$$\text{Glycerol} + 3 \text{Fatty Acids} \rightarrow \text{Triglyceride} + 3 \text{H}_2\text{O}$$

Question 1

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

Accepted Answer

Phospholipids are amphipathic, with hydrophilic heads that interact with water and hydrophobic tails that avoid water.

Question 2

A cell is placed in a solution with a higher solute concentration than its cytoplasm. What will happen to the cell?

Accepted Answer

Water will move out of the cell by osmosis, causing the cell to shrink.

Question 3

Which functional group is found in both proteins and lipids and is important for their structure?

Accepted Answer

Carboxyl group $$(-\mathrm{COOH})$$

Question 4

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

Accepted Answer

Oxygen $$(\mathrm{O}_2)$$

Question 5

Why do unsaturated fatty acids increase membrane permeability compared to saturated fatty acids?

Accepted Answer

Unsaturated fatty acids have kinks due to double bonds, preventing tight packing and increasing permeability.

Question 6

Which statement about osmosis is correct?

Accepted Answer

Osmosis is the movement of water from regions of low solute concentration to regions of high solute concentration.

Question 7

A patient with cystic fibrosis has a defect in a membrane protein. What is the primary function of this protein?

Accepted Answer

It forms a channel for chloride ions $$(\mathrm{Cl}^-) to $$pass through the membrane.

Question 8

Which of the following best describes the structure of a steroid molecule?

Accepted Answer

A molecule with four fused rings and a variable side group

Question 9

Which of the following changes would DECREASE the permeability of a phospholipid bilayer?

Accepted Answer

Adding cholesterol to the bilayer

Question 10

Which equation best represents the process of forming a fat (triglyceride) from its components?

Accepted Answer

$$	ext{Glycerol} + 3 	ext{Fatty Acids} ightarrow 	ext{Triglyceride} + 3 	ext{H}_2	ext{O}$$

Question 11

Which of the following is TRUE about facilitated diffusion?

Accepted Answer

It uses transmembrane proteins to move substances down their concentration gradient.

Question 12

A cell membrane contains both integral and peripheral proteins. Which statement best distinguishes these two types?

Accepted Answer

Integral proteins span the membrane and interact with hydrophobic tails, while peripheral proteins bind to the membrane surface.

Question 13

Which of the following best describes the role of the plasma membrane in chemical evolution?

Accepted Answer

It allowed for the compartmentalization of replicating RNA and other molecules, facilitating the origin of protocells.

Question 14

Which of the following would most likely require a protein channel to cross a cell membrane?

Accepted Answer

Potassium ion $$(\mathrm{K}^+)$$

Question 15

Which of the following is a correct statement about the fluid-mosaic model of membrane structure?

Accepted Answer

Membrane proteins and phospholipids can move laterally within the bilayer.

Question 16

Which of the following scenarios would result in the highest rate of diffusion across a phospholipid bilayer?

Accepted Answer

A bilayer with short, unsaturated hydrocarbon tails at high temperature

Question 17

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

Accepted Answer

Synthesizing proteins for the cell

Question 18

Which of the following best describes the movement of phospholipids within the bilayer?

Accepted Answer

Phospholipids move laterally within the bilayer, increasing fluidity and permeability at higher temperatures.

Question 19

Which of the following is TRUE about active transport across cell membranes?

Accepted Answer

It requires energy input, often from ATP, to move substances against their concentration gradient.

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

Study Guide - Practice Questions