Cell bio ch. 7 Flashcards

Which of the following is NOT a function or a characteristic of biological membranes?

A. Membranes provide a means of cell-to-cell communication.

B. Lipid polymers are major constituents of membrane structure.

C. Membranes contain receptors for the detection of external signals.

D. Membranes regulate the movement of substances into and out of the cell.

A scientist is investigating the properties of two different biological membranes that have different amounts of cholesterol in them. Which of the following would accurately describe the membrane that has more cholesterol compared to the membrane with less cholesterol in it?

A. The two membranes will have the same degree of fluidity at all temperatures.

B. The membrane with more cholesterol will have increased fluidity at all temperatures compared to the membrane with less cholesterol.

C. The membrane with more cholesterol will have decreased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

D. The membrane with more cholesterol will have increased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

A multipass transmembrane protein with eight transmembrane alpha-helical segments will have __________.

A. the amino- and carboxyl-termini on different sides of the membrane

B. the amino- and carboxyl-termini will be randomly distributed across the membrane

C. the amino- and carboxyl-termini on the same side of the membrane

D. the amino- and carboxyl-termini will be buried within the hydrophobic core of the membrane

Which of the following is not a function of membranes?

A. compartmentalization

B. cell-cell communication

C. regulation of transport

D. information storage

E. define cell boundaries

Match the membrane lipid group with the correct type of membrane lipid.

1. Phospholipids

2. Glycolipids

3. Sterols

triglycerides

phosphoglycerides

24-carbon fatty acids

cerebrosides

cholesterol

Which of the following molecules would not readily cross an intact cell membrane by simple diffusion?

A. ethanol

B. oxygen

C. fatty acids

D. water

E. glucose

With regard to the semipermeable nature of the plasma membrane, which of the following would readily cross without the aid of a transport protein?

A. DNA

B. glucose

C. calcium ions

D. amino acids

E. water

With respect to the outer and inner faces of the lipid bilayer of the cell membrane, the composition of lipids is

A. asymmetrical.

B. highly random and varies throughout the cell.

C. a mirror image.

D. not identical but symmetrical.

E. identical.

Based on the composition of cell membranes, the most prominent lipids are

A. glycolipids.

B. cerebrosides.

C. cholesterol.

D. phytosterol.

E. phospholipids.

Of the following lipids, which is found in approximately equal amounts in both the outer and inner portions of the lipid bilayer?

A. phosphatidylserine

B. glycolipid

C. cholesterol

D. phophatidylethanolamine

E. phophatidylinositol

A prokaryotic organism is isolated from a glacier, where it was thriving. Based on your knowledge of the plasma membrane, you would expect to find a predominance of

A. largely unsaturated fatty acids.

B. largely saturated fatty acids.

C. cell wall to define the cell because the cell membrane would not be present.

D. equal amounts of saturated and unsaturated fatty acids, as long as the chain was close to 12 carbons in length.

E. none of the above

Based on your knowledge of the chemistry of the cell membrane, which of the following compounds would you couple with a new drug in order to achieve better uptake by cells?

A. any hydrophilic substance

B. several mannose-6-phosphate monomers

C. lipids

D. carbohydrates

E. polar amino acids

Cholesterol

A. is found only in plants.

B. is found in abundance in prokaryotic cell membranes.

C. destabilizes the cell membrane.

D. intercalates between the fatty acid chains within the bilayer.

E. increases permeability for small cations.

Where would you expect to find an organism possessing a cell membrane composed of large proportions of cholesterol and a predominance of unsaturated fatty acids?

A. frozen wastelands

B. temperate regions

C. tropical region

D. supper levels of an aquatic environment

E. equatorial regions

A prokaryotic organism is isolated from a hydrothermal vent, where it has been observed to be thriving. Based on your knowledge of the plasma membrane, you would expect to find a predominance of

A. polar fatty acids.

B. largely unsaturated fatty acids.

C. equal amounts of saturated and unsaturated fatty acids, as long as the chain was close to 12 carbons in length.

D. largely saturated fatty acids.

E. none of the above

Inactivation of a fluorescent dye in a very concentrated spot on a cell so that the fluidity of membranes can be visualized is called

A. the freeze-fracture technique.

B. ferritin-conjugated lectins.

C. liposome formation.

D. photobleaching.

E. SDS-PAGE.

You are experimenting with a variety of lipids to determine their efficacy for use as drug delivery system liposomes. What is one feature of the individual lipid that would best ensure the use of a lipid for this purpose?

A. It should be exclusively hydrophilic.

B. It should be amphipathic

C. It should be exclusively hydrophobic.

D. It must be composed entirely of unsaturated fatty acids.

E. It must have a structure similar to cholesterol.

Hopanoids

A. are related to cholesterol.

B. are a type of glycolipid.

C. are a type of phospholipid.

D. are found in eukaryotes only.

E. all of the above

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

A. 10.

B. 24.

C. 16.

D. 19.

E. 7.

Which of the following is a sterol-like lipid associated with the cell membrane of prokaryotes?

A. hopanoids

B. linoleate

C. palmitate

D. phytosterol

E. stearate

Lipid rafts have been associated with which of the following?

A. immune responses

B. transport of cholera toxin into cells

C. transport of nutrients across cell membranes

D. responses to extracellular signals

E. all of the above

Which of the following disorders is the result of impaired glycosphingolipid metabolism?

A. leprosy

B. polydactyly

C. tuberculosis

D. Tay-Sachs disease

E. glycosphingolipid anemia

The technique that allows various proteins to be differentiated based on size, once the proteins have been denatured, is

A. photobleaching.

B. SDS-PAGE.

C. ferritin-conjugated lectins.

D. the freeze-fracture technique.

E. liposome formation.

Starting with shredded spinach leaves, you follow a procedure that allows for separation of cellular organelles. You are specifically looking for the fraction that contains the mitochondria. To identify this fraction, you should test for the

A. polysaccharides that specifically surround the mitochondria.

B. phospholipids unique to the mitochondrial membrane.

C. presence of enzymes associated with cellular respiration.

D. phospholipids unique to intracellular membranes.

E. general presence of enzymes that fix carbon.

With respect to the outer and inner faces of the lipid bilayer of the cell membrane, the composition of proteins is

A. a mirror image.

B. identical.

C. not identical but symmetrical.

D. highly random and varies throughout the cell.

E. asymmetrical.

A colleague gives you two membrane fractions from a plant cell lysate. One contains the plasma membrane fraction, the other the mitochondrial fraction. The tubes are not labeled, but you run the samples anyway, looking at the macromolecule composition of the samples. You know for certain that the second sample contains the mitochondrial fraction simply because it contains insignificant amounts of

A. protein.

B. specifically phospholipids.

C. lipids.

D. carbohydrates.

E. phospholipids and carbohydrates.

A means of detecting the presence of specific carbohydrate moieties on glycoproteins is

A. ferritin-conjugated lectins.

B. SDS-PAGE.

C. photobleaching.

D. liposome formation.

E. the freeze-fracture technique.

Many integral membrane proteins have not been analyzed by X-ray crystallography. However, transmembrane segments can be inferred using computer analysis of the amino acid sequence of the protein. This technique is known as

A. lipid analysis.

B. homeoviscous adaptation.

C. lipid rafting.

D. hydropathic analysis.

E. SDS-PAGE.

Cell-cell communication in plants takes place via specialized structures called

A. connexons.

B. cell wall pores.

C. plasmodesmata.

D. desmids.

E. gap junctions.

The likely number of and locations of transmembrane segments of integral membrane proteins is inferred by

A. affinity labeling.

B. X-ray crystallography.

C. western blot.

D. hydropathic analysis.

E. SDS-PAGE

Naturally occurring fatty acids are typically

A. saturated.

B. in the trans configuration.

C. unsaturated.

D. in the cis configuration.

E. comprised of an odd number of carbon atoms.

Each of the following is a function of membranes except

A. defining cell and organelle boundaries.

B regulation of transport.

C. cell - cell communication.

D. sites for specific biochemical functions.

E. information storage.

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

A. hydrogen ions

B. glucose

C. serine

D. oxygen

E. water

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

A. carbon dioxide gas

B. water

C. ethanol

D. oxygen

E. cholesterol

For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C based on the stated reasoning.

initial decrease in membrane fluidity

A. This is unlikely because membrane fluidity increases as the temperature is lowered.

B. This is unlikely because membrane fluidity decreases as the temperature is lowered.

C. This is likely because membrane fluidity increases as the temperature is lowered.

D. This is likely because membrane fluidity decreases as the temperature is lowered.

For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C based on the stated reasoning.

gradual replacement of shorter-chain fatty acids by longer-chain fatty acids in the membrane phospholipids

A. This is unlikely because longer-chain fatty acids decrease membrane fluidity.

B. This is unlikely because longer-chain fatty acids increase membrane fluidity.

C. This is likely because longer-chain fatty acids increase membrane fluidity.

D. This is likely because longer-chain fatty acids decrease membrane fluidity.

For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C based on the stated reasoning.

gradual replacement of stearate by oleate in the membrane phospholipids

A. This is unlikely because unsaturated fatty acids (oleate) will decrease membrane fluidity.

B. This is likely because unsaturated fatty acids (oleate) will increase membrane fluidity.

C. This is likely because saturated fatty acids (oleate) will increase membrane fluidity.

D. This is unlikely because saturated fatty acids (oleate) will decrease membrane fluidity.

For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C based on the stated reasoning.

enhanced rate of synthesis of unsaturated fatty acids

A. This is likely because unsaturated fatty acids will decrease membrane fluidity.

B. This is unlikely because unsaturated fatty acids will decrease membrane fluidity.

C. This is unlikely because unsaturated fatty acids will increase membrane fluidity.

D. This is likely because unsaturated fatty acids will increase membrane fluidity.

For each given statement, choose an accurate response that is either likely or unlikely to be seen when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C based on the stated reasoning.

incorporation of more cholesterol into the membrane

A. This is unlikely because bacteria do not contain cholesterol under any conditions.

B. This is likely because cholesterol will decrease membrane fluidity.

C. This is likely because cholesterol will increase membrane fluidity.

D. This is unlikely because cholesterol will disolve membrane phospholipids.

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

A. twice as concentrated in the inner monolayer as in the outer monolayer..

B. highly random for each monolayer.

C. identical in each monolayer.

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

E. asymmetrical; i.e., different in each monolayer.

The most prominent lipids in animal cell membranes are

A. cerebrosides.

B. phytosterol.

C. phospholipids.

D. glycolipids.

E. cholesterol.

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

A. yeast

B. prokaryotes

C. animals

D. algae

E. plants

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

A. 18 carbon long saturated fatty acids.

B. 20 carbon long saturated fatty acids.

C. 18 carbon long fatty acids with 1 double bond.

D. 20 carbon long fatty acids with 1 double bond.

E. 16 carbon long fatty acids with 3 double bonds

Cholesterol

A. increases permeability for Ca²⁺.

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

C. is found in abundance in prokaryotic cell membranes.

D. increases permeability for small polar molecules.

E. All of the above are correct.

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

A. transverse diffusion

B. association with cholesterol

C. rotation

D. association with a neighboring lipid

E. lateral diffusion

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 is linked to mannose

B. It is amphipathic.

C. It is short and polar like glycerol.

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

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

Hopanoids are

A. a type of glycolipid.

B. a type of phospholipid.

C. related to cholesterol.

D. found exclusively in yeast.

E. All of the above are correct.

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.

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

A. hopanoids

B. stearate

C. linoleate

D. palmitate

E. phytosterol

Lipid rafts are associated with which of the following activities?

A. immune responses

B. responding to extracellular signals

C. transport of nutrients across cell membranes

D. transport of cholera toxin into cells

E. All of the above are correct.

The technique that separates denatured proteins based on size is

A. freeze-fracture microscopy.

B. FRAP.

C. thin-layer chromatography.

D. Western blotting.

E. SDS-PAGE.

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

A. thin-layer chromatography

B. SDS-PAGE

C. Western blot analysis

D. freeze-fracture analysis

E. ferritin-linked antibodies

Naturally occurring unsaturated fatty acids typically

A. are highly branched.

B. are omega-3 fatty acids.

C. contain double bonds primarily in the cis configuration.

D. contain double bonds primarily in the trans configuration.

E. contain an odd number of carbon atoms.

• 1. A phospholipid has a "head" made up of a glycerol molecule attached to a single phosphate group, which is attached to another small molecule.
• 2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a choline group attached to phosphate.
• 3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is hydrophilic, which means it has an affinity for water.
• 4. A phospholipid also has two "tails" made up of two fatty acid molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.
• 5. Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are hydrophobic, which means they are excluded from water.

Cell - cell communication in plants takes place via specialized structures called

A. plasmodesmata.

B. lipid rafts.

C. connexons.

D. gap junctions.

E. chloroplast outer membrane pores.