IB Biology Quiz: Apply Cell Structure
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Apply Cell StructureQuestion 1 of 20

A researcher identifies a cell with a cell wall containing chitin, a plasma membrane, 80S ribosomes, and membrane-bound organelles, but lacking chloroplasts. Which conclusion about the cell's identity and function is most justified by these structural features?

It is a plant cell specialized for structural support, as indicated by the presence of a cell wall and lack of chloroplasts.
It is a prokaryotic cell from the domain Archaea, as it possesses a cell wall and ribosomes for protein synthesis.
It is a fungal cell, likely functioning as a heterotrophic decomposer, based on the chitinous cell wall and absence of chloroplasts.
It is an animal cell that has been modified for storage, as it contains membrane-bound organelles but cannot photosynthesize.
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IB Biology Quiz

IB Biology Quiz: Apply Cell Structure

Practice Apply Cell Structure in IB Biology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Apply Cell Structure, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Biology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A researcher identifies a cell with a cell wall containing chitin, a plasma membrane, 80S ribosomes, and membrane-bound organelles, but lacking chloroplasts. Which conclusion about the cell's identity and function is most justified by these structural features?

  1. It is a plant cell specialized for structural support, as indicated by the presence of a cell wall and lack of chloroplasts.
  2. It is a prokaryotic cell from the domain Archaea, as it possesses a cell wall and ribosomes for protein synthesis.
  3. It is a fungal cell, likely functioning as a heterotrophic decomposer, based on the chitinous cell wall and absence of chloroplasts. (correct answer)
  4. It is an animal cell that has been modified for storage, as it contains membrane-bound organelles but cannot photosynthesize.
Explanation: The presence of a cell wall with chitin is a defining characteristic of fungi. The 80S ribosomes and membrane-bound organelles confirm it is eukaryotic. The absence of chloroplasts indicates a heterotrophic lifestyle, consistent with a decomposer role. A is incorrect because plant cell walls contain cellulose, not chitin. B is incorrect because the cell is eukaryotic (80S ribosomes, organelles), not prokaryotic. D is incorrect because animal cells lack a cell wall.

Question 2

A scientist observes a microorganism using an electron microscope. It has a cell wall, a plasma membrane, a nucleoid region with a circular chromosome, and no visible mitochondria. However, the cell performs aerobic respiration. Where are the components of the electron transport chain most likely located in this cell?

  1. On the outer surface of the cell wall, allowing direct interaction with the environment.
  2. Freely floating in the cytoplasm, near the nucleoid region.
  3. Integrated into the plasma membrane, which is folded to increase surface area. (correct answer)
  4. Within the nucleoid region, closely associated with the cell's genetic material.
Explanation: The description matches a prokaryotic cell (nucleoid, no mitochondria). In prokaryotes that perform aerobic respiration, the enzymes and protein complexes of the electron transport chain are located in the plasma membrane. This membrane is often folded into structures called mesosomes to increase the surface area available for these reactions, analogous to the cristae of mitochondria in eukaryotes.

Question 3

Paramecium is a single-celled eukaryote that lives in freshwater. It has a specialized organelle called a contractile vacuole, which actively pumps water out of the cell. What does the presence and function of this organelle imply about the cell's structure and its environment?

  1. The Paramecium cell has a cell wall that prevents it from shrinking in a hypertonic environment.
  2. The cytoplasm of the Paramecium is hypertonic to the surrounding freshwater environment. (correct answer)
  3. The Paramecium lacks a plasma membrane, requiring a vacuole to regulate substance exchange.
  4. The cytoplasm of the Paramecium is hypotonic to the surrounding freshwater environment.
Explanation: Freshwater is a hypotonic environment relative to the cell's cytoplasm. This means the cell's cytoplasm has a higher solute concentration (is hypertonic) than the outside. Consequently, water continuously enters the cell by osmosis. The contractile vacuole is an adaptation to actively expel this excess water to prevent the cell from lysing, as it lacks a cell wall. A is incorrect as Paramecium does not have a cell wall. C is incorrect as all cells have a plasma membrane. D states the opposite of the correct osmotic relationship.

Question 4

A scientist treats a culture of eukaryotic cells with a toxin that specifically causes the breakdown of the cytoskeletal component actin filaments (microfilaments). Which cellular process would be most directly disrupted?

  1. The separation of chromosomes during anaphase of mitosis.
  2. The transport of vesicles from the Golgi apparatus to the plasma membrane.
  3. The formation of the cleavage furrow during cytokinesis in an animal cell. (correct answer)
  4. The whip-like movement of a flagellum used for cell motility.
Explanation: Actin filaments form a contractile ring that pinches the cell membrane inward, creating the cleavage furrow during animal cell cytokinesis. Disruption of actin would directly prevent this. Chromosome separation (A) is mediated by microtubules of the spindle apparatus. Vesicle transport (B) is primarily along microtubule tracks. Flagellar movement (D) is also driven by microtubules in a '9+2' arrangement. Therefore, cytokinesis is the process most dependent on actin filaments.

Question 5

Atypical cells, like giant algae (Acetabularia) and striated muscle fibres, challenge certain aspects of the cell theory.

In what way does a striated muscle fibre challenge the concept that a cell is a single, simple structural unit?

  1. It is much smaller than a typical eukaryotic cell, questioning the lower limit of cell size.
  2. It contains multiple nuclei within a single, continuous cytoplasm and cell membrane. (correct answer)
  3. It lacks a plasma membrane, instead being surrounded only by a protein-based cell wall.
  4. It functions as a complete, self-sustaining organism despite being part of a larger tissue.
Explanation: Striated muscle fibres are very large and are multi-nucleated (a syncytium). This challenges the simple idea of a cell having one nucleus. They are formed by the fusion of many individual muscle cells. A is incorrect; they are much larger, not smaller. C is incorrect; they have a plasma membrane (sarcolemma). D is incorrect; they are a specialized part of a multicellular organism, not self-sustaining.

Question 6

[HL Content] A bacteriophage is a virus that infects bacteria.

How does the fundamental structure of a bacteriophage differ from the structure of the bacterium it infects?

  1. The bacteriophage has a protein capsid and DNA, while the bacterium has a cell wall and RNA.
  2. The bacteriophage has a simple cell wall, whereas the bacterium has a complex protein capsid.
  3. The bacteriophage contains 80S ribosomes, whereas the bacterium contains 70S ribosomes.
  4. The bacteriophage lacks a plasma membrane and cytoplasm, which are present in the bacterium. (correct answer)
Explanation: Viruses, including bacteriophages, are non-cellular. They consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid). They fundamentally lack the structures of a living cell, such as a plasma membrane, cytoplasm, and organelles like ribosomes. Bacteria are cells and possess all these features. A is incorrect as bacteria have DNA (and RNA). C is incorrect as viruses lack ribosomes entirely. D incorrectly swaps the structural components of the virus and bacterium.

Question 7

A student is examining a cell under a microscope and observes that it lacks a nucleus but possesses a thick layer of peptidoglycan. They also note the presence of pili on the cell surface. Which deduction is most valid?

  1. The cell is a prokaryote from the domain Bacteria, potentially involved in conjugation. (correct answer)
  2. The cell is a prokaryote from the domain Archaea, adapted to an extreme environment.
  3. The cell is a eukaryote from the domain Fungi, likely a yeast.
  4. The cell is a plant cell that has lost its nucleus during differentiation, like a sieve tube element.
Explanation: The lack of a nucleus indicates a prokaryote. The presence of peptidoglycan in the cell wall is the defining characteristic of the domain Bacteria (Archaean cell walls lack peptidoglycan). Pili are surface appendages often used for attachment or for transferring genetic material during conjugation, a process common in bacteria. A and D are incorrect because they are eukaryotes. B is incorrect because Archaea lack peptidoglycan.

Question 8

Lysosomes are organelles containing hydrolytic enzymes. A genetic disorder causes these lysosomal enzymes to be incorrectly tagged during their synthesis, resulting in them being secreted from the cell instead of being packaged into lysosomes.

What is the most likely direct consequence for the cell's internal environment?

  1. An accumulation of damaged organelles and undigested macromolecules within the cytoplasm. (correct answer)
  2. The pH of the cytoplasm will become dangerously acidic due to the release of hydrolytic enzymes.
  3. A rapid decrease in the rate of ATP synthesis due to a lack of enzyme processing by the lysosome.
  4. The cell will be unable to synthesize proteins, as ribosomes will be digested by the misdirected enzymes.
Explanation: The primary role of lysosomes is autophagy (breaking down old organelles) and digesting macromolecules. If the enzymes are not correctly delivered to the lysosomes, these waste products cannot be broken down and will accumulate within the cell, leading to cellular damage. A is incorrect as ATP synthesis occurs in mitochondria. B is incorrect as the enzymes are secreted out of the cell, not into the cytoplasm. D is incorrect for the same reason; the enzymes are not released into the cytoplasm to digest ribosomes.

Question 9

A cell type is specialized for producing and secreting large quantities of glycoprotein-based antibodies. A mutation arises that deactivates the signal recognition particle (SRP), which is responsible for binding to a signal sequence on a newly forming polypeptide and directing the ribosome to the endoplasmic reticulum.

What is the most likely immediate consequence of this mutation for the cell's primary function?

  1. Antibody proteins will accumulate in the cytoplasm instead of entering the endomembrane system for processing and secretion. (correct answer)
  2. The Golgi apparatus will swell with unprocessed antibodies that cannot be correctly folded or glycosylated.
  3. Translation of antibody mRNA will be completely blocked, and no polypeptide chains will be formed by any ribosomes.
  4. The cell will be unable to produce sufficient ATP to power the synthesis and transport of the large antibody molecules.
Explanation: The SRP is essential for targeting proteins destined for secretion to the rough ER. Without a functional SRP, the ribosomes translating antibody mRNA will remain free in the cytoplasm, and the complete antibody proteins will be released there. They will not enter the endomembrane pathway (ER -> Golgi -> vesicles) for modification and export. B is incorrect because the proteins never reach the Golgi. C is incorrect as translation itself is not blocked, only the targeting to the ER. D is an indirect effect, not the immediate consequence of the SRP failure.

Question 10

A pharmaceutical company develops a new drug that selectively inhibits the synthesis of proteins on free ribosomes within the cytoplasm of eukaryotic cells, but does not affect ribosomes attached to the endoplasmic reticulum.

Which of the following cellular functions would be most immediately and severely compromised in a cell treated with this drug?

  1. The secretion of hormones, such as insulin, from pancreatic beta cells.
  2. The production of lysosomal enzymes required for intracellular digestion.
  3. The synthesis of enzymes essential for glycolysis in the cytoplasm. (correct answer)
  4. The insertion of protein channels into the plasma membrane.
Explanation: Free ribosomes synthesize proteins that function within the cytoplasm, such as the enzymes for glycolysis. The drug inhibits this process. Secreted proteins (A), lysosomal enzymes (B), and membrane proteins (D) are all synthesized on ribosomes attached to the rough endoplasmic reticulum, which the drug does not affect. Therefore, the synthesis of cytoplasmic enzymes would be the most directly impacted.

Question 11

A cell in a plant leaf is actively photosynthesizing. A cell in the root of the same plant is actively absorbing mineral ions from the soil. Which structural comparison between these two specialized cells is most accurate?

  1. The leaf cell has a thicker cell wall than the root cell to support the leaf structure.
  2. The root cell has a higher density of chloroplasts than the leaf cell to store energy.
  3. The leaf cell has a larger central vacuole than the root cell to store water for photosynthesis.
  4. The root cell has a higher density of mitochondria than the leaf cell to provide ATP for active transport. (correct answer)
Explanation: Active transport of mineral ions into the root is an energy-intensive process that requires large amounts of ATP. Therefore, root cells will have numerous mitochondria to supply this energy via cellular respiration. Leaf cells also have mitochondria but rely on light for energy for photosynthesis. A is incorrect, support cells like xylem have thick walls, not necessarily photosynthetic cells. B is incorrect, root cells are not photosynthetic and lack chloroplasts. C is incorrect, both cells have large vacuoles for turgor, but this is not the most significant functional difference.

Question 12

A plant cell and an animal cell are placed in a hypotonic solution. The plant cell becomes turgid, while the animal cell lyses (bursts). Which structural difference is the primary reason for this different outcome?

  1. The presence of a large central vacuole in the plant cell, which can absorb excess water and prevent lysis.
  2. The selective permeability of the plant cell's plasma membrane, which is absent in the animal cell.
  3. The presence of a rigid cellulose cell wall in the plant cell, which withstands the internal turgor pressure. (correct answer)
  4. The presence of chloroplasts in the plant cell, which utilize water for photosynthesis, reducing the osmotic potential.
Explanation: The key difference is the cell wall. In a hypotonic solution, water enters both cells via osmosis. In the animal cell, this influx of water increases pressure on the plasma membrane until it ruptures. In the plant cell, the strong, rigid cellulose cell wall exerts an opposing pressure (turgor pressure), preventing the cell from swelling indefinitely and bursting. While the vacuole (A) swells, it is the wall that provides the ultimate structural resistance to lysis. Both cells have selectively permeable membranes (B). Photosynthesis (D) would not consume water fast enough to prevent lysis.

Question 13

The Golgi apparatus modifies, sorts, and packages proteins. A cell is genetically engineered to produce a protein that is normally found in the cytoplasm, but the engineering adds a signal sequence that directs it into the rough ER. What will be the ultimate fate of this protein?

  1. It will be correctly folded in the rough ER and then returned to the cytoplasm to perform its function.
  2. It will be immediately degraded in the cytoplasm before it can enter the rough ER.
  3. It will remain in the lumen of the rough ER, as it lacks the signal to be transported to the Golgi.
  4. It will be processed by the Golgi apparatus and packaged into vesicles for secretion out of the cell. (correct answer)
Explanation: Once a protein enters the endomembrane system via the rough ER, it follows the default pathway unless it has other specific targeting signals. The default pathway is ER -> Golgi -> secretory vesicles -> exocytosis. Since the cytoplasmic protein was artificially given an ER signal sequence, it will enter this pathway and be secreted from the cell, even though that is not its normal location. There is no standard mechanism to return a protein from the ER to the cytoplasm (A). The protein will move from the ER to the Golgi (C). It enters the ER before it can be degraded in the cytoplasm (D).

Question 14

[HL Content] A researcher studying a newly discovered protist hypothesizes that its chloroplasts arose from secondary endosymbiosis.

Which structural observation would provide the strongest evidence to support this hypothesis over one of primary endosymbiosis?

  1. The chloroplast contains circular DNA and 70S ribosomes.
  2. The chloroplast is surrounded by three or more membranes. (correct answer)
  3. The protist cell itself is surrounded by a rigid cell wall.
  4. The chloroplast's inner membrane composition resembles that of a prokaryotic cell.
Explanation: Primary endosymbiosis involves a eukaryote engulfing a cyanobacterium, resulting in a chloroplast with two membranes (the cyanobacterium's plasma membrane and the host's vacuolar membrane). Secondary endosymbiosis involves a eukaryote engulfing another eukaryotic alga that already had a primary chloroplast. This results in a chloroplast surrounded by more than two membranes (typically three or four). Options A and D are evidence for endosymbiosis in general but do not distinguish between primary and secondary events. Option C is unrelated to the origin of the organelle.

Question 15

The endosymbiotic theory proposes an origin for mitochondria and chloroplasts. Which structural feature of a modern eukaryotic cell provides the weakest evidence in support of this theory?

  1. Mitochondria are a similar size to typical prokaryotic cells.
  2. Mitochondria possess their own circular DNA molecules.
  3. Mitochondria are enclosed by a double membrane.
  4. Mitochondria are found within the cytoplasm of the eukaryotic cell. (correct answer)
Explanation: While it's true mitochondria are in the cytoplasm, this is a general feature of all organelles and does not specifically support the idea of an endosymbiotic origin. The other options are strong pieces of evidence: similarity in size to prokaryotes (A), possession of their own circular DNA like prokaryotes (B), and a double membrane consistent with engulfment via endocytosis (C) all strongly support the theory.

Question 16

A cell is found to have a high density of mitochondria with numerous, tightly packed cristae. Which of the following cells best fits this structural description?

  1. A human fat cell (adipocyte) specialized for energy storage.
  2. A sperm cell, in the midpiece region connecting the head and flagellum. (correct answer)
  3. A mature human red blood cell (erythrocyte) responsible for oxygen transport.
  4. A plant xylem vessel element responsible for water transport.
Explanation: A high density of mitochondria with many cristae indicates a very high rate of aerobic respiration to produce large amounts of ATP. The flagellum of a sperm cell requires a massive and constant supply of ATP to power its movement. These mitochondria are characteristically packed into the midpiece. Adipocytes (A) store energy but are not as metabolically active. Mature erythrocytes (C) and xylem vessels (D) are anucleated and lack mitochondria entirely.

Question 17

Which of the following provides the strongest evidence for the universal common ancestry of all life, based on cellular structure?

  1. The presence of a cell wall in plants, fungi, and bacteria, indicating a shared need for structural support.
  2. The use of ribosomes to synthesize proteins using a nearly universal genetic code. (correct answer)
  3. The compartmentalization of eukaryotic cells using membrane-bound organelles.
  4. The ability of both prokaryotic and eukaryotic cells to perform glycolysis.
Explanation: The fact that organisms from all three domains of life (Bacteria, Archaea, Eukarya) use ribosomes (though differing slightly in size) to translate nucleic acid information into proteins based on the same codons is powerful evidence for a single origin of life. A is incorrect because the composition of cell walls differs significantly (cellulose, chitin, peptidoglycan), suggesting convergent evolution rather than common ancestry. C is a feature of eukaryotes only. D is strong evidence, but the universality of the genetic code and the machinery to read it (ribosomes) is considered even more fundamental evidence of a shared origin.

Question 18

A cell that is part of the lining of the small intestine is specialized for absorption. Which combination of structural features would best support this function?

  1. A smooth plasma membrane, a thick cell wall, and numerous lysosomes.
  2. A high density of microvilli, numerous mitochondria, and abundant channel proteins. (correct answer)
  3. A well-developed smooth ER, a large central vacuole, and few mitochondria.
  4. A rigid cytoskeleton, a single flagellum for movement, and a high density of ribosomes.
Explanation: Absorption of nutrients is the key function. Microvilli vastly increase the surface area of the plasma membrane for absorption. Numerous mitochondria provide the ATP needed for the active transport of many nutrients. Abundant channel and carrier proteins are necessary to facilitate the movement of substances across the membrane. A is wrong because a smooth membrane has low surface area and animal cells don't have cell walls. C describes features more typical of a plant cell or one specialized for lipid synthesis. D describes features related to structure and protein synthesis, not absorption.

Question 19

Some prokaryotes, such as cyanobacteria, are photosynthetic. How does the cellular structure of a cyanobacterium accommodate the process of photosynthesis without chloroplasts?

  1. Photosynthetic pigments are embedded directly within the peptidoglycan cell wall.
  2. The entire process of photosynthesis occurs freely within the cytoplasm.
  3. Photosynthetic pigments and enzymes are located on internal extensions of the plasma membrane called thylakoids. (correct answer)
  4. A single, large chloroplast-like structure called a chromatophore is present in the cell.
Explanation: Prokaryotes lack membrane-bound organelles like chloroplasts. In photosynthetic prokaryotes, the necessary pigments (like chlorophyll) and electron transport chains are located on extensive internal membrane systems that are infoldings of the plasma membrane. These are functionally analogous to the thylakoids in eukaryotic chloroplasts. The cell wall (A) is for structure, not photosynthesis. The cytoplasm (B) is the site of the Calvin cycle, but not the light-dependent reactions which require membranes. Chromatophore (D) is a term for a pigment-containing cell, not a prokaryotic organelle.

Question 20

Which statement best explains why the surface area to volume ratio is a critical limiting factor for the maximum size of a single cell?

  1. As volume increases faster than surface area, the rate of diffusion across the membrane becomes insufficient to support the cell's metabolic needs. (correct answer)
  2. A larger volume requires a disproportionately larger surface area for the cell wall to provide adequate structural support.
  3. As a cell grows, its surface area increases at the same rate as its volume, requiring more complex organelles.
  4. A large surface area relative to volume leads to excessive water loss and makes the cell vulnerable to lysis in hypotonic solutions.
Explanation: As a cell increases in size, its volume (proportional to the cube of its radius, r³) increases much faster than its surface area (proportional to the square of its radius, r²). The surface area (plasma membrane) is where exchange of nutrients, waste, and gases occurs. A decreasing SA:V ratio means the exchange surface becomes too small to service the metabolic needs of the much larger volume, limiting cell size. A is incorrect because the rates are different. B misidentifies the limiting factor. D describes a problem for very small cells (high SA:V ratio), not large ones.