Physician Assistant Scientific Knowledge 5

Question 1

Which type of hypersensitivity reaction is mediated by IgE antibodies and mast cell degranulation?

Accepted Answer

Type I (immediate hypersensitivity)

Answer

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?

Accepted Answer

Gram-negative bacteria have an outer membrane containing lipopolysaccharide (LPS)

Answer

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)?

Accepted Answer

AMP

Answer

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?

Accepted Answer

Decreased FEV1/FVC ratio (<0.70)

Answer

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?

Accepted Answer

Parathyroid hormone (PTH)

Answer

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.

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Physician Assistant Practice Test

Physician Assistant Scientific Knowledge 5