Deck 9: Lipids and Membranes

Question 1

A deficiency in the synthesis of sphingomyelins or cerebrosides will most likely result in the improper formation of

A) cell surfaces.
B) cell to cell communication.
C) nerve cells.
D) blood groups.
E) All of the above

Answer 1

nerve cells.

Question 2

A fatty acid designated w-3

A) has three double bonds.
B) is saturated.
C) has a double bond three carbons from the end of the chain.
D) has a double bond three carbons from the a-carbon.

Answer 2

has a double bond three carbons from the end of the chain.

Question 3

Isoprenoids are lipids which neither contain nor are derived from fatty acids and include

A) steroids.
B) waxes.
C) terpenes.
D) A and C only
E) A, B, and C

Answer 3

A and C only

Question 4

Polar heads of glycerophospholipids may be

A) + charged.
B) - charged.
C) neutral.
D) a mixture of + and - charges, but not neutral.
E) All of the above

Question 5

An unknown lipid is treated with a mixture of phospholipases A₁, A₂, C and D. Since no glycerol is formed after this treatment, the lipid is most likely

A) phosphatidylethanolamine.
B) phosphatidylcholine.
C) plasmologen.
D) ceramide.
E) A mixture of A and B

Question 6

Fatty acids required in the diet of mammals are called

A) important.
B) dietary.
C) saturated.
D) essential.
E) esters.

Question 7

Cholesterol is converted to cholesteryl esters for in cells and are more, less) hydrophobic than glycerophospholipids.

A) transport; more
B) transport; less
C) storage; more
D) storage; less
E) synthesis; more

Question 8

Trans fatty acids have physical properties like those of

A) w-3 fatty acids.
B) cis-fatty acids.
C) unsaturated fatty acids.
D) saturated fatty acids.

Question 9

A fatty acid designated as 20:0 is , while one that is designated 20:3 D^5,8,11 is .

A) simple; complex
B) complex; simple
C) saturated; unsaturated
D) unsaturated; saturated
E) monounsaturated; polyunsaturated

Question 10

are the simplest lipids but they may be a part of or a source of many complex lipids.

A) Triglycerols
B) Carbohydrates
C) Terpenes
D) Fatty acids
E) Waxes

Question 11

Triacylglycerols are not found in cell membranes because they are

A) amphipathic.
B) not amphipathic.
C) not abundant in cells.
D) charged at biological pH.

Question 12

Like plasmologens, sphingolipids are found in relative abundance in

A) bacteria.
B) plant cells.
C) nerve cells.
D) intestinal cells.
E) All of the above

Question 13

Tay-Sachs disease results from

A) a deficiency of GM₂.
B) defective lysosomes.
C) malfunction of cerebroside metabolism.
D) the accumulation of GM₂.

Question 14

Most lipids in the average human diet are

A) unsaturated fatty acids.
B) saturated fatty acids.
C) glycerophospholipids.
D) triacylglycerols.

Question 15

Plasma levels of cholesterol and triglycerides are elevated by

A) margarines.
B) cis-fatty acids.
C) trans-fatty acids.
D) plant oils.

Question 16

Lipids may be either hydrophobic or .

A) hydrophilic
B) amphoteric
C) inorganic
D) amphipathic

Question 17

Dietary triacylglycerols are digested as a result of

A) lipase action.
B) bile salts.
C) micelle formation.
D) diffusion and absorption by intestinal cells.
E) All of the above

Question 18

Sterols are steroids which have

A) a hydroxyl group at position C-17.
B) a hydroxyl group at position C-3.
C) the ability to accumulate as plaques in blood vessels.
D) 5 fused rings instead of 4 fused rings.
E) hydroxyl groups at both position C-3 and C-17.

Question 19

Ethanolamine, serine and choline can be cleaved from glycerophospholipids by treatment with

A) phospholipase A₁.
B) phospholipase A₂.
C) phospholipase B.
D) phospholipase C.
E) phospholipase D.

Question 20

Adipocytes contain fat droplets which serve to provide an animal with

A) increased cell volume.
B) insulation.
C) chemical energy.
D) A and B above
E) B and C above

Question 21

Proteins can move from one layer to the other in a cell membrane bilayer by

A) lateral diffusion.
B) biosynthesis.
C) flippases and floppases.
D) increased diffusion.

Question 22

Lipid-anchored membrane proteins that link to an isoprenoid chain via the sulfur atom of cysteine are called proteins.

A) prenylated
B) sulfide-linked
C) cysteine-anchored
D) prostaglandins

Question 23

Which does not apply to the diffusion of O₂, CO₂ and small hydrophobic molecules across a membrane?

A) Diffusion is driven by the concentration gradient across the membrane.
B) The diffusion is spontaneous and there is a decrease in free energy as diffusion occurs.
C) The transport is saturatable.
D) Membrane proteins are not needed for the diffusion process.

Question 24

You have purified a cell membrane and wish to isolate a transport protein from it. Which treatment might you select?

A) Add a detergent.
B) Change the ionic strength.
C) React with a protease.
D) Add phenylisothiocyanate PITC).

Question 25

Regions on cell membranes called lipid rafts form because

A) membrane proteins form them.
B) cholesterol preferentially associates with sphingolipids.
C) certain membrane protein patches aggregate.
D) cholesterol and proteins bind to form them.

Question 26

In the mitochondria phosphate ion PO₄^3-) and H⁺ are transported together from the intermembrane space into the matrix. Which statement applies?

A) The transport protein is a symport.
B) The transport protein must have a relatively large central channel to accommodate both ions.
C) The interior of the transport protein must be uncharged.
D) All of the above

Question 27

Which type of membrane protein might be dissociated from the membrane by changing the pH or the ionic strength?

A) integral membrane protein
B) peripheral membrane protein
C) lipid-anchored membrane protein
D) All of the above

Question 28

Which statement is false about lipid rafts?

A) Membrane proteins help maintain the integrity of membrane rafts.
B) They are distributed non-uniformly on the mammal cell surfaces.
C) They occur mostly on the outer mitochondrial membrane.
D) They are patches of cholesterol associated with sphingolipids.

Question 29

The major groups of lipids can be separated by silicic acid column chromatography by eluting with

A) silicic acid.
B) acetone.
C) chloroform, acetone and methanol.
D) methanol.
E) acetone, methanol and water.

Question 30

Determination of the tertiary structure of a membrane protein finds that the outer surface is composed primarily of hydrophobic residues. Which conclusion is most likely from this observation?

A) It is a lipid-anchored membrane protein.
B) It is an integral protein.
C) The protein must be involved in passive transport.
D) The protein can undergo transverse diffusion.

Question 31

What is the role of cholesterol in animal cell membranes?

A) Blocks the association of the fatty acyl chains of phospholipids at high temperature.
B) Aids in the transport of small hydrophobic molecules across the membrane.
C) Is a receptor site for hormones on the surface of membranes.
D) Broadens the temperature range of optimum membrane fluidity.

Question 32

Why should it not be surprising that for many cells water requires a protein for its transport across a membrane?

A) Water is very polar which inhibits its free diffusion across the membrane.
B) All molecules require transport proteins to cross a membrane.
C) The transport protein is needed to prevent the hydrolysis of the phospholipid chains as water crosses the membrane.
D) There is never a concentration gradient for water across the membrane to drive its transport.

Question 33

Triacylglycerols cannot form lipid bilayers because they

A) have hydrophobic tails.
B) do not have polar heads.
C) cannot associate with cholesterol.
D) have polar heads.
E) cannot engage in hydrophobic interactions.

Question 34

When red-blood cells are treated extensively with protease most membrane proteins are broken down into small peptides. However, some proteins are very resistant to this treatment. If cleavage by protease is the only type of reaction that occurs in this treatment, how is this explained?

A) They are lipid-anchored membrane proteins.
B) They are peripheral proteins.
C) They contain at least 2 disulfide bonds.
D) They are integral intrinsic) membrane proteins.

Question 35

Facilitated diffusion passive transport) through a biological membrane is

A) generally irreversible.
B) driven by the ATP to ADP conversion.
C) driven by a concentration gradient.
D) endergonic.

Question 36

Which statement is false about lipid-anchored membrane proteins?

A) They are found only on the outer leaflet of the plasma membrane.
B) Like integral membrane proteins, they are permanently associated with the membrane.
C) The covalent link to the membrane involves the phosphate group of the lipid anchor.
D) The protein portion that can be removed by treatment with phospholipase most resembles an integral membrane protein.

Question 37

A sea creature richer in can more likely live or migrate to an area of low temperature.

A) arachidonic acid
B) unsaturated fatty acids
C) saturated fatty acids
D) eicosanoids
E) All of the above

Question 38

Which would you expect for the fatty acyl chains of the membrane phospholipids of bacteria grown at low temperature?

A) Proportion of unsaturated fatty acyl groups increases.
B) Proportion of unsaturated fatty acyl groups decreases.
C) No change in the proportion of saturated versus unsaturated acyl groups.
D) More cholesterol is produced and is inserted between the fatty acyl chains of the membrane.

Question 39

In a typical eukaryotic plasma membrane

A) oligosaccharides face outward, not toward the cytosol.
B) proteins can move in and out of the bilayer.
C) lipids can move and diffuse through the bilayer.
D) some lipids can rotate within the bilayer.
E) All of the above

Question 40

The arrangement of lipid bilayers and other components is the basis for the currently widely accepted description which is called the

A) fluid model.
B) lipid bilayer model.
C) mosaic model.
D) diffusion model.
E) fluid mosaic model.

Question 41

Fatty acids such as linolenate can assume a variety of steric configurations.

Question 42

Which is not a similarity between active transport proteins and enzymes?

A) Both undergo conformational changes upon binding a substrate.
B) Both are susceptible to inhibition.
C) Both cause chemical modification to the substrate.
D) Both can reach a saturation limit.

Question 43

All sphingolipids are derivatives of ceramide.

Question 44

Most bacteria do not have sphingolipids or steroids.

Question 45

If the concentration of a solute is the same both inside and outside the cell, what might you expect with regard to its transport by a membrane protein?

A) Since there is no concentration gradient, no transport either in or out of the cell is possible.
B) Movement of the solute across the membrane could occur and cause accumulated on one side of the membrane by an active transport protein.
C) The transport protein has been saturated.
D) The solute must be phosphorylated with a phosphate group from ATP before further transport can occur.

Question 46

Which is not involved in signal transduction?

A) glycolytic pathway
B) receptor tyrosine kinases
C) adenylyl cyclase pathway
D) inositol-phospholipid pathway

Question 47

The membrane transport protein Na⁺-K⁺ ATPase carries both Na⁺ and K⁺ ions across the plasma membrane. Typically the concentration of K⁺ inside cells is about 30 times higher inside the cell than outside. The concentration of Na⁺ is about 20 times less inside the cell than outside. Based on this information, which statement below is false?

A) The proper functioning of Na⁺-K⁺ ATPase could serve as an energy source for secondary active transport proteins.
B) It is a symport.
C) Transport of Na⁺ and K⁺ must be coupled to an exergonic reaction.
D) Na⁺-K⁺ ATPase likely undergoes conformational changes during transport.

Question 48

Lipids derived from cholesterol aid digestion and absorption of other lipids such as triacylglycerols.

Question 49

Which can serve as an energy source for secondary active transport?

A) light
B) ion concentration gradient
C) electron transport
D) ATP → ADP

Question 50

In the adenyl cyclase signaling pathway the second messengers) isare) .

A) ATP and GTP
B) protein kinase A
C) cyclic AMP or cyclic GMP
D) AMP

Question 51

Like bacteria, plants do not contain steroids.

Question 52

The toxins from cholera and whooping cough both interfere with the proper functioning of .

A) G proteins
B) DNA polymerase
C) ATP synthesis
D) protein kinase A

Question 53

In signal transduction what is an effector enzyme?

A) An integral membrane protein that changes conformation upon binding of a ligand to a cell surface receptor.
B) A small molecule that diffuses within a cell and carries a signal to its ultimate destination.
C) A protein bound on the interior of a cell membrane that generates a second messenger.
D) Protein bound on the exterior surface of a cell and is the receptor site for a ligand.

Question 54

Another name for facilitated diffusion is .

A) active transport
B) transverse diffusion
C) lateral diffusion
D) passive transport

Question 55

Triacylglycerols may have either a net positive charge or a net negative charge.

Question 56

Margarines made from plant oils are healthier, since they are hydrogenated for spreadability.

Question 57

Very large molecules macromolecules) can be transported across membranes by .

A) pores or channels with very large openings through the center
B) active transport proteins
C) diffusion down a concentration gradient
D) endocytosis or exocytosis

Question 58

Valinomycin is an antibiotic that kills bacteria by surrounding K⁺ ions and shuttling them down their concentration gradient and across membranes. Which might be a cause of cell death?

A) Disruption of secondary transport processes that depend on the K⁺ concentration gradient.
B) Change in the pH of the bacterial cytosol.
C) Blocking of bacterial pores with K⁺ ions.
D) Massive denaturation of bacterial proteins upon change of the K⁺ concentration.

Question 59

Which statement is not true about G proteins?

A) They are integral membrane proteins.
B) They are multisubunit proteins consisting of α, β and γ subunits.
C) They are slowly inactivated by their own GTPase activity.
D) They act as transducers for hormones.

Question 60

Which does not generally use a signal transduction mechanism?

A) hydrophilic hormones
B) neurotransmitters
C) growth factors
D) steroids

Question 61

The principle advantage of a cascade mechanism in signal transduction is that one molecule of a ligand can affect many intracellular proteins without crossing the plasma membrane.

Question 62

Secondary active transport involves the conversion of ATP to ADP.

Question 63

Bactoprenol synthesis is inhibited by the antibiotic bacitracin. Therefore, it can be used to treat yeast infections.

Question 64

Cholesterol accounts for 20% to 25% of the mass of lipids in a typical mammalian plasma membrane.

Question 65

Aspirin can alleviate clinical symptoms because it inhibits the synthesis of certain eicosanoids.

Question 66

Match each lipid with the appropriate function.
wax

Question 67

The constant K_tr is the concentration of the molecule being transported at which the transport protein is half-saturated.

Question 68

Vitamins A, E and K are all isoprenoids.

Question 69

Proteins that transport water across cell membranes are called aquaporins.

Question 70

The distribution of peripheral membrane proteins is generally identical on both sides of a given membrane.

Question 71

According to the current model of cell membrane structure, the two layers of lipids in the bilayer are nearly identical chemically.

Question 72

Match each lipid with the appropriate function.
thromboxane A₂

Question 73

Match each lipid with the appropriate function.
prostaglandin E₂

Question 74

Match each lipid with the appropriate function.
leukotriene D₄

Question 75

The membrane-spanning portion of a transmembrane protein is almost always a β-strand.

Question 76

Symport and antiport proteins must be active transport proteins.

Question 77

Transport of ions and small molecules through a bacterial membrane pore requires energy from an ATP to ADP conversion.

Question 78

The formation of a specialized lipid vesicle for the transport of a toxic protein out of a cell is called endocytosis.

Question 79

Match each lipid with the appropriate function.
bactoprenol

Question 80

The proportion of lipids to proteins is the same in different cell membranes.