Physician Assistant Scientific Knowledge 2 — Questions and Answers
Question 1: Which enzyme is responsible for the rate-limiting step in cholesterol biosynthesis?
- HMG-CoA reductase (Correct answer)
- Acetyl-CoA carboxylase
- Squalene synthase
- Lanosterol synthase
Correct answer: HMG-CoA reductase
HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate, the committed and rate-limiting step in cholesterol synthesis, and is the target of statins.
Question 2: The Fick principle is used to calculate cardiac output. Which formula correctly represents it?
- CO = VO2 / (CaO2 - CvO2) (Correct answer)
- CO = (CaO2 - CvO2) / VO2
- CO = HR × SV
- CO = MAP / SVR
Correct answer: CO = VO2 / (CaO2 - CvO2)
The Fick principle states cardiac output equals oxygen consumption divided by the arteriovenous oxygen content difference.
Question 3: Which cell type produces surfactant in the lung?
- Type II pneumocytes (Correct answer)
- Type I pneumocytes
- Clara cells
- Goblet cells
Correct answer: Type II pneumocytes
Type II pneumocytes synthesize and secrete pulmonary surfactant, which reduces alveolar surface tension and prevents collapse.
Question 4: During oxidative phosphorylation, the chemiosmotic gradient drives ATP synthesis through which complex?
- Complex V (ATP synthase) (Correct answer)
- Complex I (NADH dehydrogenase)
- Complex III (cytochrome bc1)
- Complex IV (cytochrome c oxidase)
Correct answer: Complex V (ATP synthase)
Complex V (ATP synthase) uses the proton-motive force generated by the electron transport chain to synthesize ATP from ADP and inorganic phosphate.
Question 5: Which blood group system determines the Rh factor, and what antigen is most clinically significant?
- Rh system; D antigen (Correct answer)
- ABO system; A antigen
- Kell system; K antigen
- Duffy system; Fya antigen
Correct answer: Rh system; D antigen
The Rh blood group system's D antigen is the most immunogenic and clinically important, particularly in hemolytic disease of the newborn.
Question 6: In the cell cycle, at which checkpoint is DNA integrity assessed before the cell commits to DNA replication?
- G1/S checkpoint (Correct answer)
- G2/M checkpoint
- Spindle assembly checkpoint
- Restriction point
Correct answer: G1/S checkpoint
The G1/S checkpoint (restriction point) assesses DNA integrity and cell size before the cell commits to S phase DNA replication.
Question 7: Which immunoglobulin class is the first to be produced during a primary immune response?
- IgM (Correct answer)
- IgG
- IgA
- IgE
Correct answer: IgM
IgM is the predominant antibody produced early in a primary immune response and is the most efficient complement activator.
Physician Assistant Scientific Knowledge 2
Which enzyme is responsible for the rate-limiting step in cholesterol biosynthesis?