QUESTION: 613 Topic Exam C: Section 3 (science)

SDS-PAGE is a technique used by scientists to separate proteins according to their size. The compound SDS confers a uniform negative charge to individual proteins, causing these negatively charged proteins to travel toward the anode (positive end) when placed in an electric field. The migrating proteins are further placed in a uniform matrix (PAGE) in order to separate the different sizes. A bigger, heavier protein meets more resistance than a smaller, lighter one while traveling through the matrix, and hence migrates more slowly. The size of a protein is measured in Daltons (Da). The relationship between the logarithm values of the weights of seven proteins and the distances they travel in the matrix in a given period of time is illustrated in the graph. A list of the discrete data point values for each protein, as well as the corresponding weight, is presented under the graph on the next page.

Another essential protein in metabolism is made up of two units, each unit traveling a different distance from the other. The combined weight of the two units is approximately 50,000 Da. Referring to the regions W, X, Y and Z on the graph, which combination will NOT give the possible weight of each unit?

X + Z
Y + Z
X + Y
W + Y

Answer(s): B

Explanation:

All the other combinations can be manipulated to give a combined weight of approximately 50,000 Da. The highest weight that Y + Z can attain under 25,000 Da.

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QUESTION: 614 Topic Exam C: Section 3 (science)

SDS-PAGE is a technique used by scientists to separate proteins according to their size. The compound SDS confers a uniform negative charge to individual proteins, causing these negatively charged proteins to travel toward the anode (positive end) when placed in an electric field. The migrating proteins are further placed in a uniform matrix (PAGE) in order to separate the different sizes. A bigger, heavier protein meets more resistance than a smaller, lighter one while traveling through the matrix, and hence migrates more slowly. The size of a protein is measured in Daltons (Da). The relationship between the logarithm values of the weights of seven proteins and the distances they travel in the matrix in a given period of time is illustrated in the graph. A list of the discrete data point values for each protein, as well as the corresponding weight, is presented under the graph on the next page.

What would happen if an electric field were to be applied to SDS-PAGE for an indefinite length of time?

Larger proteins will reach the anode before the smaller proteins.
All proteins will eventually reach a limiting resistance in the matrix, at which point they cease to migrate further.
Proteins associated with more SDS will reach the anode while proteins associated with less SDS will stop migrating due to resistance.
All proteins will eventually reach the anode.

Answer(s): D

Explanation:

It is consistent with the information provided that, given an indefinitely long period of time, all negatively charged proteins will reach the anode at the rates determined by their sizes. Smaller proteins will arrive at the anode before the larger proteins, ruling out choice A.

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QUESTION: 615 Topic Exam C: Section 3 (science)

Passage I

The following data table represents the population of both wolves and deer during the years 19551980 in a given area.

Which of the following statements is true about the years 19551980?

The population of the wolves increased over time.
The population of the deer decreased at a constant rate over time.
The population of the wolves increased initially, but decreased after 1965.
The population of the deer decreased over time.

Answer(s): D

Explanation:

As seen in Table 1, the deer population decreased over time, but not at a constant rate.

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QUESTION: 616 Topic Exam C: Section 3 (science)

Passage I

The following data table represents the population of both wolves and deer during the years 19551980 in a given area.

Between which years is the greatest difference in the population of wolves?

19551960
19601975
19551975
19751980

Answer(s): B

Explanation:

The greatest difference between the numbers of population among the choices is from 19601975 which was 23. All other choices were less than 23.

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