Question 1

Phosphatidylethanolamine is concentrated in the inner leaflet of the plasma membrane and tends to promote the curvature of the membrane,which is important in _________.
A)membrane budding
B)membrane fragmentation
C)membrane fusion
D)signal transduction
E)both membrane budding and membrane fusion

Accepted Answer

The answer of Phosphatidylethanolamine is concentrated in the inner leaflet...

Question 2

The temperature at which a lipid bilayer shifts from a fluid state to a crystalline gel is called the _____.
A)transition temperature
B)temperature optimum
C)transition series
D)pH optimum
E)gelation temperature

Accepted Answer

The transition temperature is the temperature at which a lipid bilayer shifts from a fluid state to a crystalline gel. It is also known as the phase transition temperature. Choice B and D are not related to the topic of lipid bilayer phase transitions, and choice E includes a specific term "gelation temperature" which is not the general term used for this phenomenon. Choice C is not a commonly used term in this context.

Question 3

What amino acid is made to replace another amino acid in membrane-spanning $\alpha$-helices by site-directed mutagenesis of the gene coding for the protein? This is done in order to determine how close together two such $\alpha$-helices are in the structure of an integral protein.The amino acid is added to facilitate the formation of crosslinks between $\alpha$-helices that are in close proximity.
A)phenylalanine
B)alanine
C)cysteine
D)methionine
E)proline

Accepted Answer

Cysteine is the best choice because it contains a thiol group (-SH) that can form disulfide bonds with other cysteine residues in close proximity, thereby crosslinking the two helices together. This allows for determination of the proximity of the helices in the protein structure. None of the other amino acids listed have a group or side chain that can easily form a crosslink.

Question 4

Which of the following cell processes depend on the movement of membrane components and would probably not be possible if membranes were rigid,nonfluid structures?
A)cell movement
B)cell division
C)formation of intercellular junctions
D)endocytosis
E)All of these are correct.

Accepted Answer

All of these cell processes depend on the movement of membrane components, specifically the fluidity of the membrane, to occur. If the membrane were rigid and nonfluid, the cell would not be able to move, divide, form intercellular junctions, or undergo endocytosis.

Question 5

They are more gelated and highly ordered than the surrounding more fluid and disordered regions in artificial membranes that consist primarily of phosphoglycerides.They contain higher concentrations of sphingolipids and cholesterol and certain proteins become concentrated within them.What are they?
A)lipid islands
B)collections
C)lipid rafts
D)lipid domains
E)dense bilayers

Accepted Answer

The characteristics described in the question match those of lipid rafts, which are small, highly organised regions within cell membranes that contain high levels of sphingolipids, cholesterol and certain proteins. These regions are also referred to as lipid domains and are believed to play a role in signal transduction and membrane trafficking.

Question 6

Which of the following can be learned from a computer-based (computational)analysis of the amino acid sequence of a membrane protein,which can be readily deduced from the nucleotide sequence of its isolated gene?
A)its structure
B)its color
C)its orientation within the lipid bilayer
D)its population in each cell
E)both its structure and its orientation within the lipid bilayer

Accepted Answer

A computational analysis of the amino acid sequence of a membrane protein can provide information about its structure and orientation within the lipid bilayer. However, information about its color or population in each cell cannot be deduced from its nucleotide sequence.

Question 7

Which of the following is not a potential biological role of the lipid asymmetry of the plasma membrane?
A)The glycolipids in the outer leaflet of the membrane may serve as receptors.
B)The presence of phosphatidylinositol primarily in the inner leaflet is involved in signal transduction.
C)Maintenance of a charge differential in the two membrane leaflets.
D)Appearance of phosphatidylserine on the outer surface of aging lymphocytes marks them for destruction by macrophages.
E)Phosphatidylserine on the surface of platelets serves as a signal for blood solubilization.

Accepted Answer

The answer of Which of the following is not a...

Question 8

What directly or indirectly determines the transition temperature?
A)the ability of lipid molecules to be packed together
B)whether the fatty acid chains of the lipids are saturated or unsaturated
C)the extent to which the fatty acid chains of the lipids contain double bonds
D)the length of the fatty acid chains
E)All of these are correct.

Accepted Answer

All of these factors directly or indirectly determine the transition temperature of lipids. The ability of lipid molecules to be packed together, the level of saturation or unsaturation of the fatty acid chains, the extent of double bonds in the chains, and the length of the chains all impact the fluidity of the lipid bilayer, which in turn affects the transition temperature. As such, all of these options are correct.

Question 9

A procedure in which the gene for an integral membrane protein is altered in such a way that the spatial relationships between some of the amino acids in the protein can be revealed is called ________.
A)site-directed mutagenesis
B)site-directed amenuensis
C)hydropathy plots
D)electron paramagnetic resonance (EPR)spectroscopy
E)infrared spectroscopy

Accepted Answer

The answer of A procedure in which the gene for...

Question 10

What technique can clarify the dynamic events that occur as a protein functions by introducing into the protein chemical groups (called nitroxides)that contain an unpaired electron? The properties of these nitroxides are sensitive to the distance that separates them and the unpaired electron produces a characteristic spectrum that can be monitored by the technique in question.The technique yields information about the distance between selected protein residues.
A)site-directed mutagenesis
B)site-directed amenuensis
C)hydropathy plots
D)electron paramagnetic resonance (EPR)spectroscopy
E)infrared spectroscopy

Accepted Answer

Electron paramagnetic resonance (EPR) spectroscopy is the technique that can introduce nitroxides into a protein to monitor their distance and produce a characteristic spectrum. This technique yields information about the distance between selected protein residues. Site-directed mutagenesis involves altering specific amino acid residues while hydropathy plots and infrared spectroscopy have different principles and applications. Site-directed amenuensis is not a known scientific term.

Question 11

Hemolytic anemias are characterized by fragile,abnormally shaped erythrocytes;the disease has been traced to mutations in ________.
A)actin
B)ankyrin
C)hemoglobin
D)spectrin
E)both ankyrin and spectrin

Accepted Answer

Hemolytic anemias are caused by mutations in proteins that maintain the structural integrity of erythrocytes, such as ankyrin and spectrin. Hemoglobin is a protein involved in oxygen transport, while actin is a structural protein found in many cell types but is not specific to erythrocytes.

Question 12

While culturing some cells,you lower the temperature of the culture.What happens immediately to the membrane fluidity?
A)Nothing happens.
B)The membrane becomes less fluid.
C)The membrane becomes more fluid.
D)The membrane fluidity fluctuates back and forth from high to low.
E)The membrane fluidity fluctuates back and forth from low to high.

Accepted Answer

When the temperature is lowered, the kinetic energy of the molecules in the membrane decreases, leading to a decrease in membrane fluidity.

Question 13

Which of the following genetic diseases is characterized by fragile,abnormally shaped erythrocytes and has been traced to mutations in ankyrin or spectrin?
A)hemophilia
B)sickle cell anemia
C)hemolytic anemias
D)leukemia
E)erythroblastosis

Accepted Answer

Hemolytic anemias are a group of genetic diseases characterized by the destruction of red blood cells. One type of hemolytic anemia, hereditary spherocytosis, is characterized by abnormally shaped erythrocytes that are fragile and easily broken down. Mutations in the genes for ankyrin and spectrin, which are proteins that help form the cytoskeleton of erythrocytes, have been linked to hereditary spherocytosis. Hemophilia is a genetic disorder that affects blood clotting, sickle cell anemia is caused by a mutation in the beta globin gene, leukemia is a type of cancer that affects blood cells, and erythroblastosis is a condition in which a fetus's red blood cells are destroyed by antibodies from the mother's immune system.

Question 14

Enzymes that move certain phospholipids between leaflets have also which of the following properties?
A)Play a role in establishing and maintaining membrane lipid asymmetry
B)Interacts with neighboring epithelial cells,or the basal membrane
C)Blocks post-synaptic membrane
D)Transport proteins
E)All of the above

Accepted Answer

Enzymes that move certain phospholipids between leaflets play a crucial role in establishing and maintaining membrane lipid asymmetry. They do not interact with neighboring epithelial cells or the basal membrane, block post-synaptic membrane, or act as transport proteins.

Question 15

How was the asymmetry of membrane lipids discovered?
A)The lipid asymmetry was visualized in the electron microscope.
B)The lipid asymmetry was observed with a special stain in the light microscope.
C)Treatment of intact red blood cells with phospholipases.
D)Treatment of intact red blood cells with trypsin.
E)Treatment of liver cells with phospholipases.

Accepted Answer

The answer of How was the asymmetry of membrane lipids...

Question 16

What property of membranes allows interactions to take place within the membrane,including the assembly of membrane protein clusters at particular sites and the formation of specialized structures?
A)hydrophobicity
B)hydrophilicity
C)membrane fluidity
D)their amphipathic nature
E)their amphoteric nature

Accepted Answer

Membrane fluidity allows interactions to take place within the membrane, including the assembly of membrane protein clusters at particular sites and the formation of specialized structures. Membrane fluidity refers to the property of the membrane that allows movement and flexibility of its components, including lipids, proteins, and carbohydrates. This property is crucial for the formation and maintenance of specialized structures such as lipid rafts and for the localization and function of membrane proteins. Hydrophobicity and amphipathic nature are important properties of membrane components that contribute to membrane fluidity. However, membrane fluidity itself is the property that enables interactions and specialized structures to form.

Question 17

When membrane lipids are extracted from cells and used to prepare artificial lipid bilayers,cholesterol and sphingolipids tend to self-assemble into ________ that are more gelated and highly ordered than surrounding regions consisting primarily of _________.
A)macrodomains,phosphoglycerides
B)microdomains,integral proteins
C)microdomains,phosphoglycerides
D)liquid crystals,phosphoglycerides
E)liquid crystals,microdomains

Accepted Answer

When membrane lipids are extracted from cells and used to prepare artificial lipid bilayers, cholesterol and sphingolipids tend to self-assemble into microdomains that are more gelated and highly ordered than surrounding regions consisting primarily of phosphoglycerides.

Question 18

You have fused a mouse cell and a human cell and then treated the cell with specific antibodies that are covalently linked to fluorescent dyes (antibodies to mouse proteins - green;antibodies to human proteins - red).What does the cell look like immediately after fusion?
A)The cell is half red and half green.
B)The red and green labels are uniformly distributed across the entire membrane.
C)The red and green labels are distributed in intermingled patches.
D)The cell appears to be yellow in color.
E)The cell appears to be brown in color.

Accepted Answer

The answer of You have fused a mouse cell and...

Question 19

Which of the following is not a function of peripheral proteins?
A)mechanical support for membrane
B)enzymes
C)receptors
D)anchor for integral proteins
E)factors that transmit transmembrane signals

Accepted Answer

The answer of Which of the following is not a...

Question 20

What enzyme was instrumental in the discovery of GPI-anchored proteins? It was found that this enzyme would release certain membrane proteins from a membrane.
A)phospholipase
B)lipase
C)hydroxyurease
D)protease
E)trypsin

Accepted Answer

The answer of What enzyme was instrumental in the discovery...

Quiz 4: The Structure and Function of the Plasma Membrane

Phosphatidylethanolamine is concentrated in the inner leaflet of the plasma membrane and tends to promote the curvature of the membrane,which is important in _________.

The temperature at which a lipid bilayer shifts from a fluid state to a crystalline gel is called the _____.

Which of the following cell processes depend on the movement of membrane components and would probably not be possible if membranes were rigid,nonfluid structures?

They are more gelated and highly ordered than the surrounding more fluid and disordered regions in artificial membranes that consist primarily of phosphoglycerides.They contain higher concentrations of sphingolipids and cholesterol and certain proteins become concentrated within them.What are they?

Which of the following can be learned from a computer-based (computational) analysis of the amino acid sequence of a membrane protein,which can be readily deduced from the nucleotide sequence of its isolated gene?

Which of the following is not a potential biological role of the lipid asymmetry of the plasma membrane?

What directly or indirectly determines the transition temperature?

A procedure in which the gene for an integral membrane protein is altered in such a way that the spatial relationships between some of the amino acids in the protein can be revealed is called ________.

Hemolytic anemias are characterized by fragile,abnormally shaped erythrocytes;the disease has been traced to mutations in ________.

While culturing some cells,you lower the temperature of the culture.What happens immediately to the membrane fluidity?

Which of the following genetic diseases is characterized by fragile,abnormally shaped erythrocytes and has been traced to mutations in ankyrin or spectrin?

Enzymes that move certain phospholipids between leaflets have also which of the following properties?

How was the asymmetry of membrane lipids discovered?

What property of membranes allows interactions to take place within the membrane,including the assembly of membrane protein clusters at particular sites and the formation of specialized structures?

When membrane lipids are extracted from cells and used to prepare artificial lipid bilayers,cholesterol and sphingolipids tend to self-assemble into that are more gelated and highly ordered than surrounding regions consisting primarily of _.

You have fused a mouse cell and a human cell and then treated the cell with specific antibodies that are covalently linked to fluorescent dyes (antibodies to mouse proteins - green;antibodies to human proteins - red) .What does the cell look like immediately after fusion?

Which of the following is not a function of peripheral proteins?

What enzyme was instrumental in the discovery of GPI-anchored proteins? It was found that this enzyme would release certain membrane proteins from a membrane.