Unit 2: Cell Structure & Function
Biology · Unit 2 · Paper 2

Cell Structure & Function unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 37 terms and is the same for everyone, so a teacher can assign “Unit 2, Paper 2” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 36 min 33 points0/17 attempted
1

Cholesterol in membranes

2

Golgi apparatus

3

Tight junctions, desmosomes, gap junctions

4

Nucleolus

5

Water potential

6

Rough ER

7

Sodium-potassium pump

8

Nuclear envelope and pores

9

Surface area to volume ratio

10

Selective permeability

11

Ribosome

12

Peroxisome

Short answer 1. Define or explain: Contractile vacuole

3 pts

Short answer 2. Define or explain: Hypotonic, hypertonic, isotonic

3 pts

Short answer 3. Define or explain: Lab: Diffusion and Osmosis

3 pts

Short answer 4. Define or explain: Osmosis

3 pts

Free response

9 pts

A researcher studies a freshwater protist that lives in pond water far more dilute than its cytoplasm. The protist has a contractile vacuole that fills with water and periodically expels it across the plasma membrane. The researcher transfers protists into solutions of increasing solute concentration and records how often the contractile vacuole contracts.

Describe the direction of net water movement between the protist and pond water, and explain why it occurs.

Explain why the contractile vacuole requires ATP, even though the water entering the cell does not.

Predict how contraction rate changes as external solute concentration rises, and justify your prediction.

The researcher places protists in a solution isotonic to their cytoplasm. Predict the contraction rate and explain what this result shows about the vacuole's function.