BAT Alcohol Metabolism & Physiology 3 — Questions and Answers
Question 1: The microsomal ethanol oxidizing system (MEOS) primarily involves which enzyme?
- Alcohol dehydrogenase (ADH)
- Aldehyde dehydrogenase (ALDH)
- Cytochrome P450 2E1 (CYP2E1) (Correct answer)
- Monoamine oxidase (MAO)
Correct answer: Cytochrome P450 2E1 (CYP2E1)
CYP2E1, located in the endoplasmic reticulum, is the key enzyme of the MEOS pathway and becomes increasingly important at high alcohol concentrations.
Question 2: Henry's Law, as applied to breath alcohol testing, states that at a given temperature:
- Alcohol concentration in breath equals BAC
- The amount of alcohol dissolved in a liquid is proportional to the partial pressure of alcohol above it (Correct answer)
- Breath volume is inversely proportional to BrAC
- Body temperature does not affect breath alcohol vapor pressure
Correct answer: The amount of alcohol dissolved in a liquid is proportional to the partial pressure of alcohol above it
Henry's Law establishes that vapor pressure of a volatile substance in equilibrium with a solution is proportional to its concentration in that solution.
Question 3: A 1°C increase in body temperature above 37°C is estimated to change the breath alcohol reading by approximately:
- Decrease by 6-7%
- Increase by 6-7% (Correct answer)
- Increase by 15%
- No significant change
Correct answer: Increase by 6-7%
Each 1°C rise in body temperature increases alcohol vapor pressure and thus breath alcohol readings by approximately 6-7%, potentially overestimating true BAC.
Question 4: Which of the following conditions can cause endogenous production of mouth alcohol that may interfere with a breath test?
- Hyperglycemia only
- Gastroesophageal reflux disease (GERD) or belching (Correct answer)
- Severe anemia
- Hypothyroidism
Correct answer: Gastroesophageal reflux disease (GERD) or belching
GERD or belching can bring stomach alcohol vapors into the mouth and upper airway, potentially elevating BrAC readings if testing is not delayed.
Question 5: The standard observation period before conducting an evidential breath test is intended to ensure:
- The subject is sober enough to consent
- No mouth alcohol from regurgitation, belching, or oral alcohol sources is present (Correct answer)
- The instrument has warmed up properly
- The subject has not eaten recently
Correct answer: No mouth alcohol from regurgitation, belching, or oral alcohol sources is present
The 15-20 minute deprivation/observation period ensures that any mouth alcohol dissipates so that only deep-lung alveolar air is sampled.
Question 6: Acetate, the final major metabolic product of alcohol oxidation, is primarily:
- Excreted unchanged in urine
- Released into the bloodstream and oxidized in peripheral tissues (Correct answer)
- Converted back to ethanol under hypoxic conditions
- Stored as glycogen in the liver
Correct answer: Released into the bloodstream and oxidized in peripheral tissues
Acetate is released from the liver into the bloodstream and taken up by muscle and other peripheral tissues where it is oxidized to CO2 and water via the TCA cycle.
Question 7: Which hepatic factor most significantly limits the maximum rate of alcohol metabolism in a non-tolerant adult?
- Liver size
- NAD+ availability (NADH/NAD+ ratio) (Correct answer)
- Blood flow through the portal vein
- Bile acid concentration
Correct answer: NAD+ availability (NADH/NAD+ ratio)
The regeneration of NAD+ from NADH is the rate-limiting step; as NADH accumulates, ADH activity slows, effectively capping the elimination rate.
BAT Alcohol Metabolism & Physiology 3
The microsomal ethanol oxidizing system (MEOS) primarily involves which enzyme?