Chapter 5 Practice Quiz

What structure in the membrane causes plasma membranes to resist freezing? Unsaturated fatty acid tails Nonpolar heads of the phospholipids Channel proteins Cholesterol Saturated fatty acid tails

Unsaturated fatty acid tails

Adhesion of cells within animal tissues is accomplished by cell-to-cell junctions called plasmodesmata. gap junctions. desmosomes. tight junctions.

desmosomes.

The process in which white blood cells engulf bacteria is termed exocytosis. reception. pinocytosis. phagocytosis. recognition.

phagocytosis.

Active transport requires all of the following EXCEPT aquaporins. ATP. transport proteins. a membrane. a gradient.

aquaporins.

In biological membranes, the phospholipids are arranged in a bilayer, with the fatty acids facing outward (facing the interior and exterior of the cell). bilayer, with the phosphorus groups in the interior of the membrane. single layer, with the fatty acids facing the interior of the cell. bilayer, with the fatty acids pointing toward one another. single layer, with the phosphorus-containing region facing the interior of the cell.

bilayer, with the fatty acids pointing toward one another.

A freshwater protozoan, such as Paramecium, tends to ________ because it lives in a ________ environment. gain water; hypertonic lose water; hypertonic gain water; hypotonic lose water; hypotonic gain water; isotonic

gain water; hypotonic

Protein channels that provide passage for hormones and nutrients between animal cells are termed tight junctions. plasmodesmata. desmosomes. gap junctions.

gap junctions.

The substances in cell membranes that form a barrier to the movement of materials across the membrane are carbohydrates. lipids. internal proteins. nucleic acids. external proteins.

lipids.

The gases O2 and CO2 enter or leave a plant cell by simple diffusion. facilitated transport. active transport. osmosis. facilitated diffusion.

simple diffusion.

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

False

Compare and contrast the intercellular junctions that allow communication between plant and animal cells.

Gap junctions in animal cells and plasmodesmata in plant cells are both involved in coordinating the actions of adjacent cells.

The net movement of molecules from a high concentration to a low concentration is best described by which of the following? Passive transport Exocytosis Osmosis Active transport Endocytosis

Passive transport

If red blood cells are taken from the body and placed in a hypertonic solution, what happens to the cells? They become white blood cells. The cells swell and burst because water moves into them. The cells shrivel up because water leaves them. The cells remain unchanged due to equal water concentrations inside and outside the cells. The cells remain unchanged due to equal solute concentrations inside and outside the cells.

The cells shrivel up because water leaves them.

Which of the following accounts for the fluid aspect of the fluid mosaic model of plasma membranes? The bilayer permits diffusion of certain lipid-soluble substances. 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. The membrane is water soluble. The plasma membrane is "fluid" because of the movement of substances across the membrane. One of the components of the membrane is water.

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.

Within the fluid mosaic of a plasma membrane, what is the role of transport and channel proteins? They prevent the passage of amino acids. They are cell-surface connection sites. They permit ions and water molecules to move through the plasma membrane. They may set off cellular changes such as cell division or hormone secretion. They identify the cell.

They permit ions and water molecules to move through the plasma membrane.

Recognition proteins are most important for active transport of molecules. distinguishing foreign cells from "self" cells. facilitated diffusion of molecules. maintaining membrane fluidity. maintaining membrane integrity.

distinguishing foreign cells from "self" cells.

Molecules assisted by carrier proteins may cross a selectively permeable membrane by facilitated diffusion. osmosis. simple diffusion. active transport. endocytosis.

facilitated diffusion.

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.

facilitated; active

Recognition proteins, such as those embedded on the surface of red blood cells, are composed of phospholipases. nucleic acids. steroids. glycoproteins.

glycoproteins.

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 polar only. nonpolar only. hydrophobic only. hydrophilic only. hydrophobic and nonpolar.

hydrophobic and nonpolar.

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. isotonic; hypertonic hypertonic; hypotonic isotonic; isotonic hypertonic; isotonic hypotonic; hypertonic

hypertonic; hypotonic

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. hypertonic isotonic hypotonic

isotonic

Osmosis moves water from a region of hypertonic solution to a region of hypotonic solution. negative osmotic potential to a region of positive osmotic potential. high solute concentration to a region of low solute concentration. low solute concentration of to a region of high solute concentration. low concentration of water to a region of high concentration of water.

low solute concentration of to a region of high solute concentration.

Cell membranes do all of the following EXCEPT isolate the cell's contents from the external environment. allow communication between cells. regulate the movement of substances between the cytoplasm of the cell and the extracellular fluid. provide an energy source for the cell. provide attachments between cells.

provide an energy source for the cell.

Cells use exocytosis to ingest nutrients. create new cells. pump hydrogen molecules across the membrane. release substances from the cell. move away from danger.

release substances from the cell.

The cells of the bladder are joined to one another by ________ that prevent substances from passing between the cells of this tissue.

tight junctions

Which of the following is an energy-requiring mode of transport that brings substances into a cell? Active transport Simple diffusion Facilitated diffusion Osmosis

Active transport

Solutions that cause water to enter cells by osmosis are called hydrophilic. hypertonic. hypotonic. permeable. isotonic.

hypotonic.

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

transport proteins

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

True

Cystic fibrosis is a genetic disease that leads to the production of excessive, thick mucus in the respiratory tract, causing frequent and serious respiratory infections. The defect is due to the production of a faulty membrane protein for the transport of the chloride ion. The protein exists in membranes, but it doesn't function normally. Based on this scenario, what is occurring at the molecular level in a person with cystic fibrosis? A channel protein is being adversely affected. A carrier protein is being adversely affected. Protein filaments in the cytoplasm are being adversely affected. A receptor protein is being adversely affected. A recognition protein is being adversely affected.

A channel protein is being adversely affected.

Distinguish among the three types of endocytosis: pinocytosis, receptor-mediated endocytosis, and phagocytosis.

Pinocytosis is for fluid intake, receptor-mediated endocytosis is for the uptake of specific molecules, and phagocytosis is used to move large particles into the cell.

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

The tails are repelled by the aqueous environment, and the heads will directly interact with the aqueous solution.

According to the fluid mosaic model of cell membranes, which of the following is a TRUE statement about membrane phospholipids? They have hydrophilic tails in the interior of the membrane. They occur in an uninterrupted bilayer, with membrane proteins strictly anchored to the surface of the membrane. They frequently flip-flop from one side of the membrane to the other. They form a viscous fluid through which proteins shift and flow. They are free to depart from the membrane and are dissolved in the surrounding solution.

They form a viscous fluid through which proteins shift and flow.

Which of the following types of membrane proteins are responsible for facilitated diffusion? Recognition proteins Receptor proteins Transport proteins Enzymes Connection proteins

Transport proteins

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? Water will diffuse from solution A to solution B. Starch will diffuse from solution B to solution A. Starch will diffuse from solution A to solution B. Both water and starch will diffuse from solution B to solution A. Water will diffuse from solution B to solution A.

Water will diffuse from solution B to solution A.

Both plant cells and animal cells will swell if placed in a hypotonic solution. However, only the animal cell will burst. Why?

Water will enter both cells due to osmosis. In the animal cell, water will continue to enter as long as the extracellular solution is hypotonic, causing the pliable animal cell membrane to eventually break and the cell to burst. The stiff cell wall found in plant cells but not animal cells will not expand indefinitely. At some point, as the cytoplasm of the plant cell expands, the cell wall will exert a back pressure on the cell. Further water uptake will be prevented and the plant cell will not burst.

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? Water would leave the intestines and enter the cells by facilitated diffusion. The movement of water would not be affected. Water would leave the cells and enter the intestines by facilitated diffusion. Water would leave the intestines and enter the cells by osmosis. Water would leave the cells and enter the intestines by osmosis.

Water would leave the cells and enter the intestines by osmosis.

Imagine that beaker A has a 10% sucrose solution, and beaker B has an 8% sucrose solution. This means that beaker A is isotonic relative to beaker B. beaker A is hypertonic relative to beaker B. beaker A is hypotonic relative to beaker B.

beaker A is hypertonic relative to beaker B.

Carbon dioxide crosses the plasma membrane by simple diffusion. The rate at which carbon dioxide enters the cell is determined by the amount of transport protein in the membrane. amount of carbon dioxide outside of the cell. amount of oxygen being exported from the cell. amount of energy being produced by the cell. concentration of carbon dioxide on each side of the membrane.

concentration of carbon dioxide on each side of the membrane.

Plasma membranes are best described as a single layer of phospholipids with water molecules attached along one side. single layer of phospholipids with tails pointed toward the inside of the cell. double layer of phospholipids with hydrophobic tails facing away from each other (toward the cytoplasm of the cell and the extracellular solution). double layer of phospholipids with hydrophilic heads facing away from one another. double layer of phospholipids with hydrophobic tails facing toward one another.

double layer of phospholipids with hydrophobic tails facing toward one another.

The secretion of excess water via a contractile vesicle of a Paramecium cell is an example of active transport. simple diffusion. facilitated diffusion. exocytosis. osmosis.

exocytosis.

The hydrophilic regions of a membrane protein are most likely to be found exposed on the surface of the cell membrane. associated with the fatty acid region of the lipids. attached to carbohydrates and facing the interior of a cell. in the interior of the membrane. only in muscle cell membranes.

exposed on the surface of the cell membrane.

The electrical signal for a muscle to contract passes rapidly from one cell to the next via tight junctions. gap junctions. plasmodesmata. desmosomes. internal proteins.

gap junctions.

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 tail-head-head-tail. head-tail-head-tail. head-head-tail-tail. tail-head-tail-head. head-tail-tail-head.

head-tail-tail-head.

The hydrophobic tails of a phospholipid bilayer are oriented toward the extracellular fluid surrounding the cell. cytoplasm of the cell. interstitial fluid. both the extracellular fluid and cytoplasm. interior of the plasma membrane (i.e., toward one another).

interior of the plasma membrane (i.e., toward one another).

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. cholesterol; lipid carbohydrate; lipid protein; cholesterol lipid; protein nucleic acid; lipid

lipid; protein

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

many proteins can move around within the bilayer.

In reference to diffusion, passive really means in the air. without a membrane. no gradient. very slowly. no energy required.

no energy required.

To say that a cell is "selectively permeable" means it is permeable to different substances than other cells. sometimes water passes through, and sometimes it can't. it has different-sized perforations in the membrane. only certain molecules can pass through. permeability depends on gradient differences.

only certain molecules can pass through.

When substances move across a plasma membrane and down concentration gradients, this is called pinocytosis. active transport. passive transport. exocytosis.

passive transport.

Specialized cell junctions include all of the following EXCEPT gap junctions. tight junctions. desmosomes. phospholipases.

phospholipases.

The main lipids found in cell membranes are phospholipids. waxes. steroids. triglycerides. glycerol.

phospholipids.

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 osmotic channels. desmosomes. tight junctions. plasmodesmata. gap junctions.

plasmodesmata.

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

plasmodesmata; gap junctions

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

polar and/or hydrophilic; nonpolar and/or hydrophobic

Molecules that permeate a plasma membrane by facilitated diffusion do so much more quickly than those crossing by simple diffusion. move from an area of low concentration to an area of high concentration. require energy. require the aid of transport proteins.

require the aid of transport proteins.

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

there are a limited number of carrier proteins in the membrane.

The urinary bladder is protected from leaking by cell-to-cell junctions called gap junctions. desmosomes. tight junctions. plasmodesmata.

tight junctions.

If you forget to water your favorite plant, all of the following will occur at a cellular level EXCEPT water will move out of the cytosol by osmosis. osmosis will occur. the plasma membrane will shrink away from the cell wall. turgor pressure will build up in the cell. water will move out of the vacuoles by osmosis.

turgor pressure will build up in the cell.

Which process accounts for the movement of solid particles (such as food) into some animal cells? Simple diffusion Active transport Facilitated diffusion Osmosis Phagocytosis

Phagocytosis

The antibiotic polymyxin B attaches itself to the phospholipids in the phospholipid bilayer and increases the permeability of the membrane. Describe what will occur as a result.

The plasma membrane will lose its ability to be a selectively permeable barrier. Substances will leak out of the cell, and some previously excluded substances may enter. Eventually, the cell will die.

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

Water leaves the cell because the solution is hypertonic to the cell.

The diffusion of water molecules across a selectively permeable membrane is called exocytosis. osmosis. hydrolysis. facilitated diffusion. active transport.

osmosis.

Which of the following would NOT be found in a membrane? Receptor protein Channel protein Cholesterol Cellulose Phospholipid

Cellulose

If the radius of one cell were twice as large as the radius of another cell, how much higher or lower would its surface-area-to-volume ratio be? 2 times lower 1/2 lower 2 times higher 10 times higher

1/2 lower

The slowest rate of diffusion of dye particles in water will occur at 10°C. 20°C. 30°C. 60°C.

10°C.

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? Active transport Osmosis Infusion Facilitated diffusion Exocytosis

Active transport

Which of the following requires adenosine triphosphate? Facilitated diffusion Osmosis Simple diffusion Active transport

Active transport

Compare and contrast facilitated diffusion and active transport.

Both require membrane transport proteins. However, facilitated diffusion does not require energy and moves substances down a concentration gradient. Active transport requires energy and moves substances against a concentration gradient.

Which of the following types of membrane proteins are responsible for maintaining cell shape by linking the membrane protein with the cytoskeleton? Transport proteins Receptor proteins Enzymes Recognition proteins Connection proteins

Connection proteins

Suppose a bag made of a selectively permeable membrane was filled with a 5% solution of glucose and sealed. What would happen if the bag was placed in pure water or in a 10% glucose solution?

In pure water, the bag would swell as water moves in. In the glucose solution, the bag would shrink as water moves out.

Why is the biological membrane said to be selectively permeable?

It allows only some molecules to pass through while barring others.

What is active transport? Rapid movement of molecules in a solution Movement of molecules into or out of a cell using special proteins and not requiring an expenditure of energy Movement of molecules into or out of a cell down a concentration gradient Diffusion of molecules within a cell Movement of molecules into or out of a cell against a concentration gradient

Movement of molecules into or out of a cell against a concentration gradient

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

Phagocytosis

Which of the following groups includes carrier and channel proteins? Transport proteins Recognition proteins Connection proteins Receptor proteins

Transport proteins

The most common lipids in biological membranes are ________.

phospholipids

If a frog egg cell is placed into a hypotonic solution, it will shrivel via facilitated diffusion. shrivel via active transport. swell via osmosis. swell via facilitated diffusion. shrivel via osmosis.

swell via osmosis.

Compare and contrast osmosis and simple diffusion.

Both are passive processes. However, osmosis refers to the movement of water down its concentration gradient across a selectively permeable membrane. No membrane or membrane protein is required for simple diffusion.

Which of the following occurs as an enzyme produced by a cell is secreted from the cell? Pinocytosis Exocytosis Phagocytosis Endocytosis Receptor-mediated endocytosis

Exocytosis

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

False

For diffusion to occur, there must be ATP. water. a membrane. a gradient.

a gradient.

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

Cell B has a higher concentration of sucrose than cell A.

Why does the cell perform endocytosis in addition to active and passive transport?

Endocytosis is required for the transport of proteins, microbes, extracellular fluid, and specific molecules that are all larger than the molecule size transported by active and passive transport.

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? Simple diffusion Exocytosis Facilitated diffusion Osmosis Aquaporin transport

Facilitated diffusion

Based on these four illustrations of diffusion, which mode would most likely be used to transport oxidized zinc (which has a charge of +2) through the cell membrane? Simple diffusion through the bilayer Facilitated diffusion through carrier proteins Facilitated diffusion through channel proteins Osmosis through aquaporins

Facilitated diffusion through channel proteins

How does the cell membrane act as a "gatekeeper" for the cell?

It separates the internal and external cell environments, it regulates the exchange of substances between the external environment and the cytoplasm, and it allows for communication between cells.

What would happen if the plasma membrane were composed solely of phospholipids and no proteins? All movement of molecules across the membrane would cease. Simple diffusion and osmosis would continue to occur. Immune reactions would not be affected. The movement of molecules across the membrane would not be affected. Only water would be able to pass through the membrane.

Simple diffusion and osmosis would continue to occur.

What happens when diffusion moves molecules across the plasma membrane? The rate of diffusion cannot be influenced by the cell. Most molecules are capable of crossing the phospholipid bilayer at any location and at basically the same rate. The process is relatively slow and is driven by concentration gradients. The cell gains needed materials and gets rid of excess materials very quickly. Energy input is required to transport molecules.

The process is relatively slow and is driven by concentration gradients.

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

The red and green inks are both uniformly distributed throughout the tray.

When very small viruses infect a plant cell by crossing its membrane, the viruses often spread rapidly throughout the entire plant without crossing additional membranes. Explain how this occurs.

The viruses travel cell to cell via the plasmodesmata junctions.

All of the following may influence the rate of simple diffusion across a selectively permeable membrane EXCEPT the concentration gradient. temperature. size of the molecule. size of the cell. lipid solubility of the molecule.

size of the cell.

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

Facilitated diffusion; hydrogen ions moved into the vesicle through a channel protein.

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? Nucleic acids Cytoskeleton Phospholipids Carbohydrates Proteins

Proteins

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

Receptor proteins

What prevents your immune system from attacking your own cells? Inadequate enzymes Receptor proteins Cholesterol Fever Recognition proteins

Recognition proteins