Question 1

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?
A) large hydrophobic molecules
B) small hydrophobic molecules
C) carbon dioxide
D) small ions

Accepted Answer

Small ions are charged and therefore unable to pass through the hydrophobic region of the phospholipid bilayer.

Question 2

According to the fluid mosaic model, a membrane ________.
A) is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins
B) is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins
C) is composed of a mosaic of fluid polysaccharides and amphipathic proteins
D) is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins

Accepted Answer

According to the fluid mosaic model, a membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins. This model suggests that the components of the membrane are constantly moving and that the proteins may have different functions, such as transport, signaling, and enzymatic activity.

Question 3

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
B) Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly.
C) Unsaturated fatty acids are more nonpolar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.

Accepted Answer

The double bonds in unsaturated fatty acids create kinks in the fatty acid tails, preventing adjacent lipids from packing tightly and thus increasing membrane fluidity.

Question 4

Which of the following types of molecules lack hydrophilic domains?
A) transmembrane proteins
B) integral membrane proteins
C) peripheral membrane proteins
D) cholesterol

Accepted Answer

Cholesterol is a non-polar molecule and lacks any hydrophilic domains. Transmembrane proteins, integral membrane proteins, and peripheral membrane proteins all have hydrophilic domains that interact with the polar head groups of phospholipids in the membrane.

Question 5

For the following questions, match the labeled component of the cell membrane in the figure with its description.
-
Which component in the accompanying figure is cholesterol?
A) B
B) C
C) D
D) E

Accepted Answer

The answer of For the following questions, match the labeled...

Question 6

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?
A) Permeability to glucose will increase.
B) Permeability to glucose will decrease.
C) Permeability to glucose will stay the same.
D) Permeability will decrease initially then increase as the bilayer fills with glucose.

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipid bilayer introduces more kinks into the fatty acid tails, leading to a more fluid and less tightly packed membrane. This increased fluidity allows for easier passage of molecules like glucose, thereby increasing the membrane's permeability to glucose.

Question 7

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.
A) increasing the proportion of unsaturated phospholipids in the membrane
B) decreasing the percentage of cholesterol molecules in the membrane
C) decreasing the number of hydrophobic proteins in the membrane
D) increasing the proportion of glycolipids in the membrane

Accepted Answer

Increasing the proportion of unsaturated phospholipids in the membrane allows for more kinks in the tails of the phospholipids, preventing them from packing tightly together and therefore maintaining membrane fluidity in extremely cold temperatures.

Question 8

For a protein to be an integral membrane protein, it would have to be ________.
A) hydrophilic
B) hydrophobic
C) amphipathic, with at least one hydrophobic region
D) exposed on only one surface of the membrane

Accepted Answer

Integral membrane proteins have to be amphipathic, with at least one hydrophobic region. This allows them to embed themselves into the hydrophobic interior of the lipid bilayer, while also having hydrophilic regions that can interact with the aqueous environment on either side of the membrane.

Question 9

For the following questions, match the labeled component of the cell membrane in the figure with its description.
-
Which component in the accompanying figure is a microfilament (actin filament)of the cytoskeleton?
A) A
B) B
C) C
D) D

Accepted Answer

The answer of For the following questions, match the labeled...

Question 10

For the following questions, match the labeled component of the cell membrane in the figure with its description.
-
Which component in the accompanying figure is a protein fiber of the extracellular matrix?
A) A
B) B
C) C
D) E

Accepted Answer

The answer of For the following questions, match the labeled...

Question 11

According to the fluid mosaic model of cell membranes, phospholipids ________.
A) can move laterally along the plane of the membrane
B) frequently flip-flop from one side of the membrane to the other
C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane
D) have hydrophilic tails in the interior of the membrane

Accepted Answer

The fluid mosaic model proposes that phospholipids can move laterally along the plane of the membrane, meaning they can shift and interact with neighboring phospholipids. This contributes to the membrane's fluidity.

Question 12

An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?
A) transporting ions against an electrochemical gradient
B) cell-cell recognition
C) attaching the plasma membrane to the cytoskeleton
D) establishing a diffusion barrier to charged molecules

Accepted Answer

Carbohydrates on the external surface of the plasma membrane are involved in cell-cell recognition, which is important for various cellular processes such as immune response and embryonic development. A lack of carbohydrates would impair this function.

Question 13

What kinds of molecules pass through a cell membrane most easily?
A) large and hydrophobic
B) small and hydrophobic
C) large polar
D) small and ionic

Accepted Answer

Small and hydrophobic molecules can easily pass through the cell membrane by simple diffusion as they can dissolve in the lipid bilayer. Large and polar molecules have difficulty passing through the hydrophobic layer, while small and ionic molecules have charges that are not conducive to passing through the nonpolar membrane.

Question 14

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
A) Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical.
B) Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical.
C) The two sides of a cell membrane face different environments and carry out different functions.
D) Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.

Accepted Answer

The two sides of a cell membrane face different environments and carry out different functions. The outer side of the membrane faces the extracellular environment and interacts with other cells and substances, while the inner side faces the cytoplasm and is involved in intracellular signaling and transport. This difference in function requires the membrane to be asymmetrical.

Question 15

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?
A) It exhibits specificity for a particular type of molecule.
B) It requires the expenditure of cellular energy to function.
C) It works against diffusion.
D) It has no hydrophobic regions.

Accepted Answer

A carrier protein in a plasma membrane exhibits specificity for a particular type of molecule. This means that it can only transport certain types of molecules across the membrane. Carrier proteins do not require cellular energy to function, as they work by simply binding to a specific molecule and undergoing a conformational change to transport it across the membrane. Carrier proteins also do not work against diffusion, as they support facilitated diffusion. Carrier proteins may have hydrophobic regions as they span the membrane.

Question 16

In what way do the membranes of a eukaryotic cell vary?
A) Phospholipids are found only in certain membranes.
B) Certain proteins are unique to each membrane.
C) Only certain membranes of the cell are selectively permeable.
D) Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm.

Accepted Answer

Different membranes in eukaryotic cells have distinct sets of proteins that are unique to them. This is what gives each membrane its characteristic functions and properties. While all membranes have a similar basic structure of phospholipid bilayers, the specific proteins and lipids present in each membrane can vary extensively. Phospholipids are found in all eukaryotic membranes, making choice A incorrect. Choice C is also incorrect, as most membranes are selectively permeable to some degree. Choice D is partially true, but overall, the orientation of hydrophobic and hydrophilic surfaces in membranes is more complex and not so easily generalized across different membranes.

Question 17

For the following questions, match the labeled component of the cell membrane in the figure with its description.
-
Which component in the accompanying figure is hydrophilic?
A) A
B) B
C) C
D) D

Accepted Answer

The answer of For the following questions, match the labeled...

Question 18

For the following questions, match the labeled component of the cell membrane in the figure with its description.
-
Which component in the accompanying figure plays a critical role in cell-cell recognition?
A) A
B) B
C) C
D) E

Accepted Answer

The answer of For the following questions, match the labeled...

Question 19

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?
A) transmembrane proteins
B) integral membrane proteins
C) peripheral membrane proteins
D) cholesterol

Accepted Answer

Peripheral membrane proteins are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer. Transmembrane and integral membrane proteins can have both hydrophilic and hydrophobic portions, allowing them to interact with both the aqueous environment and the hydrophobic interior of the membrane. Cholesterol has both hydrophilic and hydrophobic portions and can therefore interact with both the aqueous and hydrophobic portions of the membrane.

Question 20

Why are lipids and proteins free to move laterally in membranes?
A) The interior of the membrane is filled with liquid water.
B) Lipids and proteins repulse each other in the membrane.
C) Hydrophilic portions of the lipids are in the interior of the membrane.
D) There are only weak hydrophobic interactions in the interior of the membrane.

Accepted Answer

The interior of the membrane is hydrophobic, which means there are only weak hydrophobic interactions in this region. This allows lipids and proteins to move freely laterally within the membrane. The presence of liquid water in the interior (A) would hinder their movement, while repulsion between lipids and proteins (B) would prevent their close association in the membrane. Additionally, the hydrophilic portions of the lipids are typically found on the exterior of the membrane (C), not in the interior where the lipids and proteins move laterally.

Quiz 7: Membrane Structure and Function

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?

According to the fluid mosaic model, a membrane ________.

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?

Which of the following types of molecules lack hydrophilic domains?

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is cholesterol?

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.

For a protein to be an integral membrane protein, it would have to be ________.

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is a microfilament (actin filament) of the cytoskeleton?

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is a protein fiber of the extracellular matrix?

According to the fluid mosaic model of cell membranes, phospholipids ________.

An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?

What kinds of molecules pass through a cell membrane most easily?

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?

In what way do the membranes of a eukaryotic cell vary?

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure is hydrophilic?

For the following questions, match the labeled component of the cell membrane in the figure with its description. - Which component in the accompanying figure plays a critical role in cell-cell recognition?

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?

Why are lipids and proteins free to move laterally in membranes?