COMLEX-USA Biomedical Sciences 2 — Questions and Answers
Question 1: Which type of collagen is most abundant in articular cartilage?
- Type I collagen
- Type II collagen (Correct answer)
- Type III collagen
- Type IV collagen
Correct answer: Type II collagen
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?
- Phosphodiesterase
- Adenylyl cyclase
- Soluble guanylyl cyclase (Correct answer)
- Protein kinase C
Correct answer: Soluble guanylyl cyclase
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?
- Chronic granulomatous disease
- Leukocyte adhesion deficiency (LAD) (Correct answer)
- Chediak-Higashi syndrome
- DiGeorge syndrome
Correct answer: Leukocyte adhesion deficiency (LAD)
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:
- 3 Na+ out and 2 K+ in per cycle (Correct answer)
- 2 Na+ out and 3 K+ in per cycle
- 3 Na+ in and 2 K+ out per cycle
- Equal Na+ and K+ in opposite directions
Correct answer: 3 Na+ out and 2 K+ in per cycle
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?
- IgG
- IgM (Correct answer)
- IgA
- IgE
Correct answer: IgM
IgM is the first antibody class produced during a primary immune response due to its pentameric structure enabling early complement activation.
Question 6: Okazaki fragments are synthesized on which strand during DNA replication?
- Leading strand
- Lagging strand (Correct answer)
- Template strand
- Non-template strand
Correct answer: Lagging strand
Okazaki fragments are short DNA segments synthesized discontinuously on the lagging strand, which runs antiparallel to the direction of replication fork movement.
COMLEX-USA Biomedical Sciences 2
Which type of collagen is most abundant in articular cartilage?