Exam 6: Lipids, Membranes, and the First Cells

Based on the accompanying figure, which of these experimental treatments would increase the rate of sucrose transport into the cell?

Phospholipids and triglycerides both ________.

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 or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?

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 with the highest initial concentration of sucrose?

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.] -A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10−7 while the concentration in the SR is 10−2, then how is the ATPase acting?

The presence of cholesterol in the plasma membranes of some animal cells ________.

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.] -A membrane protein that spans the phospholipid bilayer one or more times is ________.

Refer to the following paragraph and accompanying figure to answer the following question(s). -Gramicidin is an antibiotic that increases the permeability of bacterial cell walls to inorganic ions. What is the most likely mode of action of gramicidin?

A phospholipid is a ________.

What region of a steroid is hydrophilic?

Which of the following is a large organic molecule that is NOT assembled by polymerization of a few kinds of simple subunits?

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of ________.

Which of the following is TRUE of osmosis?

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

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.] -For a protein to be an integral membrane protein, it would have to be ________.

Which of the following processes includes all others?

Which of the following factors would tend to increase membrane fluidity?

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.

Which of the following increases the strength of the hydrophobic interactions in lipid bilayers and thus makes them less permeable to polar molecules?