Question

Suggest a reason as to why \(\mathrm{CO}\) is poisonous.

Short answer

CO binds strongly to hemoglobin, reducing oxygen transport.

Step-by-step solution

Understanding Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless gas that can be very harmful to humans. Its chemical formula is CO, consisting of one carbon atom and one oxygen atom.

Mechanism of Poisoning

CO is poisonous because it binds with hemoglobin in the blood to form carboxyhemoglobin. This compound is created when CO attaches to the iron in hemoglobin—where oxygen would typically bind.

Comparing Oxygen and CO Affinity

Hemoglobin has a much higher affinity for CO than for oxygen—about 230 times stronger. Because of this strong affinity, CO competes successfully for binding sites on hemoglobin, leading to reduced oxygen transport in the blood.

Effects on Oxygen Transport

When CO binds to hemoglobin, it severely reduces the blood's ability to carry oxygen to cells and tissues. This can lead to cellular asphyxiation, and even small amounts can have serious health effects, leading to symptoms like headaches, dizziness, or even death at high concentrations.

Key concepts

Hemoglobin Affinity

Hemoglobin is a protein in our red blood cells that plays a crucial role in transporting oxygen from the lungs to various parts of the body. This transport is possible because hemoglobin has the ability to bind with oxygen molecules. However, this ability is governed by a concept known as "affinity." Affinity refers to the strength with which hemoglobin binds to a substance, in this case, oxygen.
When carbon monoxide (CO) is inhaled, it presents a significant risk because hemoglobin exhibits an extraordinary affinity for CO, which is strikingly higher compared to its affinity for oxygen. Research has shown that hemoglobin's affinity for CO is approximately 230 times greater than its affinity for oxygen. This means, in the presence of CO, hemoglobin prefers binding with CO rather than oxygen, even if both gases are present.

• This stronger binding preference prevents hemoglobin from effectively carrying oxygen.
• It can result in limited oxygen reaching essential organs and tissues.

This significant difference in affinity is a fundamental reason CO is highly poisonous and capable of disrupting normal bodily functions.

Carboxyhemoglobin

Carboxyhemoglobin forms when carbon monoxide binds to hemoglobin. This compound is dangerous because it directly interferes with the blood's role in transporting oxygen.
The binding of CO to hemoglobin minimizes the number of available binding sites for oxygen. Every molecule of CO bound creates carboxyhemoglobin, rendering that hemoglobin molecule useless in terms of oxygen transportation.

• This not only reduces the blood's overall capacity to carry oxygen, but it also shifts the remaining oxygenated hemoglobin into a tighter binding state.
• In this tighter state, hemoglobin's ability to release oxygen to tissues becomes compromised.

The presence of carboxyhemoglobin in the blood leads to a cascade of health issues, because tissues and organs are deprived of adequate oxygen. This includes critical organs such as the brain and heart, potentially leading to symptoms such as confusion, fatigue, and heart complications.

Oxygen Transport

Oxygen transport is a critical function of the circulatory system, involving the movement of oxygen from the lungs to the body tissues and cells, and carbon dioxide back to the lungs. Hemoglobin is central to this process, enhancing oxygen's solubility in blood and enabling its widespread distribution.
When carbon monoxide is present, the process of oxygen transport is significantly disrupted. CO enters the bloodstream and binds with hemoglobin, thus forming carboxyhemoglobin, which occupies the space where oxygen would typically bind. This prevents oxygen from attaching to hemoglobin and being delivered to the body's tissues.

• The reduction in oxygen transport efficiency leads to decreased oxygen levels in body tissues, often resulting in symptoms ranging from mild, such as headaches and nausea, to severe, such as unconsciousness and death, depending on CO exposure levels.
• The healthy interaction between tissues and carbon dioxide is also disrupted, affecting the overall balance of gas exchange in the body.

Therefore, uninterrupted oxygen transport is crucial for survival, and any interference, especially from carbon monoxide, is potentially life-threatening.