Lewis/Life - Answers to End-of-Chapter Questions

Chapter 5 - Answers to End-of-Chapter Questions

TO REVIEW

1. The genetics of structure and function dictate that certain cells have certain markers, particularly at different times during the life of the organism.

2. Size, electrical charge, availability of an appropriate carrier, etc.

3a. Phospholipids
3b. HLA
3c. Dystrophin and/or glycoproteins
3d. Phospholipid bilayer -- permeability factors and/or tight junctions between cells

4. People at a party moving from room to room.

5. Definitions in text.

6. Water moves toward equilibrium. If the solute concentration outside the cell is greater than inside the cell, water will move out (in order to dilute the outside and achieve equilibrium) and the cell will shrink. Three ways cells maintain their shape are contractile vacuoles, ion pumps, restraining walls.

7. Receptors on the membrane.

8. Definitions in text.

9. Support, shape, movement, positioning of organelles, and internal structure. (Other answers may be possible.)

10a. Certain substances must attach before being transported (regardless of type of transport).
10b. This is a cascade of protein action beginning with receptors on the membrane that bind incoming molecules.
10c. Follow the explanations on page 94 and in Figure 5.16.
10d. Cell adhesion molecules guide white blood cells but prior to that, specific identifying receptors must be present.

11. Functions listed with definitions in text.

12a. Read the top paragraph on page 102.
12b. Dystrophin and the associated glycoproteins strengthen the muscle cell.
12c. One possible answer ==> A cell discriminates between those signals it responds to and those it ignores.
12d. The integrin and adhesion receptor protein pull the white blood cell between the lining cells to where damaged tissue is.

TO THINK ABOUT

1a. Leukocyte-adhesion deficiency -- Since the body lacks cell adhesion molecules, white blood cells do not stick to wounds but rather move right past so injuries do not heal.
1b. Muscular dystrophy (lacking dystrophin) -- Dystrophin adds strength and structure to the muscle and cells lacking this protein are weak.
1c. Leydig cell hypoplasia -- Reproductive cells do not receive enough testosterone and therefore do not develop.
1d. Diabetes insipidus -- ADH alters the permeability of the kidney tubule cells so that water in the urine returns to the blood stream. With diabetes insipidus, ADH release from the pituitary is inhibited.
1e. Nicotine addiction -- Nicotine binds to the nerve cell surface receptors.
1f. Multiple sclerosis -- The cells coating the nerves leading to certain muscles lack myelin. Neural messages to the muscles are blocked.
1g. Tetanus or botulism paralysis -- Toxins block the endocytosis/exocytosis cycle at the ends of the nerve cells.

2a. Cholesterol breakdown.
2b. Cell division.

3a. Active
3b. Receptor mediated endocytosis. [Depending on the interpretation of the question, other answers may be possible.]
3c. Design an experiment. Several options.
3d. One possible answer: Design a drug that will selectively bind to the P-gp protein.

4. Dystrophin adds strength to the muscle by holding together the cytoskeleton. Dynein is the building block of the components of the cytoskeleton.

5. One possible way water could leave the cell would be by osmosis -- if the environment were hypertonic to the cell. 6. Examine people with the condition and without the condition. Take HLA readings from both groups. Compare the findings.

7. Introduction of a substance to bind to the surface protein of the sperm or a substance to bind to the receptor molecule of the egg. [Other answers may be possible.]

8. Facilitated diffusion.

9. The water is leaving the cells. This is osmosis -- the tendency toward equilibrium.

10. The substance itself may or may not be dangerous. But, by destroying the blood-brain barrier, other substances which definitely are dangerous would be able to penetrate the brain.

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