Deck 3: The Plasma Membrane and Membrane Potential

Question 1

The rate at which "X" can diffuse through a plasma membrane is inversely proportional to the

A) lipid solubility of X
B) concentration gradient for X
C) molecular weight of X
D) membrane's surface area
E) lipid solubility and molecular weight of X

Answer 1

C

Question 2

Select the substance that promotes cell adhesion.

A) GLUT
B) collagen
C) elastin
D) fibronectin
E) glycolipid

Answer 2

D

Question 3

Integrins

A) create a filamentous meshwork in the inner surface of the membrane
B) act as membrane-bounded enzymes
C) are used for cell recognition purposes
D) span the membrane, providing a mechanical link between the outer membrane and the cell's surrounding
E) none of these

Answer 3

D

Question 4

The plasma membrane

A) appears under an electron microscope as a double dark line with a light space between
B) is composed primarily of a double layer of protein molecules with cholesterol molecules interspersed between them
C) has a hydrophilic region between two hydrophobic regions
D) all of these
E) none of these

Question 5

Which statement about the plasma membrane is true?

A) It appears trilaminar under a light microscope.
B) Its glycocalyx serves as receptor sites for binding chemical messengers in the ECF.
C) It is impermeable to lipid-soluble substances.
D) Some of its carriers transport ions.
E) Its channels are impermeable to any substance smaller than 0.8 nm in diameter.

Question 6

Which one of the following requires assisted membrane transport?

A) glucose moving into a cell
B) K⁺ ions moving out of a cell
C) water moving toward a hypertonic solution
D) movement of ECF into a cell via pinocytosis
E) movement of Na⁺ through a symporter

Question 7

Collagen

A) provides tensile strength to the cytoskeleton
B) is most abundant in tissues that stretch and then recoil
C) forms the intercellular filaments of desmosomes
D) is the most abundant protein in the ECM
E) all of these

Question 8

Cystic fibrosis is caused by abnormal

A) accumulation of mucus
B) levels of insulin
C) chloride channels in plasma membranes
D) potassium channels in plasma membranes
E) none of these

Question 9

Identify the true statement(s) about the plasma membrane.

A) Its lipid region allows most ions to diffuse between the cytosol and ECF.
B) Its channels allow cholesterol to diffuse between the ECF and cytosol.
C) Some of its carriers transport sodium.
D) Its phospholipids are held to one another by CAMs.
E) All except its phospholipids are held to one another by CAMs.

Question 10

Which extracellular fiber does not develop properly in scurvy?

A) actin
B) collagen
C) elastin
D) fibronectin
E) myosin

Question 11

Which of the following is not associated with an extracellular chemical binding with a membrane-bound receptor?

A) decreased activity within a certain cell
B) activation of an ATPase
C) a change in shape of a transmembrane protein
D) increased activity within a certain cell
E) opening of a sodium channel that allows Na⁺ to diffuse out of the cell

Question 12

The plasma membrane

A) has a slight excess of positive charges along its cytosol side during the resting state
B) is composed primarily of cholesterol surrounded by carbohydrates
C) is more permeable to K⁺ than to Na⁺ at the resting state
D) has peripheral proteins that act as carriers
E) all of these, except it is composed primarily of cholesterol surrounded by carbohydrates

Question 13

Identify the incorrect statement about the plasma membrane.

A) Cholesterol contributes to its stability.
B) Its lipids may surround CAMs.
C) Its primary components are glycoproteins and cholesterol.
D) Its lipid bilayer is flexible.
E) Its glycocalyx is in contact with ECF.

Question 14

Which statement about membrane proteins is incorrect?

A) Channels are water-filled pathways.
B) Channels are not highly selective.
C) Carriers are highly selective.
D) CAMs serve as binding sites for specific ions.
E) Proteins may work in conjunction with carbohydrates to provide recognition of "self."

Question 15

A single phospholipid in the plasma membrane

A) has its hydrophobic end next to either the ECF or the cytosol
B) spans the entire width of the membrane
C) can function as carrier molecule
D) all of these
E) none of these

Question 16

Identify the true statement(s) about the plasma membrane.

A) Its transmembrane proteins are also peripheral proteins.
B) Its glycocalyx functions in cell recognition.
C) Its carriers contain cholesterol.
D) Its channels allow passage of substances between 0.8 nm and 1 nm in diameter.
E) Its transmembrane proteins are also peripheral proteins, and its channels allow passage of substances between 0.8 nm and 1 nm in diameter.

Question 17

Receptor sites on the outer surface of the plasma membrane are made of

A) CAMs
B) carbohydrate
C) lipid
D) keratin
E) proteins

Question 18

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

A) Some act as channels.
B) They determine the fluidity of the membrane.
C) Some will transport glucose.
D) They include docking-marker acceptors.
E) Some act as enzymes.

Question 19

Which statement about gap junctions is incorrect?

A) They consist of protein.
B) They are anchored to plaques on the inside surface of the plasma membrane.
C) They allow materials to pass from one cell into an adjacent cell.
D) They play a role in transmitting electrical activity through the heart.
E) They consist of connexons.

Question 20

Which of the following is not part of the extracellular matrix?

A) complex carbohydrates
B) connexons
C) collagen
D) elastin
E) fibronectin

Question 21

The rate of diffusion for water-soluble substances through a membrane decreases as

A) their concentration gradient increases
B) their molecular weight increases
C) the number of cholesterol molecules in the membrane increases
D) the membrane's surface area increases
E) the number of membrane carbohydrates increases

Question 22

In a plasma membrane, simple diffusion of various substances can occur

A) through channels
B) through carriers
C) between phospholipid molecules
D) all of these
E) through channels and between phospholipid molecules

Question 23

Selective permeability of the membrane is primarily determined by

A) membrane phospholipids
B) how much cholesterol is present
C) the number and type of membrane proteins
D) the charge of the membrane
E) none of these

Question 24

An electrical gradient

A) favors the movement of K⁺ out of the cell at resting potential
B) favors the movement of Na⁺ into the cell at resting potential
C) opposes the concentration gradient for Na⁺ at the equilibrium potential for Na⁺
D) all of these
E) favors the movement of Na⁺ into the cell at resting potential and opposes the concentration gradient for Na⁺ at the equilibrium potential for Na⁺

Question 25

By osmosis, water always moves to an area of

A) lower osmotic pressure
B) higher hydrostatic pressure
C) higher solute concentration
D) higher water concentration
E) lower osmotic pressure and higher water concentration

Question 26

____ are adhering junctions, ____ are impermeable junctions, and ____ are communicating junctions.

A) Tight junctions, gap junctions, desmosomes
B) Desmosomes, gap junctions, tight junctions
C) Gap junctions, desmosomes, tight junctions
D) Gap junctions, tight junctions, desmosomes
E) none of these

Question 27

Which of the following solutions has a lower osmotic pressure than a human cell's cytosol?

A) one containing only 2% NaCl
B) one containing only 200 mOsm of NaCl
C) one containing only 0.9% NaCl
D) one containing only 300 mOsm of NaCl
E) one containing only 280 mOsm of glucose

Question 28

The concentration gradient for

A) K⁺ favors its movement into the ECF
B) Na⁺ favors its movement out of the cytosol
C) K⁺ and Na⁺ are maintained by active transport
D) all of these
E) none of these

Question 29

Carrier-mediated transport

A) involves a specific membrane protein
B) always moves substances against a concentration gradient
C) always requires energy expenditure
D) involves protein channels
E) all of these

Question 30

Solution 1 has two solutes (A and B) and an osmotic pressure of 250 mOsm. Solution 2 has only one solute (C) and an osmotic pressure of 300 mOsm. If a membrane between these solutions is permeable to only water and B, then

A) Solution 1 will gain water from solution 2.
B) Solution 2 will gain water from solution 1.
C) Some of solute C will move into solution 1.
D) Solution 1 has a higher osmotic pressure.
E) Solution 2 will gain water from solution 1, and solution 1 has a higher osmotic pressure.

Question 31

Two ATP molecules could provide energy for a sodium-potassium pump to move ____ ions out of the cell for every ____ ions it moves into the cell.

A) 6 Na^+; 3 K⁺
B) 2 Na⁺; 3 K⁺
C) 3 K⁺; 6 Na⁺
D) 3 K⁺; 2 Na⁺
E) 12 Na⁺; 6 K⁺

Question 32

Tight junctions

A) prevent passage of materials into epithelial cells
B) force materials to pass between cells
C) are commonly found in digestive tract linings
D) all of these
E) none of these

Question 33

Which statement about movement into the cytosol is false?

A) If glucose and sodium can both combine with the same carrier, the presence of one of these molecules decreases the rate of entry of the other.
B) In simple diffusion, the rate of entry of an ion is directly proportional to its concentration in the cytosol.
C) When a glucose symporter becomes saturated, the rate of glucose entry decreases.
D) None of the statements are false.
E) All of the statements are false.

Question 34

Facilitated diffusion

A) involves a protein channel
B) requires energy expenditure
C) is how glucose in the intestinal lumen moves into cells in the digestive lining
D) involves a protein channel and is how glucose in the intestinal lumen moves into cells in the digestive lining
E) all of these

Question 35

If a typical body cell is placed into a 1% saline solution, the cell

A) will gain more water than it loses
B) has a higher osmotic pressure than the ECF
C) has a lower hydrostatic pressure than the ECF
D) will gain and lose water at the same rate
E) none of these

Question 36

Which of the following is least related to glucose uptake by different cells in the body?

A) receptor-mediated endocytosis
B) facilitated diffusion
C) carrier-mediated transport
D) secondary active transport
E) cotransport

Question 37

Select the correct statement about diffusion through a membrane.

A) It depends on random motion.
B) It involves active forces.
C) Its rate increases as the membrane's surface area decreases.
D) Ions move from a lower concentration to a higher concentration.
E) Large molecules diffuse faster than small molecules.

Question 38

Which of the following can diffuse between a membrane's phospholipids into the cytosol?

A) glucose
B) sodium
C) carbon dioxide
D) integrin molecule
E) a small secretory product

Question 39

During osmosis:

A) Water moves down its own concentration gradient.
B) Water moves to an area of higher solute concentration.
C) The solute moves against its concentration gradient.
D) All of these.
E) Water moves down its own concentration gradient and moves to an area of higher solute concentration.

Question 40

Which of the following is correct?

A) Exocytosis increases the surface area of the plasma membrane.
B) Phagocytosis can help remove cytoplasmic debris from the cytosol.
C) Exocytosis is triggered by the binding of a particle in the ECF to a receptor site on the plasma membrane.
D) Exocytosis increases the surface area of the plasma membrane, and is triggered by the binding of a particle in the ECF to a receptor site on the plasma membrane.
E) None of these.

Question 41

Large, anionic intracellular proteins (A^-) cannot pass through carriers because A^- proteins are

A) greater than 0.8 nm in diameter
B) lipid soluble
C) in about the same concentration in the cytosol and ECF
D) not water soluble
E) lipid soluble and not water soluble

Question 42

With secondary active transport, the movement of

A) H⁺ out of a cell by antiport is downhill
B) amino acids into the cell by symport is uphill
C) glucose into a cell by cotransport is downhill
D) amino acids into the cell by symport is uphill and glucose into a cell by cotransport is downhill
E) none of these

Question 43

Solution 1 has a higher concentration of NaCl than solution 2. A membrane permeable only to Na⁺ and water separates the two membranes. Which of the following is true?

A) Na⁺ will diffuse into solution 2 until the two solutions become isotonic.
B) Solution 2 has a higher osmotic pressure.
C) A membrane potential will develop, with the negative region being on the side with solution 1.
D) Solution 2 will gain water from solution 1.
E) Solution 2 has a higher osmotic pressure and will gain water from solution 1.

Question 44

During the resting potential

A) K⁺ ions leave the cell along a concentration gradient and along an electrical gradient.
B) K⁺ ions leave the cell against a concentration gradient but along an electrical gradient.
C) Na⁺ ions enter the cell along a concentration gradient and along an electrical gradient.
D) Na⁺ ions enter the cell along a concentration gradient but against an electrical gradient.
E) Cl^- ions enter the cell along a concentration gradient and along an electrical gradient.

Question 45

What is primarily responsible for the development of a resting membrane potential?

A) having more diffusion and active transport of cations out of the cell than into the cell
B) pumping 2 K⁺ ions out of the cell for every three Na⁺ ions pumped into the cell
C) having more K⁺ ions diffuse into the cell than there are Na⁺ ions diffusing out of the cell
D) having more anions diffuse into the cell than are diffusing out of the cell
E) none of these

Question 46

Exocytosis of secretory products from neuron terminals is triggered by the entry of ____ into the ____.

A) K⁺; cytosol
B) Na⁺; ECF
C) Ca²⁺; cytosol
D) ATP; plasma membrane
E) A^-; ECF

Question 47

A Ca²⁺ pump in the plasma membrane

A) pumps Ca⁺ into the cell
B) is a secondary active transport carrier
C) is an ATPase
D) is a symporter
E) All of these

Question 48

The resting membrane potential of a typical nerve cell is ____ mV.

A) -60
B) +70
C) -90
D) -50
E) -70

Question 49

The rate of carrier-mediated transport is limited by

A) protein location in the membrane
B) osmolarity
C) tonicity
D) competition with other molecules
E) none of these

Question 50

Cell X has a resting potential of -80 mV. If a ____ opens and causes the potential to change 10 mV, the resulting potential will be ____.

A) Na⁺ channel; -90 mV
B) K⁺ channel; -70 mV
C) Ca²⁺ channel; -70 mV
D) Cl^- channel; -70 mV
E) Ca⁺² channel; -90 mV

Question 51

According to Fick's law of diffusion, which of the following changes would decrease the rate of net diffusion of "X" across a membrane?

A) an increase in the X's concentration gradient
B) an increase in the permeability of the membrane to X
C) an increase in the surface area of the membrane
D) an increase in the thickness of the membrane
E) a decrease in the size of X

Question 52

Pinocytosis is a form of

A) active transport
B) cytokinesis
C) endocytosis
D) exocytosis
E) hemolysis

Question 53

Which of the following may not require a carrier?

A) movement of potassium into the cell
B) movement of sodium into the cell
C) iodine uptake by thyroid gland cells
D) glucose uptake by body cells
E) all of these

Question 54

If a human cell is placed into solution X, containing water and a nonpenetrating solute, then

A) Water will diffuse into solution X until the cytosol and solution X are isotonic.
B) Water will diffuse across the membrane until a state of equilibrium is established.
C) Water will diffuse into the cell until stopped by an opposing hydrostatic pressure in the cytosol.
D) Neither the cell nor solution X will experience a net gain of water.
E) It is not possible to predict what will happen.

Question 55

Osmosis is a type of

A) carrier-mediated transport
B) diffusion
C) exocytosis
D) pinocytosis
E) primary active transport

Question 56

A membrane potential

A) refers to a difference in electrical charge on opposite sides of a membrane
B) is measured in millivolts, with the sign always designating the charge on the outside
C) exists because the ECF as a whole is positively-charged and the cytosol as a whole is negatively charged
D) is always positive during the resting state
E) all of these

Question 57

The resting membrane potential is

A) much closer to the equilibrium potential for Na⁺ than to the equilibrium potential for K⁺
B) much closer to the equilibrium potential for K⁺ than to the equilibrium potential for Na⁺
C) the same as the equilibrium potential for Cl^-
D) much closer to the equilibrium potential for Na⁺ than to the equilibrium potential for K⁺ and the same as the equilibrium potential for Cl^-
E) much closer to the equilibrium potential for K⁺ than to the equilibrium potential for Na⁺ and the same as the equilibrium potential for Cl^-

Question 58

At resting membrane potential

A) The membrane is more permeable to K⁺ than to Na⁺.
B) The membrane is more permeable to Na⁺ than to K⁺.
C) Cl^- is at its equilibrium potential.
D) The membrane is more permeable to K⁺ than to Na⁺, and Cl^- is at its equilibrium potential.
E) The membrane is more permeable to Na⁺ than to K⁺, and Cl^- is at its equilibrium potential.

Question 59

Glucose enters some cells

A) through primary active transport
B) through secondary active transport
C) through facilitated diffusion
D) all of these
E) through secondary active transport and facilitated diffusion

Question 60

Which of the following statements about the Na⁺-K⁺ pump is correct?

A) Phosphorylation of the pump must occur before Na⁺ can attach to its binding site.
B) It has ATP synthase activity.
C) It helps decrease Na⁺ and K⁺ concentration gradients across the plasma membrane.
D) It regulates cell volume by controlling the concentration of solutes inside the cell.
E) It is a countertransporter for secondary active transport.

Question 61

The surface carbohydrates within the plasma membrane serve as cell adhesion molecules (CAMs), which cells use to grip hold of one another and to surrounding connective-tissue fibers.

Question 62

The carbohydrate found in plasma membranes is believed to be involved in the aggregation of cells to form tissue.

Question 63

Na⁺ ions can move from the ECF into the ICF by passing through secondary active transport carriers, simple diffusion channels, and the sodium-potassium pumps.

Question 64

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

A) transport of polar molecules
B) transport of H⁺ into the cell
C) binding sites for vesicles
D) cell recognition
E) passageway for water molecules

Question 65

In the plasma membrane, the polar ends of the phospholipid molecules are hydrophilic.

Question 66

Connexons are carbohydrate building blocks of gap junctions that allow ions to pass from the cytosol of one cell into the cytosol of an adjacent cell.

Question 67

Under an electron microscope, the plasma membrane appears as a trilaminar structure consisting of two light layers separated by a dark middle layer.

Question 68

According to the fluid mosaic model, the plasma membrane consists primarily of a bilayer of mobile phospholipid molecules studded with an ever-changing mosaic pattern of proteins.

Question 69

In the lipid bilayer of the plasma membrane, the hydrophobic tails of the phospholipids orient toward the center of the membrane, away from water.

Question 70

The dark lines in the trilaminar appearance of the plasma membrane are likely caused by the preferential staining of the hydrophobic, nonpolar regions of the membrane constituents.

Question 71

The hydrophobic interior of the lipid bilayer of the plasma membrane blocks the passage of water-soluble substances.

Question 72

Some cell adhesion molecules are peripheral proteins and some are integral proteins.

Question 73

The primary barrier to passage of water-soluble substances across the plasma membrane is the outer layer of carbohydrates.

Question 74

Cadherins are docking-marker acceptors to which secretory vesicles bind prior to exocytosis.

Question 75

Sheets of epithelial cells are joined by gap junctions.

Question 76

Gap junctions function as channels in between cells.

Question 77

All of the following transport certain substances from regions of high concentration to low concentration except

A) carriers
B) facilitated diffusion
C) SGLT
D) GLUT
E) Ca²⁺ pump

Question 78

Which statement is false?

A) Binding of Na⁺ to the SGLT carrier increases the carrier's affinity for ATP.
B) The release of Na⁺ from the SGLT carrier increases the carrier's affinity for glucose.
C) Glucose enters the luminal side of an intestinal cell through a GLUT carrier.
D) The GLUT carrier is a symporter.
E) The SGLT carrier is a symporter.

Question 79

Gap junctions play an important role in transmission of impulses for heart contraction.

Question 80

Which one of the following requires the cell to expend energy?

A) ECF moving into a cell via pinocytosis
B) glucose moving through a facilitated diffusion carrier
C) K⁺ ions moving out of a cell
D) water moving through an aquaporin
E) Na⁺ ions moving through a leak channel