Explain how membranes participate in THREE of the following biological processes: Muscle contraction Fertilization of an egg Chemiosmotic production of ATP Intercellular signaling

Active transport must function continuously because_______. a. plasma membranes wear out b. cells must be in constant motion c. facilitated transport opposes active transport d. diffusion is constantly moving the solutes in the other direction

Which of the following methods of transport is being used to transfer the substance into the cell in the accompanying graph? a. diffusion down a concentration gradient b. osmosis c. facilitated diffusion d. active transport e. vesicular transport f. It is impossible to tell with the information provided.

Assume that a membrane permeable to Na+ but not to Cl- separates two solutions. The concentration of sodium chloride on side 1 is higher than on side 2. Which of the following ionic movements would occur? a. Na+ would move until its concentration gradient is dissipated (until the concentration of Na+ on side 2 is the same as the concentration of Na+ on side 1). b. Cl- would move down its concentration gradient from side 1 to side 2. c. A membrane potential, negative on side 1, would develop. d. A membrane potential, positive on side 1, would develop. e. None of the preceding is correct.

The tails of the phospholipids of the plasma membrane are composed of _____ and are _____? a. phosphate groups; hydrophobic b. fatty acid groups; hydrophilic c. phosphate groups; hydrophilic d. fatty acid groups; hydrophobic

In the fluid mosaic model: plasma membrane proteins orient their hydrophilic sides toward the internal bilayer. phospholipids often flip-flop between the inner and outer layers. the mosaic refers to proteins attached to the underlying cytoskeleton. the fluid refers to the phospholipid bilayer. the mosaic refers to the symmetry of the internal membrane proteins and sterols.

Which plasma membrane component can be either found on its surface or embedded in the membrane structure? a. protein b. cholesterol c. carbohydrate d. phospholipid

Organelles and Cystic Fibrosis A plasma membrane transport protein called CFTR moves chloride ions out of cells lining cavities and ducts of the lungs, liver, pancreas, intestines, and reproductive system. Water that follows the ions creates a thin film that allows mucus to slide easily through these structures. People with cystic fibrosis (CF) have too few copies of the CFTR protein in the plasma membranes of their cells. Not enough chloride ions leave the cells, and so not enough water leaves them either. The result is thick, dry mucus that clogs the airways to the lungs and other passages. Symptoms include difficulty breathing and chronic lung infections. In 2000, researchers tracked the cellular location of the CFTR protein as it was being produced in cells from people with CF (Figure 3.13). Figure 3.13 Cellular location of the CFTR protein. Graph compares the amounts of CFTR protein found in endoplasmic reticulum, vesicles travel in g from ER to Golgi, and Golgi bodies in CF cells and normal cells. Which organelle contains the least amount of CFTR protein in normal cells? In CF cells?

Organelles and Cystic Fibrosis A plasma membrane transport protein called CFTR moves chloride ions out of cells lining cavities and ducts of the lungs, liver, pancreas, intestines, and reproductive system. Water that follows the ions creates a thin film that allows mucus to slide easily through these structures. People with cystic fibrosis (CF) have too few copies of the CFTR protein in the plasma membranes of their cells. Not enough chloride ions leave the cells, and so not enough water leaves them either. The result is thick, dry mucus that clogs the airways to the lungs and other passages. Symptoms include difficulty breathing and chronic lung infections. In 2000, researchers tracked the cellular location of the CFTR protein as it was being produced in cells from people with CF (Figure 3.13). Figure 3.13 Cellular location of the CFTR protein. Graph compares the amounts of CFTR protein found in endoplasmic reticulum, vesicles traveling from ER to Golgi, and Golgi bodies in CF cells and normal cells. In which organelle is the amount of CFTR protein most similar in both types of cells?

The plasma membrane __________. a. surrounds the cytoplasm b. separates the nucleus from the cytoplasm c. separates the cell interior from the environment d. both a and c