Fluid Mosaic Model Review

How does the "fluid mosaic model" describe the structure of the plasma membrane? Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity. Which of the following cell structures exhibits selective permeability between a cell and its external environment? - Plasma membrane What function do carbohydrates fulfill in the plasma membrane? - Cell-to-cell recognition Which of the following statements concerning carbohydrates associated with the plasma membrane is correct? - Membrane carbohydrates function primarily in cell-cell recognition. A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution? - The solution is hypertonic. Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________. - B; the diffusion gradient in cell B is steeper Which of the following statements about diffusion is true? - It is a passive process. Which of the following is correct regarding integral proteins? - These proteins exhibit both hydrophilic and hydrophobic properties. Which of the following is correct regarding peripheral proteins? - These proteins are found only on the surface of the plasma membrane. Which of the following is a correct difference between active transport and facilitated diffusion? - Active transport requires energy from ATP, and facilitated diffusion does not. A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process? - Endocytosis All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________. - membrane potential; electrogenic pumps Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein? - A nonpolar molecule, such as a hydrocarbon Why is energy required for active transport? - Because it moves solutes against their concentration gradient In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape. - channel; carrier If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? - Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. Which of the following molecules is most likely to passively diffuse across the plasma membrane? - Carbon dioxide Which of these statements describes some aspect of facilitated diffusion? - Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. The sodium-potassium pump __________. - transports sodium ions out of the cell and transports potassium ions into the cell Which of the following statements about passive transport is correct? - Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule. Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability? - Proteins embedded in two layers of phospholipids The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution? - 1.0M The plasma membrane exhibits selective permeability. This means that __________. the plasma membrane allows some substances to flow through it more easily than others Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane? - Exocytosis and smooth and rough ER Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct? - Phospholipids form a selectively permeable structure. Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell? - The cell will decrease in size as water flows out of it Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? - A large polar molecule How does cholesterol affect membrane fluidity? - At body temperature, it makes the membrane less fluid. Which of the following plant cells would exhibit the most turgor pressure? - A cell placed in a hypotonic solution Which of the following molecules are most abundant in the plasma membrane? Phospholipids