Tobacco Smoke | 烟草烟雾

📚 Tobacco Smoke | 烟草烟雾

Tobacco smoke is a major preventable cause of disease and premature death worldwide. It contains thousands of chemicals that harm nearly every organ in the human body, with particularly severe effects on the respiratory and cardiovascular systems. Understanding the constituents of tobacco smoke and their mechanisms of action is a key component of the A-Level Biology syllabus, shedding light on how lifestyle choices can lead to chronic diseases such as chronic obstructive pulmonary disease (COPD), lung cancer, and coronary heart disease.

烟草烟雾是全球可预防性疾病和过早死亡的主要原因。它含有数千种化学物质，对人体几乎每个器官都有害，尤其对呼吸和心血管系统影响严重。了解烟草烟雾的成分及其作用机制是 A-Level 生物课程的重要内容，有助于阐明生活方式如何导致慢性阻塞性肺疾病（COPD）、肺癌和冠心病等慢性病。

1. Composition of Tobacco Smoke | 烟草烟雾的组成

Tobacco smoke is an aerosol produced by the incomplete combustion of tobacco leaves. It comprises both a gaseous phase and a particulate phase (tar). The gaseous phase includes carbon monoxide, carbon dioxide, nitrogen oxides, ammonia, and hydrogen cyanide, while the particulate phase contains nicotine, polycyclic aromatic hydrocarbons, nitrosamines, and heavy metals. Over 70 of the chemicals present are known carcinogens.

烟草烟雾是烟草叶不完全燃烧产生的气溶胶。它包含气相和颗粒相（焦油）。气相包括一氧化碳、二氧化碳、氮氧化物、氨和氰化氢，而颗粒相含有尼古丁、多环芳烃、亚硝胺和重金属。其中超过 70 种化学物质是已知的致癌物。

The three most significant components in terms of pathology are nicotine, tar, and carbon monoxide. Nicotine is the addictive alkaloid; tar is a viscous mix that deposits in the lungs and contains the majority of carcinogens; carbon monoxide is a toxic gas that impairs oxygen delivery.

从病理学角度最重要的三种成分是尼古丁、焦油和一氧化碳。尼古丁是致瘾的生物碱；焦油是一种沉积在肺部的黏性混合物，含有大多数致癌物；一氧化碳是一种有毒气体，会妨碍氧气运输。

2. Nicotine: The Addictive Agent | 尼古丁：成瘾因子

Nicotine is a tertiary amine alkaloid that rapidly reaches the brain after inhalation, where it binds to nicotinic acetylcholine receptors. This triggers the release of dopamine and other neurotransmitters, producing feelings of pleasure and reward, which underlie its high addiction potential.

尼古丁是一种叔胺生物碱，吸入后迅速进入大脑，与烟碱型乙酰胆碱受体结合。这触发了多巴胺等神经递质的释放，产生愉悦和奖赏感，这就是其强成瘾潜力的基础。

In the peripheral nervous system, nicotine stimulates sympathetic ganglia, causing the release of adrenaline from the adrenal medulla. This increases heart rate, constricts blood vessels, and elevates blood pressure, placing additional strain on the cardiovascular system.

在外周神经系统，尼古丁刺激交感神经节，促使肾上腺髓质释放肾上腺素。这导致心率加快、血管收缩和血压升高，给心血管系统带来额外负担。

Additionally, nicotine increases the stickiness of blood platelets, raising the risk of thrombus (blood clot) formation. This, combined with elevated blood pressure, significantly increases the likelihood of coronary thrombosis and stroke.

此外，尼古丁增加血小板的黏附性，提高血栓形成风险。这结合血压升高，显著增加了冠状动脉血栓形成和中风的可能性。

3. Tar and Carcinogens | 焦油与致癌物

Tar is the particulate matter in tobacco smoke that condenses into a sticky brown residue when cooled. It accumulates on the lining of the trachea, bronchi, and bronchioles, and is the main carrier of chemical carcinogens such as benzopyrene, nitrosamines, and aromatic amines.

焦油是烟草烟雾中冷却后凝结成黏稠棕色残留物的颗粒物。它沉积在气管、支气管和细支气管的内壁，是苯并芘、亚硝胺和芳香胺等化学致癌物的主要载体。

These carcinogens can directly damage DNA in epithelial cells. For example, benzopyrene is metabolised in the body into an epoxide that covalently binds to DNA, forming adducts. If these lesions are not repaired, they can cause mutations in tumour suppressor genes (such as TP53) and proto-oncogenes, initiating the development of cancer.

这些致癌物可直接损伤上皮细胞的DNA。例如，苯并芘在体内被代谢成环氧化物，与DNA共价结合形成加合物。如果这些损伤未被修复，就可能导致抑癌基因（如TP53）和原癌基因发生突变，启动癌症的发展。

Tar also irritates the respiratory lining, stimulating

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