AP Biology Quiz: Origins Of Cell Compartmentalization

What this quiz covers

This quiz focuses on Origins Of Cell Compartmentalization, giving you a quick way to practice the rules, question types, and explanations that matter most for AP 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.

Question 1

1. A bacterium was engulfed and retained, forming a double-membraned organelle with its own genome.
2. Plasma membrane infolding generated internal surfaces that retained surface proteins and lacked separate DNA. (correct answer)
3. Mutations caused ribosomes to become membrane-bound, forming folds as a byproduct of translation.
4. Viral infection inserted DNA into the folds, allowing the folds to replicate independently.
5. Cytoskeletal filaments polymerized into sheets that later converted directly into lipid bilayers.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is supported by the stimulus showing internal membrane folds continuous with the plasma membrane, sharing the same transporters and lacking a separate genome, which fits the infolding model where plasma membrane extensions create internal surfaces without independent replication. The observation that folds do not divide separately from the cell reinforces that these are extensions of the host membrane, consistent with AP Biology discussions of archaeal membrane complexity evolving through invagination. This mechanism allows for increased surface area for reactions while maintaining connectivity to the cell surface, unlike endosymbiotic organelles. A tempting distractor, choice A, is incorrect due to structure-function confusion, as it attributes the folds to an engulfed bacterium despite the absence of double membranes or internal DNA, which are hallmarks of endosymbiosis. To approach similar questions, evaluate membrane continuity and the absence of independent genetic material to differentiate infolding from endosymbiotic processes.

Question 2

1. Repeated plasma membrane infolding created four layers, and circular DNA arose from host chromosomes
2. Endosymbiosis followed by a second engulfment event, leaving multiple membranes and bacterial-like components (correct answer)
3. Budding from the nuclear envelope produced extra membranes, and bacterial-like ribosomes evolved independently
4. Fusion of lysosomes generated additional membranes, and circular DNA formed from degraded RNA
5. Viral infection deposited membranes and ribosomes, creating a stable organelle that divides by fission

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is supported by the four membranes and inner compartment with circular DNA and bacterial-like ribosomes, aligning with secondary endosymbiosis in AP Biology where a eukaryotic cell engulfs another with a primary endosymbiont, resulting in multiple membrane layers. The fission division and lack of connection to the host's endomembrane system indicate retained autonomy from the nested symbionts, and the remnant membrane system between inner layers suggests vestiges of the secondary host's cytoplasm. These consistent features across individuals point to an evolutionary stable integration via double engulfment. A tempting distractor, choice A, is incorrect because it attributes multiple membranes to infolding and DNA to host mutations, representing a teleology misconception by implying directed accumulation rather than symbiotic events. A transferable approach is to count membrane layers and check for nested genetic elements to infer primary versus secondary endosymbiosis.

Question 3

1. The organelle is located near the nucleus in most cells and is similar in size across individuals
2. The organelle's outer membrane is continuous with the plasma membrane during cell growth phases
3. The organelle contains circular DNA and divides by binary fission within the cell cytoplasm (correct answer)
4. The organelle's proteins are all encoded in the nucleus and imported after translation in the cytosol
5. The organelle's membrane lipids are identical to those of the endoplasmic reticulum in composition

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice C, is evidenced by the organelle's circular DNA and division by binary fission, which mirror prokaryotic characteristics and support the endosymbiotic theory in AP Biology, where mitochondria and similar organelles arose from engulfed bacteria that retained reproductive autonomy. The presence of bacterial-like ribosomes and the encoding of some proteins by the organelle's own DNA further indicate a symbiotic prokaryotic origin, as these features are not typical of autogenously formed compartments. The highly folded inner membrane and independent division from the cell cycle also align with mitochondrial traits derived from aerobic bacteria. A tempting distractor, choice D, is incorrect because it assumes all proteins are nuclear-encoded, ignoring organelle autonomy and representing a level-of-organization error by overlooking the hierarchical retention of genetic material in endosymbionts. For these question types, compare organelle autonomy and genetic features to known prokaryotic traits to identify endosymbiotic evidence.

Question 4

1. Organelle 2 arose by endosymbiosis, but its genome was transferred completely to the nucleus.
2. Organelle 2 arose from plasma membrane infolding that formed an endomembrane network continuous with the nucleus. (correct answer)
3. Organelle 2 arose when organelle 1 lost one membrane and became connected to the nuclear envelope.
4. Organelle 2 arose from bacterial infection that inserted antibiotic-resistant ribosomes into the cytosol.
5. Organelle 2 arose from assembly of lipid bilayers around chromosomes during cell division.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is evidenced by organelle 2's single membrane, lack of DNA, and continuity with a membrane network connected to the nuclear envelope, aligning with the infolding hypothesis for the endomembrane system in eukaryotes as taught in AP Biology. In contrast, organelle 1's double membrane, circular DNA, and antibiotic-sensitive ribosomes indicate endosymbiosis, highlighting organelle 2's distinct host-derived origin. This supports how infolding creates interconnected compartments for functions like protein modification without independent genetics. A tempting distractor, choice A, is incorrect due to teleology, assuming complete genome transfer to explain the lack of DNA, which overlooks the structural evidence of endomembrane continuity rather than symbiotic remnants. To approach similar questions, compare organelles within the same cell for contrasting features like membrane number and genetic presence to infer distinct origins.

Question 5

1. Both organelles likely originated by plasma membrane infolding because they are bounded by membranes
2. Organelle X likely originated by endosymbiosis, while organelle Y likely arose from membrane infolding and trafficking (correct answer)
3. Organelle X likely arose from the Golgi apparatus because it divides by fission and has two membranes
4. Organelle Y likely originated by endosymbiosis because vesicle budding resembles bacterial reproduction
5. Both organelles likely originated from the nucleus because one is connected to the nuclear envelope

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, differentiates organelle X's double membrane, circular DNA, bacterial ribosomes, and fission replication as evidence of endosymbiosis, while organelle Y's single membrane, lack of DNA, and replenishment by vesicles from a nuclear-connected network indicate autogenous infolding in AP Biology. This contrast highlights how endosymbiotic organelles retain prokaryotic traits for autonomy, whereas endomembrane-derived ones depend on host trafficking. The observations align with mitochondrial versus ER/Golgi origins, respectively. A tempting distractor, choice A, is incorrect because it assumes all membrane-bound organelles share infolding origins, representing a structure-function confusion by overlooking genetic independence as a key distinguisher. When analyzing such comparisons, categorize organelles by membrane number, genetic content, and replication method to assign origins accurately.

Question 6

1. Infolding of the plasma membrane created a compartment, and bacterial-like genes accumulated by mutation
2. The organelle originated from a lysosome that acquired DNA and ribosomes from the cytosol
3. Endosymbiosis of an alpha-proteobacterium, supported by bacterial gene similarity and fission division (correct answer)
4. The organelle formed when the nucleus pinched off, explaining its double membrane and circular genome
5. Vesicles from the ER fused into a double-membrane organelle, producing bacterial-like ribosomes over time

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice C, is confirmed by the organelle's circular genome with genes similar to alpha-proteobacteria, supporting the endosymbiotic theory in AP Biology where mitochondria originated from engulfed aerobic bacteria. The bacterial-like ribosomes and independent fission division indicate retained prokaryotic features, and the lack of continuity with the ER rules out autogenous formation. The double membrane structure aligns with engulfment, where the outer membrane derives from the host's phagocytic vesicle. A tempting distractor, choice A, is incorrect because it attributes bacterial-like genes to mutations in an infolded compartment, representing a teleology misconception by suggesting purposeful gene accumulation rather than symbiotic inheritance. For these questions, sequence organelle genomes and compare to bacterial lineages to verify endosymbiotic relationships.

Question 7

1. Infolding of the plasma membrane produced internal membranes with matching lipids and occasional continuity. (correct answer)
2. Endosymbiosis of an aerobic bacterium formed internal membranes that remained connected to the surface membrane.
3. Horizontal gene transfer created internal compartments by adding bacterial DNA to the cytosol.
4. Spontaneous assembly of ribosomes into sheets generated internal membranes independent of the plasma membrane.
5. Fusion of two cells created internal membranes by trapping extracellular fluid without membrane invagination.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice A, is supported by the stimulus describing internal membranes formed through invagination and pinching off of the plasma membrane, resulting in vesicles with matching lipid composition and occasional continuity, which aligns with the infolding hypothesis for the endomembrane system's origin in eukaryotic cells. The absence of internal DNA and the presence of only free cytosolic ribosomes further indicate that these compartments did not arise from endosymbiotic events, as they lack independent genetic material typical of organelles like mitochondria. This mechanism reflects how early eukaryotic cells could have developed internal compartments to separate biochemical reactions without engulfing prokaryotes, consistent with AP Biology concepts of eukaryotic evolution. A tempting distractor, choice B, is incorrect due to a structure-function confusion, as it assumes endosymbiosis despite the lack of internal DNA or separate ribosomes, which would be expected in an engulfed bacterium. To approach similar questions, compare the presence of independent genomes and membrane continuity to distinguish between infolding and endosymbiotic origins.

Question 8

1. Infolding of the nuclear envelope produced photosynthetic membranes and a new genome
2. Endosymbiosis of a photosynthetic bacterium that became a membrane-bound organelle (correct answer)
3. Spontaneous assembly of chlorophyll into vesicles that later acquired DNA
4. Fusion of mitochondria created a larger organelle capable of photosynthesis
5. Packaging of cytosolic enzymes into a vacuole produced a photosynthetic compartment

Explanation: This question requires analyzing the origins of cell compartmentalization to explain photosynthetic organelle evolution. The combination of double membranes, circular DNA, binary fission-like division, and bacterial-sized ribosomes provides compelling evidence for endosymbiotic origin (option B), matching the characteristics expected if a photosynthetic bacterium was engulfed and retained as an organelle. These features directly reflect the cyanobacterial ancestry of chloroplasts—the circular DNA represents the remnant bacterial genome, 70S ribosomes match bacterial protein synthesis machinery, and binary fission reflects the ancestral bacterial reproduction method. Option C (spontaneous chlorophyll assembly) is incorrect because it invokes spontaneous generation of complex structures, representing a probability error where students underestimate the improbability of random assembly of functional organelles with genetic material. To identify endosymbiotic origins, look for the complete suite of bacterial characteristics rather than focusing on single features.

Question 9

1. Compartment X most likely arose from infolding of the plasma membrane, producing a connected endomembrane system. (correct answer)
2. Compartment X most likely arose by endosymbiosis, indicated by its continuity with the nuclear envelope.
3. Compartment X most likely arose from engulfment of compartment Y, explaining its single membrane.
4. Compartment X most likely arose from de novo synthesis of membranes around ribosomes to separate translation.
5. Compartment X most likely arose from conversion of the cell wall into internal membranes during cell division.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice A, is supported by compartment X's single membrane, continuity with the nuclear envelope, and proteins matching plasma membrane sequences, aligning with the infolding hypothesis where plasma membrane invaginations form the endomembrane system including the ER and nuclear envelope in eukaryotes. In contrast, compartment Y's double membrane, circular DNA, and distinct ribosomes suggest endosymbiotic origin, highlighting X's host-derived nature per AP Biology evolutionary models. This distinction emphasizes how infolding creates interconnected compartments without separate genomes, facilitating specialized functions like protein processing. A tempting distractor, choice B, is incorrect due to a level-of-organization error, mistaking nuclear continuity for endosymbiosis, which requires double membranes and independent DNA rather than host membrane extensions. To approach similar questions, contrast membrane number, continuity, and genetic independence to classify compartments as infolded or endosymbiotic.

Question 10

1. Engulfment of an aerobic bacterium that became a mitochondrion, indicated by matching lipid composition
2. Infolding of the plasma membrane followed by vesicle formation, producing internal membranes with similar lipids (correct answer)
3. Fusion of ribosomes into sacs, forming internal membranes near DNA without requiring membrane continuity
4. Spontaneous appearance of membrane-bound organelles containing their own genomes, independent of the plasma membrane
5. Endocytosis of viruses that supplied membranes and created a nucleus-like compartment around the DNA

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is supported by the stimulus describing repeated infolding and pinching off of the plasma membrane to form internal vesicles that remain continuous with it, aligning with the autogenous model in AP Biology where endomembrane systems arise from invaginations of the cell membrane. The matching lipid composition between internal sacs and the plasma membrane further indicates they originated from the same source without external incorporation, and the formation of a double-membrane boundary around genetic material suggests an evolutionary step toward nuclear compartmentalization. Additionally, the absence of DNA in these compartments rules out endosymbiotic origins, consistent with the infolding mechanism for non-autonomous organelles. A tempting distractor, choice A, is incorrect because it confuses endosymbiosis with infolding by assuming lipid matching implies bacterial engulfment, representing a structure-function confusion where membrane similarity is misinterpreted as evidence of independent origin rather than shared derivation. To approach similar questions, evaluate evidence for membrane continuity and genetic independence to distinguish between autogenous and endosymbiotic origins.

Question 11

1. Antibiotic sensitivity of organelle translation and circular DNA support bacterial ancestry. (correct answer)
2. Double membranes show the nucleus formed by engulfing the organelle during mitosis.
3. Electron transport proteins indicate the organelle arose by plasma membrane infolding.
4. Aerobic respiration indicates the organelle evolved because cells needed more ATP.
5. Cytosolic translation unaffected shows the organelle is part of the endomembrane system.

Explanation: This question requires analyzing the origins of cell compartmentalization to identify endosymbiotic evidence. The correct answer A is supported by the specific antibiotic sensitivity pattern: antibiotics that target bacterial ribosomes inhibit the organelle but not the cytosol, directly demonstrating the organelle contains bacterial-type ribosomes distinct from eukaryotic ones. Combined with circular DNA (bacterial genome organization) and bacterial-related electron transport proteins, this provides strong molecular evidence for bacterial ancestry through endosymbiosis. Answer C incorrectly attributes electron transport proteins to membrane infolding, a structure-function confusion—infolded membranes would contain the host's proteins, not bacterial-type proteins. To confirm endosymbiotic origins, look for molecular markers that specifically link to bacterial ancestry, particularly differential antibiotic sensitivity that reveals the presence of bacterial-type translation machinery.

Question 12

1. Multiple membranes and distinct ribosomes support serial endosymbiosis involving an engulfed eukaryote. (correct answer)
2. Four membranes indicate plasma membrane infolding occurred twice to surround the organelle.
3. Circular DNA shows the nucleus fragmented into vesicles that became photosynthetic.
4. Photosynthesis indicates membranes accumulated because cells required more sugars.
5. Ribosomes between membranes show the Golgi apparatus formed by bacterial engulfment.

Explanation: This question requires analyzing the origins of cell compartmentalization to explain complex membrane arrangements. The correct answer A is supported by the four-membrane structure and intermediate compartment containing distinct ribosomes, indicating serial endosymbiosis: a eukaryote containing a cyanobacterium was itself engulfed by another eukaryote. The innermost membranes' resemblance to cyanobacteria, circular DNA, and the remnant compartment with its own ribosomes between membranes 2 and 3 provide evidence for this secondary endosymbiosis. Answer B incorrectly attempts to explain four membranes through plasma membrane infolding, a level-of-organization error—infolding cannot produce the observed pattern of distinct ribosome types in different compartments. To identify serial endosymbiosis, count membrane layers and look for remnant structures (like ribosomes) between membranes that indicate a previously independent organism.

Question 13

1. Mitochondria and chloroplasts likely arose by endosymbiosis, unlike the nuclear envelope (correct answer)
2. All double-membraned compartments likely arose by engulfment of bacteria
3. The nuclear envelope likely arose by endosymbiosis because it has two membranes
4. Chloroplasts likely arose by plasma membrane infolding because they contain circular DNA
5. Mitochondria likely arose from ribosome aggregation because they contain ribosomes

Explanation: This question requires analyzing the origins of cell compartmentalization to compare different organelle origins based on their characteristics. The presence of circular DNA in mitochondria and chloroplasts but not in the nucleus, despite all having double membranes, supports option A that mitochondria and chloroplasts arose by endosymbiosis while the nuclear envelope arose differently (likely by infolding). The circular DNA in mitochondria and chloroplasts represents retained bacterial genomes from endosymbiotic events, while the nucleus contains only the cell's own linear chromosomes, indicating it formed by membrane reorganization around existing genetic material rather than incorporating a separate organism. Option C (nuclear endosymbiosis) is incorrect because it assumes double membranes alone indicate endosymbiosis, representing a single-feature error where students focus on membrane number rather than the complete evidence package including genome presence/absence. To distinguish organelle origins, evaluate multiple features together—endosymbiotic organelles have their own DNA while infolding-derived structures do not.

Question 14

1. Infolding of the nuclear envelope created a photosynthetic compartment that later acquired bacterial genes.
2. Endosymbiosis of a cyanobacterium produced a double-membraned organelle with bacterial DNA and fission. (correct answer)
3. Spontaneous formation of thylakoid stacks occurred from cytosolic proteins assembling into membranes.
4. Fusion of multiple vesicles formed a photosynthetic organelle whose DNA originated from the host nucleus.
5. Engulfment of a mitochondrion converted it into a photosynthetic organelle through gene loss.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is indicated by the organelle's double membrane, thylakoid-like stacks, circular DNA similar to cyanobacteria, and ribosomes inhibited by chloramphenicol, all pointing to endosymbiosis of a cyanobacterium as per the AP Biology endosymbiotic theory for chloroplast origins. The independent binary fission during cell division further supports that the organelle retains prokaryotic replication traits from the engulfed symbiont. These features collectively demonstrate how photosynthetic capability was acquired through symbiosis, with the double membrane arising from the host's phagocytic membrane and the bacterium's own membrane. A tempting distractor, choice A, is incorrect due to teleology, as it implies purposeful infolding of the nuclear envelope to create photosynthesis, ignoring the lack of evidence for nuclear membrane involvement and the prokaryotic genetic similarities. To approach similar questions, look for prokaryotic traits like circular DNA and independent division to confirm endosymbiotic rather than host-derived origins.

Question 15

1. Endosymbiosis of bacteria formed internal vesicles that lacked DNA because the genomes were degraded.
2. Infolding and budding of the boundary membrane produced internal vesicles with matching lipid composition. (correct answer)
3. Independent synthesis of new membranes occurred inside the protocell from free ribosomes in solution.
4. Engulfment of mitochondria created internal vesicles that later fused into a single compartment.
5. Insertion of viral capsids into the membrane forced it to fold inward and form vesicles.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is supported by the observation of inward budding from the boundary membrane, resulting in internal vesicles with identical fatty-acid composition and no independent replication or nucleic acids, consistent with the infolding model in prebiotic systems as per AP Biology origins of life concepts. This process mimics how early membranes could form compartments through physical dynamics without symbiosis, maintaining compositional similarity to the outer membrane. The lack of nucleic acids rules out autonomous organelles, emphasizing a host-derived mechanism for basic compartmentalization. A tempting distractor, choice A, is incorrect due to teleology, assuming endosymbiosis with purposeful genome degradation, which contradicts the absence of any DNA evidence in the vesicles. To approach similar questions, examine compositional matching and genetic absence to differentiate infolding from symbiotic incorporation in model systems.

Question 16

1. Continuity of nuclear membranes with internal membranes and similarity to plasma membrane lipids support infolding (correct answer)
2. Linear chromosomes indicate the nucleus originated from an engulfed bacterium with modified DNA
3. Absence of bacterial-like ribosomes shows the nucleus formed by mitochondria donating membranes
4. Presence of an internal membrane network proves the nucleus formed after chloroplast evolution in plants
5. Similarity to plasma membrane lipids indicates the nucleus evolved to increase cell size efficiently

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice A, is supported by the continuity of nuclear and internal membranes with similar lipid composition to the plasma membrane, aligning with the autogenous infolding model in AP Biology for nuclear envelope formation from plasma membrane invaginations. The presence of linear chromosomes and absence of bacterial-like ribosomes contradict a prokaryotic ancestor, favoring an internal evolutionary process. This evidence refutes the student's engulfment claim by demonstrating integrated membrane systems without symbiotic remnants. A tempting distractor, choice B, is incorrect because it misinterprets linear chromosomes as modified bacterial DNA, representing a level-of-organization error by ignoring the distinction between prokaryotic circular and eukaryotic linear genomes. To address similar claims, evaluate membrane lipid similarities and chromosomal structure to support or refute proposed origins.

Question 17

1. Homology between pore and vesicle-coat proteins supports origin via plasma membrane infolding and budding. (correct answer)
2. Lipid similarity shows the nucleus originated by endosymbiosis of an aerobic bacterium.
3. Continuity with ER indicates the nucleus descended from a captured mitochondrion.
4. Absence of DNA shows the nucleus formed when chloroplast genes moved to the cytosol.
5. Nuclear pores indicate the nucleus evolved to control gene expression more effectively.

Explanation: This question requires analyzing the origins of cell compartmentalization to explain nuclear envelope evolution. The correct answer A is supported by molecular homology: genes for nuclear pore proteins share ancestry with vesicle coat proteins, indicating the nuclear envelope arose through the same membrane-budding mechanisms that generate other endomembrane compartments. The continuity with ER, matching lipid composition with plasma membrane, and absence of organellar DNA all support origin through membrane dynamics rather than endosymbiosis. Answer E commits a teleological error by suggesting the nucleus evolved "to control gene expression more effectively"—evolution cannot anticipate future benefits, and structures arise through available mechanisms regardless of eventual function. When evaluating nuclear origins, examine protein homologies that reveal shared evolutionary mechanisms with other membrane-trafficking systems.

Question 18

1. Endosymbiosis of an aerobic bacterium produced a double-membraned organelle with its own DNA.
2. Infolding of the plasma membrane generated internal membranes with matching lipid composition and continuity. (correct answer)
3. Horizontal gene transfer created membrane-bound compartments by inserting transport proteins into vesicles.
4. Spontaneous assembly of a nuclear envelope occurred after linear chromosomes evolved inside vesicles.
5. Selective import of enzymes into vesicles indicates they originated as engulfed prey cells.

Explanation: This question requires analyzing the origins of cell compartmentalization to determine how internal membranes formed in protocells. The correct answer B is supported by multiple lines of evidence: the vesicles have the same lipid composition as the plasma membrane, they remain connected to the plasma membrane forming continuous sheets, and no DNA is detected inside them, ruling out endosymbiosis. The infolding mechanism explains how membrane-bound enzymes concentrate on inner surfaces while transport proteins remain on the outer membrane through differential protein sorting during membrane deformation. Answer A is incorrect due to the misconception that all internal membranes arise from endosymbiosis—this teleological error ignores that endosymbiotic organelles contain their own DNA and have distinct lipid compositions from the host membrane. When evaluating compartmentalization origins, look for continuity with existing membranes, matching lipid compositions, and absence of independent genetic material as indicators of infolding rather than endosymbiosis.

Question 19

1. The organelle's outer membrane has the same lipid ratio as the plasma membrane.
2. The organelle contains circular DNA and bacterial-size ribosomes sensitive to bacterial antibiotics. (correct answer)
3. The organelle is located near the nucleus and shares cytoskeletal anchoring proteins.
4. ATP produced in the organelle diffuses into the cytosol through membrane channels.
5. The organelle increases in number when the cell is placed in high-glucose medium.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is evidenced by the organelle's circular DNA, bacterial-size ribosomes, and sensitivity to bacterial antibiotics, which directly support the endosymbiotic theory where a bacterium was engulfed and retained, contributing its own genetic and protein synthesis machinery. The inner membrane's bacterial-like electron transport proteins and the selective inhibition of organelle protein synthesis further align with the AP Biology concept that mitochondria originated from aerobic bacteria, preserving prokaryotic traits. This evidence distinguishes endosymbiotic organelles from those formed by host membrane infolding, as the organelle maintains autonomy in replication and translation. A tempting distractor, choice A, is incorrect due to a level-of-organization error, confusing shared lipid ratios at the cellular level with specific prokaryotic features like DNA and ribosomes that indicate endosymbiosis. To approach similar questions, prioritize evidence of prokaryotic remnants such as independent DNA and ribosomes over general membrane similarities to identify endosymbiotic origins.

Question 20

1. It likely originated by endosymbiosis because double membranes are unique to engulfed bacteria.
2. It likely originated from infolding and remodeling of host membranes, despite having two membranes. (correct answer)
3. It likely originated as a modified chloroplast because it divides by fission.
4. It likely originated from the nucleus because it lacks DNA and uses cytosolic ribosomes.
5. It likely originated from the cell wall because its proteins are encoded by nuclear genes.

Explanation: This question assesses the analysis of the origins of cell compartmentalization. The correct answer, choice B, is indicated by the absence of internal DNA, cytosolic-matching ribosomes, and nuclear-encoded proteins resembling endomembrane system components, suggesting origin from host membrane infolding and remodeling despite the double membrane, as per AP Biology discussions of non-endosymbiotic organelles like peroxisomes. The fission division aligns with host-controlled replication, not independent prokaryotic traits, supporting a derived endomembrane origin. This evidence challenges the typical double-membrane endosymbiosis association, highlighting gene loss or transfer in evolution. A tempting distractor, choice A, is incorrect due to structure-function confusion, overemphasizing double membranes as exclusively endosymbiotic while ignoring the lack of prokaryotic DNA and ribosomes. To approach similar questions, weigh genetic and ribosomal evidence against membrane structure to resolve atypical organelle origins.