++
Section VIII – Biochemistry of Extracellular & Intracellular Communication
++
++
++
Regarding membrane lipids, select the one FALSE answer.
++
++
++
A. The major phospholipid by mass in human membranes is generally phosphatidylcholine.
++
++
B. Glycolipids are located on the inner and outer leaflets of the plasma membrane.
++
++
C. Phosphatidic acid is a precursor of phosphatidylserine, but not of sphingomyelin.
++
++
D. Phosphatidylcholine and phosphatidylethanolamine are located primarily on the outer leaflet of the plasma membrane.
++
++
E. The flip-flop of phospholipids in membranes is very slow.
+
++
Glycolipids are located on the outer leaflet.
++
++
++
Regarding membrane proteins, select the one FALSE answer.
++
++
++
A. Because of steric considerations, α-helices cannot exist in membranes.
++
++
B. A hydropathy plot helps one to estimate whether a segment of a protein is predominantly hydrophobic or hydrophilic.
++
++
C. Certain proteins are anchored to the outer leaflet of plasma membranes via glycophosphatidylinositol (GPI) structures.
++
++
D. Adenylyl cyclase is a marker enzyme for the plasma membrane.
++
++
E. Myelin has a very high content of lipid compared with protein.
+
++
Alpha-helices are major constituents of membrane proteins.
++
++
++
Regarding membrane transport, select the one FALSE statement.
++
++
++
A. Potassium has a lower charge density than sodium and tends to move more quickly through membranes than does sodium.
++
++
B. The flow of ions through ion channels is an example of passive transport.
++
++
C. Facilitated diffusion requires a protein transporter.
++
++
D. Inhibition of the Na+-K+-ATPase will inhibit sodium-dependent uptake of glucose in intestinal cells.
++
++
E. Insulin, by recruiting glucose transporters to the plasma membrane, increases uptake of glucose in fat cells but not in muscle.
+
++
Insulin also increases glucose uptake in muscle.
++
++
++
Regarding the Na+-K+-ATPase, select the one FALSE statement.
++
++
++
A. Its action maintains the high intracellular concentration of sodium compared with potassium.
++
++
B. It can use as much as 30% of the total ATP expenditure of a cell.
++
++
C. It is inhibited by digitalis, a drug that is useful in certain cardiac conditions.
++
+...