Basic and Clinical Sciences Examination (BCSE) Practice Exam 2025 – Comprehensive All-in-One Guide for Exam Success

Carbon monoxide is primarily found in the gas phase of tobacco smoke due to its volatility and the combustion process involved in smoking. When tobacco is burned, it produces a range of gases, and carbon monoxide is a significant byproduct of incomplete combustion. It enters the lungs readily because it exists as a gas at room temperature and can easily diffuse across the alveolar membrane.

In contrast, nicotine, while present in tobacco smoke, is primarily found in the particulate phase as it condenses into liquid and solid particles. Benzo-a-pyrene is another toxic compound associated with tobacco smoke, but it is also more detectable in the particulate phase rather than the gas phase. Amino acids, although present in tobacco, do not constitute a toxic component typically analyzed in the context of tobacco toxicity.

The presence of carbon monoxide in the gas phase is particularly concerning due to its high affinity for hemoglobin, which can interfere with oxygen transport in the bloodstream, leading to potentially serious health outcomes.