Question 1

Which property of phospholipids is primarily responsible for the formation of the bilayer structure in cellular membranes?

Accepted Answer

Their amphipathic nature, with hydrophilic heads and hydrophobic tails

Question 2

What would most likely happen to the plasma membrane of a fish living in extremely cold water if its phospholipids were mostly saturated?

Accepted Answer

The membrane would become too rigid and could solidify, impairing cell function

Question 3

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic structure with proteins bobbing in a fluid bilayer of phospholipids

Question 4

A scientist fuses a mouse cell and a human cell, each with differently labeled membrane proteins. After one hour, the proteins are intermixed on the hybrid cell surface. What does this experiment demonstrate?

Accepted Answer

Membrane proteins can move laterally within the plane of the membrane

Question 5

How does cholesterol affect membrane fluidity at different temperatures?

Accepted Answer

It acts as a fluidity buffer, restraining movement at high temperatures and preventing solidification at low temperatures

Question 6

Which of the following is a function of membrane carbohydrates?

Accepted Answer

Cell-cell recognition

Question 7

A native grass species is found in very warm soil near hot springs. Compared to a related species in cooler soil, what membrane adaptation would you expect?

Accepted Answer

A higher proportion of saturated phospholipids to maintain membrane integrity

Question 8

Which type of membrane protein penetrates the hydrophobic core of the lipid bilayer and often spans the entire membrane?

Accepted Answer

Integral (transmembrane) proteins

Question 9

Which of the following best explains why unsaturated hydrocarbon tails increase membrane fluidity?

Accepted Answer

Kinks in the tails prevent tight packing of phospholipids

Question 10

Which of the following is NOT a function of membrane proteins?

Accepted Answer

DNA replication

Question 11

Why is membrane fluidity important for cell function?

Accepted Answer

It allows membrane proteins to move to where their function is needed and maintains permeability

Question 12

Which of the following best describes the sidedness (asymmetry) of cellular membranes?

Accepted Answer

The two lipid layers and associated proteins and carbohydrates differ in composition and orientation

Question 13

Which real-world example illustrates the importance of membrane proteins in medicine?

Accepted Answer

HIV infection requires the presence of the CCR5 membrane protein on host cells

Question 14

Which of the following statements about glycoproteins is correct?

Accepted Answer

They are proteins with covalently attached carbohydrate chains that function in cell recognition

Question 15

If a membrane protein is synthesized in the endoplasmic reticulum (ER) and has a carbohydrate attached in the ER lumen, where will the carbohydrate be located after the protein reaches the plasma membrane?

Accepted Answer

On the extracellular side of the plasma membrane

Question 16

Which equation best represents the relationship between membrane fluidity (F), temperature (T), and the proportion of unsaturated fatty acids (U)?

Accepted Answer

$$F \propto T + U$$

Question 17

Which of the following would most likely increase the permeability of a cell membrane to small, nonpolar molecules?

Accepted Answer

Increasing the proportion of unsaturated phospholipids

Question 18

Which of the following is a plausible consequence if a cell membrane becomes too fluid?

Accepted Answer

Membrane proteins may not function properly, and the cell could lose structural integrity

Question 19

Which of the following best explains why some bacteria and archaea can survive in extremely hot environments?

Accepted Answer

They have membranes with a higher proportion of saturated phospholipids, which resist melting

Question 20

Which of the following is NOT a function performed by proteins in the plasma membrane?

Accepted Answer

Synthesis of DNA

The Structure and Function of Cellular Membranes

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