Physician Assistant Scientific Knowledge 5 — Questions and Answers
Question 1: Which type of hypersensitivity reaction is mediated by IgE antibodies and mast cell degranulation?
- Type I (immediate hypersensitivity) (Correct answer)
- Type II (cytotoxic)
- Type III (immune complex)
- Type IV (delayed-type)
Correct answer: Type I (immediate hypersensitivity)
Type I hypersensitivity involves IgE-mediated mast cell and basophil degranulation, releasing histamine and other mediators causing anaphylaxis, asthma, and allergic rhinitis.
Question 2: What is the primary structural difference between gram-positive and gram-negative bacterial cell walls?
- Gram-negative bacteria have an outer membrane containing lipopolysaccharide (LPS) (Correct answer)
- Gram-positive bacteria lack a cell wall entirely
- Gram-negative bacteria have a thicker peptidoglycan layer
- Gram-positive bacteria contain porins in their membrane
Correct answer: Gram-negative bacteria have an outer membrane containing lipopolysaccharide (LPS)
Gram-negative bacteria possess an outer membrane containing lipopolysaccharide (endotoxin), which gram-positive bacteria lack, accounting for different staining and pathogenicity patterns.
Question 3: During glycolysis, which molecule serves as both a substrate and an allosteric activator of phosphofructokinase-1 (PFK-1)?
- AMP (Correct answer)
- ATP
- Citrate
- Glucose-6-phosphate
Correct answer: AMP
AMP allosterically activates PFK-1, signaling low cellular energy and promoting glycolysis, while high ATP inhibits PFK-1 to prevent excess glucose breakdown.
Question 4: Which pulmonary function test finding is characteristic of obstructive lung disease such as COPD?
- Decreased FEV1/FVC ratio (<0.70) (Correct answer)
- Decreased FVC with normal FEV1/FVC ratio
- Increased total lung capacity with normal FEV1/FVC
- Decreased diffusing capacity with normal FEV1/FVC
Correct answer: Decreased FEV1/FVC ratio (<0.70)
Obstructive disease is defined by a reduced FEV1/FVC ratio (<0.70 post-bronchodilator), reflecting impaired expiratory airflow due to airway obstruction.
Question 5: Which hormone stimulates osteoclast activity, increases renal calcium reabsorption, and raises serum calcium levels?
- Parathyroid hormone (PTH) (Correct answer)
- Calcitonin
- Vitamin D3 (calcitriol)
- Cortisol
Correct answer: Parathyroid hormone (PTH)
PTH raises serum calcium by stimulating osteoclast-mediated bone resorption, increasing renal calcium reabsorption, and promoting renal 1-alpha-hydroxylase activity to activate vitamin D.
Question 6: Which statistical test is most appropriate for comparing means between three or more independent groups?
- One-way ANOVA (Correct answer)
- Student's t-test
- Chi-square test
- Pearson correlation
Correct answer: One-way ANOVA
One-way ANOVA compares means across three or more independent groups while controlling the type I error rate that would inflate with multiple t-tests.
Question 7: DNA gyrase, the bacterial enzyme targeted by fluoroquinolone antibiotics, belongs to which class of enzymes?
- Type II topoisomerase (Correct answer)
- Type I topoisomerase
- DNA helicase
- DNA primase
Correct answer: Type II topoisomerase
DNA gyrase is a bacterial type II topoisomerase that introduces negative supercoils to relieve tension ahead of the replication fork; fluoroquinolones inhibit it by stabilizing the cleavage complex.
Physician Assistant Scientific Knowledge 5
Which type of hypersensitivity reaction is mediated by IgE antibodies and mast cell degranulation?