Chapter 7: Cell Membranes

Chapter 7: Cell Membranes

Chapter 7: Cell Membranes


AP BiologyMennecke

  1. Ions diffuse across membranes down their
  2. Chemical gradientsc. Electrochemical gradients
  3. Concentration gradientsd. Hypertonic gradients
  1. All of the following situations are consistent with active transport except
  2. The conversion of ATP to ADP accompanied by the movement of molecules
  3. The rate of oxygen consumption by the cell increased when molecules moved
  4. Molecules moved in or out of a cell against their concentration gradient
  5. The rate of movement of molecules across the cell membrane increases in an oxygen poor environment
  1. What does a cell use exocytosis for?
  2. To pump protonsc. To release substances from the cell
  3. To create new cellsd. To move away from danger
  1. The presence of cholesterol in the plasma membranes of some arctic animals
  2. Enables the membrane to more easily stay fluid when cell temperatures drop
  3. Enables the animal to remove hydrogen atoms from saturated phospholipids
  4. Enables the animal to add hydrogen atoms to unsaturated phospholipids
  5. Makes them more susceptible to circulatory disorders
  1. Carrier molecules in the plasma membrane are required for
  2. diffusionc. facilitated diffusion
  3. osmosisd. passive transport
  1. The movement of potassium across the cell membrane requires
  2. Low cellular concentrations of sodium
  3. High cellular concentrations of potassium
  4. ATP as an energy source
  5. Glucose for binding and releasing ions
  1. An organism with a cell wall would be unable to do which of the following?
  2. Diffusionc. phagocytosis
  3. Active transportd. facilitated diffusion
  1. Which process accounts for the movement of large solids into some animal cells?
  2. Diffusionc. phagocytosis
  3. Active transportd. facilitated diffusion
  1. All of the following are functions of membrane proteins except
  2. contractile fibersc. cell adhesion
  3. active transportd. hormone receptors
  1. The membrane activity most nearly opposite to exocytosis is
  2. Plasmolysisc. phagocytosis
  3. Osmosisd. active transport
  1. One of the functions of cholesterol in plasma membranes is to
  2. Facilitate transport of ionsc. Speed diffusion
  3. Maintain membrane fluidityd. Create ATP
  1. A cell with an internal concentration of 0.02 molar glucose is placed in a test tube containing 0.02 molar glucose solution. Assuming glucose is not actively transported into the cell, which of the following terms describes the internal concentration of the cell relative to its environment?
  2. isotonicc. hypotonic
  3. hypertonicd. turgid
  1. All of the following statements about membrane structure and function are true except
  2. Diffusion, osmosis, & facilitated diffusion do not require energy input from the cell
  3. Voltage across the membrane depends on an unequal distribution of ions across the plasma membrane
  4. Diffusion of gases requires ATP molecules activating a transport protein
  5. Special membrane proteins can co-transport two solutes by coupling diffusion with active transport, as in the sodium-potassium pump
  1. Two similar-sized animal cells are placed in a 0.5% sucrose solution. Cell A enlarges in size for a while, then stops; cell B continues to enlarge and finally ruptures. Which of the following was true at the beginning of the experiment?
  2. Cell A was hypotonic to the solution, and cell B was hypertonic
  3. Cell A was hypertonic to the solution and cell B was hypotonic
  4. Cell A was hypertonic to cell B
  5. Cell B was hypertonic to cell A
  1. Which of the following characterizes the sodium-potassium pump?
  2. Sodium ions are pumped out of a cell against their gradient
  3. Potassium ions are pumped into a cell against their gradient
  4. Each exchange costs the cell one ATP while a carrier protein undergoes a conformation change in shape
  5. All of these characterize the sodium-potassium pump
  1. Which of the following is a characteristic feature of a carrier protein in a membrane
  2. It exhibits a specificity for a particular type of molecule
  3. It always requires energy to function
  4. It works against diffusion
  5. It has few, if any, hydrophobic amino acids
  1. All of the following cellular activities require ATP except
  2. movement of oxygen into the cellc. phagocytosis
  3. pumping sodium ions out of the celld. endocytosis
  1. Which of the following moves through the lipid bilayer of a membrane most rapidly?
  2. CO2c. K+ ions
  3. Glucosed. starch
  1. The movement of uncharged molecules from a low concentration to a higher concentration is described by which of the following?
  2. diffusionc. facilitated diffusion
  3. active transportd. exocytosis
  4. What are the membrane structures that function in active transport & facilitative diffusion?
  5. cholesterolc. hydrophobic molecules
  6. carbohydratesd. integral proteins
  1. According to the fluid-mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
  2. The can move laterally along the plane of the membrane
  3. They frequently flip-flop from one side of the membrane to the other
  4. They may depart from the membrane dissolve in the surrounding solution
  5. They have hydrophilic tails in the interior of the membrane
  1. Glucose is a six carbon sugar which diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Epithelial cells lining the gut need to bring glucose made available from digestion into the body and must prevent the reverse flow of glucose from body to gut. We need a mechanism to ensure that glucose always flows into intestinal cells gets transported into the bloodstream, no matter what the gut concentration of glucose. Imagine what would happen if this were not so, and intestinal cells used facilitated diffusion carriers for glucose. Immediately after you ate a candy bar or other food rich in sugar, the concentration of glucose in the gut would be high, and glucose would flow "downhill" from the gut into your body. But an hour later, when your intestines were empty and glucose concentrations in the intestines were lower than in your blood and tissues, facilitated diffusion carriers would allow the glucose in blood and tissues to flow "downhill," back into the gut. This would quickly deplete your short-term energy reserves. Because this situation would be biologically wasteful and probably lethal, it is worth the additional energy cost to make sure that glucose transport is a one-way process. Using this information, which transport mechanism is most probably functioning in the intestinal cells?
  2. simple diffusionc. facilitated diffusion
  3. phagocytosisd. active transport pumps

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Observe the chart below showing the glucose levels of a person as it fluctuates in a 7 hour period.

  1. What is glucose?
  1. What is glycogen?
  1. What is insulin’s role in eating a meal?
  1. What is glucagon’s role in eating a meal?
  1. What process is happening between 8 and 9 am? How is glucose being converted into glycogen?
  1. What process is happening at 10 am? How is glycogen being converted to glucose?
  1. Is this person’s body at homeostasis with regard to blood glucose levels? Explain.
  1. What role do cell membranes play in this feedback loop between glucose, glycogen, insulin and glucagon?

Observe the diagram below showing glucose and insulin interacting with a cell membrane.

  1. What makes it possible for insulin to interact with the cell membrane?
  1. What makes it possible for glucose to enter a cell membrane?
  1. Explain what is happening at each step in the picture above:

Step / What is happening at each step