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AP Biology

Apbio 2.2 2.4 hard

Shared by ashtont · Oct 6, 2026 · 0 plays

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50 questions across 3 sections. After every answer you’ll see why each choice is right or wrong, not just the one you picked.

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Sections (none selected means all)

Sample questions

Open a question to see the answer choices and the correct answer.

A pancreatic cell that secretes digestive enzymes has an extensive network of rough ER and a prominent Golgi apparatus. Which statement best explains why both are necessary?
  1. A. The rough ER folds the enzymes in its lumen, and the Golgi then sorts and packages them for secretion. ✓
  2. B. The rough ER stores the finished enzymes, while the Golgi manufactures the lipids needed to wrap them for release.
  3. C. Ribosomes on the rough ER release enzymes straight into the cytoplasm, and the Golgi then destroys any faulty copies.
  4. D. The smooth ER could handle this secretory task just as well, since the rough/smooth ER distinction isn't functionally meaningful here at all.

Correct answer: A. This matches the secretory pathway's division of labor: folding at the rough ER, then sorting at the Golgi.

Liver cells that detoxify drugs have unusually abundant smooth ER. Which explanation best accounts for this adaptation?
  1. A. Smooth ER ribosomes translate detox enzymes directly from mRNA attached to its own membrane surface.
  2. B. Smooth ER enzymes chemically modify lipid-soluble toxins so they become easier for the body to excrete. ✓
  3. C. Smooth ER packages the neutralized toxins into secretory vesicles, the same job the Golgi apparatus performs.
  4. D. Smooth ER digests toxins using hydrolytic enzymes inside a strongly acidic interior, much like a lysosome does.

Correct answer: B. Smooth ER houses the enzymes that modify toxins, and liver cells need large amounts of this membrane to keep pace with detoxification demand.

Which piece of evidence most directly supports the idea that mitochondria originated as free-living prokaryotes engulfed by an ancestral eukaryotic cell?
  1. A. Mitochondria appear in nearly every eukaryotic cell type, from single-celled fungi to complex animal tissues.
  2. B. Mitochondria are wrapped in a single membrane that was derived entirely from the host cell's own cytoplasm.
  3. C. Mitochondria carry their own circular DNA and divide by a bacteria-like binary fission, separate from the nuclear cell cycle. ✓
  4. D. Mitochondria can now be fully assembled in a laboratory test tube from a mixture of purified cellular enzymes.

Correct answer: C. Independent, bacteria-like DNA and division are strong direct evidence of a separate prokaryotic ancestry.

The inner mitochondrial membrane is highly folded into cristae. How does this structural feature relate to the organelle's function?
  1. A. The folds expand the volume of the matrix, letting the organelle store a larger supply of mitochondrial DNA.
  2. B. The folds divide the mitochondrion into separate chambers, each one running a distinct stage of glycolysis.
  3. C. The folds slow the outward diffusion of ATP, trapping newly made energy molecules close to where they first form inside the matrix.
  4. D. The folds increase membrane surface area, giving more room for electron transport chain proteins and ATP synthase. ✓

Correct answer: D. More membrane surface means more room for the protein complexes that build the proton gradient and synthesize ATP.

Chloroplasts contain an extensive internal membrane system, the thylakoids, suspended in the stroma. This arrangement is functionally analogous to which feature of mitochondria?
  1. A. The thylakoid membranes, like cristae, increase surface area for the light-reaction electron transport chain and ATP synthase. ✓
  2. B. The thylakoids store surplus starch reserves, the same way the mitochondrial matrix stores its genetic material.
  3. C. The thylakoids carry out the Krebs cycle, in the same way the matrix is described as the site of glycolysis.
  4. D. The thylakoids dilute enzyme concentration, the same way the fluid stroma is said to dilute the fluid matrix.

Correct answer: A. Both cristae and thylakoids solve the same problem: packing more electron-transport and ATP synthase proteins into a confined space by folding membrane.