COMLEX-USA Biomedical Sciences 2

Question 1

Which type of collagen is most abundant in articular cartilage?

Accepted Answer

Type II collagen

Answer

Type II collagen is the predominant collagen in hyaline cartilage, providing tensile strength and resisting compression.

Question 2

Nitric oxide (NO) produces vasodilation primarily by activating which intracellular enzyme?

Accepted Answer

Soluble guanylyl cyclase

Answer

NO activates soluble guanylyl cyclase, increasing cGMP, which activates protein kinase G to cause smooth muscle relaxation and vasodilation.

Question 3

A child has recurrent pyogenic infections with bacteria and fungi. Flow cytometry shows absent CD18. Which condition is this?

Accepted Answer

Leukocyte adhesion deficiency (LAD)

Answer

LAD type I results from CD18 (beta-2 integrin) deficiency, preventing neutrophils from migrating to infection sites.

Question 4

The sodium-potassium ATPase pump maintains the resting membrane potential by moving:

Accepted Answer

3 Na+ out and 2 K+ in per cycle

Answer

The Na+/K+ ATPase pumps 3 Na+ out and 2 K+ in per ATP hydrolyzed, making it electrogenic and contributing to the negative resting membrane potential.

Question 5

Which immunoglobulin class is the first to be produced in a primary immune response?

Accepted Answer

IgM

Answer

IgM is the first antibody class produced during a primary immune response due to its pentameric structure enabling early complement activation.

COMLEX-USA Practice Test