monoclonal antibody, lambrolizumab, has been developed against this receptor. Trials found that, among 54 of 135 people with advanced skin cancer who were treated with lambrolizumab, the tumours shrank to less than half their original volume. In 6 of the 57 people who received the highest dose, the tumours vanished. Which conclusion can be made correctly from this information?

Fluid mosaic membranes

A person’s blood group is decided by the antigens found on the red blood cells. The table gives the antigens and antibodies present in the blood of people with the different blood groups. When a blood transfusion is carried out, it is vital that the recipient has no antibodies against the donor’s blood. Which blood groups may be given to a person with blood group AB?

Fluid mosaic membranes

What structures are found in a typical prokaryotic cell and a typical eukaryotic cell?

Cells as the basic units of living organisms

Which kinds of cells are caused to divide by the cytokines made by T-helper cells?

Replication and division of nuclei and cells

Which statement about viruses is true?

Infectious diseases

Samples of glucose, sucrose, and a mixture of glucose and sucrose were split into two portions, M and N. M was then tested using Benedict’s solution. N was heated with dilute hydrochloric acid, neutralised, and then tested using Benedict’s solution. The colour of the solution was compared with colour standards. Which table shows the correct colour changes for these samples?

Testing for biological molecules

In which molecules are 1,4-glycosidic bonds found?

Carbohydrates and lipids

The diagram illustrates three triglycerides, X, Y and Z. Which row gives the correct answer for these triglycerides?

Carbohydrates and lipids

Certain foods contain hydrogenated vegetable fats. These are unsaturated fats that have been converted into saturated fats. Which property of the fats will have altered?

Carbohydrates and lipids

The photomicrograph displays a bronchiole and alveoli. This image has a magnification of $\times 360$. What is the greatest diameter of the bronchiole lumen?

The microscope in cell studies

A student listed four statements about water. 1 Water has a high specific heat capacity, so it keeps the temperature of water inside cells stable. 2 Mammals depend on water having a relatively low latent heat of vaporisation in order to stay cool. 3 If a negatively charged ion is added to water, the $\delta^+$ charge on the hydrogen atom is attracted towards the ion. 4 When non-polar molecules are surrounded by water, they tend to be forced apart from each other. Which of these statements are correct?

Water

Enzymes are usually large globular proteins that possess a particular tertiary structure. Which molecular interactions are directly responsible for holding the tertiary structure in place? 1 hydrogen bonding 2 disulfide bridges 3 hydrophobic interactions

Proteins

Which statement about the Michaelis-Menten constant ($K_m$) is correct for an enzyme that has a low affinity for its substrate?

Mode of action of enzymes

Compared with short-chain, unsaturated fatty acids, long-chain, saturated fatty acids stay solid until a higher temperature is reached and then become liquid. Which type of fatty acids would be more likely to be used to make triglycerides in mammals living in cold climates?

Carbohydrates and lipids

During the culture of animal cells, a salt solution is introduced to keep the cells alive. What is the function of the salt solution?

Movement into and out of cells

The processes listed below all make it possible for materials to move into cells. 1 phagocytosis 2 active transport 3 facilitated diffusion Which processes need ATP?

Movement into and out of cells

Which features must be present for diffusion to be efficient? 1 a large surface area 2 a diffusion pathway that is short 3 keeping a constant diffusion gradient

Movement into and out of cells

What is one function of mitosis?

Replication and division of nuclei and cells

Telomeres stop genes at the ends of chromosomes from being lost during DNA replication, but they get shorter each time they are copied. In cancer cells and stem cells, the telomeres stay the same length. Which statement is true for every human cell?

Replication and division of nuclei and cells

In a mouse body cell, the nucleus during G$_1$ phase of the cell cycle contains $1.2 \times 10^{-12}\,\text{g}$ of DNA. What is the mass of DNA in the nucleus of the cell at the end of S phase and at the end of G$_2$ phase?

Replication and division of nuclei and cells

A specimen is viewed twice under a microscope: first with green light of wavelength $510\,\text{nm}$, and then with red light of wavelength $650\,\text{nm}$. How do the magnification and the resolution change when red light is used instead of green light?

The microscope in cell studies

What takes place during prophase in animal cells? 1 nuclear envelope fragments 2 nucleolus vanishes 3 stained chromosomes become visible 4 centrioles duplicate

Chromosome behaviour in mitosis

Which statement gives a description of the structure of ATP?

Proteins

Rifampicin is an antibiotic that is used in the treatment of tuberculosis. Its action is to inhibit RNA polymerase in bacteria. Which processes are directly affected by this antibiotic? 1 DNA replication 2 enzyme synthesis 3 ATP synthesis

Mode of action of enzymes

The table gives the DNA triplet codes for certain amino acids. A section of the template DNA strand that codes for part of a polypeptide is shown below. CCA ACG GCG TTA TTC GCA During DNA replication, two mutations take place in this sequence. Which changed template DNA strand would produce a shorter polypeptide?

Proteins

A number of characteristics found in transport tissues are shown. Which of these characteristics occur in xylem vessel elements?

The microscope in cell studies

The diagrams show cross-sections taken through parts of plants. Which row is the correct one?

The microscope in cell studies

Which molecules make hydrogen bonds with water as transpiration occurs?

Water

Some plant species are able to absorb heavy metal contaminants that are dissolved in soil water and then move them through the plant. In plant cells, the heavy metals collect mainly in the vacuole. Which suggestions concerning the transport and accumulation of heavy metals are valid?

Movement into and out of cells

What is the correct path taken by water as it moves from cell to cell in the apoplast pathway?

Movement into and out of cells

Which row correctly gives the order in which sucrose enters phloem sieve tubes?

Movement into and out of cells

Four students had to pair each function with the correct appearance of certain cell structures in an animal cell. The functions were numbered as follows: (1) forms the mitotic spindle during cell division; (2) makes polypeptides; (3) makes lipids. The appearances were labelled by letter: V membranes enclosing an inner cavity; W spherical structures not bounded by a membrane; X a double membrane with pores spaced through it; Y cylindrical structures not bounded by a membrane; Z membrane-bound sacs arranged in a flattened stack. Which student matched the numbered functions to the appearance of the cell structure correctly?

Cells as the basic units of living organisms

What takes place during ventricular systole in a mammalian heart?

The heart

Which plan diagram shows the tissues found in a major vein?

The circulatory system

The diagram illustrates the pressure changes in different structures on the left side of the heart during the cardiac cycle. At the end of which phase is the ventricle filled with blood?

The heart

Which description of the movement of substances as tissue fluid forms is correct?

Movement into and out of cells

Which row indicates the changes in concentration of certain substances in red blood cells as carbon dioxide diffuses from active cells?

Movement into and out of cells

Which of the following statements about the human gas exchange system are correct?

Movement into and out of cells

The gas exchange system includes four cell types, shown below. J alveolus epithelium cell K ciliated cell L goblet cell M smooth muscle cell The ticks (✓) in the table indicate specialised features of three of these cell types. Which row gives the correct pairing of specialised feature and cell?

The gas exchange system

Why is it hard to control the spread of tuberculosis?

The microscope in cell studies

Rabies is a viral disease that may be passed to humans through a bite from an infected animal. One treatment method is to inject the patient with antibodies specific to the rabies virus. Which of the following statements about this treatment are correct?

Proteins

A person’s blood group is determined by the antigens found on the red blood cells. The table lists the antigens and antibodies in the blood of people with the different blood groups. In a blood transfusion, the receiver must not have antibodies against the donor’s blood. Which blood groups may be transfused into a person with blood group B?

Proteins

What structures are present in chloroplasts and mitochondria?

Cells as the basic units of living organisms

A student used a diagram to illustrate four types of cells involved in the primary immune response. cell type 1: release chemicals that cause phagocytes to engulf antigens cell type 2: destroy cells infected with viruses which would be released into the body cell type 3: make the antibodies needed to bind to the antigen cell type 4: identify the foreign antigen, move towards it and surround it Which row is correct?

The immune system

Which characteristic is true of all known viruses?

Infectious diseases

Four extracts were prepared from different plant materials and then tested using Benedict’s solution. Each extract was boiled with Benedict’s solution for $240$ seconds, after which the final colour was noted: extract 1: red; extract 2: yellow; extract 3: blue; extract 4: green. Which sequence of plant extracts shows an increasing amount of reducing sugar?

Testing for biological molecules

Which of these have properties that depend on hydrogen bonds?

Water

Which statement is the correct one?

Cells as the basic units of living organisms

The diagram illustrates two amino acids. Several hydrogen atoms are labelled 1 to 6. Which two numbered hydrogen atoms could take part in forming one molecule of water when a peptide bond is formed between these two amino acids?

Proteins

The diagram illustrates a cross-section of epithelium present in part of the respiratory system. The epithelium shown has a height of $80\ \mu\text{m}$. What magnification is the diagram drawn at?

The microscope in cell studies

Olestra is a synthetic lipid. It is formed when fatty acids are joined to a sucrose molecule by condensation. A simplified diagram of olestra is shown below. $R$ marks the point at which fatty acids would be linked. Humans are unable to hydrolyse olestra. Other animals, however, may be able to hydrolyse it. How many water molecules would be required to hydrolyse one molecule of olestra into fatty acids, fructose and glucose?

Carbohydrates and lipids

Which molecule has at least one peptide bond?

Proteins

RNA polymerase and peptidyl transferase are both enzymes that take part in protein synthesis. Which statements describe similarities between these two enzymes?

Mode of action of enzymes

What is one feature of competitive enzyme inhibition?

Factors that affect enzyme action

Batrachotoxin is a poison present in frogs from the Colombian jungle. It is used to make poison darts. The poison acts by increasing the permeability of the cell surface membrane of nerve and muscle cells to sodium ions, causing them to move out of the cells. Four students made comments about the effect of the poison on the cells. Which comments are correct for the cells affected by batrachotoxin?

Movement into and out of cells

Which processes require ATP as an energy source?

Movement into and out of cells

This indicator has no colour in acid but turns pink in alkali. In one experiment, a petri dish containing agar was prepared with an acidic solution of this indicator. From the centre, a disc of agar $1\ \text{cm}$ in diameter was taken out to make a well. A white card with circular marker lines spaced $1\ \text{cm}$ apart was positioned below the petri dish. $1\ \text{cm}^3$ of alkali solution was added to the well in the agar, and a stop-watch was started. A pink circular disc appeared and then diffused through the agar. It arrived at the first marker line after a short time, but needed longer to reach the second marker line and a very long time to reach the third marker line. What explains these observations?

Movement into and out of cells

The diagram illustrates a segment of a glycoprotein molecule embedded within a cell surface membrane. Every amino acid is shown as a small shaded circle. Which row gives a property of the amino acids in the alpha helix and a property of amino acid Q?

Proteins

A number of cells are shown. 1 bacterial cells 2 cancer cells 3 lymphocytes 4 mature red blood cells 5 stem cells Which of these cells are able to divide by mitosis?

Replication and division of nuclei and cells

Which statements about mitosis are accurate?

Chromosome behaviour in mitosis

Four students were asked to pair each function with the appearance of certain cell structures in an animal cell. The functions were numbered as follows. 1 mRNA passes through to the ribosome 2 synthesis of polypeptides 3 packaging of hydrolytic enzymes that will remain in the cell The appearances were lettered as follows. V membranes that enclose an internal cavity W non-membrane-bound, spherical structures X a double membrane with pores between its layers Y non-membrane-bound, cylindrical structures Z membrane-bound sacs arranged in a flattened stack Which student made the correct matches between the numbered functions and the appearance of the cell structure?

Cells as the basic units of living organisms

Which of the following statements about telomeres is correct?

Replication and division of nuclei and cells

The diagram illustrates the stages of mitosis. Which is the correct order of the mitosis stages shown by the numbers on the diagram?

Chromosome behaviour in mitosis

Which statement concerning the transcription and translation of a gene is correct?

Proteins

Which statement regarding mRNA is correct?

Proteins

The diagram illustrates a section of a DNA molecule. Which label is the correct one?

Structure of nucleic acids and replication of DNA

The order of bases in DNA that codes for the first eight amino acids in the $\beta$-polypeptide of adult haemoglobin is: CAC GTG GAC TGA GGA CTC CTC TTC In haemoglobin C, which is a cause of haemolytic anaemia, this changes to: CAC GTG GAC TGA GGA TTC CTC TTC A table lists some of the DNA triplets that code for amino acids. What change takes place in the amino acid sequence of normal haemoglobin to produce haemoglobin C?

Proteins

The diagram illustrates a plant organ. Which letter correctly identifies the xylem?

Structure of transport tissues

The photomicrograph shows a vascular bundle in a plant organ. Which of the following statements about this vascular bundle are correct?

Structure of transport tissues

When sucrose is transferred from the phloem sieve tube element to an actively dividing shoot tip, how do the water potential and the volume of solution in the phloem sieve tube element change?

Movement into and out of cells

Which processes take place when sucrose is loaded into phloem sieve tubes?

Movement into and out of cells

An investigation was conducted to separate the cell structures in an animal cell. The cells were disrupted. The extract was filtered and transferred into a centrifuge tube. The tube was then spun so that the densest cell structure moved down first, collecting as pellet 1, as shown. The liquid above pellet 1 was decanted into a new centrifuge tube and spun again at a greater speed to separate the next densest cell structure. This cell structure settled at the bottom, forming pellet 2. The same process was carried out twice more to produce pellet 3 and pellet 4, with each pellet containing just one cell structure. What is a function of the cell structure extracted in pellet 1?

Cells as the basic units of living organisms

The photomicrograph displays a cross-section of a structure present in mammals, as seen under a light microscope. What are the principal components of layer W?

The circulatory system

Which option correctly connects muscular or elastic arteries with what they do?

The circulatory system

The graph illustrates how pressure changes on the left side of the heart during one cardiac cycle. What is the heart rate in beats per minute?

The heart

Which events take place during ventricular systole?

The heart

Which of the following reactions occur in a capillary in the lungs? 1. Carbonic acid is produced from carbon dioxide and water. 2. Carbaminohaemoglobin is produced from carbon dioxide and haemoglobin. 3. Haemoglobinic acid is produced from haemoglobin and hydrogen ions. 4. Carbon dioxide and water are produced from hydrogencarbonate ions and hydrogen ions.

Movement into and out of cells

Which characteristics are important in the process of oxygen diffusing out of an alveolus?

Movement into and out of cells

A student examined three slides under both low magnification and high magnification. Every slide showed a section through a different airway in the gas exchange system. The student noted three features on each slide. Slide 1: cartilage arranged irregularly; the inner layer was highly folded; cilia on epithelial cells. Slide 2: very few goblet cells; cilia on epithelial cells; a thick smooth muscle layer compared with wall thickness. Slide 3: smooth muscle tissue; blood vessels; many goblet cells. Which row correctly names the three slides?

The gas exchange system

Which of these terms may be used to describe mosquitoes’ role in the transmission of malaria? 1. malarial parasite 2. pathogen 3. vector

Infectious diseases

Rheumatoid arthritis is a condition in which the body’s immune system attacks its own cells. Monoclonal antibodies can be used to treat the disease. The table outlines the ways in which five different monoclonal antibodies can act. Inflammation and swelling in the joints are symptoms of rheumatoid arthritis. The cytokine TNFalpha activates cells in the immune system, which results in the death of cells in the joint. Which monoclonal antibody types could be used to treat rheumatoid arthritis?

Proteins

A person’s blood group is determined by antigens found on the red blood cells. Antibodies in the plasma of the blood recipient can cause some blood transfusions to be unsafe. The table gives the antigens and antibodies present in the blood of people with different blood groups. Which blood groups may be given to a person with blood group A?

Proteins

ATP molecules are produced in mitochondria. Which sugar occurs in these ATP molecules?

Carbohydrates and lipids

Some events in the primary immune response are shown below. 1. a foreign microbe is phagocytosed by a macrophage and antigen presentation occurs 2. some T-lymphocytes become T-killer cells, which destroy infected body cells 3. the T-helper cell undergoes mitosis to form T-lymphocyte clones 4. a T-helper cell with the complementary receptor binds to the antigens that are being presented What sequence of events is correct during the primary immune response?

Replication and division of nuclei and cells

Which row presents a comparison that is incorrect between a typical prokaryotic cell and a typical eukaryotic plant cell?

Cells as the basic units of living organisms

It has been proposed that primitive prokaryotic cells could be the ancestors of some organelles found in eukaryotic cells. Which organelle is compositionally most like a typical prokaryote?

Cells as the basic units of living organisms

The concentration of reducing sugar in a solution can be determined by comparing an observational measurement with a standard. Which observational measurement could be used to estimate the concentration of reducing sugar in an unknown solution? 1 the colour of the solution after 20 minutes 2 the time taken for the first colour change to happen 3 the rate at which solid particles form

Testing for biological molecules

The diagram presents three hexose sugars. Which row correctly indicates examples of carbohydrates in which these three hexose sugars are found?

Carbohydrates and lipids

Trehalose is a sugar that gives a negative result in a test with Benedict’s solution. If a molecule of trehalose is hydrolysed, it produces two $\alpha$-glucose molecules. Which row is the correct one?

Testing for biological molecules