Q- A 6-month-old infant presents with recurrent bacterial and fungal infections. Laboratory testing shows markedly decreased CD18 expression on neutrophils. Which of the following mechanisms is primarily impaired?
A- Chemotaxis toward IL-8
B- Diapedesis through endothelium
C- Phagolysosome fusion
D- Reactive oxygen species formation
Q- A patient with chronic alcoholism develops confusion, ophthalmoplegia, and ataxia. Deficiency of which enzyme activity is most directly responsible for this condition?
A- Alpha-ketoglutarate dehydrogenase
B- Glucose-6-phosphate dehydrogenase
C- Pyruvate carboxylase
D- Succinate dehydrogenase
Q- A drug selectively blocks voltage-gated sodium channels in rapidly firing neurons. Which property best explains its preferential effect?
A- Higher affinity for inactivated channels
B- Increased lipid solubility
C- Noncompetitive receptor binding
D- Rapid renal clearance
Q- A newborn is found to have ambiguous genitalia and salt-wasting. Laboratory studies show decreased cortisol and aldosterone with increased androgens. Which enzyme is most likely deficient?
A- 11-beta-hydroxylase
B- 17-alpha-hydroxylase
C- 21-hydroxylase
D- Aromatase
Q- A researcher studies a mutation that prevents dissociation of GDP from a G protein alpha subunit. Which cellular effect is most likely?
A- Decreased second-messenger production
B- Increased adenylate cyclase activity
C- Increased ligand binding to receptor
D- Prolonged receptor activation