Chapter 5 Problem set

Transcription

1 Chapter 5 Problem set Matching Choose the most appropriate answer for each of the following. 1 fluid mosaic model 2. Transport proteins 3. freeze-fracturing and freeze-etching 4. recognition proteins 5. cholesterol and phytosterol 6. phospholipid 7. lipid bilayer 8. adhesion proteins 9. centrifuge 10. receptor proteins A. Oligosaccharide chains identify specific cell types B. Two layers of phospholipids, the structural basis of cell membranes C. Bind extracellular substances such as hormones that trigger changes in cell activities D. Separates cell components according to their relative densities E. Water-soluble substances move through their interiors; also bind and release molecules or ions to move them through membranes F. Phosphate-containing head and two fatty acid tails attached to a glycerol backbone G. Helps cells of the same type locate and stick to one another H. Determination of the nature of cell membranes by observation I. The most abundant sterols in animal and plant membranes, respectively J. A mixture of phospholipids, glycolipids, sterols, and proteins; motions and interaction of component parts Fill-in-the-Blanks Membranes show selective in that they allow some substances but not others to cross them in certain ways, at certain times. refers to the number of molecules of a substance in a specified region, as in volume of fluid or air. A gradient is a difference in the number of molecules or ions of a given substance in two different regions. When like molecules move down their concentration gradient, it is called. ; this is a key factor in moving substances across cell membranes and through fluid portions of cytoplasm. When the concentration gradient is steep, diffusion is (choose one) ( ) slower ( ) faster. As the gradient decreases and the number of molecules moving down the gradient decreases, diffusion is (choose one) ( ) slower ( ) faster. When the net distribution of molecules in a diffusion system is nearly uniform in the tow adjoining regions, it is called dynamic.. Diffusion {choose one) ( ) slower ( ) faster at higher temperature.; this is due to more rapidly moving molecules that collide more often. If a difference in charge exists between two adjoining regions, the rate and direction of diffusion may be changed by an gradient. Within a cell, the side of the membrane that is negatively charged will exert a(n) (choose one) ( ) attraction ( ) repulsion for positive sodium ions and enhance the low of sodium across the membrane. A difference in pressure, and the..gradient between two adjoining diffusion regions, can also influence the rate and direction of diffusion.

2 Matching Choose the most appropriate answer for each of the following A. Refers to the relative solute concentrations of two 1. bulk flow fluids B. Having the same solute concentrations 2. osmosis C. Mass movement of one or more substances in response to pressure, gravity, or another external 3. tonicity force 4. hypotonic solution D. The amount of force preventing further inward diffusion of water 5. isotonic solutions E. The fluid on one side of a membrane that contains more solutes than the fluid on the other side of the 6. hydrostatic pressure membrane 7. osmotic pressure F. The diffusion of water in response to a water concentration gradient between two regions separated 8. plasmolysis by a selectively permeable membrane G. Osmotically induced shrinkage of cytoplasm 9. Hypertonic H. The fluid on one side of a membrane that contains fewer solutes than the fluid on the other side of the membrane I. A fluid force exerted against a cell wall and/or membrane enclosing the fluid Choice For the following question choose the best fit, a. passive transport b. active transport c. applies to both active and passive transport 1. The calcium pump 2. Part of the transport protein closes in behind the bound solute - and pan opens up to the opposite side of the membrane 3. Involves a carrier protein that has not been energized 4. A carrier protein has a specific site that weakly binds a substance 5. At any give time, the net direction of movement depends on how many solute molecules make random contact with vacant binding sites in the interior of proteins 6. The transport protein must receive an energy boost, usually from ATP 7. Solute binding to a carrier protein leads to changes in protein shape 8. The sodium-potassium pump

3 Matching 1. exocytosis 2. receptor-mediated endocytosis 3. bulk-phase endocytosis 4. Phagocytosis 5. Membrane cycling A. A cell engulfs microorganisms, large edible particles, and cellular debris. B. Membrane initially used for endocytic vesicles returns receptor proteins and lids back to the plasma membrane. C. Vesicles form around small volumes of extracellular fluid of various content D. A cytoplasmic vesicle moves to the cell surface, its own membrane fuses with the plasm membrane while its contents are released to the environment. E. Chemical recognitions and biding of specific substance; pits of clathrin baskets sink into the cytoplasm and close on themselves. 1. Protein 2. Protein 3. Protein 4. Protein (open) 5. Protein (closed) 6. Protein 7. Protein 8. Protein 9. Protein 10. Protein 11.

4 True/False If the statement is true, write a T in the blank. If the statement is false, make it correct by changing the underlined word(s) and writing the correct word(s) in the answer blank. 22. Because membranes exhibit selective permeability, concentrations of dissolved substances can increase on one side of the membrane or the other. 23. A water concentration gradient is influenced by the number of solute molecules present on both sides of the membrane. 24. The relative concentrations of solutes in two fluids is referred to as isotonic. 25. An animal cell placed in a hypertonic solution would swell and perhaps burst. 26. Water tends to move from hypotonic solutions to areas with more solutes. 27. Physiological saline is 0.9 percent NaCI; red blood cells placed in such a solution will not gain or lose water; therefore, one could state that the fluid in red blood cells is hypertonic. 28. A solution of 80 percent water, 20 percent solute is more concentrated than a solution of 70 percent water, 30 percent solute. 29. The movement of water molecules and solutes in the same direction in response to a pressure gradient is called osmosis. 30. Plant cells placed in a hypotonic solution will swell.

5 Self-Quiz 1. White blood cells use to devour disease agents invading your body.. a. diffusion b. bulk flow c osmosis d. phagocytosis 2. cells depend on the calcium pump mechanism a. Intestine b. Nerve c. Muscle d. amoeba 3. Proteins bind extracellular substances, such as hormones, and bring about changes in cell activities. a. Receptor b. Adhesion c. Transport d. Recognition 4. In a lipid bilayer, tails point inward and form a(n) region that excludes water. a. acidic b. basic c. hydrophilic d. hydrophobic 7. Which of the following is not a form of passive transport? a. Osmosis b. Passive transport c. Bulk flow d. Exocytosis 8. O 2, CO 2, H2O, and other small, electrically neutral molecules move across the cell membrane by.. a. electric gradients b. receptor-mediated endocytosis c. passive transport Ions such as H+, Na, K, and Ca move across cell membranes by a. receptor-mediated endocytosis b. pressure gradients c. passive transport 10. Receptors, pits, and clathrin baskets participate in a. passive transport b. receptor-mediated endocytosis c. bulk-phase endocytosis 5. A protistan adapted to life in a freshwater pond is collected in a bottle and transferred to a saltwater bay. Which of the following is likely to happen? a. The cell bursts. b. Salts flow out of the protistan cell. c. The cell shrinks. _ d. Enzymes flow out of the protistan cell. 6. Which of the following is not a form of active transport? a. Sodium-potassium pump b. Endocytosis c. Exocytosis d. Bulk flow