Exam 6: Lipids, Membranes, and the First Cells

For the following question(s), match the labeled component of the cell membrane in the figure with its description. -Which component is a peripheral protein?

Why are lipids and proteins free to move laterally in membranes?

Steroids are considered to be lipids because they ________.

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?

Refer to the following paragraph and accompanying figure to answer the following question(s). -Which term best describes the type of membrane protein in the figure?

Refer to the following paragraph and accompanying figure to answer the following question(s). -Under what circumstances does membrane transport require energy?

Celery stalks that are immersed in freshwater for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the freshwater ________.

Which of the following affects the osmolarity of a solution? I. concentration of cations II. concentration of anions III. concentration of water

You have just discovered an organism that lives in extremely cold environments. Which of the following would you predict to be TRUE about the phospholipids in its membranes, compared to phospholipids in the membranes of organisms that live in warmer environments?

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percentage change in mass of each bag was graphed. -A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water-equal to the volume of blood lost-is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?

Refer to the following paragraph and accompanying figure to answer the following question(s). -Where would you most likely find an integral membrane protein?

You make a phospholipid bilayer with short, saturated hydrocarbon tails. You measure the permeability of this membrane to oxygen. You then double the length of the hydrocarbon tails and remeasure membrane permeability. You then double the length of the hydrocarbon tails again and make a third measurement of membrane permeability. You graph membrane permeability as a function of hydrocarbon tail length. Which of the accompanying graphs best represents the data you expect?

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percentage change in mass of each bag was graphed. -Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

What is the most important factor in explaining why osmosis occurs spontaneously?

Which of the following is most likely TRUE of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

Which aspect of phospholipids is most important to the formation of bilayers?

Use the following information when answering the corresponding question(s). Rhodopsins are light-sensitive molecules composed of a protein (opsin) and retinal (derivative of vitamin A). Opsin is a membrane protein with several α-helical segments that loop back and forth through the plasma membrane. There are two classes of rhodopsins. According to Oded Beje, one class has relatively slow dynamics (a photocycle of approximately 0.5 second) and is well suited for light detection. The second class has faster dynamics (a photocycle of approximately 0.02 seconds) and is well suited for chemiosmosis: pumping of protons or chloride ions across cell membranes. Oded Beje was the first, in September 2000, to report on a rhodopsin (proteorhodopsin) found in the domain Bacteria. [SOURCE: O. Beje et al., Science 289 (2000): 1902.] -Which of the following types of molecules are the major structural components of the cell membrane?

Lipids that form membranes have what kind of structure?

The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. -Refer to the figure. At the beginning of the experiment,