A.   can be released from membranes only by treatment with detergents

B.   penetrate deeply into the lipid bilayer

C.   are generally noncovalently bound to membrane lipids

D.   may have functional units on both sides of the membrane

A.   a solution containing detergent

B.   hot water

C.   a chelating agent that removes divalent cations

D.   a solution of high ionic strength

E.   a buffer

A.   They can be removed from the membrane with high salt or mild denaturing agents.

B.   The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.

C.   They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.

D.   The secondary structure in the transmembrane region consists solely of alpha-helices or beta-sheets.

A.   The polar head groups face inward toward the inside of the bilayer.

B.   The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.

C.   Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.

D.   Polar, but uncharged, compounds readily diffuse across the bilayer.

E.   Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.

A.   an increase in fatty acyl chain length.

B.   an increase in the number of double bonds in fatty acids.

C.   a decrease in temperature.

D.   the binding of water to the fatty acyl side chains.

A.   shifting from aerobic to anaerobic metabolism.

B.   synthesizing thicker membranes to insulate the cell.

C.   increasing its metabolic rate to generate more heat.

D.   putting more unsaturated fatty acids into its membranes.

E.   putting longer-chain fatty acids into its membranes.

A.   driven by a difference of solute concentration

B.   endergonic

C.   generally irreversible

D.   driven by ATP

E.   not specific with respect to the substrate

A.   secondary active transport

B.   facilitated diffusion

C.   passive transport

D.   primary active transport

E.   simple diffusion

A.   There are electrostatic and hydrogen-bonding attractions between the polar head groups and water molecules.

B.   The outside surface of a beta barrel is hydrophylic

C.   In accord with the Second Law of Thermodynamics, molecules spontaneously move from a region of higher concentration to one of lower concentration

D.   An entropy increase powers diffusion across the membrane.

A.   diffusion

B.   None of the choices are correct

C.   osmosis

D.   active transport

E.   facilitated diffusion

A.   diffuser

B.   transporter

C.   oxidizer

D.   reducer

E.   pump

A.   An area of high concentration to an area of low concentration

B.   An area of low concentration to an area of high concentration

C.   An area of equilibrium to an area of high concentration

D.   All of the above

A.   Energy

B.   Water

C.   Concentrated solutes

D.   Carrier proteins

A.   Passage through a channel allows polar and charged compounds to avoid the hydrophobic core of the plasma membrane, which would otherwise block their entry into the cell.

B.   Movement of one molecule down its gradient is an entropically driven process

C.   The transport of a molecule up its gradient is an energy-requiring process.

D.   The transport of a molecule up its gradient is an exergonic process

A.   selective permeability

B.   amphipathic nature

C.   bilayer

D.   asymmetry

E.   None of the answers is correct.

A.   translocation

B.   kinesin-mediated movement

C.   lateral diffusion

D.   asymmetric longitudinal flipping

E.   flip-flopping

A.   cholesterol

B.   integral membrane proteins in contact with the cytoplasm

C.   lipid-linked proteins

D.   glycolipids

A.   carbohydrates

B.   All of the answers are correct

C.   lipids and proteins

D.   None of the answers is correct.

A.   None of the answers is correct.

B.   infinite

C.   two

D.   one

E.   varying thickness, depending on structure

A.   a bilayer made of lipids with saturated 18 carbon-fatty acids

B.   a bilayer made of lipids with saturated 16 carbon-fatty acids

C.   a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids

D.   a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids

E.   All of the above are equivalent in fluidity.

A.   positioned on the extracellular side of the membrane.

B.   positioned on the intracellular side of the membrane.

C.   also covalently attached to membrane proteins

D.   positioned equally on both sides of the membrane.

E.   positioned on the inside center of the bilayer.

A.   free fatty acids.

B.   unsaturated fatty acids.

C.   glycolipids

D.   lipids that contain sphingosine.

A.   Active transport

B.   Passage through ion channels

C.   Diffusion through a uniport

D.   facilitated diffusion

A.   membrane melting temperatures.

B.   All of the answers are correct.

C.   membrane fluidity

D.   membrane fluidity and membrane melting temperatures.

E.   membrane asymmetry

A.   proteins

B.   magnesium ions

C.   ATP

D.   cholesterol

E.   None of the answers is correct.

A.   The inner and outer halves of the lipid bilayer are identical.

B.   Lateral movement of membrane lipids is catalysed by special proteins.

C.   Lateral movement of membrane lipids occurs rapidly within the plane of the bilayer.

D.   Transverse movement of membrane lipids within the bilayer is unrestricted.

A.   Membrane fluidity is increased when there is a high proportion of saturated fatty acids in the glycerophosphate molecules that make up the bilayer.

B.   Membrane fluidity is decreased when there is a high proportion of cis unsaturated fatty acids in the glycerophosphate molecules that make up the bilayer.

C.   Membrane fluidity is increased when there is a high proportion of trans unsaturated fatty acids in the glycerophosphate molecules that make up the bilayer.

D.   Membrane fluidity is increased when there is a high proportion of cis unsaturated fatty acids in the glycerophosphate molecules that make up the bilayer.

A.   Integral membrane proteins are anchored to the lipid bilayer by ionic bonds.

B.   Integral membrane proteins have ends rich in hydrophilic amino acids.

C.   Transmembrane porins have hydrophilic amino acids that point inwards in the beta-barrels.

D.   Integral membrane proteins have transmembrane domains rich in hydrophobic amino acids.

A.   Cell membranes are impermeable to most molecules.

B.   Cell membranes maintain the shape of cells.

C.   Cell membranes retain the contents of cells.

D.   Cell membranes are permeable to most inorganic ions.

A.   Small inorganic ions can diffuse through a cell membrane along a concentration gradient.

B.   Small polar molecules require specific transport systems for passage across a membrane.

C.   Small polar molecules can diffuse through a cell membrane along a concentration gradient.

D.   Small polar molecules cannot be transported through a cell membrane against a concentration gradient.

A.   cholesterol at certain temperatures

B.   poor alignment of the fatty acids tails

C.   double bonds between carbon atoms in the fatty acid tails

D.   steroid lipids at certain temperatures

E.   all of the above

A.   passive diffusion through the lipid bilayer

B.   specific gas transport proteins

C.   secondary active transport

D.   primary active transport

A.   Facilitated diffusion

B.   Symport

C.   Simple diffusion

D.   Pump

A.   move across the membrane to the inside of the cell.

B.   move across the membrane to the outside of the cell.

C.   stop moving across the membrane.

D.   continue to move across the membrane in both directions.

A.   active transport.

B.   pinocytosis.

C.   osmosis.

D.   osmotic pressure.

A.   impossible to tell

B.   stay the same size

C.   shrink

D.   swell

A.   Diffusion

B.   Osmosis

C.   Isotonic

D.   Solution

A.   Hypotonic

B.   Isotonic

C.   Homeostasis

D.   Hypertonic

A.   Concentration gradient

B.   Semi-permeable

C.   Osmosis

D.   Diffusion

A.   water moves out of the slug, causing dehydration

B.   water moves into the slug, causing it to swell

C.   salt moves out of the slug, depriving it of essential minerals

D.   salt moves into the slug, poisoning it

A.   a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids

B.   a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids

C.   a bilayer made of lipids with saturated 18 carbon-fatty acids

D.   a bilayer made of lipids with saturated 16 carbon-fatty acids

E.   All of the above are equivalent in fluidity.

A.   Carbohydrates

B.   lipids

C.   hydrophilic heads

D.   Proteins