One type of mutation in the CFTR protein prevents the transport of chloride ions through the channel. Which of the following is most likely to be observed in the lungs of patients with this mutation?

1. dehydrated epithelial cells
2. dehydrated mucus
3. mucus with excess water
4. mucus with a high electrolyte concentration

Arsenic poisoning disrupts ATP production by inhibiting several of the enzymes in the oxidative phosphorylation pathway. Some of the symptoms of arsenic poisoning are similar to cystic fibrosis (CF; a hereditary disorder that would results in difficulty breathing and frequent lung infections). Explain what impact arsenic poisoning may have on components of the plasma membrane and transport that would result in CF-like symptoms.

1. Arsenic poisoning disrupts ATP production, leading to a decreased transport of Cl^– ions by epithelial cells. This leads to decreased electrolyte concentration in the mucus and retention of water into the cells. The mucus becomes dehydrated, as in CF.
2. Arsenic poisoning disrupts the Na⁺/Cl^– pump, leading to decreased transport of Cl^– ions out of the epithelial cells. This increases the electrolyte concentration in the mucus and movement of water out of the cells. The mucus becomes hydrated, as in CF.
3. Arsenic poisoning affects the oxidative phosphorylation pathway, leading to a decreased transport of Na⁺ ions out of the epithelial cells. This leads to increased electrolyte concentration in the mucus and movement of water into the cells. The mucus becomes dehydrated, as in CF.
4. Arsenic poisoning disrupts the binding sites for Cl^– ions, leading to a decreased transport of Cl^– ions outside the epithelial cells. This leads to decreased electrolyte concentration in the mucus and movement of water out of the cells. The mucus becomes hydrated, as in CF.

In individuals with a normally functioning CFTR protein, which substances are transported via active transport?

1. Cl−
2. mucus
3. Na⁺
4. water

The sodium-potassium (Na⁺/K⁺) pump functions like an antiporter transporting Na⁺ and K⁺ icons across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for Na⁺, K⁺, and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or g-strophanthin, a cardiac glycoside), Na⁺, and K⁺ in varying combinations inside and outside of the cells, as indicated in the given table. The transport of Na⁺ and K⁺ was measured to determine the activity of the Na⁺/K⁺ pump.

Which conclusion is supported by the data?

1. Ouabain does not disrupt ATP binding to the Na⁺/K⁺ pump.
2. ATP is required for the transport of Na⁺ and not for transport of K⁺.
3. The ATP binding site of the Na⁺/K⁺ pump is located on the intracellular domain of the pump.
4. The ATP binding site of the Na⁺/K⁺ pump is located on the extracellular domain of the pump.

Paramecia are unicellular protists that have contractile vacuoles to remove excess intracellular water. In an experimental investigation, paramecia were placed in salt solutions of increasing osmolarity. The rate at which a paramecium’s contractile vacuole contracted to pump out excess water was determined and plotted against the osmolarity of the solutions, as shown in the given graph.

Figure 5.26

Which of the following is the correct explanation for the data?

1. At higher osmolarity, lower rates of contraction are required because more salt diffuses into the Paramecium.
2. In an isosmotic salt solution, there is no diffusion of water into or out of the Paramecium, so the contraction rate is zero.
3. The contraction rate increases as the osmolarity decreases because the amount of water entering the Paramecium by osmosis increases.
4. The contractile vacuole is less efficient in solutions of high osmolarity because of the reduced amount of ATP produced from cellular respiration.

What is most likely to happen if Paramecia are moved from a hypertonic solution to solutions of decreasing osmolarity?

1. The rate of contraction would increase with decreasing osmolarity because more water diffuses into the Paramecium.
2. The rate of contraction would decrease with decreasing osmolarity because more water diffuses into the Paramecium.
3. The rate of contraction would increase with decreasing osmolarity because more salt diffuses into the Paramecium.
4. The rate of contraction would decrease with decreasing osmolarity because more salt diffuses into the Paramecium.

Describe the Na⁺/K⁺ pump, labeling the binding sites for Na⁺, K⁺, and ATP. Explain how the data indicate the location of the binding sites for Na⁺ and K⁺ on the pump. Based on the data in the table, which statement describes the location of the binding sites for Na⁺ and K⁺ on the pump?

1. The binding of Na⁺ occurs on the outer surface of the cell, as its transportation remains unaffected by the presence of ouabain. The binding of K⁺ occurs on the inner surface of the cell, as its transportation is blocked when ouabain is present inside the cell.
2. The binding of K⁺ occurs on the outer surface of the cell, and its transportation is blocked when ouabain is present outside the cell. The binding of Na⁺ occurs on the inner surface of the cell, and its transportation is blocked by the presence of ouabain.
3. The binding of K⁺ occurs on the outer surface of the cell, and the binding of Na⁺ occurs on the inner surface of the cell because they are not transported when ATP is absent.
4. The binding of Na⁺ occurs on the outer surface of the cell, and the binding of K⁺ occurs on the inner surface of the cell because they are not transported when ATP is absent.

An experiment was set up to determine the movement of molecules through a dialysis-tubing bag into water. A dialysis-tubing bag containing 5 percent lactose and 5 percent fructose was placed in a beaker of distilled water, as illustrated in the given figure. After 4 h, fructose is detected in the distilled water outside of the dialysis-tubing bag, but lactose is not.

Figure 5.27

What conclusions can be made about the movement of molecules in this experiment?

1. Fructose, being a monosaccharide, diffused through the dialysis bag into the distilled water. However, lactose, being a disaccharide, could not diffuse through the dialysis bag.
2. Fructose was homogenized by lactose, allowing the fructose to diffuse through the dialysis bag and into the distilled water. Lactose is not homogenized, so it could not pass through the dialysis bag.
3. Fructose and lactose are oppositely charged and separated out due to the force of repulsion.
4. Fructose diffused because of the pore specificity of the semipermeable membrane, not because of its concentration gradient.

Based on the information provided, which cell types are most likely to contain clathrin?

1. monocytes and mast cells
2. neutrophils, monocytes, and mast cells
3. neutrophils and mast cells
4. neutrophils and monocytes

Which of the following statements appropriately describes the role of opsonin and clathrin proteins in neutrophils, based on your understanding of phagocytosis?

1. A clathrin coating enhances phagocytosis, whereas opsonin reverses the process of phagocytosis.
2. Opsonins are proteins that enhance phagocytosis, whereas clathrin opposes phagocytosis.
3. Opsonin stabilizes the inward facing surface of the plasma membrane, which engulfs the antigen, whereas clathrin marks the antigen-for phagocytosis by the neutrophils.
4. Opsonin marks the antigen for phagocytosis by the neutrophils, whereas clathrin stabilizes the inward-facing surface of the plasma membrane, which engulfs the antigen.

Based on the information provided in the chapter, which cell types produce endosomes?

1. monocytes and mast cells
2. neutrophils, monocytes, and mast cells
3. neutrophils and mast cells
4. neutrophils and monocytes