Deck 5: Cell Membrane Structure and Function

Question 1

Phospholipids spontaneously form a bilayer in an aqueous solution. Why do the heads of the phospholipids point out and the tails point toward one another?

A) The tails are repelled by the aqueous environment, and the heads will directly interact with the aqueous solution.
B) The tails are nonpolar and form hydrogen bonds with one another.
C) The heads are repelled by the water inside and outside the cell.

Answer 1

A

Question 2

Suppose that plasma membranes were single layers of phospholipids rather than double layers, and the heads faced the extracellular fluid. The interior of this hypothetical cell would have to be

A) hydrophobic and nonpolar.
B) hydrophobic only.
C) nonpolar only.
D) hydrophilic only.
E) polar only.

Answer 2

A

Question 3

Plasma membranes are best described as a

A) double layer of phospholipids with hydrophobic tails facing toward one another.
B) single layer of phospholipids with water molecules attached along one side.
C) double layer of phospholipids with hydrophilic heads facing away from one another.
D) double layer of phospholipids with hydrophobic tails facing away from each other (toward the cytoplasm of the cell and the extracellular solution).
E) single layer of phospholipids with tails pointed toward the inside of the cell.

Answer 3

A

Question 4

The__________ portion of the cell membrane is responsible for the isolating function of the membrane, whereas the__________ portion regulates exchange and communication with the environment.

A) carbohydrate; lipid
B) lipid; protein
C) cholesterol; lipid
D) nucleic acid; lipid
E) protein; cholesterol

Question 5

What prevents your immune system from attacking your own cells?

A) Receptor proteins
B) Fever
C) Cholesterol
D) Recognition proteins
E) Inadequate enzymes

Question 6

What structure in the membrane causes plasma membranes to resist freezing?

A) Cholesterol
B) Unsaturated fatty acid tails
C) Nonpolar heads of the phospholipids
D) Saturated fatty acid tails
E) Channel proteins

Question 7

What would happen if the plasma membrane were composed solely of phospholipids and no proteins?

A) Simple diffusion and osmosis would continue to occur.
B) The movement of molecules across the membrane would not be affected.
C) All movement of molecules across the membrane would cease.
D) Immune reactions would not be affected.
E) Only water would be able to pass through the membrane.

Question 8

In general, which of the following is (are) largely responsible for moving substances across the plasma membrane, communicating with other cells, and identifying the cell?

A) Cytoskeleton
B) Proteins
C) Nucleic acids
D) Carbohydrates
E) Phospholipids

Question 9

The substances in cell membranes that form a barrier to the movement of materials across the membrane are

A) nucleic acids.
B) external proteins.
C) carbohydrates.
D) internal proteins.
E) lipids.

Question 10

Within the fluid mosaic of a plasma membrane, what is the role of transport and channel proteins?

A) They are cell-surface connection sites.
B) They identify the cell.
C) They prevent the passage of amino acids.
D) They permit ions and water molecules to move through the plasma membrane.
E) They may set off cellular changes such as cell division or hormone secretion.

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) all proteins in the plasma membrane come from a membrane other than the human or the mouse.
B) all proteins are anchored within the membrane.
C) proteins are asymmetrically distributed within the membrane.
D) many proteins can move around within the bilayer.
E) different membranes contain different proteins.

Question 12

The main lipids found in cell membranes are

A) glycerol.
B) phospholipids.
C) triglycerides.
D) waxes.
E) steroids.

Question 13

The hydrophilic regions of a membrane protein are most likely to be found

A) only in muscle cell membranes.
B) exposed on the surface of the cell membrane.
C) attached to carbohydrates and facing the interior of a cell.
D) associated with the fatty acid region of the lipids.
E) in the interior of the membrane.

Question 14

Which of the following groups includes carrier and channel proteins?

A) Transport proteins
B) Receptor proteins
C) Connection proteins
D) Recognition proteins

Question 15

According to the fluid mosaic model of cell membranes, which of the following is a TRUE statement about membrane phospholipids?

A) They occur in an uninterrupted bilayer, with membrane proteins strictly anchored to the surface of the membrane.
B) They have hydrophilic tails in the interior of the membrane.
C) They form a viscous fluid through which proteins shift and flow.
D) They are free to depart from the membrane and are dissolved in the surrounding solution.
E) They frequently flip-flop from one side of the membrane to the other.

Question 16

ISO membranes are inside-out membrane vesicles used by researchers in membrane studies. As a molecule diffuses into the vesicle, it will encounter the layers of the membrane in the following order

A) head-tail-tail-head.
B) tail-head-tail-head.
C) head-tail-head-tail.
D) tail-head-head-tail.
E) head-head-tail-tail.

Question 17

The hydrophobic tails of a phospholipid bilayer are oriented toward the

A) both the extracellular fluid and cytoplasm.
B) interstitial fluid.
C) cytoplasm of the cell.
D) interior of the plasma membrane (i.e., toward one another).
E) extracellular fluid surrounding the cell.

Question 18

Which of the following accounts for the fluid aspect of the fluid mosaic model of plasma membranes?

A) One of the components of the membrane is water.
B) The bilayer permits diffusion of certain lipid-soluble substances.
C) The membrane is water soluble.
D) The plasma membrane is ʺfluidʺ because of the movement of substances across the membrane.
E) The individual phospholipid molecules are not bonded to one another, so the movement of certain proteins and lipids is possible within and through the bilayer.

Question 19

Recognition proteins are most important for

A) maintaining membrane integrity.
B) facilitated diffusion of molecules.
C) active transport of molecules.
D) distinguishing foreign cells from ʺselfʺ cells.
E) maintaining membrane fluidity.

Question 20

In biological membranes, the phospholipids are arranged in a

A) single layer, with the phosphorus-containing region facing the interior of the cell.
B) bilayer, with the fatty acids pointing toward one another.
C) bilayer, with the fatty acids facing outward (facing the interior and exterior of the cell).
D) bilayer, with the phosphorus groups in the interior of the membrane.
E) single layer, with the fatty acids facing the interior of the cell.

Question 21

To say that a cell is ʺselectively permeableʺ means

A) sometimes water passes through, and sometimes it canʹt.
B) it is permeable to different substances than other cells.
C) only certain molecules can pass through.
D) it has different-sized perforations in the membrane.
E) permeability depends on gradient differences.

Question 22

Recognition proteins, such as those embedded on the surface of red blood cells, are composed of

A) glycoproteins.
B) phospholipases.
C) steroids.
D) nucleic acids.

Question 23

Which of the following types of membrane proteins are responsible for maintaining cell shape by linking the membrane protein with the cytoskeleton?

A) Enzymes
B) Receptor proteins
C) Recognition proteins
D) Connection proteins
E) Transport proteins

Question 24

Which of the following is an energy-requiring mode of transport that brings substances into a cell?

A) Simple diffusion
B) Facilitated diffusion
C) Osmosis
D) Active transport

Question 25

All of the following may influence the rate of simple diffusion across a selectively permeable membrane EXCEPT the

A) concentration gradient.
B) lipid solubility of the molecule.
C) temperature.
D) size of the molecule.
E) size of the cell.

Question 26

Which of the following would NOT be found in a membrane?

A) Receptor protein
B) Cellulose
C) Cholesterol
D) Channel protein
E) Phospholipid

Question 27

When substances move across a plasma membrane and down concentration gradients, this is called

A) active transport.
B) exocytosis.
C) passive transport.
D) pinocytosis.

Question 28

What is active transport?

A) Movement of molecules into or out of a cell using special proteins and not requiring an expenditure of energy
B) Rapid movement of molecules in a solution
C) Movement of molecules into or out of a cell against a concentration gradient
D) Diffusion of molecules within a cell
E) Movement of molecules into or out of a cell down a concentration gradient

Question 29

Imagine that you fill a shallow tray with water and place a drop of red ink in one end of the tray and a drop of green ink in the other end. Which of the following is TRUE at equilibrium?

A) The red and green ink do not mix at all.
B) The concentration of each ink is higher at one end of the tray than at the other end.
C) The red ink is uniformly distributed in one half of the tray, and the green ink is uniformly distributed in the other half of the tray.
D) No predictions can be made without knowing the size of the ink molecules.
E) The red and green inks are both uniformly distributed throughout the tray.

Question 30

Carbon dioxide crosses the plasma membrane by simple diffusion. The rate at which carbon dioxide enters the cell is determined by the

A) amount of energy being produced by the cell.
B) concentration of carbon dioxide on each side of the membrane.
C) amount of oxygen being exported from the cell.
D) amount of transport protein in the membrane.
E) amount of carbon dioxide outside of the cell.

Question 31

The net movement of molecules from a high concentration to a low concentration is best described by which of the following?

A) Passive transport
B) Osmosis
C) Endocytosis
D) Active transport
E) Exocytosis

Question 32

Molecules that permeate a plasma membrane by facilitated diffusion

A) require the aid of transport proteins.
B) move from an area of low concentration to an area of high concentration.
C) do so much more quickly than those crossing by simple diffusion.
D) require energy.

Question 33

Which of the following types of membrane proteins are responsible for conveying external messages such as those sent by a hormone signal?

A) Receptor proteins
B) Recognition proteins
C) Transport proteins
D) Enzymes
E) Connection proteins

Question 34

In reference to diffusion, passive really means

A) no energy required.
B) no gradient.
C) in the air.
D) without a membrane.
E) very slowly.

Question 35

The bacterium Vibrio cholerae releases a toxin that blocks a channel protein in the membranes of cells that line the intestine. This toxin prevents the movement of sodium ions from the inside of the intestine into cells. If the sodium ions could not move into the cells, how would this affect the movement of water between the inside of the intestine and the cells?

A) Water would leave the intestines and enter the cells by osmosis.
B) Water would leave the intestines and enter the cells by facilitated diffusion.
C) Water would leave the cells and enter the intestines by facilitated diffusion.
D) The movement of water would not be affected.
E) Water would leave the cells and enter the intestines by osmosis.

Question 36

Which of the following occurs as an enzyme produced by a cell is secreted from the cell?

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

Question 37

What happens when diffusion moves molecules across the plasma membrane?

A) Most molecules are capable of crossing the phospholipid bilayer at any location and at basically the same rate.
B) Energy input is required to transport molecules.
C) The rate of diffusion cannot be influenced by the cell.
D) The cell gains needed materials and gets rid of excess materials very quickly.
E) The process is relatively slow and is driven by concentration gradients.

Question 38

Which of the following types of membrane proteins are responsible for facilitated diffusion?

A) Connection proteins
B) Receptor proteins
C) Enzymes
D) Transport proteins
E) Recognition proteins

Question 39

Cell membranes do all of the following EXCEPT

A) isolate the cellʹs contents from the external environment.
B) regulate the movement of substances between the cytoplasm of the cell and the extracellular fluid.
C) provide attachments between cells.
D) allow communication between cells.
E) provide an energy source for the cell.

Question 40

For diffusion to occur, there must be

A) a gradient.
B) ATP.
C) water.
D) a membrane.

Question 41

Two aqueous solutions are separated by a selectively permeable membrane that allows water to pass through but does not allow starch to pass through. Solution A is 10% starch and solution B is 5% starch. What will occur?

A) Water will diffuse from solution B to solution A.
B) Water will diffuse from solution A to solution B.
C) Starch will diffuse from solution B to solution A.
D) Starch will diffuse from solution A to solution B.
E) Both water and starch will diffuse from solution B to solution A.

Question 42

A freshwater protozoan, such as Paramecium, tends to__________ because it lives in a__________ environment.

A) gain water; isotonic
B) lose water; hypertonic
C) lose water; hypotonic
D) gain water; hypertonic
E) gain water; hypotonic

Question 43

Osmosis moves water from a region of

A) high solute concentration to a region of low solute concentration.
B) negative osmotic potential to a region of positive osmotic potential.
C) low solute concentration of to a region of high solute concentration.
D) low concentration of water to a region of high concentration of water.
E) hypertonic solution to a region of hypotonic solution.

Question 44

Active transport requires all of the following EXCEPT

A) a gradient.
B) transport proteins.
C) ATP.
D) a membrane.
E) aquaporins.

Question 45

The blood plasma of a man who drinks salt water will become__________ to his red blood cells, whereas the red blood cells will be__________ to the blood plasma.

A) hypotonic; hypertonic
B) hypertonic; isotonic
C) hypertonic; hypotonic
D) isotonic; hypertonic
E) isotonic; isotonic

Question 46

Glucose is a six-carbon sugar that diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Given this information, which transport mechanism is most probably functioning in the intestinal cells?

A) Exocytosis
B) Facilitated diffusion
C) Aquaporin transport
D) Simple diffusion
E) Osmosis

Question 47

The gases O₂ and CO₂ enter or leave a plant cell by

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

Question 48

Two similar-sized animal cells are placed in a 0.5% sucrose solution. Cell A enlarges for a while and then stops; cell B continues to enlarge and finally ruptures. Which of the following must have been TRUE at the beginning of the experiment?

A) Cell A has a higher concentration of sucrose than cell B.
B) Cell A was hypertonic to the solution, and cell B was hypotonic.
C) Cell B has a higher concentration of sucrose than cell A.
D) Cell A was hypotonic to the solution, and cell B was hypertonic.
E) Cells A and B were isotonic to each other.

Question 49

The secretion of excess water via a contractile vesicle of a Paramecium cell is an example of

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

Question 50

If red blood cells are taken from the body and placed in a hypertonic solution, what happens to the cells?

A) The cells remain unchanged due to equal water concentrations inside and outside the cells.
B) The cells swell and burst because water moves into them.
C) The cells shrivel up because water leaves them.
D) The cells remain unchanged due to equal solute concentrations inside and outside the cells.
E) They become white blood cells.

Question 51

The cytoplasm of a certain cell, such as a neuron, already has a high concentration of K ⁺ ions. How can K⁺ ions continue to enter the cell?

A) Infusion
B) Active transport
C) Exocytosis
D) Osmosis
E) Facilitated diffusion

Question 52

The diffusion of water molecules across a selectively permeable membrane is called

A) hydrolysis.
B) osmosis.
C) facilitated diffusion.
D) exocytosis.
E) active transport.

Question 53

The rate of facilitated diffusion of a molecule across a membrane will increase as the concentration gradient of the molecule across the membrane increases to a certain point. Eventually, an increase in the concentration of the molecule will not cause any further increase in facilitated diffusion. Thus, there is a maximal rate of facilitated diffusion. This is because

A) there are a limited number of carrier proteins in the membrane.
B) facilitated diffusion requires ATP energy.
C) as the concentration gradient increases, molecules interfere with one another.
D) the diffusion constant depends on the concentration gradient.
E) the increased concentration gradient causes a situation far from equilibrium.

Question 54

Suppose you have two glucose solutions separated by a selectively permeable membrane. If there is a concentration gradient of glucose across the membrane, then the solutions cannot be relative to each other.

A) isotonic
B) hypertonic
C) hypotonic

Question 55

Molecules assisted by carrier proteins may cross a selectively permeable membrane by

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

Question 56

The slowest rate of diffusion of dye particles in water will occur at

A) 20°C.
B) 30°C.
C) 60°C.
D) 10°C.

Question 57

Imagine that beaker A has a 10% sucrose solution, and beaker B has an 8% sucrose solution. This means that

A) beaker A is hypertonic relative to beaker B.
B) beaker A is hypotonic relative to beaker B.
C) beaker A is isotonic relative to beaker B.

Question 58

More than half a century ago, two cell biologists published details of their research involving isolated membrane vesicles from chloroplasts. Normally, the fluid inside these vesicles is near neutral. In an experiment, these membrane vesicles were soaked in an acidic solution (pH 4) until the inside of the vesicle also became pH 4. Based on the details provided in this scenario, by what mechanism could hydrogen ions have crossed the vesicle membrane, and what do you think happened at the molecular level?

A) Simple diffusion; hydrogen ions moved into the vesicle through a channel protein.
B) Active transport; hydrogen ions moved out of the vesicle with the help of ATP energy.
C) Facilitated diffusion; hydrogen ions moved into the vesicle through a channel protein.
D) Pinocytosis; water moved from outside the vesicle to inside.
E) Osmosis; water moved from inside the vesicle to outside.

Question 59

Imagine an artificial cell made with a selectively permeable membrane that allows water to pass through but does not allow sugar to pass. If the artificial cell contains a 1% sugar solution and then you place the cell in a 2% sugar solution, what happens?

A) Sugar diffuses in and water diffuses out until equilibrium is reached.
B) Water enters the cell because the solution is hypotonic to the cell.
C) There is no movement of water.
D) Water leaves the cell because the solution is hypertonic to the cell.

Question 60

Solutions that cause water to enter cells by osmosis are called

A) permeable.
B) hypertonic.
C) hydrophilic.
D) isotonic.
E) hypotonic.

Question 61

Which process accounts for the movement of solid particles (such as food) into some animal cells?

A) Active transport
B) Simple diffusion
C) Facilitated diffusion
D) Phagocytosis
E) Osmosis

Question 62

The urinary bladder is protected from leaking by cell-to-cell junctions called

A) desmosomes.
B) tight junctions.
C) gap junctions.
D) plasmodesmata.

Question 63

The most common lipids in biological membranes are__________ .

Question 64

__________is used by white blood cells to consume large particles such as bacteria.

Question 65

The process in which white blood cells engulf bacteria is termed

A) exocytosis.
B) reception.
C) pinocytosis.
D) phagocytosis.
E) recognition.

Question 66

The movement of molecules across a cell membrane via a transport protein in which no energy is required is called__________ diffusion, and the movement of molecules across a cell membrane via a protein in which energy (i.e., ATP) is required is called __________transport.

Question 67

Phospholipids contain two different parts: a __________head and a pair of __________tails.

Question 68

If a frog egg cell is placed into a hypotonic solution, it will

A) swell via osmosis.
B) shrivel via active transport.
C) shrivel via facilitated diffusion.
D) shrivel via osmosis.
E) swell via facilitated diffusion.

Question 69

Which of the following requires adenosine triphosphate?

A) Active transport
B) Simple diffusion
C) Facilitated diffusion
D) Osmosis

Question 70

Carrier molecules in the plasma membrane are required only for active transport.

Question 71

Adhesion of cells within animal tissues is accomplished by cell-to-cell junctions called

A) desmosomes.
B) tight junctions.
C) gap junctions.
D) plasmodesmata.

Question 72

Facilitated diffusion and active transport both require__________for the movement of molecules across the membrane.

Question 73

If you forget to water your favorite plant, all of the following will occur at a cellular level EXCEPT

A) turgor pressure will build up in the cell.
B) water will move out of the vacuoles by osmosis.
C) water will move out of the cytosol by osmosis.
D) the plasma membrane will shrink away from the cell wall.
E) osmosis will occur.

Question 74

You observe a cell under a microscope and you can clearly see a cell wall, a vacuole, and cytoplasmic connections. These cytoplasmic connections must be

A) plasmodesmata.
B) osmotic channels.
C) tight junctions.
D) gap junctions.
E) desmosomes.

Question 75

Cells use exocytosis to

A) move away from danger.
B) ingest nutrients.
C) pump hydrogen molecules across the membrane.
D) release substances from the cell.
E) create new cells.

Question 76

Osmosis is the diffusion of water molecules across selectively permeable membranes.

Question 77

Protein channels that provide passage for hormones and nutrients between animal cells are termed

A) desmosomes.
B) tight junctions.
C) gap junctions.
D) plasmodesmata.

Question 78

Specialized cell junctions include all of the following EXCEPT

A) gap junctions.
B) desmosomes.
C) phospholipases.
D) tight junctions.

Question 79

After a dye diffuses uniformly throughout a glass of water, the dye molecules are no longer moving.

Question 80

The electrical signal for a muscle to contract passes rapidly from one cell to the next via

A) internal proteins.
B) gap junctions.
C) plasmodesmata.
D) desmosomes.
E) tight junctions.