Question 1

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

Accepted Answer

A flexible structure with proteins and lipids that can move laterally within the layer.

Question 2

Which component of the plasma membrane is primarily responsible for its selective permeability?

Accepted Answer

Phospholipid bilayer

Question 3

What is the main function of cholesterol in animal cell membranes?

Accepted Answer

To act as a fluidity buffer, maintaining membrane fluidity across temperature changes

Question 4

A red blood cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

The cell will swell and may burst due to water influx.

Question 5

Which of the following molecules would most easily diffuse through a pure phospholipid bilayer?

Accepted Answer

Oxygen ($$O_2)$$

Question 6

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It uses specific transport proteins to move substances down their concentration gradient.

Question 7

The sodium-potassium pump moves ions across the plasma membrane. Which equation correctly represents this process?

Accepted Answer

$$3\ \mathrm{Na}^+_{(in)} + 2\ \mathrm{K}^+_{(out)} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na}^+_{(out)} + 2\ \mathrm{K}^+_{(in)} + \mathrm{ADP} + \mathrm{P}_i$$

Question 8

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their kinks prevent tight packing of phospholipid tails.

Question 9

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

Accepted Answer

Synthesis of DNA

Question 10

A plant cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

It will undergo plasmolysis.

Question 11

Which of the following statements about active transport is correct?

Accepted Answer

It requires energy, usually from ATP.

Question 12

Which of the following best describes the role of glycoproteins in the plasma membrane?

Accepted Answer

They are important for cell recognition.

Question 13

Which of the following is a real-life example of cotransport in plant cells?

Accepted Answer

The sucrose-H$$^+$$ cotransporter

Question 14

Which of the following statements about membrane potential is correct?

Accepted Answer

It is the voltage difference across the plasma membrane due to unequal ion distribution.

Question 15

Which of the following best explains why cholesterol is not found in prokaryotic membranes?

Accepted Answer

Cholesterol is synthesized only in eukaryotic cells.

Question 16

Which of the following is true about the movement of phospholipids in the membrane?

Accepted Answer

They mainly move laterally within the same layer.

Question 17

A mutation causes a cell to lack aquaporins. Which process would be most directly affected?

Accepted Answer

Osmosis

Question 18

Which of the following best describes the effect of temperature on membrane fluidity?

Accepted Answer

High temperature increases fluidity, low temperature decreases fluidity.

Question 19

Which of the following is a function of peripheral membrane proteins?

Accepted Answer

Loosely attaching to the membrane surface, often for signaling or structural support

Question 20

Which of the following best explains why plant cells rarely burst in hypotonic solutions?

Accepted Answer

Their cell wall provides structural support against osmotic pressure.

LEC 5:Membrane Structure and Function: A Comprehensive Study Guide

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