Question 1

Which site in a neuron receives incoming information from external sources?

Accepted Answer

A)  Dendrites
B)  Axon
C)  Axon hillock
D)  Terminal knob
E)  Cell body A

Question 2

A channel that opens in response to changes in ionic charge across a membrane is called a ________.

Accepted Answer

A)  voltage-gated channel
B)  charge-gated channel
C)  ligand-gated channel
D)  positive-gated channel
E)  electric-gated channel A

Question 3

How do Na+ ions enter a neuron when an action potential is initiated?

Accepted Answer

A)  the Na+/K+-ATPase
B)  a gated Na+ pump
C)  a voltage-gated Na+ channel
D)  the ligand-gated Na+ channel
E)  a voltage-gated Na+ facilitated transporter C

Question 4

How is a nerve impulse usually transmitted across a synapse from a presynaptic to a postsynaptic cell?

Accepted Answer

A)  via a direct connection
B)  via a spark
C)  via a neurotransmitter
D)  via Na+ ions
E)  via plasmodesmata

Question 5

Diffusion during which the substance to be transported binds selectively to a membrane-spanning protein, which helps the process along, is called ________.

Accepted Answer

A)  osmosis
B)  facilitated osmosis
C)  simple diffusion
D)  facilitated diffusion
E)  active transport

Question 6

A channel that opens in response to the binding of a specific molecule, which is usually not the solute that passes through the channel is called a ________.

Accepted Answer

A)  voltage-gated channel
B)  charge-gated channel
C)  ligand-gated channel
D)  positive-gated channel
E)  electric-gated channel

Question 7

Enzymes which play a role in maintaining cellular integrity by stabilizing membrane fluidity include all of the following EXCEPT:

Accepted Answer

A)  dehydrogenases
B)  desaturases
C)  phospholipases
D)  acyltransferases
E)  phospholipid synthesizing enzymes

Question 8

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 ________.

Accepted Answer

A)  site-directed mutagenesis
B)  site-directed hydropathy
C)  hydropathy plots
D)  electron paramagnetic resonance (EPR) spectroscopy
E)  infrared spectroscopy

Question 9

The ability, possessed by all organisms, to respond to external stimulation is known as _______.

Accepted Answer

A)  excitation
B)  irritability
C)  irritation
D)  irrigation
E)  receptiveness

Question 10

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 _________.

Accepted Answer

A)  macrodomains, phosphoglycerides
B)  microdomains, integral proteins
C)  microdomains, phosphoglycerides
D)  liquid crystals, phosphoglycerides
E)  liquid crystals, microdomains

Question 11

Long-term potentiation is associated with NMDA receptors, one of several types of receptors that bind to the excitatory neurotransmitter __________. Its binding opens an internal cation channel within the receptor that allows __________ influx into the postsynaptic neuron, triggering a cascade of biochemical changes that lead to synaptic strengthening.

Accepted Answer

A)  GABA, Ca2+ ion
B)  glutamate, Ca2+ ion
C)  glutamate, K+ ion
D)  GABA, K+ ion
E)  acetylcholine, Ca2+ ion

Question 12

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?

Accepted Answer

A)  cell movement
B)  cell division
C)  formation of intercellular junctions
D)  endocytosis
E)  all of these are correct

Question 13

What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface and is covalently linked to a membrane lipid situated within the bilayer?

Accepted Answer

A)  integral protein
B)  lipid-anchored protein
C)  peripheral proteins
D)  carbohydrate-anchored protein
E)  transmembrane

Question 14

In the Na+/glucose cotransporter, _________ moving down its gradient drives the transport of __________ against its gradient.

Accepted Answer

A)  Na+ ions, K+ ions
B)  Na+ ions, glucose
C)  glucose, Na+ ions
D)  glucose, K+ ions
E)  K+ ions, glucose

Question 15

Which protein(s)below is(are)thought to be involved in and influence the stability of red blood cell membranes and the cells themselves by imparting strength, elasticity, and pliability to the membrane?

Accepted Answer

A)  actin and tropomyosin
B)  spectrin
C)  band 3
D)  ankyrin
E)  all of these are correct

Question 16

What causes the membrane potential to return to the normal negative value after an action potential has occurred?

Accepted Answer

A)  opening of a voltage-gated K+ channel
B)  opening of a voltage-gated Na+ channel
C)  closing of a voltage-gated K+ channel
D)  opening of a ligand-gated Na+ channel
E)  opening of a voltage-gated K+ facilitated transporter

Question 17

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

Accepted Answer

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)  The cell has the ability to maintain 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.

Question 18

Which part of a neuron conducts impulses away from the cell body toward the target cell(s)?

Accepted Answer

A)  axon hillock
B)  cell body
C)  dendrites
D)  axon
E)  terminal knob

Question 19

Why would a transverse diffusion or flip-flop of membrane phospholipids from one leaflet to the other be so rare?

Accepted Answer

A)  Flippases are enzymes which are transiently stable and expressed at low concentrations.
B)  For flip-flop to occur, it would be necessary for the hydrophilic head of a phospholipid to move through the hydrophobic part of the bilayer, an extremely unlikely event.
C)  For flip-flop to occur, it would be necessary for the hydrophobic head of a phospholipid to move through the hydrophilic part of the bilayer, an extremely unlikely event.
D)  Other membrane activities like flexing and lateral shift inhibit phospholipid flip-flop.

Question 20

Gorter and Grendel extracted lipids from human red blood cells. They calculated the total surface area for these red blood cell lipids and found it to be 36 µm2. How much surface area would these lipids cover once they were spread across the surface of water?

Accepted Answer

A)  72 µm2
B)  36 µm2
C)  18 µm2
D)  144 µm2
E)  30 µm2

Exam 4: The Structure and Function of the Plasma Membrane

Which site in a neuron receives incoming information from external sources?

A channel that opens in response to changes in ionic charge across a membrane is called a ________.

How do Na⁺ ions enter a neuron when an action potential is initiated?

How is a nerve impulse usually transmitted across a synapse from a presynaptic to a postsynaptic cell?

Diffusion during which the substance to be transported binds selectively to a membrane-spanning protein, which helps the process along, is called ________.

A channel that opens in response to the binding of a specific molecule, which is usually not the solute that passes through the channel is called a ________.

Enzymes which play a role in maintaining cellular integrity by stabilizing membrane fluidity include all of the following EXCEPT:

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 ________.

The ability, possessed by all organisms, to respond to external stimulation is known as _______.

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 _.

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?

What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface and is covalently linked to a membrane lipid situated within the bilayer?

In the Na⁺/glucose cotransporter, _ moving down its gradient drives the transport of __ against its gradient.

Which protein(s) below is(are) thought to be involved in and influence the stability of red blood cell membranes and the cells themselves by imparting strength, elasticity, and pliability to the membrane?

What causes the membrane potential to return to the normal negative value after an action potential has occurred?

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

Which part of a neuron conducts impulses away from the cell body toward the target cell(s) ?

Why would a transverse diffusion or flip-flop of membrane phospholipids from one leaflet to the other be so rare?

Gorter and Grendel extracted lipids from human red blood cells. They calculated the total surface area for these red blood cell lipids and found it to be 36 µm². How much surface area would these lipids cover once they were spread across the surface of water?