Question 1

Which of the following best describes the structure of a phospholipid in the plasma membrane?

Accepted Answer

A molecule with a hydrophilic head and two hydrophobic tails

Question 2

What is the primary driving force for the spontaneous self-assembly of phospholipids into a bilayer structure?

Accepted Answer

The hydrophobic effect, which minimizes the exposure of hydrocarbon tails to water

Question 3

Which equation best represents the lateral diffusion of membrane lipids as measured by FRAP (Fluorescence Recovery After Photobleaching)?

Accepted Answer

$D = \frac{r^2}{4t}$

Question 4

Integral membrane proteins differ from peripheral membrane proteins in that:

Accepted Answer

Integral proteins are embedded within the lipid bilayer and can only be separated by disrupting the membrane

Question 5

A mutation causes the phosphate head of a phospholipid to become nonpolar. What is the most likely consequence for the plasma membrane?

Accepted Answer

Phospholipids will fail to form a bilayer, disrupting membrane integrity

Question 6

Which of the following statements about membrane proteins is TRUE?

Accepted Answer

Integral membrane proteins are tightly bound and require detergents for purification

Question 7

Why do hydrophobic groups in phospholipids avoid water?

Accepted Answer

Because they are nonpolar and water is polar, leading to unfavorable interactions

Question 8

Which of the following best explains the role of the plasma membrane in cellular exchange?

Accepted Answer

It allows for dynamic interaction and selective exchange between the cell and its environment

Question 9

A scientist uses FRAP to study membrane protein mobility. After photobleaching, fluorescence recovers in the region. What does this indicate?

Accepted Answer

Membrane proteins and lipids can diffuse laterally within the bilayer

Question 10

Which of the following is a real-world example of a peripheral membrane protein?

Accepted Answer

Cytochrome c

Question 11

If a cell's plasma membrane is composed primarily of saturated fatty acids, what effect would this have on membrane fluidity?

Accepted Answer

Membrane fluidity would decrease

Question 12

Which of the following best describes the arrangement of phospholipids in the plasma membrane?

Accepted Answer

Phospholipids form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward

Question 13

Which process is primarily responsible for the recovery of fluorescence in a FRAP experiment?

Accepted Answer

Lateral diffusion of membrane components

Question 14

A patient has a genetic defect that prevents the formation of integral membrane proteins. Which cellular function would be most directly affected?

Accepted Answer

Selective transport of molecules across the plasma membrane

Question 15

Which of the following statements about the plasma membrane is FALSE?

Accepted Answer

It is impermeable to all substances

Question 16

Which type of interaction is most important for the association of peripheral membrane proteins with the plasma membrane?

Accepted Answer

Hydrogen bonding and electrostatic interactions

Question 17

In a cell, which component is most responsible for the selective permeability of the plasma membrane?

Accepted Answer

Phospholipid bilayer

Question 18

Which of the following best explains why membrane proteins are often purified using detergents?

Accepted Answer

Detergents solubilize hydrophobic regions of integral membrane proteins

Question 19

A researcher observes that a certain membrane protein is only loosely attached to the surface and can be removed by changing the pH. This protein is most likely:

Accepted Answer

A peripheral membrane protein

Structure and Function of Biological Membranes

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