ACT Science Practice

If you plan to go to college, you will more than likely need to take an entrance exam, depending on the school that you wish to attend. One entrance exam that you will need to take is the ACT exam.

The ACT exam measures high-school students on what they have learned during high school and determines if they are ready to enter college-level classes. The ACT also gives you an idea as to which college-level classes you are prepared to take.

What to Expect on the ACT Exam

The ACT exam consists of four sections:

  1. English
  2. Math
  3. Reading
  4. Science

There is also a Writing Section on the ACT exam that is optional.

To prepare for the ACT exam, it is best to take multiple ACT practice tests to see which areas you will need more work on as well as what you can expect on the actual exam. Our ACT Science Practice is similar to those science questions you will be asked on the actual ACT exam.

What’s on the ACT Exam


The Science section of the ACT exam includes 40 questions and is timed for 35 minutes. The Science section measures the interpretation, analysis, evaluation, reasoning, and problem-solving skills that are required in the natural sciences. The Science section includes questions about:

  • Interpretation of Data
  • Scientific Investigation
  • Evaluation of Models, Inferences, and Experimental Results

Blood consists of a liquid called plasma, in which many different types of blood cells are suspended. The plasma also contains many dissolved proteins. These proteins may be studied by subjecting the plasma to electrophoresis, in which it is subjected to an electric field, which pulls the proteins through a porous gel. Proteins typically have a negative charge on their surface, so they move toward the anode (positive electrode) in an electric field. The gel acts as a molecular sieve: it interferes with the movement, or migration, of the larger proteins more than the small ones, allowing the proteins to be separated on the basis of size. The further the proteins move during the experiment, the smaller they must be. 

The experiment results in an electropherogram, such as the one shown in the figure below. This is a plot, or graph, of protein concentration versus migration, and corresponds to a graph of concentration versus size. Concentration is measured by passing light of a certain wavelength through the gel: proteins absorb the light, and the resulting absorbance measurement is proportional to protein concentration. Many major blood component proteins, such as albumin and several identified by Greek letters, have been discovered in this way. When disease is present, some component proteins may break down into smaller fragments. Others may aggregate, or clump together, to form larger fragments. This results in a change in the electropherogram: new species, corresponding to the aggregates or breakdown products, may be present, and the sizes of the normal peaks may be changed as the concentration of normal products is altered.

The Figure shows an electropherogram from a sick patient with an abnormal component in her blood (arrow). Peaks corresponding to some normal plasma proteins have been labeled. Please examine the electropherogram and answer the following questions.

ACT Science

The blood of healthy individuals does not contain the unknown component indicated by the arrow. The experiment therefore proves: 

F. The unknown component causes the patient’s sickness.

G. The unknown component results from the patient’s sickness.

H. The more of the unknown component there is, the sicker the patient will be.

J. None of the above.

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ACT Flashcards
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ACT Secrets







J: The experiment shows only that this patient’s blood contains an unknown component. It does not demonstrate that the component causes the patient’s disease, or that it results from it. It may be unrelated. Further experiments are required to fully characterize the relationship between the component and the illness.

Published by

Jay Willis

Jay Willis joined Mometrix as Vice President of Sales in 2009, and has developed several key strategic relationships that have enhanced the distribution of Mometrix products. With nearly 20 years of sales experience in the publishing industry, his dedication to providing the highest quality experience for customers, coupled with his sales and marketing expertise, has resulted in significant growth of the Institutional Sales division.

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