B2.2 Organelles and compartmentalization
Practice exam-style IB Biology questions for Organelles and compartmentalization, aligned with the syllabus and grouped by topic.
Question 1
A cell structure is described as a discrete subunit adapted to carry out a specific function. Which structure fits this description as an organelle in this syllabus?
A.
Cell wall
B.
Ribosome
C.
Cytoplasm
D.
Cytoskeleton
Question 2
The plasma membrane is considered an organelle in this syllabus because it is a defined cell structure with specific functions. Which function is most directly associated with it?
A.
Storage of cellulose outside animal cells
B.
Control of movement of substances into and out of the cell
C.
Production of chromosomes by translation
D.
Formation of a cell-wide filament network
Question 3
What is an advantage of separating the nucleus from the cytoplasm in eukaryotic cells?
A.
Ribosomes are prevented from synthesizing proteins.
B.
DNA leaves the nucleus to be translated directly.
C.
Translation can occur before transcription has finished.
D.
mRNA can be modified before meeting ribosomes.
Question 4
During cell fractionation, why are cells usually homogenized in a cold, buffered solution?
A.
To increase enzyme activity and dissolve organelle membranes
B.
To convert all organelles into ribosomes
C.
To slow enzyme activity and help maintain suitable pH
D.
To make the cytoplasm an extracellular structure
Question 5
Which statement gives a benefit of concentrating enzymes and metabolites in a membrane-bound compartment?
A.
It prevents all metabolic reactions from occurring.
B.
It makes metabolites identical to membranes.
C.
It removes the need for enzymes in metabolism.
D.
It increases the probability of enzyme–substrate collisions.
Question 6
In chloroplasts, where are photosystems located?
A.
Mitochondrial matrix
B.
Nuclear pores
C.
Thylakoid membranes
D.
Golgi cisternae
Question 7
State one reason why a ribosome is considered an organelle.
[1]
State one cell structure that is not considered an organelle in this syllabus.
[1]
Question 8
The diagram shows a cell engulfing a bacterium by phagocytosis.
Identify the compartment labelled X that contains the engulfed bacterium.
[1]
State the organelle that can fuse with X.
[1]
State the result of this fusion.
[1]
Question 9
A phagocytic vacuole fuses with a lysosome. What is the main benefit of this compartmentalization?
A.
It converts ribosomes into lysosomal enzymes.
B.
It allows digestion of engulfed material without releasing hydrolytic enzymes into the cytoplasm.
C.
It prevents any movement of water across membranes.
D.
It stores chromosomes away from the cytoplasm.
Question 10
A homogenate is centrifuged at increasing speeds. Which fraction would normally form a pellet before ribosomes?
A.
Nuclei
B.
Individual amino acids
C.
mRNA molecules
D.
Soluble enzymes
Question 11
What is the advantage of the small volume of the mitochondrial intermembrane space?
A.
Hydrolytic enzymes can digest engulfed bacteria.
B.
A proton concentration gradient can build up rapidly.
C.
Glucose can be stored as starch in the matrix.
D.
DNA can be translated before transcription.
Question 12
A protein is synthesized for secretion from a pancreatic cell. Where is its translation most likely to occur?
A.
In the thylakoid lumen
B.
On ribosomes attached to rough endoplasmic reticulum
C.
On free ribosomes for retention in the cytoplasm
D.
Inside nuclear pores
Question 13
What is the role of the trans face of the Golgi apparatus?
A.
Shipping processed proteins in vesicles to their destinations
B.
Binding mRNA during translation
C.
Pumping protons across cristae
D.
Receiving unprocessed proteins directly from free ribosomes
Question 14
During mitosis, what happens to the nuclear envelope in many eukaryotic cells?
A.
It breaks into vesicles that can later fuse to reform nuclear envelopes.
B.
It is translated by ribosomes into chromosomes.
C.
It becomes a permanent cell wall around the chromosomes.
D.
It converts to thylakoid membranes for photosynthesis.
Question 15
Cells are broken open to produce a homogenate before differential centrifugation.
Define homogenate.
[1]
Outline how differential centrifugation separates organelles.
[1]
Question 16
State where transcription occurs in a eukaryotic cell.
[1]
Explain how the nucleus allows post-transcriptional modification of mRNA before translation.
[1]
Question 17
A lysosome contains hydrolytic enzymes.
State the function of a lysosome.
[1]
Explain why containing these enzymes in a membrane-bound organelle is advantageous.
[1]
Question 18
Explain how the development of ultracentrifuges contributed to understanding the functions of organelles. [2]
Question 19
State the location of enzymes and substrates of the Krebs cycle in a mitochondrion.
[1]
Explain one advantage of this compartmentalization.
[1]
Question 20
Contrast free ribosomes and ribosomes attached to rough endoplasmic reticulum. [4]
Question 21
The graph shows the relative amount of different cell components recovered in pellets after centrifuging a liver-cell homogenate at increasing speeds.
Identify the component that pellets at the lowest centrifugation speed.
[1]
Describe the relationship between centrifugation speed and the size of components remaining in the supernatant.
[1]
Explain why differential centrifugation allowed organelle function to be investigated.
[1]
Suggest why the homogenate was kept cold.
[1]
Question 22
The table classifies several cell structures according to whether they are discrete, membrane-bound and adapted to a specific function.
| Cell structure | Discrete subunit | Membrane-bound | Specific function |
|---|---|---|---|
| Ribosome | Yes | No | Polypeptide synthesis |
| Nucleus | Yes | Yes | Stores DNA; controls gene expression |
| Vesicle | Yes | Yes | Transport or storage of substances |
| Plasma membrane | No | Yes | Selective boundary controlling exchange |
| Cytoplasm | No | No | Medium for many metabolic reactions |
| Cytoskeleton | Yes | No | Cell support and movement |
| Cell wall | No | No | Rigid support and protection |
Identify one non-membrane-bound organelle from the table.
[1]
Identify one structure in the table that is not an organelle.
[1]
Explain why being membrane-bound is not a necessary condition for being an organelle in this syllabus.
[1]
Question 23
Why can translation begin on an mRNA molecule before transcription has finished in prokaryotes?
A.
Prokaryotic ribosomes are inside a double membrane.
B.
Prokaryotic transcription occurs on the rough endoplasmic reticulum.
C.
Prokaryotic mRNA is translated only after leaving the nucleus.
D.
Prokaryotes have no nuclear compartment separating DNA from ribosomes.
Question 24
What is a functional benefit of pores in the nuclear envelope?
A.
They prevent any protein from entering the nucleus.
B.
They allow controlled passage of large molecules such as mRNA and ribosomal subunits.
C.
They form clathrin coats on vesicles.
D.
They pump protons into thylakoids.
Question 25
What is the role of clathrin in vesicle formation?
A.
It catalyses peptide bond formation at ribosomes.
B.
It absorbs light energy in photosystems.
C.
It hydrolyses proteins inside lysosomes.
D.
It forms a coat that helps curve a membrane into a budding vesicle.
Question 26
The cristae of mitochondria are extensive in cells with high ATP demand. What explains this relationship?
A.
Cristae increase surface area for proteins involved in oxidative phosphorylation.
B.
Cristae digest worn-out organelles using hydrolytic enzymes.
C.
Cristae store mRNA before it leaves the nucleus.
D.
Cristae contain photosystems for light absorption.
Question 27
Distinguish between gene expression in eukaryotes and prokaryotes with respect to separation of transcription and translation. [2]
Question 28
A cell carries out a metabolic pathway in a small membrane-bound compartment.
State what is meant by a metabolite.
[1]
Suggest two advantages of compartmentalizing the pathway.
[1]
Question 29
Outline how thylakoids are adapted for the light-dependent reactions of photosynthesis. [3]
Question 30
The nuclear envelope is a double membrane with pores.
State one type of molecule or structure that exits the nucleus through nuclear pores.
[1]
Explain why nuclear pores must be regulated.
[1]
Question 31
Describe the role of the Golgi apparatus in protein secretion. [3]
Question 32
The diagram shows a coated pit forming at the plasma membrane.
Identify the coat protein labelled C.
[1]
Describe how this protein contributes to vesicle formation.
[1]
Question 33
The table compares gene expression in two cell types.
| Feature | Cell type A | Cell type B |
|---|---|---|
| Membrane-bound nucleus | Absent | Present |
| Ribosome location | Cytoplasm | Cytoplasm and rough ER |
| Transcription site | Cytoplasm | Nucleus |
| Translation site | Cytoplasm | Cytoplasm |
| Transcription and translation in same compartment | Yes | No |
| Ribosomes on newly forming mRNA | Observed | Not observed |
Identify which cell type is eukaryotic.
[1]
State the evidence from the table that supports your answer.
[1]
Explain why post-transcriptional modification of mRNA is more likely in the eukaryotic cell.
[1]
Question 34
A researcher measured the rate of digestion of a protein substrate by lysosomal enzymes under different conditions.
Identify the condition with the highest digestion rate.
[1]
Compare digestion when lysosomal enzymes are inside intact vesicles with digestion when vesicles are ruptured into neutral cytoplasm.
[1]
Suggest why lysosomal compartmentalization protects the cell.
[1]
Question 35
The graph compares mitochondrial structure in two muscle fibre types.
Identify the fibre type with the greater cristae surface area per mitochondrion.
[1]
State the relationship between cristae surface area and ATP production rate shown.
[1]
Explain the relationship using mitochondrial structure.
[1]
Suggest why both fibre types still have a small intermembrane space.
[1]
Question 36
The graph shows the effect of thylakoid lumen volume on the time taken to establish a proton gradient during illumination.
Describe the trend shown.
[1]
Explain why a smaller thylakoid lumen affects gradient formation.
[1]
State where the Calvin cycle enzymes are compartmentalized in a chloroplast.
[1]
Question 37
Explain how the structure of a chloroplast separates light-dependent reactions from the Calvin cycle while allowing the products of the light-dependent reactions to be used. [4]
Question 38
Explain two functional benefits of the double membrane of the nucleus during the cell cycle. [4]
Question 39
The diagram shows two models for organizing enzymes of the same metabolic pathway in a eukaryotic cell.
Identify the model predicted to give the higher reaction rate at low substrate concentration.
[1]
Give one reason for your answer.
[1]
Suggest one possible disadvantage of keeping the pathway in a separate organelle.
[1]
Evaluate the claim that compartmentalization always increases metabolic efficiency.
[1]
Question 40
A pulse-label experiment used radioactive amino acids to follow newly synthesized proteins in secretory cells. Radioactivity was measured in cell fractions over time.
Identify the organelle fraction labelled first after the pulse.
[1]
Identify the fraction with peak radioactivity later in the experiment.
[1]
Explain why proteins for secretion are first associated with the organelle identified in (a).
[1]
Suggest the route taken by these proteins after leaving that organelle.
[1]
Question 41
Cells were treated with a drug that disrupts Golgi cisternae but does not stop translation. The table shows amounts of three proteins inside cells and secreted outside cells.
| Protein | Control inside / a.u. | Control outside / a.u. | Drug inside / a.u. | Drug outside / a.u. |
|---|---|---|---|---|
| Secreted enzyme | 15 | 82 | 74 | 11 |
| Plasma-membrane protein | 22 | 64 | 67 | 18 |
| Cytosolic enzyme | 88 | 4 | 90 | 3 |
Identify the protein most affected in secretion by the drug.
[1]
Describe the effect of the drug on intracellular accumulation of secretory proteins.
[1]
Explain the role of the Golgi apparatus that accounts for these results.
[1]
Suggest why a cytosolic enzyme is much less affected.
[1]
Question 42
Outline what is meant by an organelle, using two examples from this syllabus.
[1]
Discuss how cell fractionation and ultracentrifugation contributed to understanding organelle function.
[1]
Question 43
State the sites of transcription and translation in eukaryotic cells.
[1]
Compare and contrast the relationship between transcription and translation in eukaryotic and prokaryotic cells.
[1]
Question 44
Distinguish between an organelle and a cell structure that is not considered an organelle.
[1]
Discuss structure–function correlation in organelles, using examples from SL content.
[1]
Question 45
The graph shows the number of internalized receptors in cells with normal clathrin and in cells where clathrin expression was reduced.
Compare receptor internalization in the two cell types.
[1]
Explain how clathrin normally promotes vesicle formation.
[1]
Suggest one effect of reduced clathrin on transport of membrane proteins.
[1]
Predict whether secretion of soluble proteins from Golgi-derived vesicles would necessarily stop completely. Give a reason.
[1]
Question 46
Outline two advantages of compartmentalization in the cytoplasm.
[1]
Evaluate the importance of compartmentalization using lysosomes and phagocytic vacuoles as examples.
[1]
Question 47
Outline two adaptations of the mitochondrion for ATP production.
[1]
Compare and contrast how mitochondria and chloroplasts use compartmentalization to support energy transformations.
[1]
Question 48
Outline the structure of the nuclear envelope.
[1]
Discuss functional benefits of the double nuclear membrane during interphase and nuclear division.
[1]
Question 49
Distinguish between free ribosomes and rough ER-bound ribosomes in terms of protein destination.
[1]
Evaluate the statement: "Protein secretion depends on compartmentalization of the endomembrane system."
[1]
Question 50
Describe the structure of a vesicle and the role of clathrin in forming some vesicles.
[1]
Discuss how vesicles contribute to compartmentalization and protein traffic in eukaryotic cells.
[1]
The Fast Track To Your
Best IB Coursework & College Essays
All content on this website has been developed independently from and is not endorsed by the International Baccalaureate Organization. International Baccalaureate and IB are registered trademarks owned by the International Baccalaureate Organization.