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AP Biology MCQs

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AP Biology practice questions by unit

Fiveable has 20,789 AP Biology multiple-choice practice questions across 8 units, plus 249 stimulus-based question sets built around a source. Practice one unit or topic at a time.

  • Unit 1 – Chemistry of Life: 1,055 multiple-choice questions, 19 stimulus sets
  • Unit 2 – Cells: 3,137 multiple-choice questions, 44 stimulus sets
  • Unit 3 – Cellular Energetics: 1,868 multiple-choice questions, 39 stimulus sets
  • Unit 4 – Cell Communication and Cell Cycle: 2,012 multiple-choice questions, 24 stimulus sets
  • Unit 5 – Heredity: 1,855 multiple-choice questions, 15 stimulus sets
  • Unit 6 – Gene Expression and Regulation: 2,691 multiple-choice questions, 29 stimulus sets
  • Unit 7 – Natural Selection: 4,792 multiple-choice questions, 49 stimulus sets
  • Unit 8 – Ecology: 3,379 multiple-choice questions, 30 stimulus sets

Sample AP Biology practice question

A mutation prevents a cell from producing functional cyclin-dependent kinase (CDK), but cyclin proteins are still made. What effect on the cell cycle is most likely?

Cells fail to pass key checkpoints because cyclin-CDK complexes cannot phosphorylate targets

Correct answer

Cells speed through key checkpoints because cyclins alone can activate DNA replication proteins

Cells bypass key checkpoints because loss of CDK eliminates all checkpoint signaling proteins entirely

Cells complete normal mitosis because CDK is required only for cytokinesis, not checkpoints

Explanation

Linking checkpoint control to cyclin-CDK activity explains the disruption. Without functional CDK, cyclins cannot activate the kinase activity needed to phosphorylate proteins that drive progression through G1/S and G2/M checkpoints.

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