Defining Biological Terms Chapter 3

Which of the following is an accurate description of the plasma membrane? Two layers of phospholipids with a number of proteins embedded within What is a phospholipid? A special kind of lipid with a water-loving head and 2 water-fearing tails How many layers of phospholipids make up the plasma membrane? 2 According to the fluid mosaic model, a membrane ________. is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins Which would most likely pass unaided through a plasma membrane? Something small and nonpolar, such as nitrogen gas What is the main role of membrane proteins? Regulate the passage of materials in and out of the cell  The passive transport of water is specifically called ________.osmosis Which form of transport requires the expenditure of energy? Active transport Diffusion of ions across membranes through specific ion channels is driven by ________.ion electrochemical gradients Which of the following statements correctly describesosmosis? In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. What might happen to your red blood cells if you were suddenly unable to regulate the solute concentration of your blood and it began to rise? Your blood cells would shrivel because water would move out of the cells via osmosis. For a protein to be an integral membrane protein, it would have to be ________. amphipathic, with at least one hydrophobic region What is the definition ofendocytosis? It is the transport of large molecules into the cell. The voltage across a membrane is called the ________. membrane potential The sodium-potassium pump is called an electrogenic pump because it ________. is used to drive the transport of glucose against a concentration gradient Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? The two sides of a cell membrane face different environments and carry out different functions. Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. Which of the following statements about diffusion is true? It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane? There is random movement of substances into and out of the cell. According to the fluid mosaic model of cell membranes, phospholipids ________. can move laterally along the plane of the membrane Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15Msalt solution become limp. From this we can deduce that the fresh water ________. is hypotonic and the salt solution is hypertonic to the cells of the celery stalks What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water? The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes? What variable(s) influence(s) whether a nonpolar molecule can move across a membrane by passive diffusion? aquaporins   