B2.3 Cell specialization
Practice exam-style IB Biology questions for Cell specialization, aligned with the syllabus and grouped by topic.
Question 1
What causes cells in the same early embryo to develop into different specialized cell types?
A.
Different mutations occur in each daughter cell after every mitotic division.
B.
Different cells lose most genes that are not needed for their final function.
C.
Different genes are expressed in different cells during development.
D.
Different daughter cells receive different numbers of chromosomes from mitosis.
Question 2
Which pair of properties defines a stem cell?
A.
It is always found only in an early embryo and never in adult tissues.
B.
It has no nucleus and therefore cannot become specialized.
C.
It divides repeatedly and can give rise to more than one specialized cell type.
D.
It cannot divide but can carry out one function very efficiently.
Question 3
What is the function of a stem cell niche in adult tissue?
A.
To remove all differentiated cells from the tissue
B.
To convert all adult stem cells into totipotent stem cells
C.
To prevent stem cells from ever entering mitosis
D.
To provide a local environment that regulates stem cell maintenance and differentiation
Question 4
What is an advantage of the small, thin shape of a human red blood cell?
A.
It provides abundant cytoplasm for early embryonic development.
B.
It increases the distance oxygen must diffuse through the cytoplasm.
C.
It enables rapid oxygen exchange and passage through narrow capillaries.
D.
It allows long-distance electrical communication in the body.
Question 5
In an early embryo, a gradient of a signalling molecule is established from one end to the other. What is the most likely direct effect on cells at different positions?
A.
They immediately contain different genetic codes.
B.
They receive different signal concentrations and activate different genes.
C.
They become gametes before any differentiation occurs.
D.
They stop using ribosomes to synthesize proteins.
Question 6
What adaptation increases membrane surface area on the apical surface of proximal convoluted tubule cells?
A.
Cortical granules
B.
Microvilli
C.
Lamellar bodies
D.
Intercalated discs
Question 7
State what is produced by fertilization.
[1]
Outline why early embryonic cells can later become different cell types even though they arise by mitosis.
[1]
Question 8
State two properties of stem cells.
Question 9
A cell can form several related blood cell types but cannot form neurons or muscle cells. What is the best description of this cell?
A.
Gametic
B.
Pluripotent
C.
Totipotent
D.
Multipotent
Question 10
Why does increasing cell size create a constraint on exchange with the environment?
A.
Large cells cannot contain membrane transport proteins.
B.
Volume increases faster than surface area, so exchange demand increases faster than exchange capacity.
C.
Surface area increases faster than volume, so wastes cannot be produced.
D.
Large cells always contain fewer mitochondria than small cells.
Question 11
What is the main adaptation of a type I pneumocyte for its function?
A.
A biconcave shape for oxygen transport in blood
B.
Many lamellar bodies for surfactant secretion
C.
Extreme thinness to reduce diffusion distance
D.
A flagellum for movement through mucus
Question 12
What is the role of lamellar bodies in type II pneumocytes?
A.
They bind oxygen for transport through capillaries.
B.
They store and secrete surfactant into the alveolar lumen.
C.
They digest pathogens inside phagocytes.
D.
They contract the alveolar wall during breathing.
Question 13
Which feature is characteristic of human striated skeletal muscle fibres rather than cardiac muscle cells?
A.
They are usually very long, unbranched and multinucleate.
B.
They are short, branched and usually have one nucleus.
C.
They secrete surfactant from lamellar bodies.
D.
They lack myofibrils and therefore do not show striations.
Question 14
What is the function of cortical granules in the human egg cell after fertilization?
A.
They release enzymes that modify the zona pellucida to help prevent polyspermy.
B.
They beat in a 9 + 2 arrangement to move the egg along the oviduct.
C.
They form haemoglobin for oxygen transport to the embryo.
D.
They secrete surfactant to reduce surface tension.
Question 15
What feature helps cardiac muscle cells contract as a coordinated network?
A.
A single long unbranched fibre containing hundreds of nuclei
B.
A zona pellucida surrounding the plasma membrane
C.
Branching and specialized junctions between adjacent cells
D.
Apical microvilli and basal membrane infoldings
Question 16
The diagram shows an early embryo with a higher concentration of a signalling molecule at one end than the other.
State the term for this spatial difference in concentration.
[1]
Explain how this can lead to different cell fates.
[1]
Question 17
Name one adult human location of a stem cell niche.
[1]
Outline two possible effects of the niche on stem cells.
[1]
Question 18
Explain how cell size is related to function in two named human cell types.
Question 19
Explain how two adaptations of proximal convoluted tubule cells increase reabsorption.
Question 20
Distinguish between type I and type II pneumocytes in relation to their adaptations and functions.
Question 21
Outline three structural features of cardiac muscle cells that relate to their function.
Question 22
Compare flattening, microvilli and invagination as adaptations that increase surface area-to-volume ratio or membrane area.
Question 23
The graph shows the concentration of a signalling molecule along the length of an early embryo. Expression of gene X was measured in cells taken from the same positions.
Identify the region of the embryo where gene X expression is highest.
[1]
Describe the relationship between signalling molecule concentration and expression of gene X.
[1]
Explain how this relationship could contribute to differentiation.
[1]
Question 24
The table shows dimensions calculated for cube models of cells with different side lengths.
| Side length / cm | Surface area / cm² | Volume / cm³ | SA:V / cm⁻¹ |
|---|---|---|---|
| 1.0 | 6.0 | 1.0 | 6.0 |
| 2.0 | 24.0 | 8.0 | 3.0 |
| 3.0 | 54.0 | 27.0 | ? |
| 4.0 | 96.0 | 64.0 | 1.5 |
Calculate the missing surface area-to-volume ratio for one cube.
[1]
Describe the trend in surface area-to-volume ratio as side length increases.
[1]
Explain why this trend limits the maximum size of many cells.
[1]
Question 25
A cube model of a cell has a side length of 3.0 mm. What is its surface area-to-volume ratio?
A.
0.50 mm⁻¹
B.
18 mm⁻¹
C.
27 mm⁻¹
D.
2.0 mm⁻¹
Question 26
What structure in a human sperm cell contains enzymes that help penetrate the zona pellucida?
A.
Flagellum
B.
Midpiece
C.
Acrosome
D.
Cortical granule
Question 27
Why do basal infoldings in proximal convoluted tubule cells increase reabsorption capacity?
A.
They increase membrane area for transport proteins on the side facing tissue fluid.
B.
They produce surfactant that prevents collapse of the tubule.
C.
They join cells electrically so that the nephron contracts as one unit.
D.
They decrease all diffusion distances by removing the nucleus.
Question 28
Distinguish between totipotent, pluripotent and multipotent stem cells.
Question 29
A cube is used as a model cell. Its side length is 4.0 mm.
Calculate its surface area.
[1]
Calculate its volume.
[1]
Calculate its surface area-to-volume ratio.
[1]
Question 30
Explain why cube models are useful but limited for investigating constraints on cell size.
Question 31
Explain two hypotheses for why striated skeletal muscle fibres are very long and multinucleate.
Question 32
Explain how the structure of a human sperm cell is adapted for fertilization.
Question 33
Explain two adaptations of the human egg cell that promote normal fertilization and early development.
Question 34
The table shows the numbers of stem cells and newly differentiated cells counted in cultured human hair follicle niches under three signalling conditions.
| Signalling condition | Stem cells / count | Newly differentiated cells / count |
|---|---|---|
| Maintenance signal | 48 | 8 |
| Proliferation signal | 92 | 11 |
| Differentiation signal | 31 | 57 |
Identify the condition with the greatest proliferation of stem cells.
[1]
Describe the effect of the differentiation signal on the number of differentiated cells.
[1]
Suggest how a stem cell niche can help maintain a tissue such as a hair follicle.
[1]
Question 35
The graph compares the approximate lengths or diameters of selected human cells.
Identify the cell type with the greatest measured length.
[1]
Compare the size of a red blood cell with a white blood cell in the graph.
[1]
Explain one advantage of a very large egg cell.
[1]
Evaluate why cell size alone is insufficient to infer cell function.
[1]
Question 36
Cells were isolated from three sources and tested for their ability to differentiate into different cell types. The results are shown.
| Cell source | Extra-embryonic tissue | Neuron | Muscle cell | Epithelial cell | Red blood cell | White blood cell | Platelet |
|---|---|---|---|---|---|---|---|
| Very early embryo | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Embryonic inner cell population | No | Yes | Yes | Yes | Yes | Yes | Yes |
| Adult bone marrow | No | No | No | No | Yes | Yes | Yes |
Identify the source containing totipotent cells.
[1]
Identify the source containing multipotent cells.
[1]
Suggest why cells from adult bone marrow did not form neurons in this investigation.
[1]
Question 37
The graph shows the rate of glucose reabsorption by cultured proximal convoluted tubule cells with normal microvilli and with shortened microvilli.
Identify which cells have the higher maximum reabsorption rate.
[1]
Describe the effect of shortening microvilli on glucose reabsorption.
[1]
Explain the effect in terms of cell specialization.
[1]
Question 38
Discuss whether a striated skeletal muscle fibre should be considered a cell.
Question 39
The graph shows surfactant secretion by type II pneumocytes during fetal lung development and the percentage of alveoli remaining open after exhalation.
Describe the relationship between surfactant secretion and alveoli remaining open.
[1]
State the vesicles in type II pneumocytes that contain surfactant.
[1]
Suggest why premature infants with low surfactant secretion may have difficulty inflating their lungs.
[1]
Identify the pneumocyte type mainly responsible for rapid gas diffusion.
[1]
Question 40
Electron micrographs of two muscle tissues were analysed. The table shows measurements of cell or fibre length, number of nuclei per cell or fibre, branching and presence of myofibrils.
| Feature | Tissue A | Tissue B |
|---|---|---|
| Cell/fibre length / µm | 60–120 | 10 000–30 000 |
| Nuclei per cell/fibre | 1, sometimes 2 | many (>50) |
| Branching | present | absent |
| Myofibrils | present | present |
Identify which tissue is cardiac muscle.
[1]
Identify one feature shared by both tissues.
[1]
Compare the branching and nuclei data for the two tissues.
[1]
Suggest how the cardiac muscle feature identified in
[1]
supports heart function.
[1]
Question 41
The table shows results from human fertilization experiments using sperm with normal acrosomes, damaged acrosomes or reduced mitochondrial activity.
| Sperm treatment | Motility / % | Zona binding / sperm per egg | Eggs penetrated / % |
|---|---|---|---|
| Normal acrosome | 82 | 28 | 68 |
| Damaged acrosome | 78 | 24 | 18 |
| Reduced mitochondrial activity | 35 | 10 | 30 |
Identify which sperm treatment produced the lowest percentage of eggs penetrated.
[1]
Suggest why damaged acrosomes reduce penetration of the zona pellucida.
[1]
Explain why reduced mitochondrial activity affects sperm movement.
[1]
Evaluate whether the data show that the acrosome is the only sperm structure needed for fertilization.
[1]
Question 42
Outline how unspecialized cells are produced after fertilization.
[1]
Discuss how regulated gene expression and gradients contribute to cell differentiation in an early embryo.
[1]
Question 43
Define cell potency.
[1]
Compare totipotent, pluripotent and multipotent stem cells, using examples from animal development or adult tissues.
[1]
Question 44
State two adult human locations of stem cell niches.
[1]
Explain the roles of stem cells and their niches in tissue maintenance and repair.
[1]
Question 45
Two drugs were tested on isolated alveolar epithelial cells. Drug P reduced lamellar body exocytosis. Drug Q increased the thickness of type I pneumocytes. The results are shown.
| Treatment | Exocytosis / events min⁻¹ cell⁻¹ | Surfactant / relative units | Type I thickness / µm | O₂ diffusion / relative units |
|---|---|---|---|---|
| Control | 18.2 | 100 | 0.20 | 100 |
| Drug P | 5.1 | 43 | 0.21 | 96 |
| Drug Q | 17.6 | 98 | 0.41 | 50 |
Identify which drug would most directly reduce surfactant release.
[1]
Identify which drug would most directly reduce gas diffusion rate.
[1]
Explain the effect of drug Q on diffusion.
[1]
Evaluate why the alveolar epithelium contains more than one specialized cell type.
[1]
Question 46
Calculate the surface area-to-volume ratio of a cube with side length 2.0 mm.
[1]
Evaluate the use of cube models to explain constraints on cell size.
[1]
Question 47
Outline the adaptation of type I pneumocytes.
[1]
Compare the adaptations and functions of type I and type II pneumocytes in alveoli.
[1]
Question 48
State two features shared by cardiac muscle cells and striated skeletal muscle fibres.
[1]
Discuss how differences in branching, length and nuclei relate to their different functions.
[1]
Question 49
Outline two features shared by human sperm and egg cells.
[1]
Evaluate how contrasting specializations of sperm and egg cells contribute to successful fertilization and early development.
[1]
Question 50
Describe the biconcave shape of human erythrocytes.
[1]
Evaluate adaptations that increase surface area-to-volume ratio or membrane area in erythrocytes and proximal convoluted tubule cells.
[1]
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