AP Biology Practice Test 32

Test Information

Question 13 questions

Time 16 minutes

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Questions 1-3 refer to the following information.

Five dialysis bags, made from a semipermeable membrane that is impermeable to glucose, were filled with various concentrations of glucose and placed in separate beakers containing 0.5 M glucose solution. The bags were weighed every 10 minutes and the percent change in mass for each bag was graphed:

1. Which line represents the bag that contained a solution isotonic to the 0.5 M solution?

2. Which line represents that bag with the highest initial concentration of glucose?

3. Which line or lines represent bags that contain a solution that is hypertonic at 50 minutes?

4. A mutation in a bacterial enzyme changed a previously polar amino acid into a nonpolar amino acid. This amino acid was located at a site distant from the enzyme’s active site. How might this mutation alter the enzyme’s substrate specificity?

Questions 5-6 refer to the following information.

Use the following picture of DNA to answer questions

5. Based on the preceding picture, which direction would RNA polymerase move?

6. If the DNA segment is a transcriptional unit, where would the promoter be located?

7. A single gene from five related species of leafhopper was compared, and the nucleotide differences between the genes are as shown in the table:

Nucleotide Differences

Which of the following phylogenetic trees best shows the correct evolutionary relationship between the leafhoppers?

Questions 8-9 refer to the following information.

Answer questions based on the following cladogram:

8. What is the common ancestor for B and E?

9. Which two species are most closely related?

10. The protein tropomyosin is present in a variety of cells, including muscle cells. During RNA processing, the primary RNA transcript that codes for tropomyosin is spliced in a manner specific to cell type. In smooth muscle cells (the type of muscle found in the walls of blood vessels and the digestive tract), exons 1, 2, 4, 5, and 6 are spliced. In contrast, in striated muscle cells (the type of muscle attached to bones that cause movements of the body), exons 1, 3, 4, 5, and 6 are spliced. The following figure illustrates the results of this process.

Which of the following describes all possible conditions for exons 2 and 3 if the tropomyosin protein coded for by the mRNA in both cell types is expected to function properly?

Questions 11-13 refer to the following information.

Cystic fibrosis is an inherited disorder that produces a buildup of thick mucus in the lungs that leads to constricted airways, persistent coughing, and bacterial infections of the lungs. Also, mucus buildup from pancreatic cells blocks the secretion of pancreatic digestive enzymes and results in incomplete digestion and diarrhea. Life expectancy is 30 to 40 years for individuals who inherit two copies of the autosomal recessive trait.

The disorder is caused by a mutation in the cystic fibrosis transmembrane regulator (CFTR), an ATP-activated ion channel protein. Binding of ATP to CFTR triggers the opening of a channel that allows Cl- to passively flow across the plasma membrane. In epithelial lung cells, the channel enables the movement of Cl- out of the cell, though in other cell types, the channel can be structured so as to promote Cl- into the cell.

In normal individuals, epinephrine initiates a signal transduction pathway by binding to a G protein-coupled receptor (GPCR) on the plasma membrane of epithelial lung cells. The GPCR then activates an exchange of a GTP for a GDP on a nearby G protein. This G protein, now activated with the GTP, binds to the GPCR. This allows the release of a G subunit (Gα) that binds to and activates adenylyl cyclase. Adenylyl cyclase then catalyzes the conversion of ATP to cyclic AMP (cAMP) and cAMP activates a protein kinase (PKA). PKA enables two ATP molecules to bind to the CFTR protein, triggering the opening of a gated channel in the CFTR and allowing for the passive passage of Cl- out of the cell.

The movement of Cl- into the extracellular fluid creates an electrochemical gradient across the plasma membrane that induces water to move out of the cell. A Na+/K+ pump, also activated by PKA and ATP, helps regulate the electrochemical gradient to maintain an appropriate surface liquid on the epithelial cells.

11. A signal molecule for this signal transduction pathway is

12. In epithelial cells expressing the cystic fibrosis mutation, the CFTR protein is not functional. How does this contribute to the symptoms of the disorder?

13. Sweat is produced by cells of the sweat glands and transported to the skin surface through ducts. The sweat of individuals with cystic fibrosis is very high in salt (NaCl), so much so that sweat is analyzed for its Cl- content as a test for cystic fibrosis. This can best be explain by