Introduction to Membranes

7.1 Introduction to Membranes Question 1 Which of the following statements best describes a characteristic of biological membranes? Phospholipids move laterally within the plane of the membrane. Phospholipids frequently flip-flop from one layer of the membrane to the other. Phospholipids generally occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. Phospholipids are arranged with hydrophilic tails in the interior of the membrane. Question 2 Which of the following statements best explains the reason that lipids and proteins are free to move laterally in membranes? The interior of the membrane is filled with liquid water. Lipids and proteins repulse each other in the membrane. Hydrophilic portions of the lipids are in the interior of the membrane. There are only weak hydrophobic interactions in the interior of the membrane Question 3 Which of the following statements best describes how unsaturated fatty acids increase membrane fluidity at lower temperatures? The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly. Unsaturated fatty acids are more nonpolar than saturated fatty acids. The double bonds block interaction among the hydrophilic head groups of the lipids. Question 4 The significance of the figure shown in textbook figure 7.4, showing mixing of mouse and human proteins is that The immune system of humans does not reject mouse proteins That membrane proteins move fairly rapidly within the membrane That mouse cells and human cells have different surface proteins Question 5 Which of the following is NOT a function of biological membranes? Creating separate compartments within eukaryotic cells Allowing cells to be attached together to create sheets of tissue Facilitating communication between the cell and other cells All of the above are functions of biological membranes 7.2 Membrane permeability & passive transport Question 1 Which of the following statements about the transport of water is TRUE? Water cannot freely cross biological membranes because it is large Water cannot freely cross biological membranes because it is polar Water can easily cross biological membranes because it is small and non-polar Water can cross biological membranes, but slowly because it is polar Question 2 A cell containing a 0.9% salt solution is placed in a beaker containing a 0.8% salt solution. Which of the following will happen? Water will leave the cell because the beaker solution is hypertonic to the cell solution Water will enter the cell because the beaker solution is hypotonic to the cell solution Water will leave the cell because the beaker solution is hopotonic to the cell solution Water will enter the cell because the beaker solution is hypertonic to the cell solution Question 3 When a transporter protein is saturated: It will stop functioning It will start to transport substances in the other direction Increasing the concentration of the substance to be transported will have no further effect on transport rate None of the above are correct Question 4 Facilitated diffusion is an example of Active transport Passive transport Bulk transport None of the above 7.3 Active Transport Question 1: The Na+-K+ pump is an example of: Facilitated diffusion Primary active transport Secondary active transport None of the above are correct Question 2 The SGLT transporter transports glucose into cells against its concentration gradient using energy released when sodium is moved into the cell. This is an example of: Facilitated diffusion Primary active transport Secondary active transport Bulk transport Not enough information is provided to determine Question 3 Which of the following statements about the Na+-K+ pump is FALSE? It exchanges sodium ions for an equal number of potassium ions A complete cycle of this pump requires 1 molecule of ATP It is abundant in most animal cells It transports sodium out of cells and potassium into cells All of the above are actually true Question 4 In humans, this type of bulk transport is carried out primarily by cells of the immune system: Pinocytosis Phagocytosis Receptor-mediated endocytosis Exocytosis