Deck 5: Cell Membranes and Signaling

Question 1

Which type of membrane protein would likely be most easily removed in a laboratory experiment?

A) Integral membrane proteins
B) Channel proteins
C) Peripheral membrane proteins
D) Transmembrane proteins
E) Gated channels

Answer 1

C

Question 2

The two sides of a membrane can be split apart from each other by an experimental technique known as freeze-fracturing.When one side of a freeze-fractured membrane is examined under the electron microscope,the exposed interior of the membrane bilayer appears to be covered with bumps.These bumps are most likely

A) integral membrane proteins.
B) ice crystals.
C) glycolipids.
D) organelles.
E) vesicles.

Answer 2

A

Question 3

Which statement about cholesterol molecules is true?

A) They help hold a membrane together.
B) They alter the fluidity of the membrane.
C) They attach to carbohydrates.
D) They disrupt membrane function.
E) They transport ions across membranes.

Answer 3

B

Question 4

Contact with ice numbs a person's fingers because at lower temperatures

A) membrane fluidity is reduced in nerve cells.
B) no ATP can be produced in the fingers.
C) protein kinases are activated in the nerves.
D) membranes in nerve cells unzip.
E) there are changes in the lipid composition of the membranes in nerve cells.

Question 5

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

A) synthesizing new forms of cholesterol.
B) closing protein channels.
C) decreasing the number of hydrophobic proteins present.
D) replacing saturated fatty acids with unsaturated fatty acids.
E) using fatty acids with longer tails.

Question 6

The hydrophilic regions of a membrane protein are most likely

A) present only in muscle cells.
B) associated with the fatty acid region of the lipids.
C) in the interior of the membrane.
D) exposed on the surface of the membrane.
E) either on the surface or inserted into the interior of the membrane.

Question 7

Biological membranes are composed primarily of

A) nucleotides and nucleosides.
B) enzymes,electron acceptors,and electron donors.
C) fatty acids.
D) monosaccharides.
E) lipids.

Question 8

In biological membranes,the phospholipids are arranged in a _______,with the _______.

A) bilayer;fatty acids pointing toward each other
B) bilayer;fatty acids facing outward
C) single layer;fatty acids facing the interior of the cell
D) single layer;phosphorus-containing region facing the interior of the cell
E) bilayer;phosphorus groups in the interior of the membrane

Question 9

Which statement about peripheral membrane proteins is true?

A) They have hydrophobic regions within the lipid portion of the bilayer.
B) They have hydrophilic regions that protrude in aqueous environments on both sides of the membrane.
C) They frequently flip from one side of the bilayer to the other.
D) They control the rate of simple diffusion.
E) Their polar regions interact with complementary regions of integral membrane proteins.

Question 10

The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are

A) integral membrane proteins.
B) carbohydrates.
C) lipids.
D) nucleic acids.
E) peripheral membrane proteins.

Question 11

When a mouse cell and a human cell are fused,the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell.This occurs because

A) many proteins can move around within the bilayer.
B) all proteins are anchored within the membrane.
C) proteins are asymmetrically distributed within the membrane.
D) all proteins in the plasma membrane are peripheral.
E) different membranes contain different proteins.

Question 12

Which of the following functions as a recognition site for interactions between cells?

A) RNA
B) Phospholipid
C) Cholesterol
D) Fatty acid
E) Glycolipid

Question 13

A protein that forms an ion channel through a membrane is most likely

A) a peripheral membrane protein.
B) a transmembrane protein.
C) a phospholipid.
D) an enzyme.
E) entirely outside the phospholipid bilayer.

Question 14

In hibernating animals during the winter,

A) signal transduction pathways cease.
B) membrane lipid composition changes: saturated fatty acids are replaced with unsaturated fatty acids.
C) membranes toughen as more saturated fatty acids accumulate in them.
D) there are no changes in lipid composition.
E) integral proteins shrink as temperatures fall.

Question 15

How do the cell membranes of a hibernating animal change in colder temperatures?

A) They release all of their peripheral membrane proteins.
B) Saturated fatty acids are more tightly packed.
C) Integral membrane proteins increase in number.
D) Unsaturated fatty acids make up more of the lipid composition.
E) Fatty acids with longer tails increase in number.

Question 16

Plasma membranes are relatively impermeable to water-soluble molecules because

A) the membranes are waxy.
B) water molecules are nonpolar.
C) their bilayer is comprised of phospholipids.
D) they have salt crystals embedded within them.
E) large proteins extend through both sides of the membranes.

Question 17

A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the

A) ratio of one protein molecule for every 25 phospholipid molecules.
B) capacity of lipids to associate and maintain a bilayer organization.
C) constant length of the fatty acid chain and the degree of saturation.
D) ability of phospholipid molecules to flip over and trade places with other phospholipid molecules.
E) asymmetrical distribution of membrane transport proteins.

Question 18

The LDL receptor is an integral membrane protein that crosses the plasma membrane,with portions of the protein extending both outside and into the interior of the cell.The amino acid side chains (R groups)in the region of the protein that crosses the membrane are most likely

A) charged.
B) hydrophilic.
C) hydrophobic.
D) carbohydrates.
E) lipids.

Question 19

Houseplants adapted to indoor temperatures may die if they are left outdoors,because in a cold environment their

A) DNA cannot function.
B) membranes lack adequate fluidity.
C) photosynthesis is impaired.
D) membranes contain too many unsaturated fatty acids.
E) membranes need more cholesterol.

Question 20

The rate at which a substance diffuses is not affected by the

A) diameter of the molecules or ions.
B) temperature of the solution.
C) color of the substance.
D) concentration gradient in the system.
E) Both a and b

Question 21

Which of the following is the driving force for facilitated diffusion?

A) Concentration gradient
B) ATP hydrolysis
C) ADP hydrolysis
D) Phosphorylation
E) GTP-GDP exchange

Question 22

When placed in water,wilted plants lose their limpness because of

A) active transport of salts from the water into the plant cells.
B) active transport of salts into the water from the plant cells.
C) osmosis of water into the plant cells.
D) osmosis of water from the plant cells.
E) diffusion of water from the plant cells.

Question 23

The difference between osmosis and diffusion is that

A) diffusion is passive transport,whereas osmosis is active transport.
B) only in diffusion do molecules move from areas of high concentration to areas of low concentration.
C) only diffusion refers to the movement of materials across a semipermeable membrane.
D) osmosis refers specifically to the movement of water,whereas diffusion refers to the movement of any type of molecules.
E) only the process of osmosis varies according to the kinds of particles present.

Question 24

In a hypothetical study,cells are placed in a solution of glucose in which the concentration of glucose is gradually increased.At first,the rate at which glucose enters the cells is found to increase as the concentration of the glucose solution is increased.But when the glucose concentration of the solution is increased above 10 M,the rate no longer increases.Which of the following is the likely mechanism for glucose transport into these cells?

A) Facilitated diffusion via a carrier protein
B) Facilitated diffusion via a channel protein
C) Pinocytosis
D) Tertiary active transport
E) Hydrolysis

Question 25

The existence of a concentration gradient of glucose across a membrane means that

A) there is a high concentration of glucose on both sides of the membrane.
B) the glucose molecules are more crowded on one side of the membrane than on the other.
C) there is a high concentration of water on both sides of the membrane.
D) the glucose molecules are chemically bonded more tightly on one side of the membrane than on the other.
E) there are more glucose molecules within the bilayer of the membrane than outside of the membrane.

Question 26

If a hospital patient is mistakenly given an IV of pure water instead of a saline solution that is isotonic to blood,the patient's red blood cells will

A) shrink and collapse.
B) release water to the plasma along its concentration gradient.
C) absorb water from the plasma and eventually burst.
D) transport equal amounts of water across the cell membrane in both directions.
E) work with white blood cells to maintain the water level in the plasma.

Question 27

Osmosis moves water from a region of _______ to a region of _______.

A) high concentration of dissolved material;low concentration of dissolved material
B) low concentration of dissolved material;high concentration of dissolved material
C) hypertonic solution;hypotonic solution
D) hypertonic solution;isotonic solution
E) low concentration of water;high concentration of water

Question 28

When a severely dehydrated patient is brought to the hospital,an IV of normal saline is started immediately.Distilled water is not used because

A) it would cause water to leave the cells of the patient and the cells would collapse.
B) nutrients are provided by the saline.
C) it would cause the patient's blood cells to swell and eventually burst.
D) normal saline is more economical.
E) the distilled water might be contaminated by bacteria.

Question 29

If a drop of red ink is placed in one end of a shallow pan filled with water,and a drop of green ink is placed in the other end,which of the following will be true at equilibrium?

A) The red ink will be uniformly distributed in one half of the pan,and the green ink will be uniformly distributed in the other half of the pan.
B) The red and green inks will be uniformly distributed throughout the pan.
C) Each ink will begin moving down its concentration gradient.
D) The concentration of each ink will be higher at one end of the pan than at the other end.
E) No predictions can be made without knowing the molecular weights of the pigment molecules.

Question 30

When placed in a hypertonic solution,animal cells

A) shrink.
B) swell.
C) burst.
D) transport water out using ATP.
E) transport water in using ATP.

Question 31

If aquaporins are injected into the membranes of epithelial cells that line blood vessels,

A) the flow of Na⁺ through aquaporins will increase.
B) the intracellular concentration of K⁺ will increase.
C) carrier proteins will bind glucose and enter the bloodstream.
D) the membranes will become more permeable to water.
E) the electrical properties of the cells will be altered.

Question 32

Which of the following is the driving force for simple diffusion?

A) Concentration gradient
B) ATP hydrolysis
C) ADP hydrolysis
D) Phosphorylation
E) GTP-GDP exchange

Question 33

You are doing a summer internship in a cell biology lab.Your supervisor asks you to change the medium on some cells she is growing.You do so and then examine the cells under a microscope.To your dismay,you can't find any cells and see only what looks like cell debris.What most likely happened to your cells and why?

A) The cells shrank because the new medium was hypotonic to the cells.
B) The cells shrank because the new medium was hypertonic to the cells.
C) The cells burst because the new medium was hypertonic to the cells.
D) The cells burst because the new medium was hypotonic to the cells.
E) The cells burst,although the new medium could not have been the cause.

Question 34

The process of osmosis allows water molecules to pass through specialized channels in membranes.Which statement about osmosis is true?

A) Water will move across a membrane to a region with less solute.
B) Water will move across a membrane to a region with more solute.
C) The direction of osmosis is temperature dependent.
D) If the membrane does not allow solutes to pass,water will be equal on both sides.
E) A higher solute concentration on one side of a membrane indicates a higher water concentration on that side.

Question 35

Which statement about diffusion is false?

A) Diffusion does not require ATP.
B) Diffusion continues until the molecular concentrations are in equilibrium.
C) In diffusion,molecules move from areas of greater concentration to areas of lesser concentration.
D) Diffusion is a random process.
E) Simple diffusion depends upon specific carrier proteins.

Question 36

Osmosis

A) helps plant cells maintain turgor pressure.
B) moves macromolecules from one cell to another.
C) facilitates the "flipping" of proteins from one side of the membrane to the other.
D) keeps concentrations uniform in all cells.
E) causes cells to lose water when they are placed in a hypotonic solution.

Question 37

If a red blood cell is placed in an isotonic solution,it will

A) shrivel.
B) swell and burst.
C) shrivel and then return to normal.
D) swell and then return to normal.
E) take up and release water at equal rates.

Question 38

Osmosis is a specific form of

A) diffusion.
B) pinocytosis.
C) active transport.
D) secondary active transport.
E) movement of water by carrier proteins.

Question 39

Which of the following is an example of passive transport?

A) Facilitated diffusion
B) The sodium-potassium pump
C) Phagocytosis
D) Exocytosis
E) Pinocytosis

Question 40

Which of the following is not one of the functional roles of membrane proteins?

A) Allowing movement of molecules that otherwise would be excluded by the lipid components of the membrane
B) Transferring signals from outside the cell to inside the cell
C) Facilitating the movement of water across the membrane
D) Facilitating the transport of macromolecules across the membrane
E) Stabilizing the lipid bilayer

Question 41

Chemical signals reaching a cell deep inside a multicellular organism may come from

A) the brain.
B) the lymphatic system.
C) glands.
D) other cell types.
E) All of the above

Question 42

For each molecule of ATP consumed during active transport of sodium and potassium,there is an import of _______ ion(s)and an export of _______ ion(s).

A) two Na⁺;three K⁺
B) two Na⁺;one K⁺
C) one K⁺;three Na⁺
D) two K⁺;three Na⁺
E) three K⁺;two Na⁺

Question 43

What is the membrane property that helps ensure the diffusion of glucose into a cell that has a high energy need?

A) A glucose pump
B) Specific carrier proteins found only in large muscle cells
C) A high number of carrier proteins specific for glucose
D) Special sensitivity to an extracellular environment high in glucose
E) Additional pores through which water can flow,carrying dissolved glucose

Question 44

Receptor-mediated endocytosis is the primary mechanism for import of

A) clathrin.
B) all macromolecules.
C) ions.
D) cholesterol.
E) integral membrane proteins.

Question 45

Active transport usually moves molecules

A) in the same direction as diffusion moves them.
B) in a direction opposite to the one in which diffusion moves them.
C) in a direction that tends to bring about equilibrium.
D) from a solution with a lower pH toward one with a higher pH.
E) from inside to outside the cell.

Question 46

In a signal transduction pathway,the signal activates a(n)

A) paracrine molecule.
B) responder.
C) receptor.
D) hormone.
E) effector molecule.

Question 47

Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as

A) simple diffusion.
B) active transport.
C) passive transport.
D) facilitated diffusion.
E) cellular respiration.

Question 48

Which process does not involve the uptake of materials into the cell?

A) Exocytosis
B) Pinocytosis
C) Endocytosis
D) Receptor-mediated endocytosis
E) Phagocytosis

Question 49

If you were designing a drug with an intracellular target,which type of transport system would you want to include in your design as the most efficient way to deliver the drug?

A) Secondary active transport
B) Primary active transport
C) Simple diffusion
D) Facilitated diffusion
E) Facilitated diffusion via a carrier protein

Question 50

Phagocytosis refers to

A) the specific import of small molecules.
B) invagination of the plasma membrane.
C) the export of macromolecules.
D) the delivery of receptor proteins to specific locations within the cell.
E) the nonspecific intake of fluids by the cell.

Question 51

Amino acids enter cells against their concentration gradients by means of

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

Question 52

To respond to a signal,a cell must have a(n)_______ molecule that can detect the signal.

A) paracrine
B) receptor
C) autocrine
D) responder
E) All of the above

Question 53

In the intestine,Na⁺ and an amino acid bind to the same transport protein that moves the two substances in the same direction.This is an example of

A) passive transport.
B) simple diffusion.
C) secondary active transport.
D) facilitated diffusion.
E) simple secondary diffusion.

Question 54

If a cell needs to acquire dissolved solutes continuously,which mechanism will most likely aid this process?

A) Osmosis
B) Diffusion
C) Receptor-mediated endocytosis
D) Phagocytosis
E) Pinocytosis

Question 55

One reason cancer therapy often fails is that the targeted cells become resistant to the drugs that are supposed to kill them.Which of the following is the most likely mechanism of this resistance?

A) Carrier proteins block diffusion of the drugs into the cancer cells.
B) Membrane proteins pump nutrients into the cancer cells.
C) Drugs diffuse into the cancer cells via simple diffusion.
D) Membrane proteins actively transport the drugs out of the cancer cells.
E) Channel proteins pump ions into the cancer cells.

Question 56

Which transport system can move an ion across the plasma membrane against its concentration gradient without using ATP?

A) Secondary active transport
B) Primary active transport
C) Simple diffusion
D) Facilitated diffusion
E) Facilitated diffusion via a carrier protein

Question 57

A selectively permeable membrane ensures that

A) a cell can maintain its ion concentrations by diffusion.
B) macromolecules can be obtained through active transport.
C) dissolved substances can be taken up by pinocytosis.
D) essential macromolecules and other polar molecules cannot leave the cell by diffusion.
E) fluids can be obtained rapidly.

Question 58

Which of the following is the driving force for active transport?

A) Concentration gradient
B) ATP hydrolysis
C) ADP hydrolysis
D) Phosphorylation
E) GTP-GDP exchange

Question 59

Which of the following is not involved in secondary active transport?

A) The direct use of ATP
B) Coupling to another transport system
C) Use of an existing concentration gradient
D) The plasma membrane
E) The ability to concentrate the transported molecule

Question 60

Which statement does not correctly describe the processes by which materials are taken up by the cell?

A) Vesicles touch the cell membrane and release their contents through a pore.
B) The plasma membrane forms small vesicles around fluids and dissolved substances.
C) Bacteria are engulfed by the plasma membranes of white blood cells.
D) Specific molecules are transported through receptor-mediated endocytosis.
E) Phagosomes formed by the plasma membrane fuse with lysosomes.

Question 61

Which statement about the insulin receptor is false?

A) It is not an ion channel.
B) It is a protein kinase receptor.
C) It catalyzes the phosphorylation of insulin-response substrates.
D) It is located entirely within the cytoplasm.
E) It is not regulated by phosphorylation.

Question 62

After the GTP-bound subunit of the G protein separates from the rest of the G protein,it travels until it encounters

A) an activator.
B) a receptor.
C) an effector protein.
D) a protein kinase.
E) another G protein.

Question 63

Signal ligands can be divided into two groups according to the location of their receptors.Which of the following are the two classes of receptors?

A) Plasma membrane and ion channel
B) Plasma membrane and protein kinase
C) Ion channel and cytoplasmic
D) G protein-linked and protein kinase
E) Membrane and intracellular

Question 64

Which molecule has an ion channel receptor?

A) Insulin
B) Estrogen
C) Acetylcholine
D) Epinephrine
E) Norepinephrine

Question 65

Vitamin A is a relatively small,lipid-soluble molecule that can behave as a hormone.Most likely its receptor

A) is an ion channel receptor.
B) is a protein kinase receptor.
C) involves a G protein.
D) is not connected to the cell membrane.
E) highly vulnerable to antagonists.

Question 66

Signals that travel to distant cells through the circulatory system are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 67

G proteins do not bind to

A) GTP.
B) GDP.
C) their receptor.
D) effector proteins.
E) glucose.

Question 68

Which statement is false?

A) Cells are bombarded with numerous signals,but they respond to only a few.
B) A cell's receptors determine whether or not the cell will respond to a signal.
C) Receptor proteins are very specific.
D) Protein kinase receptors are a type of cytoplasmic receptor.
E) All of the above are true;none is false.

Question 69

Which of the following bind(s)to the acetylcholine receptor?

A) Estrogen
B) Acetylcholine
C) Sodium
D) Insulin
E) Protein kinases

Question 70

The signals that bind to receptors on nearby cells are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 71

Which molecule has a protein kinase receptor?

A) Insulin
B) Estrogen
C) Acetylcholine
D) Sodium
E) G protein

Question 72

In what way do ligand-receptor interactions differ from enzyme-substrate reactions?

A) The ligand signal is not usually metabolized into useful products.
B) Receptor-ligand interactions do not obey the laws of mass action.
C) Inhibitors never bind to the ligand-binding site.
D) Reversibility never occurs in ligand-receptor interactions.
E) Enzyme-substrate reactions and the ligand-receptor interactions do not differ.

Question 73

In general,all cell signaling causes

A) increased expression of genes.
B) an influx of ions.
C) protein kinase activity.
D) G protein activation.
E) a change in receptor conformation.

Question 74

The signals that bind to receptors of the same cell that made them are known as

A) paracrine signals.
B) parasitic signals.
C) autocrine signals.
D) hormones.
E) responders.

Question 75

Which statement about G proteins is true?

A) G proteins contain only one important binding site.
B) When a G protein binds to an activated receptor protein,ADP is exchanged for ATP.
C) G protein-linked receptors are transmembrane proteins.
D) G proteins usually float free in the cytoplasm.
E) G proteins signal only the cell from which they are secreted.

Question 76

For a G protein to play its part in moving events forward in a signal pathway,

A) GDP must be released,and a GTP must occupy the nucleotide-binding site.
B) GTP must be released,and a GDP must occupy the nucleotide-binding site.
C) cGMP must occupy the otherwise empty nucleotide-binding site.
D) cGMP must leave the otherwise occupied nucleotide-binding site.
E) it must be linked to a specific intracellular receptor.

Question 77

If a G protein were unable to release its bound nucleotide but could hydrolyze it,signal transduction would

A) cease.
B) be continuous.
C) be unaffected.
D) be constantly switching on and off.
E) be unpredictable.

Question 78

Which statement about ligands and receptors is true?

A) For most ligand-receptor complexes,binding is favored.
B) Ligand-receptor interactions are reversible.
C) Many drugs that alter human behavior prevent the binding of receptors' specific ligands.
D) Ligand-receptor interactions often induce conformational changes in channels.
E) All of the above

Question 79

Which statement about acetylcholine is true?

A) It binds to a sodium channel receptor.
B) It acts as a neurotransmitter.
C) When bound to its receptor,it allows sodium to diffuse down its concentration gradient.
D) It binds to receptors on skeletal muscle cells.
E) All of the above

Question 80

A molecule that binds to the particular three-dimensional structure of another molecule's receptor site is known as a(n)

A) responder.
B) receptor.
C) ligand.
D) ion channel.
E) filament.