Deck 5: Cell Membrane Structure and Function

Question 1

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

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

Answer 1

B

Question 2

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

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

Answer 2

C

Question 3

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

Answer 3

A

Question 4

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

Question 5

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

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

Question 6

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

Question 7

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

Question 8

In biological membranes, the phospholipids are arranged in a

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

Question 9

Which of the following groups includes carrier and channel proteins?

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

Question 10

What prevents your immune system from attacking your own cells?

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

Question 11

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

Question 12

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

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

Question 13

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

A) 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.
B) The plasma membrane is "fluid" because of the movement of substances across the membrane.
C) One of the components of the membrane is water.
D) The membrane is water soluble.
E) The bilayer permits diffusion of certain lipid- soluble substances.

Question 14

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

Question 15

Recognition proteins are most important for

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

Question 16

The main lipids found in cell membranes are

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

Question 17

Plasma membranes are best described as a

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

Question 18

The hydrophobic tails of a phospholipid bilayer are oriented toward the

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

Question 19

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

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

Question 20

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

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

Question 21

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

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

Question 22

In reference to diffusion, passive really means

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

Question 23

For diffusion to occur, there must be

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

Question 24

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

Question 25

What happens when diffusion moves molecules across the plasma membrane?

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

Question 26

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

Question 27

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

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

Question 28

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

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

Question 29

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

Question 30

To say that a cell is "selectively permeable" means

A) it is permeable to different substances than other cells.
B) it has different- sized perforations in the membrane.
C) sometimes water passes through, and sometimes it can't.
D) only certain molecules can pass through.
E) permeability depends on gradient differences.

Question 31

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

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

Question 32

What is active transport?

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

Question 33

Cell membranes do all of the following EXCEPT

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

Question 34

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

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

Question 35

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

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

Question 36

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

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

Question 37

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

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

Question 38

Molecules that permeate a plasma membrane by facilitated diffusion

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

Question 39

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

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

Question 40

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

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

Question 41

Active transport requires all of the following EXCEPT

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

Question 42

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

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

Question 43

A freshwater protozoan, such as Paramecium, tends to because it lives in a environment.

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

Question 44

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

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

Question 45

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

Question 46

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 47

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

Question 48

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

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

Question 49

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

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

Question 50

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

Question 51

Solutions that cause water to enter cells by osmosis are called

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

Question 52

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

Question 53

Osmosis moves water from a region of

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

Question 54

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

Question 55

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

Question 56

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

Question 57

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

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

Question 58

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

Question 59

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

Question 60

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

A) 10°C.
B) 60°C.
C) 20°C.
D) 30°C.

Question 61

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

Question 62

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

Question 63

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) osmosis will occur.
C) the plasma membrane will shrink away from the cell wall.
D) water will move out of the vacuoles by osmosis.
E) water will move out of the cytosol by osmosis.

Question 64

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

Question 65

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

Question 66

The process in which white blood cells engulf bacteria is termed

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

Question 67

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

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

Question 68

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

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

Question 69

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 70

Phospholipids contain two different parts: a head and a pair of _ tails.

Question 71

Which of the following requires adenosine triphosphate?

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

Question 72

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 73

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

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

Question 74

Specialized cell junctions include all of the following EXCEPT

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

Question 75

The most common lipids in biological membranes are _.

Question 76

Cells use exocytosis to

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

Question 77

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

Question 78

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

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

Question 79

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 80

Communication between cells occurs via in plant cells and via in animal cells.