Free Physician Assistant College Admission Test Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Physician Assistant College Admission Test practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A spinal nerve leaves the vertebral column between adjacent vertebrae. Through which opening does it pass?

   1. A.Vertebral foramen
   2. B.Intervertebral foramenCorrect answer: B
   3. C.Transverse foramen
   4. D.Foramen magnum

   Explanation: OpenStax identifies the intervertebral foramen as "the opening through which a spinal nerve exits from the vertebral column". The vertebral foramina instead align to form the spinal canal; the question concerns the lateral exit between vertebrae.

   Reference: OpenStax Anatomy and Physiology 2e — 7.3, General Structure of a Vertebra

2. 2ADH increases collecting-duct water reabsorption primarily through which mechanism?

   1. A.Removing aquaporins from the membrane
   2. B.Blocking all sodium transport
   3. C.Increasing glucose filtration
   4. D.Inserting aquaporins into the membraneCorrect answer: D

   Explanation: OpenStax states, "In the collecting ducts, ADH stimulates aquaporin channel insertion to increase water recovery and thereby regulate osmolarity of the blood." More water channels increase permeability and water recovery; the opposite change would reduce reabsorption.

   Reference: OpenStax Anatomy and Physiology 2e — Chapter 25 Review, 25.6 Tubular Reabsorption

3. 3Two atoms of the same element have different mass numbers. Which particle count must differ between them?

   1. A.Protons
   2. B.NeutronsCorrect answer: B
   3. C.Valence electrons only
   4. D.Protons and electrons equally

   Explanation: OpenStax states, "isotopes of an element, therefore, differ from each other only in the number of neutrons within the nucleus." The elemental identity fixes proton number. The isotope difference is neutron number, not an obligatory change in electron count.

   Reference: OpenStax Chemistry 2e — Chapter 2 Summary, 2.3 Atomic Structure and Symbolism

4. 4A secreted protein has completed processing in the rough endoplasmic reticulum. Which organelle chiefly sorts and packages it for distribution?

   1. A.Lysosome
   2. B.Golgi apparatusCorrect answer: B
   3. C.Nucleolus
   4. D.Peroxisome

   Explanation: OpenStax states, "Sorting, tagging, packaging, and distributing lipids and proteins take place in the Golgi apparatus." Golgi sorting differs from lysosomal digestion, nucleolar ribosome assembly and peroxisomal metabolism.

   Reference: OpenStax Biology 2e — Chapter 4 Summary, 4.4 The Endomembrane System and Proteins

5. 5Which envelope feature is characteristic of a gram-positive bacterium?

   1. A.A thick peptidoglycan layerCorrect answer: A
   2. B.A thin peptidoglycan layer inside an outer membrane
   3. C.A chitin wall without peptidoglycan
   4. D.A protein capsid instead of a cell wall

   Explanation: OpenStax states, "Gram-positive bacterial cells are characterized by a thick peptidoglycan layer, whereas gram-negative bacterial cells are characterized by a thin peptidoglycan layer surrounded by an outer membrane." The thick peptidoglycan layer distinguishes gram-positive envelopes. Chitin is characteristic of fungi, and a capsid is a viral structure.

   Reference: OpenStax Microbiology — Chapter 3 Summary, 3.3 Unique Characteristics of Prokaryotic Cells

6. 6Two heterozygous parents, Aa × Aa, have offspring for a fully penetrant autosomal recessive trait. What is the probability of an aa offspring in each pregnancy?

   1. A.0%
   2. B.25%Correct answer: B
   3. C.50%
   4. D.75%

   Explanation: OpenStax states, "one quarter are homozygous dominant, half are heterozygous, and one quarter are homozygous recessive." Each parent transmits a with probability 1/2, so P(aa) = 1/2 × 1/2 = 1/4 = 25%. Half refers to heterozygotes and 75% to the dominant phenotype under these assumptions.

   Reference: OpenStax Biology 2e — Chapter 12 Summary, 12.2 Characteristics and Traits

7. 7A reversibly binding inhibitor resembles an enzyme's substrate and competes with it for the same free-enzyme active site. Which type of inhibition is described?

   1. A.Noncompetitive inhibition
   2. B.Competitive inhibitionCorrect answer: B
   3. C.Uncompetitive inhibition
   4. D.Irreversible covalent inhibition

   Explanation: OpenStax states, "the enzyme is inhibited through competitive inhibition, because an inhibitor molecule competes with the substrate for active site binding". Reversible competition for the free enzyme’s substrate site defines competitive inhibition. Noncompetitive inhibition does not involve this direct site competition; uncompetitive inhibition binds the enzyme-substrate complex, and irreversible covalent inhibition contradicts the stated reversible binding.

   Reference: OpenStax Biology 2e — 6.5 Enzymes, Enzyme Regulation

8. 8Researchers repeatedly assess the same participants from adolescence into adulthood. Which research design is this?

   1. A.LongitudinalCorrect answer: A
   2. B.Cross-sectional
   3. C.Naturalistic observation at a single time
   4. D.Single-participant clinical case study

   Explanation: OpenStax states, "Longitudinal research has been incredibly helpful to researchers who need to collect data on how people change over time. Cross-sectional research compares multiple segments of a population at a single time." Repeated assessment of the same cohort over time is longitudinal. The cross-sectional and single-time observational alternatives do not follow change within that cohort. A clinical case study may also span time, but the listed single-participant study does not describe this multi-participant cohort design.

   Reference: OpenStax Psychology 2e — Chapter 2 Summary, 2.2 Approaches to Research

9. 9Events A and B are independent, with P(A) = 0.20 and P(B) = 0.40. What is P(B | A)?

   1. A.0.40Correct answer: A
   2. B.0.08
   3. C.0.20
   4. D.0.60

   Explanation: OpenStax states, "Two events A and B are independent if the knowledge that one occurred does not affect the chance the other occurs." Independence gives P(B | A) = P(B) = 0.40. The value 0.08 is P(A and B), 0.20 uses the wrong event, and 0.60 adds the probabilities.

   Reference: OpenStax Introductory Statistics 2e — Chapter 3 Review, 3.2 Independent and Mutually Exclusive Events

10. 10Which pair of normal spinal curvatures develops after birth?

    1. A.Thoracic and sacrococcygeal
    2. B.Cervical and thoracic
    3. C.Lumbar and sacrococcygeal
    4. D.Cervical and lumbarCorrect answer: D

    Explanation: OpenStax states, "The cervical curve of the neck region develops as the infant begins to hold their head upright when sitting. Later, as the child begins to stand and then to walk, the lumbar curve of the lower back develops." These are the secondary curves; thoracic and sacrococcygeal curves retain fetal curvature.

    Reference: OpenStax Anatomy and Physiology 2e — 7.3, Curvatures of the Vertebral Column