Question 1

Which of the following best explains why phospholipids form bilayers in water?

Accepted Answer

Their hydrophilic heads interact with water, while their hydrophobic tails avoid water.

Question 2

A researcher adds cholesterol to a synthetic phospholipid bilayer. What is the most likely effect on the membrane's permeability?

Accepted Answer

Permeability will decrease because cholesterol increases the packing density of the hydrophobic tails.

Question 3

Which of the following molecules would cross a pure phospholipid bilayer most rapidly?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

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

Accepted Answer

The cell will shrink because water moves out of the cell.

Question 5

Which of the following best describes the role of the sodium-potassium pump ($$Na^+/K^+-$$ATPase) in cells?

Accepted Answer

It moves sodium and potassium ions against their concentration gradients using energy from ATP.

Question 6

Which of the following statements about membrane proteins is correct?

Accepted Answer

Integral membrane proteins can span the membrane and have hydrophobic and hydrophilic regions.

Question 7

A mutation causes the fatty acid tails of a cell's phospholipids to become longer and more saturated. What is the most likely effect on the cell membrane?

Accepted Answer

The membrane will become less permeable and more rigid.

Question 8

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of substances down their concentration gradient through membrane proteins without energy input.

Question 9

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

It will remain the same size because there is no net movement of water.

Question 10

Which of the following is a function of membrane lipids in cells?

Accepted Answer

They form waterproof coatings and store chemical energy.

Question 11

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

Accepted Answer

Double bonds create kinks, preventing tight packing of phospholipid tails.

Question 12

Which of the following is true about the movement of phospholipids within the plasma membrane?

Accepted Answer

Phospholipids can move laterally within the same layer but rarely flip-flop between layers.

Question 13

A patient with cystic fibrosis has a mutation in the CFTR protein. What is the direct consequence of this mutation at the cellular level?

Accepted Answer

Chloride ions cannot efficiently leave the cell, leading to thick mucus.

Question 14

Which of the following best describes secondary active transport (co-transport)?

Accepted Answer

It uses the energy stored in an electrochemical gradient to move another molecule against its gradient.

Question 15

Which of the following equations best represents the movement of water during osmosis?

Accepted Answer

$$Water: Low\ solute\ concentration \rightarrow High\ solute\ concentration$$

Question 16

Which of the following is a property of amphipathic molecules?

Accepted Answer

They contain both hydrophilic and hydrophobic regions.

Question 17

A scientist creates a planar bilayer with phospholipids containing short, unsaturated fatty acid tails. Which of the following is most likely true about this membrane?

Accepted Answer

It will have high permeability to small molecules.

Question 18

Which of the following best describes the fluid-mosaic model of membrane structure?

Accepted Answer

Membranes are dynamic, with proteins and lipids moving laterally within the bilayer.

Question 19

Which of the following is a real-world example of passive transport in human physiology?

Accepted Answer

Glucose entering a cell through GLUT-1 carrier protein down its concentration gradient.

Chapter 6: Lipids, Membranes, and the First Cells – Study Notes

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