AP Biology Final Exam

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoACoA. Acetyl-CoACoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoACoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). The maximum production rate of acetyl-CoA under condition 1 is closest to which of the following?

1 micromole/sec

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoACoA. Acetyl-CoACoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoACoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Pyruvate dehydrogenase deficiency is a genetic disease most commonly linked to a mutation in the alpha-subunit of the mitochondrial enzyme that causes the enzyme to cease functioning. As a result of themutation, affected individuals build up dangerous amounts of lactic acid. Which of the following best explains the buildup of lactic acid in individuals with the mutation?

Cells undergo fermentation because pyruvate cannot be metabolized to proceed into the Krebs cycle.

What evolutionary advantage does compartmentalization of core metabolic processes offer eukaryotes?

Evolution of a nucleus in eukaryotes separates the processes of transcription and translation and they can be regulated separately.

A student placed a semipermeable membrane inside a U-shaped channel with two chambers, as shown. The membrane permits the movement of water but not salt. The student wants to vary the rate of osmosis that occurs across the membrane. Which of the following experimental designs will result in the fastest net rate of water movement into chamber A?

Placing sat water in chamber A and distilled water in chamber B

Protein X activates gene expression only in cells exposed to a specific signaling molecule. In a study, researchers determined the intracellular location of Protein X in cultured cells both before and after exposing the cells to the signaling molecule. The results of the study are shown in the diagram. Based on the results, which of the following best describes what Protein X is?

Protein X is a transcription factor.

Humans produce sweat as a cooling mechanism to maintain a stable internal temperature. Which of the following best explains how the properties of water contribute to this physiological process?

The high heat of vaporization of water allows the body to remove excess heat through a phase change of water from liquid to gas.

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoACoA. Acetyl-CoACoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoACoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Which of the following observations provides the best evidence that acetyl-CoA negatively regulates pyruvate dehydrogenase activity?

The rate of the pyruvate dehydrogenase- catalyzed reaction is slower in the presence of a higher concentration of acetyl-CoA.

The diagram shows how water can adhere to the xylem in the stems of plants, which contributes to water movement in the plant. Which of the following best explains how water is able to move upward from the roots of a plant, through its xylem in the stem, and out to the leaves?

Water and the xylem are both polar. Water molecules have the ability to form hydrogen bonds with each other and with the walls of the xylem.

Which of the following best describes the role of water in photosynthesis?

Water molecules donate electrons to the electron transport chain.

Pyruvate dehydrogenase is an enzyme that converts pyruvate to acetyl-CoACoA. Acetyl-CoACoA is further metabolized in the Krebs cycle. A researcher measured the accumulation of acetyl-CoACoA in a reaction containing pyruvate and pyruvate dehydrogenase under several different conditions (Figure 1). Which of the following best describes the cellular location where pyruvate dehydrogenase is most likely active?

the mitochondrial matrix