AP Biology Practice Test 33

Test Information

Question 12 questions

Time 15 minutes

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Questions 1-3 refer to the following information.

Questions refer to the following figure showing four chromosomes (A, B, C, D), each consisting of two chromatids, arranged midway between opposite poles of a cell.

1. Which of the following best describes the process that happens next?

2. Assuming no mutations during DNA replication, which of the following possesses the same genes?

3. Which of the following most closely describes the stage of the cell cycle illustrated in the figure?

Questions 4-6 refer to the following information.

Web-building spiders typically eat flies, crickets, and moths. Lizards eat these same foods and also eat spiders. Researchers surveyed the lizards and web-building spiders on 16 Caribbean islands. Half of the islands did not have any lizards; on these islands, they found more spiders and spider species than on islands with lizards. To investigate why this was so, they introduced lizards to four of the eight lizard-free islands and returned every 2 years to resurvey. During each survey, they found lizards and spiders occupying the same areas. The results after 8 years are summarized in the following figure.

4. Which of the following conclusions is best supported by the data?

5. When the researchers dissected some of the lizards, they found evidence of flies, moths, and crickets in their digestive tracts, but no spiders. How then can the data be explained?

6. What does the pattern of variation in the numbers of spiders from year 3 to year 8 on islands both with and without lizards suggest?

Questions 7-9 refer to the following information.

A biologist uses paper chromatography to separate pigments obtained from chloroplasts. In this procedure, leaf extracts containing a mixture of pigments are streaked near the bottom edge of a strip of chromatography paper. Chromatography paper is made of cellulose, an organic, polar molecule. The paper is mounted so that its bottom edge makes contact with a relatively nonpolar, organic solvent.

After the paper touches the solvent, the solvent and the pigments in the leaf extract move up the chromatography paper. The figure that follows shows the leading edges of four pigments relative to the point of pigment application.

7. The Rf value of a pigment is the ratio of the distance traveled by a pigment to the distance traveled by the solvent. Which pigment has the greatest Rf value?

8. Which of the following is most responsible for the separation of pigments on the chromatography paper?

9. Molecules of which of the following pigments are the most polar or contain the most polar groups?

Questions 10-12 refer to the following information.

Long periods of studying or other kinds of stressful mental activity cause the buildup of adenosine molecules in brain tissue. Adenosine is a ligand that binds to a G protein-coupled receptor on brain cells, activating a G protein by replacing its bound GDP with a GTP. A subunit of the G protein then binds to and activates adenylyl cyclase (AC), a membrane-bound effector protein. Adenylyl cyclase then catalyzes the conversion of ATP to cyclic AMP (cAMP), a second messenger. The cellular response to cAMP varies widely in different types of cells. In brain cells and other cells of the central nervous system, cAMP activates a protein kinase (PKA), which slows brain activity and causes drowsiness. Normally, cAMP concentrations in the cell are kept low by the enzyme cAMP phosphodiesterase (PDE), converting cAMP to regular AMP (not cyclic). But high levels of cAMP can be attained during periods of mental fatigue or other kinds of stress.

10. What activates adenylyl cyclase (AC)?

11. Because caffeine has a structure very similar to adenosine, it can bind to the adenosine receptor but cannot activate it. Which of the following best describes the effect of caffeine when it binds to the adenosine receptor?

12. In general, the hormone epinephrine (adrenaline) causes increases in blood pressure, breathing rate, and the rate of cell metabolism—all activities associated with the fight-or-flight response. Like adenosine, epinephrine is also a ligand for a G protein-coupled receptor. Though different from adenosine in other respects, the epinephrine signal transduction pathway, like that of adenosine, produces cAMP and activates PKA. Which of the following is most likely the mechanism that describes how epinephrine works?