Question 1

Which of the following lipids do you expect to be a canonical scramblase substrate in the plasma membrane?

Accepted Answer

A)  Ganglioside GM₁ 
B)  Cholesterol 
C)  Glycosylphosphatidylinositol 
D)  Phosphatidylethanolamine 
E)  Galactocerebroside 
A)  Ganglioside GM₁ 
B)  Cholesterol 
C)  Glycosylphosphatidylinositol 
D)  Phosphatidylethanolamine 
E)  Galactocerebroside D

Question 2

Which of the following is normally NOT found in a eukaryotic membrane?

Accepted Answer

A)  Cholesterol 
B)  Phosphatidylinositol 
C)  Sphingomyelin 
D)  Ganglioside GM₁ 
E)  Octylglucoside 
A)  Cholesterol 
B)  Phosphatidylinositol 
C)  Sphingomyelin 
D)  Ganglioside GM₁ 
E)  Octylglucoside E

Question 3

In the following schematic drawing of an abundant plasma membrane phosphoglyceride, which part is positively charged?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E A

Question 4

What is the typical thickness of a lipid bilayer such as the plasma membrane of our cells?

Accepted Answer

A)  0.5 nm 
B)  5 nm 
C)  50 nm 
D)  100 nm 
E)  500 nm 
A)  0.5 nm 
B)  5 nm 
C)  50 nm 
D)  100 nm 
E)  500 nm

Question 5

What do all β-barrel transmembrane proteins have in common?

Accepted Answer

A)  The number of β strands. 
B)  The diameter of the barrel. 
C)  The number of negative peaks in their hydropathy plots. 
D)  The general function, i.e. membrane transport. 
E)  The structural rigidity compared to α-helical transmembrane proteins. 
A)  The number of β strands. 
B)  The diameter of the barrel. 
C)  The number of negative peaks in their hydropathy plots. 
D)  The general function, i.e. membrane transport. 
E)  The structural rigidity compared to α-helical transmembrane proteins.

Question 6

Which of the following is NOT correct regarding the molecule whose structural formula is shown below?

Accepted Answer

A)  It is an amphiphilic molecule. 
B)  It is a sterol. 
C)  It makes the membrane less permeable to small hydrophilic molecules. 
D)  It is found in membranes of virtually all living cells. 
E)  It affects the fluidity of the lipid bilayer. 
A)  It is an amphiphilic molecule. 
B)  It is a sterol. 
C)  It makes the membrane less permeable to small hydrophilic molecules. 
D)  It is found in membranes of virtually all living cells. 
E)  It affects the fluidity of the lipid bilayer.

Question 7

The two monolayers of the plasma membrane in a human red blood cell …

Accepted Answer

A)  have different overall electrical charges, with negatively charged phospholipids (e.g. phosphatidylserine) normally enriched in the inner monolayer. 
B)  have the same abundance of phosphatidylinositol. 
C)  exchange phospholipids only through spontaneous flip-flops. 
D)  both contain glycolipids. 
E)  both contain gangliosides. 
A)  have different overall electrical charges, with negatively charged phospholipids (e.g. phosphatidylserine) normally enriched in the inner monolayer. 
B)  have the same abundance of phosphatidylinositol. 
C)  exchange phospholipids only through spontaneous flip-flops. 
D)  both contain glycolipids. 
E)  both contain gangliosides.

Question 8

In the following schematic drawing of the cytosolic side of human red blood cell plasma membrane, which of the labeled proteins is spectrin?

Accepted Answer

In the spectrin-based filamentous cytos

Question 9

Transmembrane proteins …

Accepted Answer

A)  are typically exposed only to one side of the membrane. 
B)  can be released from the membrane by a gentle extraction procedure such as salt treatment. 
C)  are often further attached to the membrane via a GPI anchor. 
D)  are sometimes covalently attached to a fatty acid chain that inserts into the membrane. 
E)  cannot contain β sheets in the part of their structure that interacts with the membrane interior. 
A)  are typically exposed only to one side of the membrane. 
B)  can be released from the membrane by a gentle extraction procedure such as salt treatment. 
C)  are often further attached to the membrane via a GPI anchor. 
D)  are sometimes covalently attached to a fatty acid chain that inserts into the membrane. 
E)  cannot contain β sheets in the part of their structure that interacts with the membrane interior.

Question 10

Under certain conditions, about 20 molecules, on average, are predicted to exist in each β-octylglucoside detergent micelle. If the critical micelle concentration for this detergent is about 20 mM under these conditions, at what total β-octylglucoside concentration are about half of the detergent molecules found in micelles?

Accepted Answer

A)  1 mM 
B)  10 mM 
C)  20 mM 
D)  21 mM 
E)  40 mM 
A)  1 mM 
B)  10 mM 
C)  20 mM 
D)  21 mM 
E)  40 mM

Question 11

The motion of lipid molecules in a synthetic bilayer can be studied by various techniques. Which of the following has been observed in these systems?

Accepted Answer

A)  Phospholipids diffuse rapidly within and between the two leaflets of a bilayer. 
B)  An average lipid molecule can diffuse the length of about 2 micrometers in a fraction of a millisecond. 
C)  The flip-flops are very rare for phospholipids but cholesterol molecules flip-flop more often. 
D)  Within a bilayer, lipid molecules rarely rotate about their long axis, but diffuse laterally at very high rates. 
E)  All of the above. 
A)  Phospholipids diffuse rapidly within and between the two leaflets of a bilayer. 
B)  An average lipid molecule can diffuse the length of about 2 micrometers in a fraction of a millisecond. 
C)  The flip-flops are very rare for phospholipids but cholesterol molecules flip-flop more often. 
D)  Within a bilayer, lipid molecules rarely rotate about their long axis, but diffuse laterally at very high rates. 
E)  All of the above.

Question 12

In the schematic drawing below, a protein is present on one side of a membrane in a high-enough quantity to induce curvature in this region of the membrane. In each of the following scenarios, indicate whether the protein would induce positive (P) or negative (N) curvature in the membrane. Your answer would be a three-letter string composed of letters P and N only, e.g. PPP.
   
( )	The protein inserts a hydrophobic domain into the membrane leaflet that is facing it.
( )	The protein is a phospholipase that cleaves the head group in specific phospholipids.
( )	The protein binds cooperatively to multiple phospholipids with very large head groups.

Accepted Answer

Proteins can use various strategies to

Question 13

In intestinal epithelial cells, the different plasma membrane domains are separated from each other by special barriers. Indicate true (T) and false (F) statements below regarding this separation. Your answer would be a four-letter string composed of letters T and F only, e.g. FFFF.
( )	These barriers are set up by nanoscale lipid raft domains.
( )	Proteins normally cannot pass through these barriers, whereas any membrane lipid can do so freely.
( )	The asymmetric distribution of membrane proteins resulting from these barriers is functionally important.
( )	These barriers are a result of proteins of the apical surface forming a large aggregate together that excludes proteins of the other domains.

Accepted Answer

The barriers are set up by special cel

Question 14

Many cells store lipids in droplets of varying sizes. These droplets …

Accepted Answer

A)  are enclosed by a phospholipid monolayer (instead of a bilayer). 
B)  mostly store cholesterol and phospholipids. 
C)  are produced by and released from the Golgi apparatus. 
D)  have mostly protein-free bilayer membranes. 
E)  are composed primarily of charged amphiphilic lipids. 
A)  are enclosed by a phospholipid monolayer (instead of a bilayer). 
B)  mostly store cholesterol and phospholipids. 
C)  are produced by and released from the Golgi apparatus. 
D)  have mostly protein-free bilayer membranes. 
E)  are composed primarily of charged amphiphilic lipids.

Question 15

Glycolipids such as gangliosides …

Accepted Answer

A)  may contain oligosaccharide chains with negatively charged residues. 
B)  are found to constitute about 10% of the total lipid mass in the plasma membrane of neurons. 
C)  are found in the extracellular leaflet (facing away from the cytosol) in the cellular membranes. 
D)  affect the electrical environment of the membrane. 
E)  All of the above 
A)  may contain oligosaccharide chains with negatively charged residues. 
B)  are found to constitute about 10% of the total lipid mass in the plasma membrane of neurons. 
C)  are found in the extracellular leaflet (facing away from the cytosol) in the cellular membranes. 
D)  affect the electrical environment of the membrane. 
E)  All of the above

Question 16

Integrins are single-pass integral membrane proteins in the plasma membrane of animal cells and are involved in the interaction of the cell with the surrounding extracellular matrix. Which of the following descriptions do you think matches the transmembrane part of an integrin molecule?

Accepted Answer

A)  It forms a β barrel. 
B)  It is an α helix that is bent in the middle. 
C)  It is about 10 amino acids long, with every other amino acid side chain being hydrophobic. 
D)  It folds in a conformation with maximal intrachain hydrogen-bonding. 
E)  It is about 100 amino acids long. 
A)  It forms a β barrel. 
B)  It is an α helix that is bent in the middle. 
C)  It is about 10 amino acids long, with every other amino acid side chain being hydrophobic. 
D)  It folds in a conformation with maximal intrachain hydrogen-bonding. 
E)  It is about 100 amino acids long.

Question 17

Which of the following is correct regarding the composition of various biological membranes?

Accepted Answer

A)  Bacterial plasma membranes are often composed of one main type of phospholipid and lack cholesterol. 
B)  Cholesterol in the eukaryotic plasma membrane induces phase transition to the gel state. 
C)  Inositol phospholipids are the most abundant lipids in the endoplasmic reticulum membrane. 
D)  The mitochondrial and bacterial membranes are rich in glycolipids. 
E)  Yeast cells synthesize more fatty acids with cis?-double bonds when the temperature in the environment rises. 
A)  Bacterial plasma membranes are often composed of one main type of phospholipid and lack cholesterol. 
B)  Cholesterol in the eukaryotic plasma membrane induces phase transition to the gel state. 
C)  Inositol phospholipids are the most abundant lipids in the endoplasmic reticulum membrane. 
D)  The mitochondrial and bacterial membranes are rich in glycolipids. 
E)  Yeast cells synthesize more fatty acids with cis?-double bonds when the temperature in the environment rises.

Question 18

Which of the following changes is more likely to further confine a membrane protein within a corral established by the cortical cytoskeletal network?

Accepted Answer

A)  Increased temperature 
B)  Protease cleavage of the extracellular domain of the protein 
C)  Binding to an extracellular ligand 
D)  Protease cleavage of the cytosolic domain of the protein 
E)  Binding of the protein to other transmembrane proteins 
A)  Increased temperature 
B)  Protease cleavage of the extracellular domain of the protein 
C)  Binding to an extracellular ligand 
D)  Protease cleavage of the cytosolic domain of the protein 
E)  Binding of the protein to other transmembrane proteins

Question 19

On the plasma membrane of the archaeon Halobacterium salinarum, bacteriorhodopsin is found in high density in patches of purple membrane. This protein …

Accepted Answer

A)  is a light-gated anion channel. 
B)  is a single-pass transmembrane protein. 
C)  uses the energy stored in the proton gradient to transport small molecules. 
D)  changes conformation in response to light. 
E)  All of the above. 
A)  is a light-gated anion channel. 
B)  is a single-pass transmembrane protein. 
C)  uses the energy stored in the proton gradient to transport small molecules. 
D)  changes conformation in response to light. 
E)  All of the above.

Question 20

Which of the following proteins is NOT in the same superfamily as the other four? The other four share an overall architecture composed of seven closely-packed transmembrane helices.

Accepted Answer

A)  Bacteriorhodopsin 
B)  Channelrhodopsin 
C)  G-protein-coupled receptor 
D)  Aquaporin 
E)  Rhodopsin 
A)  Bacteriorhodopsin 
B)  Channelrhodopsin 
C)  G-protein-coupled receptor 
D)  Aquaporin 
E)  Rhodopsin

Exam 10: Membrane Structure

Which of the following lipids do you expect to be a canonical scramblase substrate in the plasma membrane?

Which of the following is normally NOT found in a eukaryotic membrane?

In the following schematic drawing of an abundant plasma membrane phosphoglyceride, which part is positively charged?

What is the typical thickness of a lipid bilayer such as the plasma membrane of our cells?

What do all β-barrel transmembrane proteins have in common?

Which of the following is NOT correct regarding the molecule whose structural formula is shown below?

The two monolayers of the plasma membrane in a human red blood cell …

In the following schematic drawing of the cytosolic side of human red blood cell plasma membrane, which of the labeled proteins is spectrin?

Transmembrane proteins …

The motion of lipid molecules in a synthetic bilayer can be studied by various techniques. Which of the following has been observed in these systems?

Many cells store lipids in droplets of varying sizes. These droplets …

Glycolipids such as gangliosides …

Integrins are single-pass integral membrane proteins in the plasma membrane of animal cells and are involved in the interaction of the cell with the surrounding extracellular matrix. Which of the following descriptions do you think matches the transmembrane part of an integrin molecule?

Which of the following is correct regarding the composition of various biological membranes?

Which of the following changes is more likely to further confine a membrane protein within a corral established by the cortical cytoskeletal network?

On the plasma membrane of the archaeon Halobacterium salinarum, bacteriorhodopsin is found in high density in patches of purple membrane. This protein …

Which of the following proteins is NOT in the same superfamily as the other four? The other four share an overall architecture composed of seven closely-packed transmembrane helices.

Cells and Genomes

Cell Chemistry and Bioenergetics

Proteins

DNA, Chromosomes, and Genomes

DNA Replication, Repair, and Recombination

How Cells Read the Genome: From DNA to Protein

Control of Gene Expression

Analyzing Cells, Molecules, and Systems

Visualizing Cells

Membrane Transport of Small Molecules and the Electrical Properties of Membranes

Intracellular Compartments and Protein Sorting

Intracellular Membrane Traffic

Energy Conversion: Mitochondria and Chloroplasts

Cell Signaling

The Cytoskeleton

The Cell Cycle

Cell Death

Cell Junctions and the Extracellular Matrix

Cancer

Development of Multicellular Organisms

Stem Cells and Tissue Renewal

Pathogens and Infection

The Innate and Adaptive Immune Systems

Filters