5 Written questions
3 Matching questions
- 15) In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?
A) The membrane is only fluid across a very narrow temperature range.
B) Proteins rarely move, even though they possibly can do so.
C) Unsaturated lipids are excluded from the membranes.
D) The concentration of protein molecules is now known to be much higher.
E) The proteins are known to be made of only acidic amino acids.
- 16) A protein that spans the phospholipid bilayer one or more times is
A) a transmembrane protein.
B) an integral protein.
C) a peripheral protein.
D) an integrin.
E) a glycoprotein.
- Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes.
73) In the small airways of the lung, a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung. One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane. How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?
A) Sodium ion transport will increase; higher osmotic potential will increase airway surface liquid volume.
B) Sodium ion transport will increase; higher osmotic potential will decrease airway surface liquid volume.
C) Sodium ion transport will decrease; lower osmotic potential will decrease airway surface liquid volume.
D) Sodium ion transport will decrease; lower osmotic potential will increase the airway surface liquid volume.
E) Sodium ion transport will be unaffected; lack of chloride transport still reduces osmotic potential and decreases the airway surface liquid volume.
- a d
- b c
- c a
5 Multiple choice questions
5 True/False questions
23) Why are lipids and proteins free to move laterally in membranes?
A) The interior of the membrane is filled with liquid water.
B) Lipids and proteins repulse each other in the membrane.
C) Hydrophilic portions of the lipids are in the interior of the membrane.
D) There are only weak hydrophobic interactions in the interior of the membrane.
E) Molecules such as cellulose can pull them in various directions. → c
4) Which of the following types of molecules are the major structural components of the cell membrane?
A) phospholipids and cellulose
B) nucleic acids and proteins
C) phospholipids and proteins
D) proteins and cellulose
E) glycoproteins and cholesterol → e
10) When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are
A) peripheral proteins.
D) integral proteins.
E) cholesterol molecules. → d
27) Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
B) an amino acid
E) starch → a
37) Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
A) simple diffusion
C) active transport pumps
E) facilitated diffusion → e