Chapter 7 Flashcards


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1

1) Each of the following is a function of membranes except

A) defining cell and organelle boundaries.

B) sites for specific biochemical functions.

C) information storage.

D) regulation of transport.

E) cell–cell communication

C

2

2) Each of the following is a model for membrane structure except

A) Overton lipid coat.

B) Langmuir monolayer.

C) Gorter and Grendel bilayer.

D) Singer and Nicholson fluid mosaic.

E) Watson and Crick double helix

E

3

3) In response to temperature changes, cell membranes change state to become more solid or more fluid by undergoing

A) lipid raft formation.

B) membrane folding.

C) a phase transition.

D) transverse diffusion.

E) differential scanning calorimetry

C

4

4) When a mouse cell and a human cell with different cell-surface protein markers are fused using polyethylene glycol (PEG) and immediately placed at 0°C, what would you expect happens to the mouse and human marker proteins?

A) Both the mouse and human marker proteins will rapidly disperse evenly throughout the fused membrane.

B) Only the mouse cell marker proteins will disperse throughout the fused membrane; the humanmarker proteins will remain confined to the original human region of the fused membrane.

C) The mouse and human markers will migrate to opposite poles of the fused membrane.

D) The mouse and human markers will migrate little and remain confined to their original membrane regions.

E) Both mouse and human markers will be endocytosed by the fused cell and destroyed in the fused cell

D

5

5) Of the following molecules, which would you predict diffuses most readily across membranes?

A) water

B) glucose

C) oxygen

D) serine

E) hydrogen ions

C

6

6) Which of the following molecules enters kidney cells via a specific transporter?

A) water

B) carbon dioxide gas

C) cholesterol

D) ethanol

E) oxygen

A

7

7) Each of the following is a type of cell–cell junctions except

A) adhesive.

B) tight.

C) gap.

D) plasmodesmata.

E) All are cell–cell junctions.

E

8

8) When examining an electron micrograph of cells obtained from a new deep-sea life-form, you notice that the plasma membranes appear as two dark lines separated by a lightly stained region. Which of the following investigator(s) used a similar observation as the basis for a model of membrane structure?

A) Robertson

B) Gorter and Grendel

C) Unwin and Henderson

D) Overton

E) Singer and Nicolson

A

9

9) Which of the following proposed the "sandwich" model of membranes, in which lipid bilayersare coated on both sides with thin sheets of proteins?

A) Overton

B) Langmuir

C) Gorter and Grendel

D) Davson and Danielli

E) Robertson

D

10

10) The composition of lipids in the outer and inner monolayers of cell membrane lipid bilayers is

A) asymmetrical; i.e., different in each monolayer.

B) identical in each monolayer.

C) twice as concentrated in the inner monolayer as in the outer monolayer.

D) highly random for each monolayer.

E) the same for all cell plasma membranes but different from the composition in mitochondrial and chloroplast membranes.

A

11

11) The most prominent lipids in animal cell membranes are

A) phospholipids

B) glycolipids.

C) cholesterol.

D) phytosterol.

E) cerebrosides

A

12

12) Which of the following types of organisms contain sphingomyelin in cell membranes?

A) prokaryotes

B) algae

C) animals

D) yeast

E) plants

C

13

13) Which of the following lipids would you expect to find associated with chloroplast membranes?

A) phosphatidylserine

B) glycosphingolipid

C) monogalactosyldiacylglycerol

D) galactocerebroside

E) hopanoids

C

14

14) Which of the following lipids is found concentrated in lipid rafts in animal cell plasma membranes?

A) cholesterol

B) phosphatidylcholine

C) phosphatidylserine

D) phophatidylethanolamine

E) phosphatidylinositol

A

15

15) Which of the following would you expect to find predominating in the plasma membrane of a unicellular eukaryotic organism thriving in glacier ice?

A) 20 carbon long saturated fatty acids.

B) 18 carbon long saturated fatty acids.

C) 20 carbon long fatty acids with 1 double bond.

D) 18 carbon long fatty acids with 1 double bond.

E) 16 carbon long fatty acids with 3 double bonds

E

16

16) Cholesterol

A) is found in abundance in prokaryotic cell membranes.

B) buffers membrane fluidity by increasing fluidity at low temperature and decreasing fluidity at high temperature.

C) increases permeability for Ca2+.

D) increases permeability for small polar molecules.

E) All of the above are correct

B

17

17) Which of the following would be the most thermodynamically unfavorable membrane lipid activity in a membrane?

A) lateral diffusion

B) transverse diffusion

C) association with a neighboring lipid

D) association with cholesterol

E) rotation

B

18

18) Each of the following is typical characteristics of an integral membrane protein transmembrane segment except

A) α-helical structure.

B) 20–30 amino acids long.

C) composed primarily of hydrophobic amino acids.

D) amphipathic.

E) All are characteristics of a typical transmembrane segment.

D

19

19) Each of the following is true about homeoviscous adaptation in membranes except

A) maintains membrane viscosity despite changes in environmental temperature.

B) may decrease the average length of membrane lipid fatty acid tails.

C) may increase the unsaturation of membrane lipid fatty acid tails.

D) occurs primarily in homeothermic (warm-blooded) organisms and only rarely in poikilothermic (cold-blooded) organisms.

E) may increase the proportion of cholesterol in animal cell membranes.

D

20

20) Using a laser beam to inactivate fluorescence dye molecules connected to proteins or lipids on a cell membrane is called

A) liposome formation.

B) electrophoresis.

C) photobleaching.

D) freeze-fracturing.

E) affinity labeling.

C

21

21) Predict which of the following lipid characteristics would be most important to form the best liposomes for delivering a drug into a cell.

A) It contains a carbon ring structure similar to that in cholesterol.

B) It is linked to mannose

C) It is short and polar like glycerol.

D) It is amphipathic.

E) It has three fatty acid chains like a triglyceride.

D

22

22) Hopanoids are

A) found exclusively in yeast.

B) related to cholesterol.

C) a type of glycolipid.

D) a type of phospholipid.

E) All of the above are correct.

B

23

23) The most common number of carbons in fatty acid hydrocarbon chains of membrane phospholipids is

A) 7.

B) 10.

C) 16.

D) 19.

E) 24.

C

24

24) Which of the following is a sterol-like lipid associated with plant cell membranes?

A) stearate

B) phytosterol

C) linoleate

D) palmitate

E) hopanoids

B

25

25) E. coli uses which of the following enzymes to regulate membrane fluidity?

A) glucose-6-phosphatase

B) desaturase

C) fatty acid convertase

D) gangliosidase

E) kinase

B

26

26) Lipid rafts are associated with which of the following activities?

A) responding to extracellular signals

B) transport of nutrients across cell membranes

C) immune responses

D) transport of cholera toxin into cells

E) All of the above are correct

E

27

27) Which of the following diseases results from impaired glycosphingolipid degradation?

A) heart disease

B) glycosphingolipid anemia

C) metabolic syndrome

D) erythrocyte spherocytosis

E) Tay-Sachs disease

E

28

28) The technique that separates denatured proteins based on size is

A) SDS-PAGE.

B) FRAP.

C) thin-layer chromatography.

D) Western blotting.

E) freeze-fracture microscopy.

A

29

29) Starting with shredded spinach leaves, you follow a procedure that separates cellular organelles into different fractions. To identify the fraction that contains the mitochondria, you should test for the presence of

A) aquaporin.

B) insulin receptors.

C) phospholipids present only in the mitochondrial outer membrane.

D) mitochondrial wall polysaccharides.

E) electron transport proteins.

E

30

30) Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength?

A) GPI-anchored protein

B) fatty acid-anchored protein

C) integral protein

D) peripheral protein

E) glycosylated integral protein

D

31

31) A colleague gives you two tubes containing membrane fractions from an animal cell lysate. One tube contains the plasma membrane fraction, and the other tube contains the mitochondrial inner membrane fraction, but the tubes are not labeled. When you analyze the macromolecule composition of the samples, you are confident that the second tube contains the mitochondrial fraction, because the sample has

A) a higher ratio of cholesterol to phospholipids.

B) a higher protein to lipid ratio.

C) a lower protein to lipid ratio.

D) more carbohydrate in glycoproteins.

E) more GPI-anchored proteins.

B

32

32) Which of the following would best detect a specific carbohydrate sugar on a glycoprotein?

A) thin-layer chromatography

B) freeze-fracture microscopy

C) photobleaching

D) ferritin-conjugated lectins

E) SDS-PAGE

D

33

33) Localized regions of plasma membranes that contain cholesterol and proteins involved in cellsignaling are known as

A) gap junctions.

B) arterial plaques.

C) cadherin junctions.

D) lipid rafts.

E) plasmodesmata.

D

34

34) The number and location of transmembrane segments in an integral membrane protein can beinferred from the amino acid sequence of the protein by a computer-generated

A) Western blot.

B) DNA sequence.

C) freeze-fracture replica.

D) hydropathy plot.

E) prediction of glycosylation sites.

D

35

35) Cell–cell communication in plants takes place via specialized structures called

A) plasmodesmata.

B) chloroplast outer membrane pores.

C) gap junctions.

D) lipid rafts.

E) connexons.

A

36

36) Which of the following would best be used to determine the lipid content of an isolated membrane fraction?

A) freeze-fracture analysis

B) thin-layer chromatography

C) SDS-PAGE

D) ferretin-linked antibodies

E) Western blot analysis

B

37

37) FRAP has revealed that some proteins move in cell membranes much slower than they move in reconstituted liposomes. Which of the following could account for limited mobility of proteinsin cell plasma membranes?

A) association with other proteins in a large complex.

B) association with lipid rafts.

C) anchorage to the extracellular matrix.

D) anchorage to the cell cytoskeleton.

E) All could limit protein mobility.

E

38

38) Naturally occurring unsaturated fatty acids typically

A) are highly branched.

B) are omega-3 fatty acids.

C) contain double bonds primarily in the trans configuration.

D) contain double bonds primarily in the cis configuration.

E) contain an odd number of carbon atoms.

D

39

39) Each of the following contributes to the system providing structural support to the erythrocyte plasma membrane except

A) the peripheral protein spectrin.

B) the integral protein glycophorin.

C) the peripheral protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

D) the peripheral protein ankyrin.

E) short actin filaments.

C

40

40) Which of the following is true about glycosylated plasma membrane proteins?

A) Carbohydrate is added only after the protein is in the plasma membrane.

B) The carbohydrate usually is one sugar and rarely more than 5 sugars long.

C) Only one specific site is glycosylated on each protein.

D) N-linked carbohydrates are linked to hydroxyl groups in protein R groups.

E) The carbohydrates can be detected experimentally with ferretin-linked lectins.

E

41

41) Individuals with the O blood group are known as universal donors because the Gal and GlcNAc groups that are recognized by the antibodies in A, B, and AB in other individuals are missing. Which of which of the following types of erythrocyte plasma membrane components lacks these GlcNAc groups?

A) a glycoprotein

B) a glycolipid

C) glycophorin

D) a GPI-anchored protein

E) a glycocalyx protein

B