A2.2 Cell structure
Practice exam-style IB Biology questions for Cell structure, aligned with the syllabus and grouped by topic.
Question 1
Cell theory allows a prediction to be made about a newly discovered organism. What is this prediction?
A.
It will contain chloroplasts in all cells.
B.
It will have cells with nuclei.
C.
It will be composed of one or more cells.
D.
It will be visible using a light microscope.
Question 2
A student focuses a temporary mount under low power before changing to high power. What adjustment should be used to sharpen the image at high power?
A.
Fine focus only
B.
Stage micrometer only
C.
Coarse focus only
D.
Condenser removed from the microscope
Question 3
A cell is 60 mm long in a photomicrograph taken at ×1500 magnification. What is the actual length of the cell?
A.
40 µm
B.
9000 µm
C.
400 µm
D.
90 µm
Question 4
What structures are found in typical cells of all living organisms?
A.
Nucleus, cytoplasm and a cell wall
B.
Mitochondria, DNA and ribosomes
C.
Chloroplasts, cytoplasm and a plasma membrane
D.
DNA, cytoplasm and a plasma membrane
Question 5
What observation supports the endosymbiotic origin of mitochondria?
A.
Mitochondria contain linear chromosomes with histones.
B.
Mitochondria are formed from Golgi vesicles.
C.
Mitochondria contain naked circular DNA.
D.
Mitochondria have 80S ribosomes in their matrix.
Question 6
What is an example of an environmental trigger for differentiation?
A.
Identical activation of every gene in the genome
B.
Permanent removal of the plasma membrane
C.
Random loss of ribosomes from the cytoplasm
D.
A chemical signal from neighbouring cells
Question 7
A student prepares a temporary mount of onion epidermis.
State one reason for lowering the cover slip at an angle.
[1]
Outline why iodine solution may be added.
[1]
State one feature of a specimen that makes it suitable for viewing with a light microscope.
[1]
Question 8
What feature of electron microscopy explains its ability to reveal cell ultrastructure?
A.
Electrons have a shorter wavelength than visible light.
B.
Electron beams pass through thick whole organisms.
C.
Electron microscopes produce naturally coloured images.
D.
Electrons stain living tissues more strongly than dyes.
Question 9
A small cell has a thick peptidoglycan wall, cytoplasm, 70S ribosomes and a pale nucleoid region. What type of cell is it?
A.
Plant mesophyll cell
B.
Fungal hyphal cell
C.
Gram-positive eubacterial cell
D.
Animal epithelial cell
Question 10
What structure is bounded by a double membrane with pores and contains chromosomes made of DNA associated with histones?
A.
Golgi apparatus
B.
Rough endoplasmic reticulum
C.
Nucleus
D.
Lysosome
Question 11
According to endosymbiotic theory, what event occurred after the origin of mitochondria in some eukaryotic lineages?
A.
The nucleus was lost from the ancestral eukaryote.
B.
All eukaryotes became photosynthetic organisms.
C.
A photosynthetic prokaryote was retained as a chloroplast.
D.
Mitochondrial 70S ribosomes changed into 80S ribosomes.
Question 12
What prediction follows from the theory that mitochondria evolved from bacterial endosymbionts?
A.
Mitochondrial genes should show similarity to bacterial genes.
B.
Mitochondria should be absent from all unicellular eukaryotes.
C.
Mitochondria should divide only during nuclear envelope breakdown.
D.
Mitochondrial membranes should be made of cellulose.
Question 13
What is the immediate molecular basis of cell differentiation in a multicellular organism?
A.
Loss of all housekeeping genes
B.
Identical protein production in every tissue
C.
Different patterns of gene expression
D.
Replacement of DNA by RNA in specialized cells
Question 14
What statement about the evolution of multicellularity is supported by current biological diversity?
A.
Multicellularity evolved once before the origin of all prokaryotes.
B.
Multicellularity is found only in animals.
C.
Multicellularity always replaces unicellular life in every habitat.
D.
Multicellularity evolved repeatedly in different eukaryotic lineages.
Question 15
A scale bar labelled 25 µm measures 12.5 mm on a printed photomicrograph.
Calculate the magnification of the printed image.
[1]
State one advantage of including a scale bar rather than only writing a magnification.
[1]
Question 16
Distinguish between magnification and resolution in microscopy. [2]
Question 17
Outline four structural features of a typical Gram-positive eubacterial cell. [4]
Question 18
A unicellular freshwater organism has cilia, food vacuoles and a contractile vacuole.
Identify the process of life shown by the cilia.
[1]
Identify the process of life shown by food vacuoles.
[1]
Explain the role of the contractile vacuole.
[1]
Question 19
Outline three pieces of evidence for the endosymbiotic origin of mitochondria. [3]
Question 20
Define cell differentiation.
[1]
State what is meant by a housekeeping gene.
[1]
Question 21
State three advantages of multicellularity. [3]
Question 22
A photomicrograph of pond cells was taken with a calibrated eyepiece graticule.
| Measurement | Value |
|---|---|
| Graticule calibration | 1 division = 8.0 µm |
| Length of cell X on graticule | 12.5 divisions |
| Length of cell X on printed image | 50.0 mm |
State the actual length of cell X using the graticule scale.
[1]
Calculate the magnification of the printed image of cell X.
[1]
Suggest one source of error when measuring cell length from this image.
[1]
Question 23
A eukaryotic cell has a cell wall but no chloroplasts. Chemical testing shows the wall contains chitin. What is the most likely cell type?
A.
Animal cell
B.
Plant cell
C.
Gram-positive bacterial cell
D.
Fungal cell
Question 24
What condition could natural selection favour during an early transition to multicellularity?
A.
Every cell must immediately lose its genome.
B.
Daughter cells remain attached and cooperate after division.
C.
All cells become completely independent after each division.
D.
Cell specialization disappears from the population.
Question 25
A liver cell and a nerve cell from the same mammal have different shapes and functions mainly because they have different patterns of what process?
A.
Plasma membrane lipid formation
B.
Chromosome number in every nucleus
C.
Gene expression
D.
Genetic code usage
Question 26
Explain why typical cells have a lipid-based plasma membrane and cytoplasm composed mainly of water. [3]
Question 27
Compare prokaryotic and eukaryotic cells with reference to genetic material and ribosomes. [4]
Question 28
Distinguish red blood cells, skeletal muscle fibres and aseptate fungal hyphae using number of nuclei. [3]
Question 29
Explain how natural selection could favour a host cell retaining an aerobic endosymbiont. [3]
Question 30
Explain how an environmental signal can lead to development of a specialized tissue. [3]
Question 31
Explain why multicellularity is not considered a universal improvement over unicellularity. [3]
Question 32
Suggest how a simple group of cells that remains attached after division could evolve into a more integrated multicellular organism. [3]
Question 33
The electron micrograph shows three cell types labelled A, B and C.
Identify the cell type labelled A.
[1]
Give one visible feature that supports your identification of A.
[1]
Identify one structure labelled in cell B that is evidence it is eukaryotic.
[1]
Compare cell B and cell C using two visible features.
[1]
Question 34
The graph shows the minimum distance that can be resolved by three imaging systems.
Identify the imaging system with the greatest resolving power.
[1]
Describe the trend shown in minimum resolvable distance from the unaided eye to electron microscopy.
[1]
Explain why increasing magnification without improving resolution may not reveal more cell detail.
[1]
Question 35
An electron micrograph of an intestinal epithelial cell is shown.
Identify structure X.
[1]
State the function of structure X.
[1]
Identify organelle Y.
[1]
Suggest why many copies of organelle Y are present near the surface of the cell.
[1]
Question 36
The table compares features of isolated mitochondria, chloroplasts, bacterial cells and eukaryotic nuclei.
| Feature | Mitochondria | Chloroplasts | Bacteria | Euk. nuclei |
|---|---|---|---|---|
| Ribosome type | 70S | 70S | 70S | None |
| DNA form | Circular DNA | Circular DNA | Circular DNA | Linear DNA |
| Replication | Fission | Fission | Binary fission | Mitosis |
| Membranes | 2 | 2 | 1 | 2 |
Identify one feature shared by mitochondria and bacteria.
[1]
Identify one feature shared by chloroplasts and bacteria.
[1]
Explain how the data support the endosymbiotic origin of mitochondria and chloroplasts.
[1]
Suggest one additional molecular comparison that could test the theory.
[1]
Question 37
Evaluate the statement: “A theory is strengthened when it explains observations and supports predictions,” using endosymbiotic theory as an example. [4]
Question 38
The table summarizes observations of a unicellular organism during 10 minutes in freshwater.
| Time / min | Light direction | Net swimming | CV contractions / min | Food vacuoles / cell | Cell length / µm |
|---|---|---|---|---|---|
| 0 | none | random | 3 | 0 | 124 |
| 2 | none | random | 4 | 1 | 125 |
| 4 | left | turns left | 4 | 1 | 125 |
| 6 | left | left | 5 | 2 | 126 |
| 8 | left | left | 5 | 2 | 127 |
| 10 | left | left | 4 | 3 | 128 |
Identify the process of life indicated by repeated contraction of the contractile vacuole.
[1]
Describe how the movement of the organism changes when light is shone from one side.
[1]
Explain how two observations in the table show that a single cell can carry out life functions.
[1]
Suggest why metabolic waste can be removed without a specialized excretory organ.
[1]
Question 39
The graph shows relative expression of four genes in three specialized cell types from the same animal.
Identify the gene most likely to be a housekeeping gene.
[1]
Identify the gene most strongly associated with cell type 2.
[1]
Explain how the graph supports the idea that differentiation is based on differential gene expression.
[1]
Question 40
Stem cells were grown with different concentrations of a signalling molecule. The percentage of cells expressing a muscle-specific protein was measured.
Describe the relationship between signal concentration and muscle-specific protein expression.
[1]
Suggest why a control with no signalling molecule was included.
[1]
Explain how the results show that environment can trigger differentiation.
[1]
Question 41
A population of unicellular algae was observed for 200 generations. Some lineages formed clusters because daughter cells did not separate after division.
Describe the change in average cluster size over the experiment.
[1]
Suggest why clusters may have had higher survival when a filter-feeding predator was present.
[1]
Explain how natural selection could increase the frequency of cluster-forming lineages.
[1]
Question 42
Outline two features common to typical cells in all living organisms.
[1]
Compare and contrast prokaryotic and eukaryotic cell structure.
[1]
Question 43
Describe two advantages of electron microscopy for studying cells.
[1]
Evaluate the use of different microscopy techniques for investigating cell structure and function.
[1]
Question 44
Identify two atypical eukaryotic cell structures with no nucleus at maturity.
[1]
Explain how atypical numbers of nuclei are related to function in red blood cells, phloem sieve tube elements and skeletal muscle fibres.
[1]
Question 45
The diagram shows a simplified phylogeny of eukaryotes with unicellular, colonial and multicellular forms marked on different branches.
State how many separate origins of multicellularity are indicated.
[1]
Identify one lineage in which multicellularity is shown.
[1]
Explain how the pattern supports repeated evolution of multicellularity.
[1]
Suggest one advantage that could have favoured multicellular forms in one of these lineages.
[1]
Question 46
State three structural features that can distinguish plant, fungal and animal cells.
[1]
Discuss how differences in eukaryotic cell structure are related to function, using plant, fungal and animal cells.
[1]
Question 47
Outline the sequence of events proposed by endosymbiotic theory for the origin of mitochondria and chloroplasts.
[1]
Evaluate the evidence that mitochondria and chloroplasts had an endosymbiotic origin.
[1]
Question 48
Define gene expression and cell differentiation.
[1]
Discuss how different specialized tissues can develop from cells with the same genome.
[1]
Question 49
State two predictions supported by endosymbiotic theory.
[1]
Discuss why endosymbiotic theory is considered a compelling theory.
[1]
Question 50
Outline two advantages of multicellularity.
[1]
Evaluate how natural selection can explain both the evolution of multicellularity and the continued success of unicellular organisms.
[1]
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