Q: Which equation best represents the movement of water during osmosis across a selectively permeable membrane?

$$\text{Water moves from low solute concentration (high water potential) to high solute concentration (low water potential)}$$

Question 1

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

Accepted Answer

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

Question 2

A researcher creates two artificial membranes: Membrane A is made of phospholipids with long, saturated hydrocarbon tails; Membrane B is made of phospholipids with short, unsaturated hydrocarbon tails. Which membrane will have higher permeability to small, uncharged molecules, and why?

Accepted Answer

Membrane B, because unsaturated and short tails increase fluidity and permeability.

Question 3

Which of the following best describes the function of cholesterol in animal cell membranes?

Accepted Answer

Cholesterol decreases membrane fluidity at high temperatures and increases it at low temperatures.

Question 4

A red blood cell is placed in a solution with a higher solute concentration than its cytoplasm. What will happen to the cell, and what is the term for this type of solution?

Accepted Answer

The cell will shrink; the solution is hypertonic.

Question 5

Which of the following statements about diffusion is correct?

Accepted Answer

Diffusion moves substances from areas of high concentration to low concentration, increasing entropy.

Question 6

Which equation best represents the movement of water during osmosis across a selectively permeable membrane?

Accepted Answer

$$	ext{Water moves from low solute concentration (high water potential) to high solute concentration (low water potential)}$$

Question 7

Which of the following is a key difference between channel proteins and carrier proteins in facilitated diffusion?

Accepted Answer

Channel proteins form pores for specific molecules, while carrier proteins change shape to transport molecules.

Question 8

The sodium-potassium pump (Na+/K+ ATPase) is an example of which type of membrane transport?

Accepted Answer

Active transport

Question 9

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

Accepted Answer

Their double bonds create kinks, preventing tight packing of phospholipids.

Question 10

A cell uses a protein to move glucose from an area of low concentration outside the cell to a higher concentration inside the cell. Which process is being used?

Accepted Answer

Active transport

Question 11

Which of the following statements about the fluid-mosaic model of membranes is correct?

Accepted Answer

Membranes are dynamic, with proteins and lipids able to move laterally within the bilayer.

Question 12

Which of the following best describes the role of integral membrane proteins?

Accepted Answer

They span the membrane and can facilitate the transport of molecules across the bilayer.

Question 13

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

Accepted Answer

Synthesizing DNA from RNA

Question 14

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

Accepted Answer

O2

Question 15

A vesicle containing a 0.2 M sucrose solution is placed in a beaker containing a 0.5 M sucrose solution. What will happen to the vesicle?

Accepted Answer

Water will move out of the vesicle, causing it to shrink.

Question 16

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

Accepted Answer

It uses the energy from one molecule moving down its gradient to move another molecule against its gradient.

Question 17

Which of the following functional groups is found in both proteins and lipids and is important for forming ester linkages in fats?

Accepted Answer

Carboxyl group ($$-COOH)$$

Question 18

Which of the following best explains why ions such as Na+ and Cl- cannot easily cross a pure phospholipid bilayer?

Accepted Answer

They are repelled by the hydrophobic core of the bilayer due to their charge.

Question 19

Which of the following is a real-world example of facilitated diffusion?

Accepted Answer

Glucose entering a muscle cell via the GLUT-1 transporter.

Question 20

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have a hydrophilic head and two hydrophobic tails.

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

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