Chapter 8 Cell Membranes

Chapter8(Cell membranes) 1) Which of the following statements about diffusion is true? ConcepL8.3) SHOW HINT It involves only the movement of water molecules. It always requires integral proteins of the cell membrane. It occurs when molecules move from a region of lower concentration to a region of higheг concentration It is a passive process. It requires expenditure of energy by the cell. Correct. Diffusion is the tendency of molecules to spread out in the available space. A substance will diffuse from an area of higher concentration to an area of lower concentration without energy input. 2) A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? Concept 8.3) SHOW HINT Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease The added salt would enter the cell, causing the cell to take up water and swell. There would be no osmotic movement of Water in response to the added salt. Water would enter the cell by osmoes, and the cett would swell The added salt makes the colution hypotonic соmрaгed to the cell. Water will enter the cell by Correct. The added salt makes the solution hypertonic compared to the cell. Water will leave the cell by osmosis. 3) Seawater is hypertonic to cytoplasm in vertebrate cells and in plant cells, if a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? Concept 83) SHOW HINT The red blood cell would shrink, and the plant celt would gain water. Both cello will gain water, but cell walls will prevent both cells from turutirig The red blood cell would burst and the plant cel would shink. Both cells would gain water by osmosis, the red blood cell would burst, and the plant call would испеасe in turgar pressure Both cells would lose water, the red blood cell would shrivel, and the plant plasma поbrane would pull away from the cell wall Correct. Seawater will cause both cells to lose water 4) Which of these statements describes some aspect of facilitated diffusion? (Concept 8.3) SHOW HINT There is only one kind of protein pore for facilitated diffusion Facilitated diffusion requires energy to drive concentration gradient Facilitated diffusion is another name for osmosis Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. Correct. The passageways for facilitated diffusion may be either protein pores or carrier proteins. 5) Which of the following is FALSE in regard to facilitated diffusion? Concept 8.3) SHOW HINT Facilitated diffusion can move ions across membranes. Facilitated diffusion can occur by means of transport proteins5. Facilitated diffusion requires a concentration gradient. Facilitated diffusion requires the hydrolysis of ATP Facilitated diffusion can occur through protein channels. Correct. This statement is false. Facilitated diffusion, like simple diffusion, needs only a concentration gradient-no energy input is required. 6) Active transport requires an input of energy and can also generate voltages across membranes. Based on this information, which of the following statements is true? Concept 8.4) SHOW HINT The sodium-potassium pump hydrolyzes ATP and results in a net positive change outside the cell membrane Active transport can use ATP as its energy source and ensures that there is no voltage across the cell membrane The source of energy for active transport of a solute up its gradient can be ATP or a concentration gradient of a second solute This second gradient of solutes maintains no net difference in voltage across the membrane. Active transport uses channel proteins and ensures that the interior of the cell is always positive compared to the exterior of the cell. Active transport moves solutes down their concentration gradients and always uses ATP as the source of energy to do this