Review Questions Chp 5 (key)

Review Questions Chapter 5

A Closer Look at Cell Membranes (Ignore page numbers) 1. What is the relationship between mutated CFTR’s and biofilms? (82)

CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR; CFTR

Faulty CFTR’S cause mucus to form on the lung’s epithelial surface. This mucus impedes the lung epithelial cilia’s activity (they can’t clear the lungs of air-born microorganisms). In turn microorganism populations build up to form biofilms (the pili stick the microbes to the lung’s surface).These microorganisms in turn produce low grade infections (the most common colonizer is Pseudomonas aeruginos.). These infections can shorten one’s life (early on-set of lung failure). 2. How are Golgi bodies, ribosomes (in the rough ER) and the plasma membrane related? (83)

Ribosomes manufacture proteins; these are moved via the ER to the Golgi bodies by membrane bound vesicles; these vesicles fuse with the membrane of the GB’s and the protein is transferred to the GB’s interior; the protein is packaged in a GB vesicle (which buds off the GB’s surface) and this exocytic vesicle moves to the plasma membrane where the vesicle’s membrane fuses with the PM and the protein is either excreted or incorporated in the PM.

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3. The plasma membrane allows some molecules to freely diffuse while others can’t move across it with out help. Give examples of both types of molecules. A. Gases and small electrically-neutral molecules can readily cross the lipid bilayer. B. Glucose and other large, polar molecules cannot pass through the bilayer directly but must rely on passage through the interior of transport proteins.

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4. At biological temperatures what is the major factor that drives molecules down a concentration gradient? (86)

The concentration difference is the major factor.

5. What are several factors that may influence the rate of diffusion? (87) Several factors influence the rate and direction of diffusion: concentration differences, temperature (higher = faster), molecular size (smaller = faster), electric gradients (a difference in charge), and pressure gradients. 6. What molecule is almost always associated with active transport? (89)

ATP 7. What is an example of a co-transporter system? (89)

The sodium-potassium pump is an example of a co-transporter system that moves these ions in different directions across a plasma membrane. Also: “cotransporter” Refer to : http://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase

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for an in depth optional discussion of the Na+/K+ ATPase system.

New pump transports 3 Na+ ions out of the cell and 2 K+ ions into the cell. •Gets energy from ATP, obtained from the Mitochondria Energy Plant. •Anion peoples have migrated to near the membrane to polarize the cell as a result of the emigration of Sodium ions to outside the cell and immigration of Potassium ions into the cell.” •”

8. Refer to figure 5.13. Explain why the cell shrinks in the hypertonic condition. Do the same for the hypotonic condition. (90) Effects of Tonicity 1. Tonicity denotes the relative concentration of solutes in two fluids--extracellular fluid and cytoplasmic fluid, for example. 2. Three conditions are possible: a. An isotonic fluid has the same concentration of solutes as the fluid in the cell; immersion in it causes no net movement of water.

b. A hypotonic fluid has a lower concentration of solutes than the fluid in the cell; cells

immersed in it may swell.

hypertonic fluid has a greater concentration of solutes than the fluid in the cell; cells in it may shrivel.

c. A

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9. What is plasmolysis? Give an example. (91)

When plants lose water, there is shrinkage of the cytoplasm called plasmolysis. When a plant cell (onion for example) is immersed in a hypertonic salt solution, the cell will shrink. 10. What are the three pathways of endocytosis and how do they differ? (92) a. In receptor-mediated endocytosis, specific molecules are brought into the cell by specialized regions of the plasma membranes that form coated pits which sink into the cytoplasm. b. In bulk-phase endocytosis, a vesicle forms around a small volume of extracellular fluid without regard to what substances might be dissolved in it.

c. Pha goc ytos is , is an active form of endocytosis by which a cell engulfs microorganisms, particles, or other debris; this is seen in protistans and white blood cells.

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