A.   are generally noncovalently bound to membrane lipids

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

C.   penetrate deeply into the lipid bilayer

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

A.   a buffer

B.   a solution containing detergent

C.   a solution of high ionic strength

D.   hot water

E.   a chelating agent that removes divalent cations

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

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

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

D.   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.

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

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

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

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

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

A.   an increase in fatty acyl chain length.

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

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

D.   a decrease in temperature.

A.   increasing its metabolic rate to generate more heat.

B.   shifting from aerobic to anaerobic metabolism.

C.   synthesizing thicker membranes to insulate the cell.

D.   putting more unsaturated fatty acids into its membranes.

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

A.   endergonic

B.   not specific with respect to the substrate

C.   driven by a difference of solute concentration

D.   generally irreversible

E.   driven by ATP

A.   secondary active transport

B.   simple diffusion

C.   primary active transport

D.   passive transport

E.   facilitated diffusion

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

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

C.   An entropy increase powers diffusion across the membrane.

D.   The outside surface of a beta barrel is hydrophylic

A.   osmosis

B.   None of the choices are correct

C.   facilitated diffusion

D.   diffusion

E.   active transport

A.   reducer

B.   transporter

C.   pump

D.   diffuser

E.   oxidizer

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.   Concentrated solutes

B.   Carrier proteins

C.   Water

D.   Energy

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

B.   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.

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.   amphipathic nature

B.   None of the answers is correct.

C.   bilayer

D.   asymmetry

E.   selective permeability

A.   asymmetric longitudinal flipping

B.   lateral diffusion

C.   kinesin-mediated movement

D.   translocation

E.   flip-flopping

A.   cholesterol

B.   integral membrane proteins in contact with the cytoplasm

C.   glycolipids

D.   lipid-linked proteins

A.   lipids and proteins

B.   None of the answers is correct.

C.   carbohydrates

D.   All of the answers are correct

A.   varying thickness, depending on structure

B.   two

C.   infinite

D.   None of the answers is correct.

E.   one

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

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

C.   a bilayer made of lipids with saturated 16 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 intracellular side of the membrane.

B.   positioned equally on both sides of the membrane.

C.   positioned on the extracellular side of the membrane.

D.   positioned on the inside center of the bilayer.

E.   also covalently attached to membrane proteins

A.   unsaturated fatty acids.

B.   free fatty acids.

C.   lipids that contain sphingosine.

D.   glycolipids

A.   Passage through ion channels

B.   facilitated diffusion

C.   Active transport

D.   Diffusion through a uniport

A.   membrane melting temperatures.

B.   membrane fluidity

C.   membrane fluidity and membrane melting temperatures.

D.   membrane asymmetry

E.   All of the answers are correct.

A.   ATP

B.   proteins

C.   None of the answers is correct.

D.   magnesium ions

E.   cholesterol

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

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

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

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

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

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

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

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

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

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

A.   Cell membranes maintain the shape of cells.

B.   Cell membranes are impermeable to most molecules.

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 can diffuse through a cell membrane along a concentration gradient.

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

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

A.   poor alignment of the fatty acids tails

B.   steroid lipids at certain temperatures

C.   cholesterol at certain temperatures

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

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.   Pump

B.   Facilitated diffusion

C.   Simple diffusion

D.   Symport

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

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

C.   stop moving across the membrane.

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

A.   osmosis.

B.   active transport.

C.   osmotic pressure.

D.   pinocytosis.

A.   shrink

B.   stay the same size

C.   swell

D.   impossible to tell

A.   Osmosis

B.   Isotonic

C.   Solution

D.   Diffusion

A.   Homeostasis

B.   Hypertonic

C.   Hypotonic

D.   Isotonic

A.   Semi-permeable

B.   Osmosis

C.   Concentration gradient

D.   Diffusion

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

B.   salt moves into the slug, poisoning it

C.   water moves out of the slug, causing dehydration

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

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

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

C.   a bilayer made of lipids with saturated 16 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.   Proteins

B.   Carbohydrates

C.   hydrophilic heads

D.   lipids