Deck 10: Lipids, Membranes and Cellular Transport

Question 1

What alcohol containing a quaternary amine is commonly found esterified to glycerophospholipids?

A)ethanolamine
B)choline
C)serine
D)inositol
E)cholesterol

Answer 1

B

Question 2

The movement of potassium ions across a membrane aided by valinomycin is an example of _______________.

A)facilitated diffusion by transport through a pore
B)facilitated diffusion by transport using a carrier molecule
C)facilitated diffusion by use of a permease
D)primary active transport since valinomycin is a sodium-potassium ATPase
E)secondary active transport since valinomycin only moves with the aid of the sodium ion gradient

Answer 2

B

Question 3

The transient association of lipid rafts is thought to play a significant role in which of the following?

A)cell signaling
B)bacterial entry into host cells
C)protein trafficking
D)membrane receptor dimerization
E)all of the above

Answer 3

E

Question 4

The fatty acid designated 18:2c $\Delta$ 9,12 is best described as a _______ fatty acid.

A)saturated
B)unsaturated
C)polyunsaturated
D)hydrogenated
E)partially hydrogenated

Question 5

A ceramide is derived from which combination of the following?

A)a molecule of sphingosine and a monosaccharide
B)a molecule of sphingosine and a molecule of phosphocholine
C)a molecule of sphingosine and a fatty acid
D)a molecule of sphingosine and two fatty acids
E)a molecule of sphingosine, a fatty acid and a monosaccharide

Question 6

Which of the following would most likely move across a membrane by simple diffusion?

A)potassium ions
B)glucose
C)carbon dioxide
D)sodium ions
E)water

Question 7

In animals, the bulk of energy is stored as __________.

A)fatty acids
B)triacylglycerols
C)glycogen
D)waxes
E)glycerophospholipids

Question 8

Partial hydrogenation accomplishes which of the following?

A)prevents oxidative cleavage of carbon-carbon double bonds, thus preventing spoilage of fats
B)raises the melting point of fatty acids
C)converts cis double bonds to trans double bonds
D)converts oils into fats
E)all of the above

Question 9

Which of the following would be considered an $\omega$ -3 fatty acid?

A)linoleic acid: 9,12-octadecadieneoic acid (18:2c $\Delta$ 9,12)
B)eicosapentaenoic acid: 5,8,11,14,17-eicosapentaenoic acid (20:5c $\Delta$ 5,8,11,14,17)
C) $\gamma$ -linolenic acid: 6,9,12-octadecatrieneoic acid (18:3c $\Delta$ 6,9,12)
D)arachidonic acid: 5,8,11,14-eicosatetraenoic acid (20:4c $\Delta$ 5,8,11,14)
E)all of the above

Question 10

Which of the following is a common mechanism for the covalent attachment of a lipid to a peripheral membrane protein?

A)addition of a geranylgeranyl group to the hydroxyl of serine, forming an ether
B)addition of a farnesyl group to the thiol of cysteine, forming a thioether
C)addition of a myristoyl group to the amine of lysine, forming an amide
D)reaction of the amine group of phosphatidylethanolamine with the carboxylate of glutamic acid, forming an amide
E)all of the above

Question 11

When comparing the sequences of a peripheral membrane protein with an integral membrane protein, which of the following amino acids would most likely be present in a higher percentage in the integral membrane protein?

A)aspartic acid
B)leucine
C)histidine
D)serine
E)none of the above

Question 12

Movement of ions across a cell membrane by the Na/K ATPase is best described as ________.

A)sodium moved outside to inside, potassium inside to outside
B)sodium moved inside to outside, potassium outside to inside
C)sodium moved inside to outside, potassium inside to outside
D)sodium moved outside to inside, potassium outside to inside
E)none of the above

Question 13

Addition of a functional group to the pro-R carbon of glycerol places that group on carbon _____ while addition of a second functional group to the pro-S carbon of glycerol places the second group on carbon _____ of sn-glycerol.

A)1; 2
B)1; 3
C)3; 2
D)3; 1
E)2; 2

Question 14

Which of the following is correctly defined?

A)sphingomyelin: ceramide + choline
B)glycoglycerolipid: glycerol + fatty acid + monosaccharide + phosphate
C)cerebroside: ceramide + monosaccharide
D)ganglioside: sphingomyelin + oligosaccharide
E)none of the above

Question 15

A flippase is an enzyme that moves lipids from one side of a lipid bilayer to another in order to maintain the concentrations of specific lipids on each side of the bilayer. Which of the following can be said regarding the reaction of the flippase enzyme?

A)it works against a concentration gradient and requires ATP
B)it works against a concentration gradient but does not require ATP
C)it works with a concentration gradient and requires ATP
D)it works with a concentration gradient but does not require ATP
E)none of the above

Question 16

Which of the following does not specifically cause a membrane to be more rigid or fluid, but rather causes the T_m to occur over a greater range?

A)increasing the content of unsaturated fatty acids
B)raising the temperature
C)increasing the cholesterol content
D)decreasing the phosphatidylcholine content while increasing the phosphatidylethanolamine content
E)all of the above

Question 17

Fatty acids are _______ meaning that they have both a hydrophobic and hydrophilic region of the molecule

A)aliphatic
B)amphipathic
C)saturated
D)unsaturated
E)phosphorylated

Question 18

Which of the following is used to drive glucose uptake by intestinal epithelial cells?

A)potassium gradient across the blood vessel/epithelial cell membrane
B)potassium gradient across the intestinal lumen/epithelial cell membrane
C)sodium gradient across the blood vessel/epithelial cell membrane
D)sodium gradient across the intestinal lumen/epithelial cell membrane
E)none of the above

Question 19

When fatty acids are added to an aqueous solution, they can either sit on top of the solution, forming a ________ or form spherical ________ throughout the solution.

A)monolayer; micelles
B)bilayer; micelles
C)monolayer; bilayer
D)bilayer; monolayer
E)micelle; bilayer

Question 20

The sequence of glycophorin A displays which of the following?

A)the N-terminal domain contains large amounts of hydrophobic amino acids indicating only the N-terminus is embedded in the membrane
B)the C-terminal domain contains a high concentration of Ser and Thr for attachment of O-linked oligosaccharides
C)both the N-terminal and C-terminal domains contain high concentrations of Ser and Thr for attachment of O-linked oligosaccharides
D)the middle portion contains large amounts of hydrophobic amino acids indicating a transmembrane protein
E)none of the above

Question 21

Which of the following mechanisms of membrane transport is correctly defined?

A)simple diffusion: uses concentration gradient to move highly polar molecules and ions across membranes
B)facilitated diffusion: uses proteins such as ion channels to move substances against their concentration gradient across a membrane
C)primary active transport: uses ATP hydrolysis to move ions against their concentration gradient across a membrane
D)secondary active transport: uses ATP hydrolysis along with an ion gradient to move polar molecules or ions against their concentration gradient across a membrane
E)all of the above

Question 22

Draw a molecule of phosphatidylserine with palmitic acid (16:0)and oleic acid (18:1c $\Delta$ 9)present. Make sure to put the saturated and unsaturated fatty acids in their proper location.

Question 23

Given the following concentrations (in mM)for sodium and potassium ions, a membrane potential of 60 mV (inside negative), a temperature of 37 ^$\circ$ C and a $\Delta$ G for ATP hydrolysis of -51 kJ/mol, what is the % efficiency of the Na/K ATPase?
inside
outside
Na⁺
12
145
K⁺
140
4

Question 24

Draw the following fatty acid: 18:3c $\Delta$ 9,12,15 as it would appear at physiological pH. With reference to the omega carbon, what type of fatty acid is this? Draw the result if this fatty acid underwent partial hydrogenation to produce 18:1t $\Delta$ 11

Question 25

Which of the following correctly relates the status of the sodium channel during an action potential cycle? (m-gate = activation gate, h-gate = inactivation gate)

A)while resting, both the m-gate and h-gate are closed
B)during depolarization, both the m-gate and h-gate open allowing Na⁺ to exit the cell
C)during repolarization, only the m-gate is closed
D)during the refractory period, both the m-gate and h-gate are closed
E)none of the above