Deck 5: Membranes

Question 1

The fluid nature of the membranes is attributed to a lateral movement of

A)protein channels.
B)phospholipid molecules.
C)antigen molecules.
D)pumps such as the proton pump.
E)the entire lipid bilayer.

Answer 1

B

Question 2

If two solutions have unequal concentrations of a solute,the solution with the lower concentration is called

A)isotonic.
B)hypertonic.
C)hypotoniC.
D)hypnotic.
E)osmosis.

Answer 2

C

Question 3

The lipid layer that forms the foundation of cell membranes is primarily composed of molecules called ____________.

A)phospholipids
B)fats
C)carbohydrates
D)proteins

Answer 3

A

Question 4

The plasma membrane is a thin sheet of lipid embedded with

A)proteins.
B)carbohydrates.
C)polymers.
D)nucleotides.
E)sodium and potassium ions.

Question 5

The cell's transactions with the environment mediated by its plasma membrane include all of the following except

A)ingesting food as molecules and sometimes as entire cells.
B)returning waste and other molecules back to the environment.
C)responding to a host of chemical cues.
D)directing the synthesis of various food-digesting proteins.
E)passing of messages to other cells.

Question 6

While water continually orients phospholipids into a lipid bilayer,it does not fix the lipids permanently into position.Thus,the bilayer is considered to be _______ in nature.

A)static
B)fluid
C)fluctuating
D)charged

Question 7

Which of the following properties is not true of membrane phospholipids?

A)The hydrophobic tails are oriented towards the interior.
B)The hydrophilic heads are oriented towards the exterior.
C)Only the saturated fatty acids are always present.
D)Once they are incorporated they remain in the membrane permanently.
E)The bilayers made up of them are randomly interspersed with proteins.

Question 8

Both active transport and facilitated transport utilize specific ______________ proteins embedded in the cell membrane.

A)carrier
B)cytoskeletal
C)structural
D)targeted

Question 9

If a cell has the same concentration of dissolved molecules as of its outside environment,the cell's condition is called as being

A)isotonic.
B)hypertonic.
C)hypotoniC.
D)hydrophobic.
E)hydrophilic.

Question 10

Membrane proteins are not very soluble in water,because they possess long stretches of non-polar amino acids that

A)are too long to interact with the water molecules.
B)are hydrophobic.
C)are transmembranal.
D)are hydrophilic.
E)serve as transport channels.

Question 11

The following are all functions of a typical plasma membrane except

A)transport of water and bulk material.
B)selective transport of certain molecules and material.
C)reception of information.
D)expression of cellular identity.
E)permanence in composition.

Question 12

________ is the net movement of substances to regions of lower concentration.

A)Osmosis
B)Active transport
C)Facilitation
D)Diffusion

Question 13

Glycoproteins and glycolipids are examples of _________________ associated with the cell membrane.

A)organelles
B)phospholipids
C)cell surface markers
D)cytoskeletal fibers

Question 14

Osmosis is the diffusion of water across a membrane in response to the concentration of one or more of the ________.

A)solutes
B)membranes
C)compartments
D)cells

Question 15

The movement of substances to regions of lower concentration is called

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

Question 16

Osmosis occurs as water can cross the lipid bilayer through __________________,specialized channels for water movement.

A)proteins
B)carbohydrates
C)membrane pores
D)aquaporins

Question 17

A type of transport of a solute across a membrane,up its concentration gradient,using protein carriers driven by the expenditure of chemical energy is known as

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

Question 18

Which of the following protein classes are not found as membrane proteins?

A)transport channels
B)hormones
C)receptors
D)enzymes
E)identity markers

Question 19

The part of a membrane protein that extends through the phospholipid bilayer is primarily composed of amino acids that are

A)highly polar.
B)negatively charged.
C)non-polar.
D)positively chargeD.
E)water solublE.

Question 20

On the outer surface of the plasma membrane there are marker molecules that identify the cell-type.Often these molecules are

A)ATP.
B)amino acids.
C)nucleotides.
D)carbohydrate chains.
E)inorganic ions.

Question 21

The Fluid Mosaic Model proposed by Singer and Nicolson in 1972 included that

A)the cell membrane was composed of lipids and proteins.
B)the cell membrane was composed of a phospholipid bilayer between two layers of globular proteins.
C)the cell membrane was composed of a phospholipid bilayer with globular proteins actually inserted into the bilayer.
D)the cell membrane was composed of a phospholipid bilayer but the polar ends of the phospholipid molecules were reverseD.

Question 22

As a scientist you perform an experiment in which you create an artificial cell with a selectively permeable membrane through which only water can pass.You put a 5M solution of glucose into the cell and you place that into a beaker of water.What observations do you expect to see?

A)Water moves out of the cell.
B)Glucose moves out of the cell.
C)No net change in cell weight.
D)Water moves into the cell.
E)Glucose moves into the cell.

Question 23

The actual transport of protons by the proton pump is mediated by a transmembrane protein which undergoes a change in its

A)conformation.
B)amino acid sequence.
C)net charge.
D)solubility.
E)immunity.

Question 24

Cholesterol functions in the plasma membrane to

A)transport ions.
B)serve as an energy molecule.
C)maintain fluidity.
D)mediate steroid action.
E)maintain hypertension.

Question 25

Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones.Requirements for facilitated diffusion include which of the following?

A)The carrier molecule must be specific to the molecule that is transported.The direction of movement is always with the concentration gradient,never against the gradient.
B)The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always with the concentration gradient,never against the gradient.
C)The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always against the concentration gradient,never with the gradient.
D)The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier.The direction of movement is always against the concentration gradient,never with the gradient.

Question 26

The type of diffusion that is specific and passive,and which becomes saturated if all of the protein carriers are in use is

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

Question 27

The accumulation of amino acids and sugars in animal cells occurs through

A)ATP pumps.
B)sodium-potassium pumps.
C)glucose pumps.
D)coupled transport.
E)proton pumps.

Question 28

A phospholipid molecule has a polar and a nonpolar end.Because of this,water molecules form

A)polar bonds with the nonpolar end of the phospholipid molecule.
B)polar bonds with the polar end of the phospholipid molecule.
C)hydrogen bonds with the nonpolar end of the phospholipid molecule.
D)hydrogen bonds with the polar end of the phospholipid molecule.
E)covalent bonds with the nonpolar end of the phospholipid moleculE.

Question 29

Membrane proteins serve many functions.One of the functions is transportation of substances across the membrane.If a cell biologist placed cells into an environment in which a chemical has been added that blocks the function of these transport proteins,which process will be blocked?

A)active transport
B)osmosis
C)diffusion
D)phagocytosis
E)pinocytosis

Question 30

One day during the summer you and some friends made ice cream using an electric ice cream maker.A few days later you noticed a yellow circle of dead grass where the ice cream freezer had been placed.What happened?

A)The ice and salt mixture that spilled out when the freezer was moved froze the grass.
B)The grass was frost bitten by the ice and salt mixture that spilled out when the freezer was moved.
C)The ice and salt mixture was isosmotic to the grass cells and caused the yellow circle of dead grass.
D)The ice and salt mixture was hyperosmotic to the grass cells and caused the yellow circle of dead grass.
E)The ice and salt mixture was hypoosmotic to the grass cells and caused the yellow circle of dead grass.

Question 31

Cell-walled organisms cannot carry out

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

Question 32

Osmosis can only occur if water travels through the

A)cell wall.
B)semi-permeable membrane.
C)vacuole.
D)ER.
E)cytoskeleton.

Question 33

The process often thought of as "cell eating" is

A)osmosis.
B)pinocytosis.
C)phagocytosis.
D)diffusion.
E)active transport.

Question 34

In a single sodium-potassium pump cycle,ATP is used up with the result that

A)3 sodium ions leave and 2 potassium ions enter.
B)1 sodium ion enters and 1 potassium ion leaves.
C)1 sodium ion leaves and 1 potassium ion enters.
D)3 sodium ions enter and 2 potassium ions leave.
E)sodium and potassium ions enter and water leaves.

Question 35

Which of the following is not a component of an animal cell membrane?

A)phospholipids
B)polynucleotides
C)aquaporins
D)glycolipids
E)cholesterol

Question 36

If a blood research laboratory is attempting to collect the content of human red blood cells,the researchers should use which of the following types of solutions to cause blood cell lysis (bursting)?

A)hyperosmotic
B)isosmotic
C)hypoosmotic
D)osmotic

Question 37

Carrier-mediated transport is also called

A)facilitated diffusion.
B)active transport.
C)exocytosis.
D)endocytosis.
E)phagocytosis.

Question 38

For the process of diffusion to occur,molecules must

A)move from areas of high concentration to areas of lesser concentration until an equilibrium is reached.
B)move from areas of low concentration to areas of higher concentration until an equilibrium is reached.
C)remain stationary until their molecular motion allows for an equilibrium to be reached.
D)move from areas of high concentration to areas of lesser concentration until facilitated transport can assist the molecular equilibrium.
E)move from areas of high concentration to areas of lesser concentration until an equilibrium is reached by active transport.

Question 39

The type of transport that is specific,which requires specific carrier molecules and energy is

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

Question 40

In bacteria,fungi,and plants the high internal pressure generated by osmosis is counteracted by the mechanical strength of their

A)plasma membranes.
B)organelles.
C)cytoskeletons.
D)cell walls.
E)flagella.

Question 41

Which of the following does not influence membrane fluidity?

A)a decrease in temperature
B)the addition of cholesterol
C)hydrogen bonding of water holding the membrane together
D)introduction of double bonds into fatty acids

Question 42

During neuronal signaling,a change in membrane potential will cause sodium channels to open and let Na⁺ ions diffuse down their concentration gradient into the cell.Which of the following helps establish the concentration gradient necessary for this process to occur?

A)Na⁺/K⁺ channel
B)voltage-gated Na⁺ channel
C)Na⁺ symporter
D)Na⁺/K⁺ pump

Question 43

Diapedesis is the movement of white blood cells through intact blood vessel walls into surrounding body tissue.It typically happens when an area of the body is injured or damaged,and an inflammation response is required.What role would you expect cell adhesion molecules to play in this process?

A)Cell adhesion molecules will allow the white blood cells to cling to one another to form a migrating clot.
B)Cell adhesion molecules help white blood cells adhere to the blood vessel wall so that they can migrate across the wall and infiltrate into the underlying tissue.
C)Cell adhesion molecules will allow the white blood cells to attach to the injured area.

Question 44

Protein X contains four transmembrane domains,a short N-terminus and a long C-terminus.Following protein synthesis,the N-terminus of the protein faces the lumen (the inside)of the ER.After protein X is transported to the cell surface via exocytosis,you would expect the C-terminus of the protein X to be

A)extracellular.
B)cytoplasmic.
C)in the lumen.
D)in the lipid bilayer of the plasma membrane.

Question 45

In individuals with normal blood sugar levels,glucose is reabsorbed into the bloodstream in the kidney by members of the GLUT transporter family,which form an aqueous pore across the membrane through which glucose can move in a passive manner.As a result,no glucose is excreted in urine.However,in people with untreated diabetes mellitus,blood sugar levels are high and glucose is often present in the urine.Which of the following best explains this occurrence?

A)High blood glucose levels reverse the concentration gradient,allowing untransported glucose to be excreted in urine.
B)High blood glucose levels interfere with the coupled transport of water and glucose,allowing untransported glucose to be excreted in urine.
C)The GLUT transporters become saturated,allowing untransported glucose to be excreted in urine.
D)The GLUT transporters cannot hydrolyze ATP quickly enough for ATP to transport the extra glucose,thereby allowing untransported glucose to be excreted in urine.

Question 46

Which of the following statements about receptor-mediated endocytosis is false?

A)Receptor-mediated endocytosis is a dynamic process.
B)Receptor-mediated endocytosis indirectly helps to increase membrane fluidity by helping to transport cholesterol into the cell.
C)Receptor-mediated endocytosis requires a clathrin coat.
D)Receptor-mediated endocytosis is used to internalize molecules into the cytoplasm of the cell.

Question 47

Incubation of cells at 20 ^$\circ$ C blocks the release of proteins from the trans-Golgi.Under such conditions,you would expect to see

A)an increase in exocytosis.
B)a decrease in exocytosis.
C)an increase in endocytosis.
D)a decrease in endocytosis.

Question 48

Cyclodextrins can be used to remove cholesterol from a membrane.Which of the following is the most likely effect of cyclodextrin treatment?

A)an increase in transmembrane proteins
B)a disruption of the bilayer
C)an increase in membrane fluidity
D)a disruption of lipid rafts

Question 49

As a scientist you perform an experiment in which you create an artificial cell with a selectively permeable membrane through which only water can pass.You put a 5M solution of glucose into the cell and you place that into a beaker of 10M glucose.What observations do you expect to see?

A)Water moves out of the cell.
B)Glucose moves out of the cell.
C)No net change in cell weight.
D)Water moves into the cell.
E)Glucose moves into the cell.

Question 50

How can freeze-fracture be used to determine the orientation of a protein in a membrane?

A)Freeze-fracture allows a cell to be cleaved in between the lipid bilayer,splitting the plasma membrane into two layers.
B)Freeze-fracture allows a cell to be cleaved in such a way as to preserve the embedded proteins.
C)Freeze-fracture cuts the membrane in protein-sized components for viewing under an electron microscope.

Question 51

The turgor pressure observed in plants is a direct result of the plant cells being _________________ to their environment.

A)hypoosmotic
B)isosmotic
C)osmosis
D)hyperosmotic

Question 52

If you were to replace the phosphate group of a phospholipid with a fatty acid chain,you would have

A)glycerol.
B)a triglyceride.
C)cholesterol.
D)glycolipiD.

Question 53

Which of the following mutations would be most likely to interfere with the proper insertion of a protein in the plasma membrane?

A)a polar amino acid to a non-polar amino acid within a transmembrane domain
B)a non-polar amino acid to a polar amino acid within a transmembrane domain
C)a polar amino acid to a non-polar amino acid within a cytoplasmic domain
D)a non-polar amino acid to a polar amino acid within a cytoplasmic domain

Question 54

Which of the following is not a part of the sodium-potassium pump?

A)Three sodium ions bind to the cytoplasmic side of the protein.
B)Three sodium ions are translocated out of the cell.
C)Phosphate facilitates potassium ion binding to transport protein.
D)Two potassium ions are transported into the cell.
E)ATP binds to the protein which becomes phosphorylated (ADP is released).

Question 55

While eating lobster for dinner one night you begin thinking about the fact that this type of marine invertebrate is isosmotic with respect to the surrounding seawater.Your friend asks what would happen if the lobster you were eating had not been caught,but instead was moved to a bay with a slightly lower concentration of salt.You reply that in order for the lobster to be isosmotic with respect to new environment,

A)it must move water in to match the solute concentration of its new environment.
B)it regulates its internal concentration of solutes to match that of its new environment.
C)it must move water out to match the solute concentration of its new environment.
D)it moves water in or out and regulates its internal concentration of solutes as needeD.

Question 56

If you were a very thirsty cell,which process would you use to take in some nutrients secreted by one of your neighbors?

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

Question 57

GABA_A receptors play an essential role in neurotransmission in the central nervous system.In response to the appropriate signal,these receptors open up and allow Cl^- to flow into the cell.Given this information,GABA_A receptors can be classified as a

A)gated ion channel.
B)gated carrier protein.
C)symporter.
D)Cl^- pump.

Question 58

If a cell has a normal osmotic pressure of 4500 mmHg and is placed into a solution with an osmotic pressure of 3500 mmHg,what will happen to the cell?

A)The cell will lose water and its osmotic pressure will decrease.
B)The cell will gain water and its osmotic pressure will decrease.
C)The cell will lose water and its osmotic pressure will increase.
D)The cell will lose water and its osmotic pressure will increase.