Question 1

Which of the following best describes an amphipathic molecule, such as a phospholipid, and explains its behavior in water?

Accepted Answer

It contains both hydrophilic and hydrophobic regions, allowing it to form bilayers in aqueous environments.

Question 2

A researcher observes that a cell placed in a solution shrinks and loses water. Which term best describes the solution, and what is the direction of water movement?

Accepted Answer

The solution is hypertonic; water moves out of the cell.

Question 3

Which of the following changes would most likely increase the permeability of a phospholipid bilayer?

Accepted Answer

Increasing the proportion of unsaturated fatty acid tails in the phospholipids.

Question 4

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

Accepted Answer

Their hydrophilic heads interact with water while their hydrophobic tails avoid water, leading to a stable bilayer structure.

Question 5

A cell membrane is described as 'selectively permeable.' What does this mean in the context of molecular transport?

Accepted Answer

The membrane allows some substances to diffuse across more readily than others.

Question 6

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of water across a selectively permeable membrane from a region of lower solute concentration to higher solute concentration.

Question 7

A vesicle with a membrane containing mostly saturated fatty acids is placed in a cold environment. What is the most likely effect on the membrane's permeability?

Accepted Answer

The membrane's permeability will decrease due to tight packing of saturated tails and reduced fluidity at low temperature.

Question 8

Which of the following best describes the structure of a triglyceride?

Accepted Answer

A molecule consisting of three fatty acids linked to a glycerol backbone by ester bonds.

Question 9

Which of the following scenarios would most likely result in a cell bursting (lysis)?

Accepted Answer

The cell is placed in a hypotonic solution, causing water to enter the cell.

Question 10

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

Accepted Answer

The kinks in unsaturated hydrocarbon tails prevent tight packing, increasing fluidity.

Question 11

A scientist creates an artificial vesicle with a membrane composed entirely of phospholipids. Which of the following molecules would most easily diffuse across this membrane?

Accepted Answer

Small, nonpolar molecules such as $$O_2$$

Question 12

Which of the following best describes the process of facilitated diffusion?

Accepted Answer

Movement of substances across a membrane down their concentration gradient with the help of membrane proteins, without energy input.

Question 13

Which of the following is a key difference between a micelle and a lipid bilayer?

Accepted Answer

A micelle is a single-layered sphere with hydrophobic tails inward, while a bilayer is a double-layered sheet with hydrophobic tails sandwiched between hydrophilic heads.

Question 14

If a cell is placed in an isotonic solution, what will happen to the cell's volume?

Accepted Answer

The cell's volume will remain unchanged because there is no net movement of water.

Question 15

Which of the following best describes the role of ester linkages in lipid structure?

Accepted Answer

Ester linkages are covalent bonds formed by condensation reactions between a hydroxyl group of glycerol and a carboxyl group of a fatty acid.

Question 16

A cell membrane is composed of phospholipids with long, saturated hydrocarbon tails. Which of the following is most likely true about this membrane?

Accepted Answer

It will have low permeability and decreased fluidity.

Question 17

Which of the following best explains why early protocells with simple, permeable membranes could have supported the origin of life?

Accepted Answer

They allowed small molecules, such as nucleotides, to diffuse in and out, enabling basic metabolic processes.

Question 18

Which of the following statements about diffusion is correct?

Accepted Answer

Diffusion is the spontaneous movement of a substance from a region of high concentration to a region of low concentration.

Question 19

Which of the following best describes the function of vesicles in eukaryotic cells?

Accepted Answer

Vesicles are membrane-enclosed compartments that transport substances within the cell or secrete them outside the cell.

Study Notes: Lipids, Membranes, and the First Cells

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