Ch. 7 Membranes - Their Lipids and Fluidity

Which of the following types of organisms contain sphingomyelin in cell membranes? 1) Animals 2) Yeast 3) Plants 4) Prokaryotes 5) Algae

1) Animals

Which of the following is a sterol-like lipid associated with plant cell membranes? 1) Phytosterol 2) Stearate 3) Hopanoids 4) Linoleate 5) Palmitate

1) Phytosterol

Gradual replacement of shorter-chain fatty acids by longer-chain fatty acids in the membrane phospholipids. 1) This is unlikely because longer-chain fatty acids decrease membrane fluidity. 2) This is likely because longer-chain fatty acids decrease membrane fluidity. 3) This is unlikely because longer-chain fatty acids increase membrane fluidity. 4) This is likely because longer-chain fatty acids increase membrane fluidity.

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

Cholesterol 1) Increases permeability for small polar molecules. 2) Buffers membrane fluidity by increasing fluidity at low temperature and decreasing fluidity at high temperature. 3) Increases permeability for Ca2+. 4) Is found in abundance in prokaryotic cell membranes. 5) All of the above are correct.

2) Buffers membrane fluidity by increasing fluidity at low temperature and decreasing fluidity at high temperature.

Imagine a new type of cell was discovered on Mars in an organism growing in benzene, a nonpolar liquid. The cell had a lipid bilayer made of phospholipids, but its structure was very different from that of our cell membranes. How might you isolate and visualize these unusual membranes? 1) It may require hydrophobic solvents to solubilize these membranes and release embedded proteins prior to visualization by conventional means. 2) It may require hydrophilic solvents to solubilize these membranes and release embedded proteins prior to visualization by conventional means. 3) It may require amphipathic solvents to solubilize these membranes and release embedded proteins prior to visualization by conventional means.

2) It may require hydrophilic solvents to solubilize these membranes and release embedded proteins prior to visualization by conventional means.

The most prominent lipids in animal cell membranes are 1) Cholesterol. 2) Phospholipids. 3) Cerebrosides. 4) Phytosterol. 5) Glycolipids.

2) Phospholipids.

Imagine a new type of cell was discovered on Mars in an organism growing in benzene, a nonpolar liquid. The cell had a lipid bilayer made of phospholipids, but its structure was very different from that of our cell membranes. What might be characteristic features of the phospholipid head groups? 1) The phospholipid head groups would likely bind to each other with covalent bonds that would pack well and not be bulky. 2) The phospholipid head groups would likely have equal numbers of positively and negatively charged groups that would pack well and not be bulky. 3) The phospholipid head groups would likely have equal numbers of hydroxyl and amino groups that would pack well and not be bulky. 4) The phospholipid head groups would likely bind to each other with hydrogen bonding that would pack well and not be bulky.

2) The phospholipid head groups would likely have equal numbers of positively and negatively charged groups that would pack well and not be bulky.

Enhanced rate of synthesis of unsaturated fatty acids. 1) This is likely because unsaturated fatty acids will decrease membrane fluidity. 2) This is likely because unsaturated fatty acids will increase membrane fluidity. 3) This is unlikely because unsaturated fatty acids will decrease membrane fluidity. 4) This is unlikely because unsaturated fatty acids will increase membrane fluidity.

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

Which of the following lipids is found concentrated in lipid rafts in animal cell plasma membranes? 1) Phosphatidylcholine 2) Phophatidylethanolamine 3) Cholesterol 4) Phosphatidylinositol 5) Phosphatidylserine

3) Cholesterol

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? 1) The membrane with more cholesterol will have increased fluidity at all temperatures compared to the membrane with less cholesterol. 2) 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. 3) 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. 4) The two membranes will have the same degree of fluidity at all temperatures.

3) 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.

Initial decrease in membrane fluidity 1) This is unlikely because membrane fluidity decreases as the temperature is lowered. 2) This is likely because membrane fluidity increases as the temperature is lowered. 3) This is likely because membrane fluidity decreases as the temperature is lowered. 4) This is unlikely because membrane fluidity increases as the temperature is lowered.

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

Gradual replacement of stearate by oleate in the membrane phospholipids. 1) This is unlikely because unsaturated fatty acids (oleate) will decrease membrane fluidity. 2) This is likely because saturated fatty acids (oleate) will increase membrane fluidity. 3) This is likely because unsaturated fatty acids (oleate) will increase membrane fluidity. 4) This is unlikely because saturated fatty acids (oleate) will decrease membrane fluidity.

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

Incorporation of more cholesterol into the membrane. 1) This is likely because cholesterol will decrease membrane fluidity. 2) This is unlikely because cholesterol will disolve membrane phospholipids. 3) This is unlikely because bacteria do not contain cholesterol under any conditions. 4) This is likely because cholesterol will increase membrane fluidity.

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

Lipid rafts are associated with which of the following activities? 1) Responding to extracellular signals 2) Transport of nutrients across cell membranes 3) Transport of cholera toxin into cells immune responses 4) All of the above are correct.

4) All of the above are correct.

The composition of lipids in the outer and inner monolayers of cell membrane lipid bilayers is 1) Highly random for each monolayer. 2) Twice as concentrated in the inner monolayer as in the outer monolayer. 3) Identical in each monolayer. 4) Asymmetrical; i.e., different in each monolayer. 5) The same for all cell plasma membranes but different from the composition in mitochondrial and chloroplast membranes.

4) Asymmetrical; i.e., different in each monolayer.

Hopanoids are 1) A type of phospholipid. 2) A type of glycolipid. 3) Found exclusively in yeast. 4) Related to cholesterol. 5) All of the above are correct.

4) Related to cholesterol.

Which of the following would you expect to find predominating in the plasma membrane of a unicellular eukaryotic organism thriving in glacier ice? 1) 18 carbon long saturated fatty acids. 2) 18 carbon long fatty acids with 1 double bond. 3) 20 carbon long saturated fatty acids. 4) 20 carbon long fatty acids with 1 double bond. 5) 16 carbon long fatty acids with 3 double bonds

5) 16 carbon long fatty acids with 3 double bonds.

Imagine a new type of cell was discovered on Mars in an organism growing in benzene, a nonpolar liquid. The cell had a lipid bilayer made of phospholipids, but its structure was very different from that of our cell membranes. What properties would you expect to find in membrane proteins embedded in this membrane? (Hydrophobic or Hydrophillic) Membrane proteins embedded in themembrane would likely have _____________ regions spanning the membrane with ____________ groups protruding from both sides. Protein transporters would be required for _____________ compounds that could not otherwise pass through the _______________ membrane interior.

Membrane proteins embedded in the membrane would likely have hydrophilic regions spanning the membrane with hydrophobic groups protruding from both sides. Protein transporters would be required for hydrophobic compounds that could not otherwise pass through the hydrophilic membrane interior.

Match the membrane lipid group on the Top with the correct type of membrane lipid on the Bottom. Phosphoglycerides: Phosphosphingolipids: Glycosphingolipids: Glycoglycerolipid: Sterols: Phosphatidylserine Cerebrosides Cholesterol Monogalactosyl- Diacylglycerol (MGDG) Sphingomyelin

Phosphoglycerides: Phosphatidylserine Phosphosphingolipids: Sphingomyelin Glycosphingolipids: Cerebrosides Glycoglycerolipid: Monogalactosyl- Diacylglycerol (MGDG) Sterols: Cholesterol

Imagine a new type of cell was discovered on Mars in an organism growing in benzene, a nonpolar liquid. The cell had a lipid bilayer made of phospholipids, but its structure was very different from that of our cell membranes. Describe what might be a possible structure for this new type of membrane. 1) This membrane would have the polar groups on the two surfaces facing the nonpolar solvent, and it would have a hydrophilic interior. 2) This membrane would have the nonpolar groups on the two surfaces facing the nonpolar solvent, and it would have a hydrophilic interior. 3) This membrane would have the nonpolar groups on the two surfaces facing the nonpolar solvent, and it would have a hydrophobic interior. 4) This membrane would have the polar groups on the two surfaces facing the nonpolar solvent, and it would have a hydrophobic interior.

This membrane would have the nonpolar groups on the two surfaces facing the nonpolar solvent, and it would have a hydrophilic interior.