IB Biology Quiz: Understand Cell Structure
20 questions · exam conditions
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Understand Cell StructureQuestion 1 of 20

A cell from the pancreas is specialized for secreting digestive enzymes, which are proteins. A cell from the adrenal cortex is specialized for secreting steroid hormones, which are lipids. Which option correctly predicts the relative abundance of certain organelles in these two cells?

The pancreatic cell has abundant smooth endoplasmic reticulum, while the adrenal cell has abundant rough endoplasmic reticulum.
The pancreatic cell has abundant rough endoplasmic reticulum, while the adrenal cell has abundant smooth endoplasmic reticulum.
Both cell types will have an equal and large amount of rough endoplasmic reticulum for general protein synthesis.
Both cell types will have an equal and large amount of smooth endoplasmic reticulum for detoxification processes.
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IB Biology Quiz

IB Biology Quiz: Understand Cell Structure

Practice Understand 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 Understand 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.

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Question 1

A cell from the pancreas is specialized for secreting digestive enzymes, which are proteins. A cell from the adrenal cortex is specialized for secreting steroid hormones, which are lipids. Which option correctly predicts the relative abundance of certain organelles in these two cells?

  1. The pancreatic cell has abundant smooth endoplasmic reticulum, while the adrenal cell has abundant rough endoplasmic reticulum.
  2. The pancreatic cell has abundant rough endoplasmic reticulum, while the adrenal cell has abundant smooth endoplasmic reticulum. (correct answer)
  3. Both cell types will have an equal and large amount of rough endoplasmic reticulum for general protein synthesis.
  4. Both cell types will have an equal and large amount of smooth endoplasmic reticulum for detoxification processes.
Explanation: The function of an organelle is linked to its abundance in specialized cells. The pancreatic cell secretes proteins (enzymes), so it requires extensive rough ER (with ribosomes for protein synthesis) and Golgi apparatus for processing and packaging. The adrenal cortex cell secretes lipids (steroids), so it requires extensive smooth ER, which is the site of lipid synthesis. The other options reverse this relationship or incorrectly equate the needs of the two different cell types.

Question 2

A scientist is performing differential centrifugation on a homogenate of plant leaf cells. This technique separates organelles based on their size and density, with larger, denser components forming a pellet at lower centrifugation speeds. What is the most likely order in which the following three components will be isolated in the pellet as centrifugation speed is progressively increased?

  1. Ribosomes -> Mitochondria -> Nuclei
  2. Nuclei -> Chloroplasts -> Mitochondria (correct answer)
  3. Chloroplasts -> Mitochondria -> Nuclei
  4. Mitochondria -> Ribosomes -> Chloroplasts
Explanation: In differential centrifugation, the largest and densest organelles pellet first at low speeds. The order from largest/densest to smallest/least dense is: Nuclei > Chloroplasts > Mitochondria > Ribosomes. Therefore, at the lowest speed, nuclei will pellet. Increasing the speed will then pellet chloroplasts, followed by mitochondria at even higher speeds. Ribosomes would require the highest speeds (ultracentrifugation) to be pelleted.

Question 3

Lysosomes are crucial for cellular digestion. A defect in a lysosomal enzyme can lead to a class of diseases called lysosomal storage disorders. In such a condition, what would be the direct consequence within the affected cells?

  1. Failure to synthesize essential proteins, leading to apoptosis.
  2. Accumulation of undigested macromolecules, causing cellular swelling and damage. (correct answer)
  3. Inability to produce ATP, resulting in a severe energy deficit.
  4. Disruption of lipid synthesis, leading to a deficiency in steroid hormones.
Explanation: Lysosomes contain hydrolytic enzymes that break down macromolecules. If an enzyme is defective, its specific substrate cannot be broken down and will accumulate within the lysosome. This accumulation causes the lysosomes to swell, which can damage the cell and impair its function. A is incorrect; protein synthesis occurs at ribosomes. C is incorrect; ATP production is the primary role of mitochondria. D is incorrect; lipid synthesis occurs in the smooth ER.

Question 4

Giant algae such as Acetabularia can grow up to 10 cm in length yet consist of a single cell with one nucleus located in the rhizoid ('foot'). How does the existence of this organism challenge conventional aspects of cell theory?

  1. It contradicts the idea that all living things are composed of cells, as it is a macroscopic organism.
  2. It challenges the expectation that cells are simple in structure and must be microscopic in size. (correct answer)
  3. It disproves the concept that all cells arise from pre-existing cells through division.
  4. It provides evidence against the idea that the cell is the fundamental unit of structure and function in living organisms.
Explanation: Cell theory is robust, but atypical examples test its nuances. Acetabularia is still a cell and arises from pre-existing cells, so C and D are incorrect. It is composed of a cell, so A is incorrect. Its large size and complex structure (differentiated into a cap, stalk, and rhizoid) challenge the typical expectation that cells are microscopic and structurally simple, making it an exception to the general pattern.

Question 5

A researcher identifies a single-celled organism with 70S ribosomes, a circular chromosome in a nucleoid region, and a peptidoglycan cell wall. A novel antibiotic is found to be effective against this organism by disrupting the synthesis of its cell wall. Which of the following would be a logical consequence of this discovery?

  1. The antibiotic is likely to be highly toxic to human cells as it will disrupt the formation of the extracellular matrix.
  2. The antibiotic may have limited effectiveness against fungal infections due to the different chemical composition of their cell walls. (correct answer)
  3. The antibiotic would probably inhibit protein synthesis in human mitochondria, leading to significant side effects.
  4. The antibiotic is expected to be effective against plant cells by preventing the synthesis of cellulose.
Explanation: The organism is a prokaryote (bacterium) due to the 70S ribosomes, nucleoid, and peptidoglycan cell wall. The antibiotic targets peptidoglycan. Fungal cell walls are made of chitin, not peptidoglycan, so the antibiotic would likely be ineffective. A is incorrect because human cells lack a cell wall and the extracellular matrix has a different composition. C is a plausible misconception because mitochondria have 70S ribosomes, but the antibiotic targets the cell wall, not ribosomes. D is incorrect because plant cell walls are made of cellulose.

Question 6

A cell produces two types of proteins: actin, which functions in the cytoplasm as part of the cytoskeleton, and insulin, which is exported from the cell. Which statement correctly distinguishes the synthesis of these two proteins?

  1. Both proteins are synthesized on ribosomes attached to the rough ER, but only insulin enters the Golgi apparatus.
  2. Actin is synthesized by free ribosomes in the cytoplasm, while insulin is synthesized by ribosomes attached to the rough ER. (correct answer)
  3. Insulin is synthesized by free ribosomes and then imported into the rough ER for modification.
  4. The synthesis of actin requires a signal peptide to keep it in the cytoplasm, while insulin synthesis does not.
Explanation: The location of protein synthesis depends on the protein's final destination. Proteins destined to function within the cytoplasm (like actin) are synthesized on free ribosomes. Proteins destined for secretion (like insulin), or for insertion into membranes or specific organelles, are synthesized on ribosomes attached to the RER. A is incorrect because actin is not made on the RER. C is incorrect as secreted proteins are synthesized directly into the RER lumen. D reverses the role of the signal peptide, which directs proteins like insulin to the RER.

Question 7

In the synthesis and export of a glycoprotein hormone from an endocrine cell, several organelles must interact in a specific sequence. What is the correct pathway for this molecule from its initial synthesis to its release from the cell?

  1. Ribosome on RER -> Golgi apparatus -> Transport vesicle -> Smooth ER -> Plasma membrane
  2. Cytosolic ribosome -> Golgi apparatus -> Lysosome -> Plasma membrane
  3. Ribosome on RER -> RER lumen -> Transport vesicle -> Golgi apparatus -> Secretory vesicle (correct answer)
  4. Nucleus -> Ribosome on RER -> Lysosome -> Secretory vesicle -> Plasma membrane
Explanation: The process begins with translation on a ribosome attached to the rough endoplasmic reticulum (RER), with the polypeptide entering the RER lumen for folding. It is then packaged into a transport vesicle and sent to the Golgi apparatus for modification (like glycosylation) and packaging. Finally, it is enclosed in a secretory vesicle that fuses with the plasma membrane for exocytosis. Option A incorrectly places Smooth ER after the Golgi. Option B starts with the wrong type of ribosome for a secreted protein. Option D incorrectly involves the lysosome in the secretory pathway.

Question 8

In eukaryotic cells, the extensive folding of the inner mitochondrial membrane to form cristae is a critical structural feature. This is analogous to the thylakoids in chloroplasts. What is the primary functional advantage conferred by this extensive folding in both organelles?

  1. It decreases the internal volume of the organelle, concentrating substrates for faster reaction rates.
  2. It provides a rigid internal structure that protects the organelle from osmotic stress.
  3. It dramatically increases the surface area available for membrane-bound enzyme complexes and electron transport chains. (correct answer)
  4. It separates the organelle into distinct compartments, allowing anabolic and catabolic reactions to occur simultaneously.
Explanation: The key processes of cellular respiration (electron transport chain and ATP synthase) and photosynthesis (light-dependent reactions) involve proteins embedded in these inner membranes. Folding these membranes into cristae and thylakoids vastly increases the surface area, allowing for a much higher number of these protein complexes to be present, thus maximizing the rate of ATP production. A is incorrect; it increases surface area without significantly decreasing volume. B is incorrect; this is not the primary role. D describes compartmentalization, which is an advantage of organelles in general, but the folding specifically relates to increasing surface area for membrane-bound processes.

Question 9

[HL] The theory of endosymbiosis proposes that mitochondria originated from aerobic prokaryotes engulfed by an ancestral host cell. Although mitochondria have their own DNA and ribosomes, they have lost many genes essential for their function to the host cell's nucleus. What is a direct consequence of this gene transfer?

  1. Mitochondria must import most of their necessary proteins from the cytoplasm, synthesized under the direction of the nucleus. (correct answer)
  2. The host cell can no longer perform anaerobic respiration because it has become dependent on the mitochondria.
  3. Mitochondrial DNA replication is now synchronized with the host cell cycle, occurring only during the S phase.
  4. The mitochondrial genetic code has evolved to be identical to the nuclear genetic code of the host cell.
Explanation: Because many genes required for mitochondrial structure and function (like enzymes for the Krebs cycle and proteins for the electron transport chain) are now located in the nucleus, the proteins must be synthesized in the cytoplasm on eukaryotic ribosomes and then imported into the mitochondria. This makes the mitochondrion an integrated organelle rather than an independent endosymbiont. B is incorrect; the host cell retains the ability to perform glycolysis and anaerobic respiration. C is incorrect; mitochondrial replication is not strictly tied to the S phase. D is incorrect; the mitochondrial genetic code has some minor differences from the standard nuclear code.

Question 10

The fluid mosaic model describes the plasma membrane. Which statement accurately contrasts the plasma membrane of an animal cell with the outer membrane of its mitochondria?

  1. Only the plasma membrane contains cholesterol, while the mitochondrial outer membrane is significantly richer in proteins like porins. (correct answer)
  2. Both membranes have an identical phospholipid composition, but the mitochondrial outer membrane lacks integral proteins.
  3. The plasma membrane is primarily involved in transport via endocytosis, while the mitochondrial outer membrane specializes in chemiosmosis.
  4. The mitochondrial outer membrane contains glycoproteins for cell-cell recognition, whereas the plasma membrane does not.
Explanation: Cholesterol is a key component of animal cell plasma membranes, modulating fluidity, but it is largely absent from inner and outer mitochondrial membranes. The mitochondrial outer membrane is highly permeable due to protein channels called porins. B is incorrect; their compositions differ, and the mitochondrial membrane is rich in proteins. C is incorrect; chemiosmosis occurs across the inner mitochondrial membrane, not the outer. D is incorrect; glycoproteins for cell recognition are a feature of the plasma membrane, not the mitochondrial membrane.

Question 11

In many prokaryotes, genetic information is found in the nucleoid and also in small circular DNA molecules called plasmids. What is a key biological role of plasmids?

  1. They contain essential genes required for basic metabolic functions and cell division under all conditions.
  2. They are the primary site of transcription and translation for all proteins within the prokaryotic cell.
  3. They often carry non-essential genes that can confer a selective advantage, such as antibiotic resistance or toxin production. (correct answer)
  4. They serve as the template for the synthesis of ribosomal RNA (rRNA) and transfer RNA (tRNA).
Explanation: Plasmids are extrachromosomal DNA molecules that replicate independently of the main chromosome. They are not essential for the bacterium's survival under normal conditions, but they can carry genes that provide advantages in specific environments, such as genes for resistance to antibiotics or for metabolizing unusual substrates. A is incorrect; essential genes are on the main chromosome. B is incorrect; transcription and translation occur based on both chromosomal and plasmid DNA, but the main chromosome is the primary source. D is incorrect; genes for rRNA and tRNA are typically located on the main chromosome.

Question 12

The cell wall of a plant cell and the extracellular matrix (ECM) of an animal cell both provide external support. Which statement correctly contrasts these two structures?

  1. The plant cell wall is a dynamic structure primarily composed of proteins like collagen, while the ECM is a static, inert layer of cellulose.
  2. The ECM is synthesized entirely within the Golgi apparatus, while the plant cell wall is synthesized by free ribosomes in the cytoplasm.
  3. The plant cell wall is located inside the plasma membrane, whereas the ECM is located outside the plasma membrane.
  4. The ECM is directly involved in cell-to-cell communication and adhesion, while the plant cell wall primarily provides rigid structural support and prevents osmotic lysis. (correct answer)
Explanation: The ECM of animal cells, composed of glycoproteins like collagen and fibronectin, is crucial for cell adhesion, migration, and signaling. In contrast, the primary roles of the cellulose-based plant cell wall are to provide a fixed shape, resist turgor pressure, and prevent the cell from bursting in a hypotonic environment. A reverses the descriptions. C is incorrect; both are external to the plasma membrane. D is incorrect; components of both are processed through the endomembrane system, and cellulose is synthesized at the plasma membrane itself.

Question 13

[HL] Which statement provides the strongest evidence for the theory of endosymbiosis?

  1. Mitochondria and chloroplasts are both surrounded by a double membrane.
  2. Mitochondria and chloroplasts contain 70S ribosomes, similar to those found in prokaryotes. (correct answer)
  3. Mitochondria and chloroplasts are roughly the same size as a typical prokaryotic cell.
  4. Mitochondria and chloroplasts cannot survive and reproduce independently outside of a host eukaryotic cell.
Explanation: While all options are pieces of evidence for endosymbiosis, the presence of 70S ribosomes is very strong evidence. Eukaryotic ribosomes are 80S, so having prokaryotic-style ribosomes inside these organelles is a specific and compelling link. The double membrane (A) is also good evidence but could have arisen through other means (e.g., autogenous invagination). Size (C) is consistent but not as specific. Inability to survive alone (D) is a consequence of their long co-evolution and gene transfer to the host nucleus, rather than primary evidence of their origin.

Question 14

Which of the following describes a key structural difference between a typical fungal cell and a typical plant cell?

  1. Fungal cells store carbohydrates as glycogen, whereas plant cells store them as starch.
  2. Fungal cells possess a cell wall composed of chitin, whereas plant cells have a cell wall of cellulose. (correct answer)
  3. Fungal cells are prokaryotic, lacking a true nucleus, while plant cells are eukaryotic.
  4. Fungal cells contain multiple small vacuoles, whereas mature plant cells have a single large central vacuole.
Explanation: The cell wall composition represents a fundamental structural difference between these cell types. Fungal cell walls are composed primarily of chitin, while plant cell walls are composed primarily of cellulose. A describes a biochemical difference in storage molecules rather than structural architecture. C is incorrect as both fungi and plants are eukaryotes. D describes a difference in organelle organization that is generally true but less fundamental than cell wall composition.

Question 15

The cytoskeleton provides structure and facilitates movement. If a cell was treated with a drug that specifically depolymerizes microtubules, which cellular process would be most directly inhibited?

  1. Formation of the cleavage furrow during animal cell cytokinesis.
  2. Contraction of muscle cells.
  3. Amoeboid movement through the extension of pseudopods.
  4. Movement of chromosomes during anaphase of mitosis. (correct answer)
Explanation: Microtubules form the mitotic spindle, which is essential for separating chromosomes during mitosis. Depolymerizing microtubules would cause the spindle to break down, halting chromosome movement. A, C, and D are all processes that depend on microfilaments (actin filaments). The cleavage furrow is formed by a contractile ring of actin, amoeboid movement uses actin polymerization, and muscle contraction involves actin and myosin filaments.

Question 16

The Golgi apparatus modifies, sorts, and packages proteins and lipids. Which statement best describes the structural basis for its function?

  1. It consists of a single, continuous, folded membrane called a cisterna, which provides a large surface area for modification.
  2. It is studded with ribosomes that perform final modifications on proteins before they are packaged into vesicles for transport.
  3. It is a network of interconnected tubules continuous with the rough endoplasmic reticulum, allowing direct transfer of proteins.
  4. It is a stack of flattened, separate membrane-bound sacs called cisternae, which have distinct cis, medial, and trans regions with different enzymes. (correct answer)
Explanation: The Golgi apparatus is not a single continuous membrane but a stack of separate sacs (cisternae). This stack has polarity: the cis face receives vesicles from the ER, and the trans face dispatches vesicles. The different compartments (cis, medial, trans) contain different sets of enzymes, allowing for a stepwise modification of proteins and lipids as they pass through. A is incorrect because the cisternae are separate. C describes the endoplasmic reticulum. D is incorrect; the Golgi apparatus does not have ribosomes.

Question 17

Peroxisomes and lysosomes are both single-membrane vesicles containing enzymes. Which of the following correctly distinguishes their origins and primary functions?

  1. Lysosomes bud off from the Golgi and perform hydrolysis, while peroxisomes self-replicate and perform oxidation reactions. (correct answer)
  2. Lysosomes are formed by endocytosis and digest external material, while peroxisomes bud from the ER and synthesize lipids.
  3. Both organelles bud from the Golgi, but lysosomes perform digestion at a low pH while peroxisomes neutralize free radicals.
  4. Lysosomes self-replicate and contain catalases, while peroxisomes are part of the endomembrane system and contain hydrolases.
Explanation: Lysosomes are part of the endomembrane system, budding off the trans-Golgi network, and contain acid hydrolases for digestion. Peroxisomes are not part of the endomembrane system; they are formed from the ER and can self-replicate by fission. Their primary role involves various metabolic reactions using oxygen to break down substances (oxidation), which often produces hydrogen peroxide that is then detoxified by catalase. B is incorrect about peroxisome function. C is incorrect about peroxisome origin. D reverses the characteristics of the two organelles.

Question 18

Which of the following provides the best evidence that prokaryotic cells evolved before eukaryotic cells?

  1. The oldest fossilized cells resemble modern prokaryotes and are found in rocks older than the first eukaryotic fossils. (correct answer)
  2. Prokaryotic cells are structurally simpler than eukaryotic cells, suggesting they are a more primitive form of life.
  3. Prokaryotes can survive in a wider range of extreme environments than most eukaryotes.
  4. The metabolic pathways, such as glycolysis, are nearly identical in both prokaryotes and eukaryotes.
Explanation: The most direct and compelling evidence for the sequence of evolution comes from the fossil record. Microfossils dating back 3.5 billion years resemble prokaryotes, while the first clear eukaryotic fossils appear much later, around 1.8 billion years ago. B is an observation that is consistent with the theory but is not direct evidence; simplicity does not always mean older. C is an observation about modern organisms and does not directly prove evolutionary history. D suggests a common ancestor but does not establish the order in which prokaryotes and eukaryotes appeared.

Question 19

Some biology textbooks state that a key difference between plant and animal cells is the presence of centrioles in animal cells. Why is this statement an oversimplification?

  1. While most animal cells have centrioles, mature neurons and muscle cells typically lack them and cannot divide.
  2. Centrioles are present in animal cells and higher plant cells, but are absent in fungal cells and prokaryotes.
  3. Cells of lower plants like mosses and ferns possess centrioles, while cells of higher (flowering) plants do not. (correct answer)
  4. Centrioles are only functional during S-phase of the cell cycle and are disassembled in both plant and animal cells during G1.
Explanation: The general rule taught is 'no centrioles in plant cells', but this is not universally true. Lower plant forms (like mosses and ferns) have flagellated sperm that require basal bodies, which are derived from centrioles. Higher, flowering plants (angiosperms) lack centrioles. This makes the original statement an oversimplification. A is true but doesn't address the plant side of the comparison. B is incorrect as higher plants lack centrioles. D is incorrect as centrioles replicate during S-phase but are not disassembled during G1.

Question 20

Eukaryotic cells are highly compartmentalized. Which statement most accurately describes the primary advantage of this compartmentalization?

  1. It increases the total volume of the cell, allowing for the storage of more nutrients and water.
  2. It eliminates the need for a plasma membrane to regulate the passage of substances into and out of the cell.
  3. It provides a rigid internal framework that gives the eukaryotic cell a fixed and definite shape.
  4. It allows for the separation of incompatible or specialized chemical reactions, increasing metabolic efficiency. (correct answer)
Explanation: The main advantage of compartmentalization is the separation of cellular processes. For example, the acidic environment required for lysosomal enzymes is contained within the lysosome, preventing it from damaging the rest of the cell. Similarly, DNA replication and transcription are protected within the nucleus. This separation allows for the optimization of conditions for specific metabolic pathways, increasing efficiency and preventing interference between reactions. A is not the primary advantage. C is the role of the cytoskeleton, not compartmentalization by membranes. D is incorrect as the plasma membrane is essential.