Cell Physiology and Body Fluids-Critical thinking
Thinking questions:
1. Container A has a 10% salt
solution, and container B has a 20% salt solution. If the two solutions are
connected, is the net movement of water by diffusion from container A to B or B
to A? Is the net movement of salt from container A to B or B to A?
2. Given the
setup in figure 3.5, what would happen to osmotic pressure if the membrane were
not selectively permeable but instead allowed all solutes and water to pass
through it?
3. Suppose a woman ran a long-distance race in the summer. During
the race, she lost a large amount of hyposmotic sweat. Would her cells shrink,
swell, or stay the same size?
4. The body of a man was found floating in the salt water of Grand-Pacific Bay, which has a concentration that is slightly greater than body fluids. When seen during an autopsy, the cells in his lung tissues were clearly swollen. Choose the most logical conclusion.
a. He probably drowned in the bay.
b. He may have been murdered elsewhere.
c. He did not drown.
5. Why does a surgeon irrigate a surgical wound from which a tumor has been removed with sterile distilled water rather than with sterile isotonic saline?
6. Patients with kidney failure can be kept alive by dialysis, which removes toxic waste products from the blood. In a dialysis machine, blood flows past one side of a selectively permeable dialysis membrane, and dialysis fluid flows on the other side of the membrane. Small substances, such as ions, glucose, and urea, can pass through the dialysis membrane, but larger substances, such as proteins, cannot. If you wanted to use a dialysis machine to remove only the toxic waste product urea from blood, what could you use for the dialysis fluid?
a. a solution that is isotonic and contains only protein
b. a solution that is isotonic and contains the same concentration of substances as blood, except for having no urea in it
c. distilled water
d. blood
7. Secretory vesicles fuse with the plasma membrane to release their contents to the outside of the cell. In this process the membrane of the secretory vesicle becomes part of the plasma membrane. Because small pieces of membrane are continually added to the plasma membrane, one would expect the plasma membrane to become larger and larger as secretion continues. The plasma membrane stays the same size, however. Explain how this happens.
8. Suppose that a cell has the following characteristics: many mitochondria, well-developed rough ER, well-developed Golgi apparatuses, and numerous vesicles. Predict the major function of the cell. Explain how each characteristic supports your prediction.
9. If you had the ability to inhibit mRNA synthesis with a drug, explain how you could distinguish between proteins released from secretory vesicles in which they had been stored and proteins released from cells in which they had been newly synthesized.
10. The proteins (hemoglobin) in red
blood cells normally organize relative to one another, forming “stacks” of
proteins, which are in part responsible for the normal shape of red blood
cells. In sickle-cell anemia, proteins inside red blood cells do not stack
normally. Consequently, the red blood cells become sickle-shaped and plug up
small blood vessels. It is known that sickle-cell anemia is hereditary and
results from changing one nucleotide for a different nucleotide within the gene
that is responsible for producing the protein. Explain how this change results
in an abnormally functioning protein
11. Certain nerves to the heart release the neurotransmitter norepinephrine.
If these nerves are removed in experimental animals, the heart becomes
extremely sensitive to the administration of a drug that is an agonist of
norepinephrine. Explain why this may happen, in terms of receptor physiology.
12. Blood volume must be restored in a person who has lost large amounts of blood due to serious injury. This is often accomplished by infusing isotonic NaCl solution into the blood. Why is this better than infusing an isoosmotic solution of a penetrating solute, such as urea?
13.Compare the osmotic pressure of
plasma with that of plasma proteins.
14. Why is albumin the first plasma
protein to appear in the urine in renal disease?
16. In blood, the ratio of white blood cells to red blood cells is about 1: 1000. But in the bone marrow, white cell precursors outnumber red cell precursors, the myeloid/erythroid ratio being 4:1. What is the reason for this apparent discrepancy?
16. What is the difference between plasma osmotic pressure and plasma colloid osmotic pressure?