Deck 5: Cell Membrane Structure and Function

Question 1

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

Answer 1

C

Question 2

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

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

Answer 2

A

Question 3

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

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

Answer 3

C

Question 4

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 extrinsic.
E)different membranes contain different proteins.

Question 5

In biological membranes, the phospholipids are arranged in a:

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

Question 6

The hydrophobic tails of a phospholipid bilayer are oriented toward the:

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

Question 7

Recognition proteins are most important for:

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

Question 8

The ________ portion of the cell membrane is responsible for the isolating function of the membrane, while the ________ portion regulates exchange and communication with the environment.

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

Question 9

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

A)polar heads of the phospholipids
B)channel proteins
C)cholesterol
D)saturated fatty acid tails
E)unsaturated fatty acid tails

Question 10

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 tails are repelled by the aqueous environment.
C)The heads are repelled by the water inside and outside the cell.

Question 11

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

A)All movement of molecules across the membrane would cease.
B)Diffusion and osmosis would continue to occur.
C)Facilitated diffusion, active transport, and osmosis would not occur.
D)The movement of molecules across the membrane would not be affected.
E)Immune reactions would not be affected.

Question 12

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

A)only in muscle cell membranes.
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)attached to carbohydrates and facing the interior of a cell.

Question 13

Which of the following groups includes carrier and channel proteins?

A)receptor proteins
B)recognition proteins
C)attachment proteins
D)transport proteins

Question 14

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

A)phospholipids
B)carbohydrates
C)proteins
D)nucleic acids
E)cytoskeleton

Question 15

Plasma membranes are BEST described as a:

A)double layer of phospholipids with hydrophobic tails directed toward the cytoplasm of the cell.
B)single layer of phospholipids with water molecules attached along one side.
C)double layer of phospholipids with hydrophilic heads directed toward one another.
D)double layer of phospholipids with hydrophobic tails oriented toward one another.
E)single layer of phospholipids with tails pointed toward the inside of the cell.

Question 16

Suppose that plasma membranes were single layers of phospholipids with heads facing the external environment. The interior of this hypothetical cell would have to be:

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

Question 17

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

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

Question 18

The main lipids found in cell membranes are:

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

Question 19

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

Question 20

What prevents your immune system from attacking your own cells?

A)inadequate enzymes
B)fever
C)cholesterol
D)recognition proteins
E)receptor proteins

Question 21

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 positively charged sodium ions out of the intestine and into these cells. If the sodium ions could not move into the cells, how would this affect the movement of water?

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

Question 22

Cell membranes do all of the following EXCEPT:

A)isolate the cell's contents from the external environment.
B)communicate with other cells.
C)regulate the movement of substances between the cell and the extracellular fluid.
D)provide attachments between cells.
E)provide shape and structure to a cell.

Question 23

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

A)endocytosis
B)phagocytosis
C)pinocytosis
D)receptor-mediated endocytosis
E)exocytosis

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

Question 25

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 ink is uniformly distributed in one half of the tray, and the green ink is uniformly distributed in the other half of the tray.
B)The red and green inks are both uniformly distributed throughout the tray.
C)Each ink is moving down its concentration gradient.
D)The concentration of each ink is higher at one end of the tray than at the other end.
E)No predictions can be made without knowing the size of the ink molecules.

Question 26

What is active transport?

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

Question 27

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

A)facilitated diffusion
B)osmosis
C)receptor-mediated endocytosis
D)simple diffusion

Question 28

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

A)transport proteins
B)recognition proteins
C)enzymes
D)receptor proteins
E)attachment proteins

Question 29

What happens when diffusion moves molecules across the plasma membrane?

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

Question 30

When substances move through a plasma membrane and down gradients of concentration, this is called:

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

Question 31

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

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

Question 32

In reference to diffusion, "passive" really means:

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

Question 33

Some of the most important molecules that are embedded within the bilayer membrane of a cell, such as the molecules that allow for transport and cell recognition, are:

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

Question 34

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

A)transport proteins
B)recognition proteins
C)enzymes
D)receptor proteins
E)attachment proteins

Question 35

Molecules that permeate a plasma membrane by facilitated diffusion:

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

Question 36

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

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

Question 37

Which of the following types of membrane proteins are responsible for connecting cells to one another?

A)transport proteins
B)recognition proteins
C)enzymes
D)receptor proteins
E)attachment proteins

Question 38

For diffusion to occur, there must be:

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

Question 39

To say that a cell is "selectively permeable" means:

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

Question 40

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

A)cellulose
B)cholesterol
C)phospholipid
D)channel protein
E)receptor protein

Question 41

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

A)10°C.
B)20°C.
C)30°C.
D)60°C.

Question 42

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

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

Question 43

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

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

Question 44

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

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

Question 45

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

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

Question 46

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

Question 47

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

Question 48

Osmosis moves water from a region of:

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

Question 49

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

Question 50

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)exocytosis
C)active transport
D)facilitated diffusion
E)osmosis

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)active transport
B)facilitated diffusion
C)osmosis
D)endocytosis
E)infusion

Question 52

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

A)hypotonic.
B)isotonic.
C)hypertonic.

Question 53

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 was hypotonic to the solution, and cell B was hypertonic.
B)Cell A was hypertonic to the solution, and cell B was hypotonic.
C)Cell A was hypertonic to cell B.
D)Cell B was hypertonic to cell A.
E)Cells A and B were isotonic to each other.

Question 54

The blood plasma of a man who drinks saltwater will become ________ to his red blood cells, whereas the red blood cells will be ________ to the blood plasma.

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

Question 55

Solutions that cause water to enter cells by osmosis are called:

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

Question 56

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. This is because:

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

Question 57

The secretion of excess water via the contractive vacuole of a Paramecium cell is an example of:

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

Question 58

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

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

Question 59

Active transport requires all of the following EXCEPT:

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

Question 60

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

A)Water enters the cell.
B)Water leaves the cell.
C)Water does not leave or enter the cell.
D)Sugar diffuses in and water diffuses out until equilibrium is reached.

Question 61

Which of the following requires adenosine triphosphate?

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

Question 62

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

A)desmosomes.
B)tight junctions.
C)gap junctions.
D)plasmodesmata.
E)cell plates.

Question 63

The process in which white blood cells engulf bacteria is termed:

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

Question 64

The phospholipid contains two different parts: a ________ head and a pair of ________ tails.

Question 65

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

Question 66

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

Question 67

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

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

Question 68

Which process accounts for the movement of solids into some animal cells?

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

Question 69

Carrier molecules in the plasma membrane are required only for active transport. True or False?

Question 70

Osmosis is the diffusion of water molecules across selectively water-permeable membranes. True or False?

Question 71

The major lipids in biological membranes are called ________.

Question 72

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

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

Question 73

Cells use exocytosis to:

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

Question 74

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

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

Question 75

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

Question 76

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

Question 77

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

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

Question 78

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

Question 79

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 80

Specialized cell junctions include all of the following EXCEPT:

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