AP Bio Unit 2.2 Quiz: Cell Size, Plasma Mem, Passive Transport

Organisms living in extremely cold climates have adapted their cell membranes to maintain functionality at low temperatures. Which of the following adaptations would you expect to find in the membrane composition of such organisms?

• A. Many unsaturated fatty acid chains to maintain membrane fluidity and prevent tight packing of the phospholipids at low temperatures.

• B. Increased cholesterol content to enhance membrane rigidity and stability.

• C. Many saturated fatty acid chains to create a more stable and less fluid membrane at low temperatures.

• D. Short fatty acid chains to enhance membrane permeability and flexibility.

Examine the chart shown. Which cell would be most efficient at exchanging material across its plasma membrane?

• A. Cell A

• B. Cell B

• C. Cell C

• D. Cell D

Examine the chart shown. Which cell would be best for the storage of materials?

• A. Cell A

• B. Cell B

• C. Cell C

• D. Cell D

Which option best explains why these projections play such a vital role in the intestinal cells?

• A. The projections change the composition of the plasma membrane, thus altering its selective permeability to allow for increased nutrient uptake.

• B. The villi and microvilli allow the cells to be larger than normal cells, thus maximizing the exchange of materials and nutrients across the plasma membrane.

• C. The villi and microvilli increase the surface area-to-volume ratio of the intestinal cells, which allows for more efficient absorption of nutrients.

• D. The villi and microvilli increase the volume of the cells, thereby increasing the metabolic needs of the cells and allowing them to maximize nutrient absorption.

The plasma membrane is described as a "fluid mosaic model." Which of the following statements best describes the "fluid" aspect of this model?

• A. The plasma membrane is composed of a variety of different macromolecules.

• B. The membrane is held together by weak hydrophobic interactions, allowing lipids and proteins to move laterally.

• C. The membrane contains carbohydrate molecules that aid in cell-to-cell recognition.

• D. The plasma membrane has selective permeability, allowing only certain molecules to pass through.

6A. Describe the amphipathic nature of phospholipids in the plasma membrane and EXPLAIN how this property contributes to the membrane's selective permeability.

6B. Using the provided image of a plasma membrane, IDENTIFY the structure that represents an integral protein. Provide reasoning to JUSTIFY your identification.

6C. Unlike water, which requires aquaporins to pass through the plasma membrane efficiently, other molecules can pass freely across the membrane. Identify ONE example of a molecule that can pass freely across the membrane. DESCRIBE the properties of this molecule that allow it to do so.

(This questions is not on the paper) What does it mean if a molecule is identified as amphipathic?

• A molecule that is completely hydrophobic.
• A molecule that is entirely hydrophilic.
• A molecule that has no polar regions.
• A molecule that has both hydrophilic and hydrophobic parts.