Question 1
What combination of properties defines a stem cell?
A.
It has completed differentiation and has a fixed structure and function.
B.
It contains only the genes needed for one specialized function.
C.
It divides repeatedly and can produce daughter cells that differentiate along different pathways.
D.
It cannot divide but can change rapidly into any mature cell type.
Question 2
Cells in an early embryo are exposed to a gradient of a signalling molecule. Cells at one end of the embryo develop into a different specialized cell type from cells at the other end. What explains this difference?
A.
The cells have different numbers of chromosomes after mitosis.
B.
The cells become haploid before differentiating into tissues.
C.
The cells activate different genes in response to different signal concentrations.
D.
The cells lose genes that are not needed for their final function.
Question 3
A local microenvironment around adult stem cells contains neighbouring cells, extracellular matrix and signalling molecules. What is its role?
A.
It removes all differentiated cells from the tissue.
B.
It prevents mitosis in all cells in the surrounding tissue.
C.
It converts all stem cells into totipotent embryonic cells.
D.
It maintains stem cells or promotes their proliferation and differentiation when needed.
Question 4
A stem cell in adult bone marrow can produce red blood cells, several types of white blood cells and platelets, but not neurons or muscle fibres. What is its potency?
A.
Unipotent
B.
Pluripotent
C.
Totipotent
D.
Multipotent
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Question 5
A human egg cell is much larger than a human sperm cell. What is the functional significance of the larger egg cell size?
A.
It allows the egg to pass through the narrowest blood capillaries.
B.
It stores cytoplasm and materials that support the zygote and early embryo.
C.
It reduces drag so the egg can swim through the oviduct.
D.
It provides a long axon for communication across the body.
Question 6
Human erythrocytes are biconcave discs rather than spheres. How does this shape help their function?
A.
It increases volume so that each cell can store large quantities of cytoplasm.
B.
It increases surface area-to-volume ratio and shortens the diffusion path for oxygen.
C.
It provides a surface for secretion of surfactant into alveoli.
D.
It provides branches for rapid electrical conduction between cells.
Question 7
What correctly matches the two alveolar pneumocyte types with their main adaptations?
A.
Type I pneumocytes have myofibrils; type II pneumocytes have flagella.
B.
Type I pneumocytes contain lamellar bodies; type II pneumocytes are thin for diffusion.
C.
Type I pneumocytes are thin for diffusion; type II pneumocytes contain lamellar bodies for surfactant secretion.
D.
Type I pneumocytes form microvilli; type II pneumocytes form biconcave discs.
Question 8
Stem cells are important during development and in some adult tissues.
State one property of stem cells.
[1]
Outline why stem cells are needed in multicellular organisms.
[2]
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Question 9
Three cube models are used to investigate surface area-to-volume ratio. The cubes have the same shape but increasing side length. What happens as side length increases?
A.
Surface area-to-volume ratio increases because surface area increases.
B.
Surface area-to-volume ratio remains constant because shape is unchanged.
C.
Surface area-to-volume ratio decreases because surface area decreases.
D.
Surface area-to-volume ratio decreases because volume increases faster than surface area.
Question 10
A proximal convoluted tubule cell in the nephron has many membrane proteins for selective reabsorption. What pair of adaptations increases membrane area for transport at its two main surfaces?
A.
Apical acrosomes and basal cortical granules
B.
Apical microvilli and basal membrane infoldings
C.
Apical lamellar bodies and basal cilia
D.
Apical myofibrils and basal flagella
Question 11
What comparison of cardiac muscle cells with striated skeletal muscle fibres is correct?
A.
Cardiac muscle cells are multinucleate fibres formed only by cell fusion; skeletal muscle fibres are usually singly nucleate.
B.
Cardiac muscle cells lack myofibrils; skeletal muscle fibres contain myofibrils.
C.
Cardiac muscle cells are usually branched and singly nucleate; skeletal muscle fibres are long, unbranched and multinucleate.
D.
Cardiac muscle cells are long and unbranched; skeletal muscle fibres are short and branched.
Question 12
After one sperm enters a human egg cell, enzyme-containing vesicles near the egg plasma membrane release their contents. What is the main result of this event?
A.
Formation of the sperm flagellum with a microtubule arrangement
B.
Digestion of a path through the zona pellucida before fertilization
C.
Activation of lamellar bodies to secrete surfactant into the lumen
D.
Modification of the zona pellucida to help prevent polyspermy
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Question 13
A human sperm cell must reach and fuse with an egg cell. What set of adaptations is directly involved in movement and entry into the egg?
A.
A flagellum for motility, mitochondria in the midpiece for ATP supply and an acrosome containing enzymes
B.
A large cytoplasm with stored materials, cortical granules and a zona pellucida
C.
Lamellar bodies, surfactant and an extremely thin cytoplasm
D.
A biconcave shape, haemoglobin and no nucleus for gas transport
Question 14
In an early animal embryo, cells at different positions are exposed to different concentrations of a signalling molecule.
State the term for the process by which an unspecialized embryonic cell becomes suited to a particular function.
[1]
Explain how a chemical gradient can lead to cells in the embryo becoming different specialized cell types.
[2]
Question 15
Adult humans contain stem cell niches in tissues such as bone marrow and hair follicles.
Define a stem cell niche.
[1]
State one function of the bone marrow stem cell niche.
[1]
Explain how a stem cell niche can contribute to tissue repair or replacement.
[2]
Question 16
Human cells vary greatly in size and shape. Four specialized cells are shown, not to scale.
Identify the cell shown that is specialized for long-distance communication in the body.
[1]
Suggest one advantage of the large size of a human egg cell.
[1]
Explain how the small size and biconcave shape of a red blood cell help its function.
[2]
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Question 17
The alveolar epithelium contains type I pneumocytes and type II pneumocytes.
State the main adaptation of type I pneumocytes for gas exchange.
[1]
Explain how type II pneumocytes help prevent alveolar collapse.
[2]
Suggest why the alveolar epithelium contains more than one cell type.
[1]
Question 18
A human sperm cell is specialized for movement and for delivering a haploid nucleus to an egg cell.
State the function of the acrosome.
[1]
Explain how the midpiece and flagellum adapt the sperm cell for fertilization.
[2]
Suggest one advantage of the sperm cell having very little cytoplasm.
[1]
Question 19
Measurements were made of several specialized human cells. Cell size was compared with selected features related to cell function.
Cell type | Length / m | Width / m | Approx. volume / m | Feature related to function |
|---|---|---|---|---|
Sperm cell | 60 | 3 | 25 | Narrow cell body; little cytoplasm; long flagellum |
Egg cell (ovum) | 120 | 120 | Large cytoplasm with nutrient stores | |
Inactive lymphocyte | 7 | 7 | Small cell; little cytoplasm | |
Plasma cell | 15 | 15 | Large cell; abundant rough ER and Golgi for protein secretion |
Identify the cell type with the greatest volume in the data.
[1]
Describe one way in which the size of a sperm cell is related to its function.
[1]
Describe one way in which the size of an egg cell is related to its function.
[1]
Suggest why a plasma cell is larger than an inactive lymphocyte.
[1]
Question 20
The developmental potential of stem cells becomes more restricted as animal development proceeds.
Distinguish between totipotent and pluripotent stem cells.
[2]
Explain why bone marrow stem cells are described as multipotent rather than pluripotent.
[2]
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Question 21
Cubes can be used as simplified models to investigate the relationship between cell size and surface area-to-volume ratio.
Cube model | Calculation | Surface area / | Volume / |
|---|---|---|---|
1 mm cube | SA = ; V = | 6 | 1 |
2 mm cube | SA = ; V = | 24 | 8 |
Calculate the surface area-to-volume ratio for a cube with side length .
[2]
Explain why an increase in cell size can limit exchange with the environment.
[2]
Question 22
Erythrocytes and proximal convoluted tubule cells are both specialized for rapid exchange across membranes.
Explain how the biconcave shape of an erythrocyte increases the rate of oxygen exchange.
[2]
Distinguish between the adaptations of the apical and basal membranes of a proximal convoluted tubule cell.
[2]
Question 23
Cardiac muscle cells and striated skeletal muscle fibres both contain contractile myofibrils.
State one feature shared by cardiac muscle cells and striated muscle fibres.
[1]
Compare the branching and number of nuclei in cardiac muscle cells and striated muscle fibres.
[2]
Suggest why branching is useful in cardiac muscle tissue.
[1]
Question 24
The human egg cell has adaptations that support fertilization and the earliest stages of development.
State one function of the abundant cytoplasm in an egg cell.
[1]
Explain how the zona pellucida is involved in fertilization.
[2]
State the role of cortical granules after sperm entry.
[1]
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Question 25
An early animal embryo was exposed to a signalling molecule that forms a concentration gradient from the anterior end to the posterior end. Expression of two developmental genes was measured in groups of cells at different positions.
Describe the change in concentration of the signalling molecule along the embryo.
[1]
State the region of the embryo in which gene A is most strongly expressed.
[1]
Explain how this gradient could lead to differentiation of cells in different regions of the embryo.
[2]
Question 26
Stem cells from adult human bone marrow and hair follicles were cultured with or without molecules extracted from their normal tissue microenvironment. The numbers of stem cells and differentiating daughter cells were recorded after several days.
Tissue | Factors | Stem cells / cells | Differentiating daughter cells / cells |
|---|---|---|---|
Bone marrow | Absent | 5 | 15 |
Bone marrow | Present | 20 | 5 |
Hair follicle | Absent | 8 | 24 |
Hair follicle | Present | 16 | 8 |
Calculate the percentage increase in the number of bone marrow stem cells when niche factors were added.
[1]
Outline two properties of stem cells shown by the data.
[2]
Suggest one function of the stem cell niche in adult tissues.
[1]
Question 27
Cells were isolated from three developmental sources and placed in culture. Researchers recorded the range of tissues produced by each cell population.
Cell population | Tissues produced in culture |
|---|---|
Very early embryo cells | placenta; yolk sac; nerve tissue; muscle tissue |
Early embryo cells | nerve tissue; muscle tissue; skin tissue; liver tissue |
Adult bone marrow cells | red blood cells; white blood cells; platelets |
Identify the potency category of the cell population that can form both embryonic and extra-embryonic tissues.
[1]
Identify the potency category of the adult bone marrow cell population shown in the table.
[1]
Explain why the remaining early embryonic cell population is classified as pluripotent rather than totipotent.
[2]
Question 28
Cells from the same early embryo were sampled after several rounds of mitosis. Gene expression was measured in cells that later developed into two different specialized cell types.
State why the two sampled cell groups are expected to contain the same genes.
[1]
Describe the main difference in gene expression between the two cell groups.
[1]
Suggest how different gene expression could result in different specialized cells.
[1]
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Question 29
Human erythrocytes were compared with artificial spherical cells of similar volume. Oxygen uptake and geometric measurements were recorded.
Cell type | Surface area / | Volume / | Central thickness / | Oxygen uptake time / s |
|---|---|---|---|---|
Spherical model cell | 97 | 90 | 5.6 | 20 |
Human erythrocyte | 136 | 90 | 1.0 | 10 |
Calculate the percentage decrease in the time taken for oxygen uptake by the biconcave erythrocyte compared with the spherical model cell.
[1]
Identify the adaptation of erythrocyte shape shown in the diagram.
[1]
Explain how this adaptation improves the function of an erythrocyte.
[2]
Question 30
Two cell types from human alveolar epithelium were examined by microscopy and by measuring their secretory activity.
Identify cell types X and Y.
[2]
Explain how the structure of a type I pneumocyte supports gas exchange.
[1]
Explain the function of lamellar bodies in type II pneumocytes.
[1]
Question 31
Human gametes were examined before and after fertilization. Structures involved in movement, recognition and prevention of polyspermy were recorded.
Identify the sperm structure that contains enzymes used to penetrate the zona pellucida.
[1]
Identify the sperm region that contains many mitochondria for movement.
[1]
Explain how cortical granules help prevent polyspermy.
[1]
Suggest why the egg cell is much larger than the sperm cell.
[1]
Question 32
A striated skeletal muscle fibre is very long and contains many nuclei within one plasma membrane. This has led to discussion about whether it should be regarded as a single cell.
State how striated skeletal muscle fibres form during development.
[1]
Explain one possible advantage of many nuclei in a striated muscle fibre.
[1]
Evaluate whether a striated muscle fibre should be considered a cell.
[2]
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Question 33
Cubes made from agar containing an indicator were used to model the effect of cell size on exchange. The cubes were placed in an alkaline solution for the same length of time. For a cube, surface area is and volume is , where is side length.
Side length / m | Surface area / m | Volume / m |
|---|---|---|
10 | 600 | 1000 |
20 | 2400 | 8000 |
40 | 9600 | 64000 |
80 | 38400 | 512000 |
Calculate the surface area-to-volume ratio for the cube with side length .
[1]
Describe the relationship between cube side length and surface area-to-volume ratio.
[1]
Explain why a low surface area-to-volume ratio can constrain cell size.
[2]
Evaluate the use of cubes as models for cells in this investigation.
[1]
Question 34
Epithelial cells from the proximal convoluted tubule of a human nephron were examined. Uptake from the filtrate and export towards the blood were measured before and after partial removal of membrane folds.
Identify the surface of the cell that faces the filtrate in the tubule lumen.
[1]
Distinguish between the adaptations of the apical and basal membranes shown in the cell.
[2]
Suggest why loss of microvilli reduces reabsorption rate.
[1]
Explain why both microvilli and basal infoldings are useful in the same specialized cell.
[1]
Question 35
Samples of human cardiac muscle and skeletal striated muscle were examined by light microscopy. Structural features were compared with their functions.
Compare the branching and nuclei of cardiac muscle cells with skeletal striated muscle fibres.
[2]
State the feature present in both muscle types that enables contraction.
[1]
Suggest why branching is advantageous in cardiac muscle.
[1]
Discuss whether a skeletal striated muscle fibre should be regarded as a cell.
[1]
Question 36
A developing animal embryo contains cells with the same genome, but cells at different positions are exposed to different concentrations of a signalling molecule.
Use the information in the diagram to explain how cells in the embryo can begin to follow different developmental pathways.
I.
Outline how a chemical gradient provides positional information to embryonic cells.
[1]
II.
Explain how this positional information can lead to differentiation.
[2]
Explain why two specialized cells in the same individual usually contain the same genes but have different structures.
[2]
Discuss the importance of regulated gene expression during early development.
[2]
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Question 37
Stem cells are important in development and in the maintenance of some adult tissues.
Describe the properties that distinguish stem cells from fully differentiated cells.
I.
State one property of stem cells related to cell division.
[1]
II.
Explain one property of stem cells related to differentiation.
[2]
Explain why some daughter cells of a stem cell division may remain stem cells while others differentiate.
[2]
Discuss why control of stem cell division is necessary in multicellular organisms.
[2]
Question 38
Human cells vary greatly in size and shape. The same cell size is not optimal for all functions.
Explain how cell size contributes to specialization in two named human cell types.
I.
Outline one advantage of small size in a named human cell type.
[1]
II.
Explain one advantage of large size or great length in a named human cell type.
[2]
Explain why red blood cells are small and biconcave rather than large spherical cells.
[2]
Evaluate the statement that smaller cells are always better adapted than larger cells.
[2]
Question 39
Adult stem cells are maintained in specialized local environments called stem cell niches.
Use the diagram to describe two adult human stem cell niches.
I.
State one location of an adult human stem cell niche shown in the diagram.
[1]
II.
Outline the function of each of the two niches shown.
[2]
Explain how a stem cell niche can regulate the behaviour of stem cells.
[2]
Discuss why the presence of stem cells alone may not be sufficient for complete regeneration of a tissue.
[2]
Question 40
An experimental model of alveolar injury was used to investigate how changes in the two pneumocyte types affect overall alveolar function. Gas diffusion rate and surfactant secretion were measured over several days after injury.
Describe the relationship between type I pneumocyte surface coverage and gas diffusion rate in the model.
[1]
Suggest why an increase in type II pneumocyte abundance does not fully restore gas diffusion rate immediately after injury.
[2]
Explain why surfactant secretion remains important even when gas diffusion rate is reduced.
[1]
Evaluate the statement that one specialized cell type would be sufficient for alveolar epithelium.
[1]
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Question 41
During animal development, the range of possible fates of cells generally becomes more restricted.
Use the developmental pathway to distinguish between levels of stem cell potency.
I.
Identify the potency of cells in the earliest stages of an animal embryo.
[1]
II.
Distinguish pluripotent stem cells from multipotent stem cells.
[2]
Compare totipotent, pluripotent and multipotent stem cells.
[3]
Discuss why bone marrow stem cells are classified as multipotent rather than pluripotent.
[2]
Question 42
Cubes of different side length can be used as models for investigating surface area-to-volume ratio in cells.
Cube model | Side length / cm |
|---|---|
A | 1 |
B | 2 |
C | 4 |
Use the cube model to analyse how increasing size affects exchange.
I.
Calculate the surface area-to-volume ratio for one cube using .
[2]
II.
State the trend in surface area-to-volume ratio as cube side length increases.
[1]
Explain why a decreasing surface area-to-volume ratio can limit cell size.
[3]
Evaluate the use of cubes as models for surface area-to-volume relationships in cells.
[2]
Question 43
Erythrocytes and proximal convoluted tubule cells both have adaptations that increase exchange across membranes.
Compare adaptations that increase surface area-to-volume ratio or membrane area in the two cell types.
I.
Describe how the shape of an erythrocyte aids gas exchange.
[1]
II.
Contrast microvilli and invagination in proximal convoluted tubule cells.
[2]
Explain why proximal convoluted tubule cells need different membrane specializations at their apical and basal surfaces.
[3]
Evaluate why increasing surface area is not achieved simply by making these cells much larger.
[2]
Question 44
The alveolar epithelium contains more than one specialized cell type.
Use the diagram to explain how the two pneumocyte types are adapted to their functions.
I.
Explain the adaptation of type I pneumocytes for gas exchange.
[1]
II.
Explain the adaptation of type II pneumocytes for secretion.
[2]
Explain how surfactant contributes to the function of alveoli.
[2]
Discuss why the alveolar epithelium requires more than one cell type.
[2]
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Question 45
Human sperm cells and egg cells are both gametes but have contrasting specializations for fertilization and early development.
Use the diagram to explain adaptations of the sperm cell.
I.
Explain how the sperm cell is adapted for movement.
[2]
II.
State one adaptation of the sperm head for fertilization.
[1]
Explain how the egg cell is adapted for fertilization and early development.
[3]
Compare the reproductive strategies shown by the specializations of sperm and egg cells.
[2]
Question 46
Cardiac muscle cells and striated muscle fibres are both contractile, but their structures differ.
Compare the structural adaptations of cardiac muscle cells and striated muscle fibres.
I.
State one structural feature shared by both muscle types.
[1]
II.
Contrast branching and nuclei in the two muscle types.
[2]
Explain how these structural differences are related to function.
[2]
Evaluate whether a striated muscle fibre should be considered a single cell.
[3]
Question 47
Premature infants may have insufficient surfactant in their alveoli. This affects the function of the alveolar epithelium.
Condition | Relative surfactant level / % | Alveolar surface tension / a.u. | Alveolar inflation / % of normal | Gas exchange surface area / % of normal |
|---|---|---|---|---|
Adequate surfactant | 100 | 20 | 100 | 100 |
Low surfactant | 20 | 80 | 60 | 60 |
Use the information to relate surfactant deficiency to pneumocyte specialization.
I.
Identify the pneumocyte type most directly involved in surfactant secretion.
[1]
II.
Explain how the cytoplasm of this cell type is specialized for secretion.
[2]
Explain why insufficient surfactant reduces the effectiveness of gas exchange.
[2]
Evaluate why type I pneumocytes alone cannot maintain normal alveolar function.
[2]
Question 48
Several specialized human cells increase exchange or transport efficiency by modifying shape, membrane area or internal structures.
Analyse how the structures shown increase efficiency in two of the cells.
I.
Explain how one feature of the erythrocyte increases oxygen transport efficiency.
[1]
II.
Explain how two features of the proximal convoluted tubule cell increase reabsorption efficiency.
[2]
Discuss how the sperm cell illustrates specialization for movement and delivery of genetic material rather than exchange.
[3]
Evaluate the general principle that cell specialization involves more than changing cell size.
[2]
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