AP Exam Prep · AP Biology

AP Biology Unit 2 Practice Test: Cells

Unit 2 is about how a cell's parts and its membrane let it stay alive and different from its surroundings. Expect questions that ask you to predict which way water or solutes will move, and to explain why cells stay small or fold their membranes.

Exam weighting:: 10–13%
Questions:: 12 multiple choice
Time:: about 16 minutes
Cost:: Free, no sign-up

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Question 1 of 12 · 0 answered

Topic 2.1 · Apply it

Cells in the pancreas secrete large amounts of digestive enzymes, which are proteins. Which organelles would you expect these cells to have in unusually large amounts?

Rough endoplasmic reticulum and Golgi apparatusSmooth endoplasmic reticulum and lysosomesLarge central vacuoles and chloroplastsPeroxisomes and a cell wall

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Topic 2.2 · Data analysis

Model cells shaped as cubes
Side length (µm)	Surface area (µm²)	Volume (µm³)	Surface area : volume
1	6	1	6 : 1
2	24	8	3 : 1
4	96	64	1.5 : 1

Which conclusion about cell size is best supported by the data?

As cell size increases, the surface area to volume ratio increases.Volume increases more slowly than surface area as a cell grows.Larger cells can exchange materials with their environment more efficiently per unit of volume.As cell size increases, each unit of volume is served by less membrane, making exchange less efficient.

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Topic 2.6 · Data analysis

Glucose uptake by red blood cells (no ATP is used by this transporter)
Glucose outside the cell (mM)	Uptake rate (relative units)
1	20
2	38
5	70
10	88
20	95
40	96

Which explanation best accounts for the uptake rate levelling off at high glucose concentrations?

Glucose diffuses directly through the bilayer, which becomes full.The cells run out of ATP needed to power the transporter.The glucose carrier proteins are all occupied, so adding more glucose cannot increase the rate.The concentration gradient reverses at high glucose concentrations.

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What AP Bio Unit 2 covers

Unit 2, Cells, makes up 10–13% of the multiple-choice section and usually takes ~14–16 class periods. These are the topics in the current course framework, and every question in the test above is tagged with one of them.

2.1Cell Structure and Function
2.2Cell Size
2.3Plasma Membrane
2.4Membrane Permeability
2.5Membrane Transport
2.6Facilitated Diffusion
2.7Tonicity and Osmoregulation
2.8Mechanisms of Transport
2.9Cell Compartmentalization
2.10Origins of Cell Compartmentalization

Unit 2 key ideas

Organelles divide the work

Ribosomes make proteins; rough ER and the Golgi modify and ship them; mitochondria and chloroplasts transform energy; lysosomes and vacuoles break down and store materials.

Surface area limits size

As a cell grows, its volume rises faster than its surface area, so exchange with the environment becomes less efficient. Folds and flattening increase surface area.

Membranes are selectively permeable

Small nonpolar molecules cross the phospholipid bilayer directly. Ions and polar molecules need channel or carrier proteins. Moving a substance against its gradient needs energy.

Water follows water potential

Water moves from higher to lower water potential. In AP Biology, water potential is solute potential plus pressure potential, and solute potential is −iCRT.

Common Unit 2 mistakes

Saying that facilitated diffusion uses ATP; it does not.
Predicting that a plant cell bursts in a hypotonic solution; the cell wall prevents it.
Thinking water moves toward higher water potential instead of lower.

How to study this unit

When a question gives concentrations, first label each side hypertonic or hypotonic, then decide the direction of net water movement.
Link each piece of endosymbiosis evidence (double membrane, circular DNA, own ribosomes) to the claim it supports.

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More AP Biology practice tests

Full AP Biology practice exam →60 questions from all 8 units, weighted like the real exam, with a 90-minute timer.

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StudyCoach wrote these questions for this test. Each one is mapped to a topic in the College Board's current AP Biology course framework. Every answer key was also checked by a separate AI review, and any disagreement was rechecked by hand. They have not yet been reviewed by an AP Biology teacher. If you think an answer is wrong, email support@studycoach.io.

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