Deck 10: Membranes and Membrane Transport

Question 1

Which of the following are the 2 major phospholipids on the outer leaflet of erythrocytes?

A)phosphatidylcholine and phosphatidylethanolamine
B)phosphatidylcholine and sphingomyelin
C)phosphatidylethanolamine and sphingomyelin
D)phosphatidylserine and sphingomyelin

Answer 1

B

Question 2

Which of the following mechanisms associates the Ras proteins to the membrane?

A)thioester-linked fatty acyl anchor
B)thioether-linked prenyl anchor
C)carboxy-terminal ester-linked prenyl anchor
D)insertion of a portion of an amphipathic helix into the membrane

Answer 2

B

Question 3

Which of the following structural motifs are utilized by the porin proteins?

A)single transmembrane a-helix
B)multiple transmembrane a-helices
C)single ?-sheet
D)multiple ?-sheet

Answer 3

multiple ?-sheet

Question 4

Which of the following is a feature of liposomes?

A)They can be prepared with only one type of phospholipid.
B)They are able to fuse with the nucleus.
C)They are used to introduce contrast agents into the body for diagnostic imaging procedures.
D)They are highly unstable structures.

Question 5

How do micelles differ from lipid bilayers?

A)They are self-limiting structures.
B)They form spontaneously.
C)They are stable in aqueous solution.
D)They often transform into vesicles.

Question 6

Which of the following properties of lipids allows them to spontaneously form micelles,monolayers,and bilayers?

A)polyisoprenoid nature
B)polar nature
C)amphipathic nature
D)bipolar nature

Question 7

Which of the following is NOT the responsibility of the plasma membrane?

A)energy transduction
B)signal transduction
C)allowing free passage of certain toxic ions and molecules into the cell
D)accumulation of cell nutrients

Question 8

In eukaryotic cells phospholipids,glycolipids,and cholesterol are synthesized by enzymes located in the endoplasmic reticulum a Golgi.Which of the following mediates the flow of these components to other membranes in the cell?

A)osmosis
B)flippases
C)plasma membrane content
D)lipid transfer proteins

Question 9

How are G protein-a-subunits anchored into membranes?

A)by amine-linked myristoyl anchors
B)by thioester-linked fatty acyl anchors
C)by amide-linked prenyl anchors
D)by thioester-linked prenyl anchors

Question 10

Which of the following is an example of a unilamellar vesicle?

A)a monolayer
B)a bilayer
C)a liposome
D)a micelle

Question 11

Which of the following terms represent 12-TMS?

A)12-trans-methyl synthase
B)12-tris-methyl sulfate
C)12-trans-model symmetry
D)12-transmembrane segments

Question 12

Which of the following regarding membrane function is correct?

A)A caveola contains a very high concentration of cholesterol and unsaturated phospholipids.
B)Scaffolding proteins,particularly those containing BAR domains,result in curvature of the cell membrane.
C)Lateral membrane diffusion within a biological membrane is a completely unrestricted process.
D)Membrane fusion with vesicles is often accomplished independently of a SNARE protein.

Question 13

Which of the following best describes asymmetrical biological membranes?

A)The proteins are not evenly distributed over the surface of the membrane.
B)Patches of cholesterol and other lipids occur on the surface of the membrane.
C)The lipids are evenly distributed transversely in the membrane.
D)Certain membrane proteins seem to prefer association with specific lipids.

Question 14

Which of the following is NOT a lipid-anchoring motif found to date?

A)glycine-linked myristoyl anchors
B)thioester-linked fatty acyl anchors
C)thioether-linked prenyl anchors
D)amide-linked myristoyl anchors

Question 15

Which of the following describes the energy and transport systems,respectively,associated with passive diffusion?

A)kinetically favoured;using a transport protein
B)kinetically favoured;without a specific transport system/molecule
C)thermodynamically favoured;using a transport protein
D)thermodynamically favoured;without a specific transport system/molecule

Question 16

Which of the following would be the most likely interaction between a membrane and a peripheral membrane protein that contained high lysine content?

A)ionic interaction
B)hydrophobic interaction
C)hydrogen bonding
D)covalent bonding

Question 17

Flippases are enzymes that flip cellular components.Which of the following best describes their mechanism of action?

A)flipping fatty acids from one position on glycerol to another position
B)flipping glucose from a- to b-glucose
C)flipping amino acids from one position to another in a protein
D)flipping phospholipids across to the other side of a membrane

Question 18

Which of the following is a property of integral membrane proteins?

A)They only have hydrophobic surfaces.
B)They have significant lateral mobility.
C)They remain in the membrane when treated with salt solutions.
D)They get exposed to one aqueous surface of the membrane.

Question 19

Which of the following is correct regarding the phase transitions of lipid bilayers?

A)Solutes interacting with membrane lipids affect transition temperatures.
B)The transitions are exothermic.
C)Pure phospholipid bilayers have wide transition ranges.
D)Functional group changes usually are associated with phase transitions.

Question 20

Which of the following is a feature of the membrane protein glycophorin?

A)multiple transmembrane segments
B)most of the mass oriented outside the surface of the cell
C)about 10% carbohydrate and 90% protein
D)transmembrane b-barrel segments

Question 21

Which of the following ions does the anion transporter of erythrocytes exchange HCO₃- for?

A)Cl-
B)HPO4-
C)Ca²⁺
D)H⁺

Question 22

Which of the following structure(s)sequester(s)nearly all the calcium ions in muscle?

A)mitochondria
B)sarcoplasmic reticulum
C)endoplasmic reticulum
D)secretory vesicles

Question 23

Which of the following describes secondary active transport?

A)establishment of a cation or anion gradient with an ATPase that subsequently drives transport of an amino acid or sugar against a concentration gradient
B)the use of an ATPase to establish an anion or cation gradient
C)the antiport process of transporting species in opposite directions
D)establishment of an ATP gradient across a membrane,which drives uptake of sugars

Question 24

H⁺-transporting ATPases are found in osteoclasts and break down bone during normal bone remodelling.Which of the following types of ATPases are they?

A)vacuolar (V-)
B)H⁺,K⁺-ATPase
C)H⁺,Na+-ATPase
D)Na+,K⁺-ATPase

Question 25

Which of the following is a characteristic for facilitated diffusion of neutral metabolites?

A)Lineweaver-Burk plots which pass through the origin
B)a linear plot when velocity is plotted versus the concentration of the metabolite
C)an upper limit in the transport velocity as the metabolite concentration increases
D)the ability to facilitate net movement against the thermodynamically favoured direction

Question 26

Which of the following fungal metabolites is a competitive inhibitor of facilitated diffusion glucose transport in erythrocytes?

A)amygdalin
B)cytochalasin B
C)dodecyl octa(oxyethylene)ether
D)glycophorin

Question 27

The system A,for alanine transport into liver,can be activated by alanine and hormones.Which of the following terms defines the transport mechanism of system A?

A)Na+ symport
B)K⁺ symport
C)H⁺ antiport
D)ATP antiport

Question 28

Ouabain is an effective inhibitor of Na⁺,K⁺-ATPase.Which of the following characteristics does it exhibit?

A)It binds tightly to the enzyme/ATP complex in producing the inhibition.
B)It contains an saturated lactone ring at C-17.
C)It binds on the intracellular surface of Na+,K⁺-ATPase.
D)It has a basic steroid structure.

Question 29

Which of the following is a characteristic of the gastric proton pump?

A)It is a H⁺,K⁺-ATPase.
B)It requires high levels of dietary K⁺ to create a K⁺ gradient.
C)It maintains a pH gradient of about 4.6 across the mucosal cell membrane.
D)It produces a net efflux of HCl into the stomach.

Question 30

Which of the following is NOT a similarity between muscle Ca²⁺-ATPase and Na⁺,K⁺-ATPase?

A)Both have residence on the sarcoplasmic reticulum.
B)Both form covalent E-P intermediates during ATP hydrolysis.
C)Both have similar mechanisms of ATP hydrolysis.
D)Both have similar ion transport mechanisms.

Question 31

What do hydropathy plots for transport proteins reveal?

A)amino acid residues that may be highly modified
B)amino acid residues that may be directly involved in facilitated transport
C)stretches of amino acid residues that make up hydrophobic regions,which may be directly associated with the lipid bilayer
D)amino acid residues that are hyperreactive due to their location

Question 32

In the Na⁺,K⁺-ATPase mechanism,which of the following processes does NOT involve ATP?

A)binding E2 to change conformation to E1 and release of K⁺
B)binding E1 to facilitate binding of Na+
C)transferring a phosphate group to make sodium phosphate
D)hydrolysis to ADP and E1-P

Question 33

Which of the following is a feature of melittin,a 26-residue peptide in honeybee venom?

A)It is a phospholipase that attacks red blood cells causing hemolysis.
B)It is toxic to Na+,K⁺-ATPase.
C)It forms a-helical aggregates with amphipathic character in membranes.
D)It discharges mitochondrial proton gradients and thus inhibits ATP synthesis.

Question 34

Yeast a-factor ATPase and MDR ATPase are 2 members of a superfamily of transport proteins.Which of the following do they both actively transport?

A)H⁺ to dissolve bone mineral
B)Ca²⁺ into the sarcoplasm
C)a broad group of diverse organic molecules across membranes
D)Mg²⁺ against a concentration gradient

Question 35

Which of the following does the tandem repeat protein multiple drug resistant (MDR)-ATPase use to actively transport a wide variety of drugs out of the cell?

A)GTP hydrolysis
B)calcium gradient
C)glucose gradient
D)ATP hydrolysis

Question 36

People with high blood pressure have high blood levels of an endogenous Na⁺,K⁺-ATPase inhibitor.Which of the following 2 ions accumulate in cells lining the blood vessel wall as a result of this?

A)magnesium and sodium
B)hydrogen and calcium
C)sodium and calcium
D)magnesium and calcium

Question 37

Bacteriorhodopsin affects a light-driven outward proton transport that results in a proton gradient.Which of the following processes can sufficiently be driven by this proton gradient?

A)Na+ import
B)ATP synthesis
C)K⁺ export
D)light emission

Question 38

Pore-forming toxins solve the problem of a need to provide hydrogen-bonding partners for the polypeptide background N-H and C=O groups in the bilayer that lacks hydrogen-bond donors and acceptors.Which of the following structure(s)do they use extensively to do this?

A)salt bridge formation
B)disulfide bond formation
C)b-turns
D)a-helices and b-sheets

Question 39

Which of the following is a unique characteristic of active transport?

A)transport of hydrophobic molecules
B)absolute requirement for ATP hydrolysis and light energy,or ion gradient energy will not work
C)transport of a molecule or ion across a membrane,with the species going from a greater concentration to a lesser concentration
D)the tight coupling of an input of energy to drive a thermodynamically unfavourable reaction

Question 40

Which of the following is a component of the Ca²⁺-ATPase?

A)transmembrane domain of 12 a-helical segments
B)an actuator domain
C)a large extracellular domain with nucleotide binding domain
D)a hydrolytic domain

Question 41

Which of the following variables influences transport by mobile carriers and pores (or channels)?

A)pH
B)ionic strength
C)proton gradient
D)temperature

Question 42

Ionophore antibiotics are small-molecule toxins produced by microorganisms to facilitate ion transport across membranes.Which of the following antibiotics is NOT an ionophore?

A)actinomycin
B)valinomycin
C)nonactin
D)monensin

Question 43

Which of the following does NOT directly affect the ability of gap junctions to allow cells to communicate metabolically?

A)pH changes
B)membrane potentials
C)intracellular calcium levels
D)DNA replication