ACT science practice test 30

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


Antigens occur on the surface of many cell types and provide a unique chemical signature that allows the body to determine the cell's identity. Antibodies are proteins that attack foreign substances that may pose an immune threat to the body. Antibodies identify a substance as foreign by recognizing and binding to its surface antigens. Each type of antibody is antigen-specific, attacking only one type of antigen.

Human blood is classified into different blood groups based on the presence of certain antigens on the red blood cells. The most commonly used blood group system is ABO. This system classifies blood into four groups (types) according to the presence or absence of A and/or B antigens on the blood cells. Cells may contain A antigens only, B antigens only, both A and B antigens, or neither antigen. Blood also contains antibodies against the antigens that are absent from the red blood cells. For example, type A blood contains A antigens and anti-B antibodies. Table 3.1 identifies the antigens and antibodies present in each blood type.

TABLE 3.1 ABO Blood Types

Blood can also be classified as Rh-positive (Rh+) or Rh-negative (Rh-), based on the presence or absence of a different antigen on the red blood cells. Table 3.2 identifies whether the Rh antigen or antibody is present in each blood type.

TABLE 3.2 Rh Blood Types

The ABO and Rh blood group systems are combined to determine an individual's medical blood type. Figure 3.1 illustrates the distribution of medical blood types in the general population of the United States.

Figure 3.1

Source: https://www.armydogtags.com.

Table 3.3 indicates the distribution of medical blood types by ethnicity in the United States. The values listed represent the percentage of individuals within the given ethnic group that exhibit each blood type.

TABLE 3.3 Blood Type Demographics

Source: http://www.redcrossblood.org/learn-about-blood/blood-types.

1. What is the total number of medical blood types possible for a human being?

A. Two
B. Four
C. Six
D. Eight

2. The name of each ABO blood type is derived from the:

A. antibodies that are present in the blood.
B. antigens that are present on the red blood cells.
C. prevalence of each blood type in the general population.
D. antigens that are absent from the red blood cells.

3. According to the passage, antigens:

A. distinguish one cell type from another.
B. recognize and attack antibodies.
C. are only found on harmful cells.
D. block antibodies from attacking cells.

4. Rh + blood always contains:

A. Rh antigen.
B. anti-Rh antibodies.
C. A and B antigens.
D. anti-A and anti-B antibodies.

5. Blood containing anti-A and anti-Rh antibodies and B antigens would be identified as which blood type?

A. A+
B. B-
C. AB-
D. B+

6. According to Figure 3.1, what percentage of the general population has type B blood?

A. 9%
B. 2%
C. 11%
D. 16%

7. The least common blood type in the United States is type:

A. O+.
B. AB+.
C. B-.
D. AB-.

8. Based on the data in Table 3.3, which continent's population can be inferred to have the greatest incidence of blood type B + ?

A. Asia
B. Europe
C. Africa
D. South America

9. In what percentage of the general population are A antigens present on red blood cells?

A. 39%
B. 33%
C. 44%
D. 37%

10. The data in Table 3.3 support the statement that more than half of the:

A. Caucasian population has type O blood.
B. Hispanic population has type O+ blood.
C. general population with type O blood is Caucasian.
D. general population with type O+ blood is Hispanic.

11. An individual of African-American ethnicity has a greater chance of having a B+ blood type than:

A. the general population.
B. an A+ blood type.
C. an individual of Asian ethnicity.
D. an O+ blood type.

12. Based on the information in Table 3.1, if an individual with an AB blood type receives donated type A blood, the donated blood will cause:

A. the conversion of existing B antigens to A antigens, altering the individual's blood type.
B. an immune reaction because the existing B antigens will attack the new A antigens.
C. no immune reaction because the individual has no antibodies against the new blood.
D. the individual's body to begin producing anti-A antibodies in response to the new blood.

13. Blood type O- is often referred to as the "universal donor" because it can be donated to any of the other blood types. This is because it has:

A. no antibodies to attack antigens.
B. no antigens to trigger an attack by antibodies.
C. both A and B antibodies to attack antigens.
D. both A and B antigens to prevent attack by antibodies.

14. An individual with blood type A- can safely receive a transfusion of which of the following blood types?

A. A+ or A-
B. A- or AB-
C. A- or O-
D. O- or O+

15. The percentage of the Caucasian population that has blood type AB- is:

A. the same as the percentage for the Hispanic population.
B. less than the percentage for the African-American population.
C. equal to the percentage for the general population.
D. greater than the percentage for the general population.