Man dies in an atmosphere of carbon monoxide because

It combines with the haemoglobin of the blood making it incapable of absorbing oxygen

The correct answer is option 3. It combines with the haemoglobin of the blood making it incapable of absorbing oxygen.

Let us dive deeper into the biochemical mechanism and physiological consequences of carbon monoxide \((CO)\) poisoning:

Hemoglobin is a protein in red blood cells responsible for transporting oxygen from the lungs to the tissues and returning carbon dioxide from the tissues to the lungs. Hemoglobin has four subunits, each containing a heme group with an iron atom at its center. Oxygen binds to the iron atom in the heme group, forming oxyhemoglobin \((HbO_2)\).

Carbon Monoxide's Affinity for Hemoglobin

Carbon monoxide \((CO)\) is a colorless, odorless gas that is produced by the incomplete combustion of carbon-containing fuels. \(CO\) has a very high affinity for hemoglobin, about 200-250 times greater than oxygen. When \(CO\) is inhaled, it competes with oxygen for the binding sites on the heme groups in hemoglobin.

Formation of Carboxyhemoglobin

When \(CO\) binds to hemoglobin, it forms carboxyhemoglobin \((COHb)\). The binding of \(CO\) to hemoglobin is effectively irreversible under normal physiological conditions. This has several critical effects:

1. Reduction in Oxygen-Carrying Capacity:

With \(CO\) occupying the binding sites on hemoglobin, fewer sites are available for oxygen. This significantly reduces the oxygen-carrying capacity of the blood.

2. Increased Affinity for Oxygen in Remaining Sites:

The binding of \(CO\) to hemoglobin increases the affinity of the remaining sites for oxygen. This makes it harder for the hemoglobin to release oxygen to the tissues, even where it is needed most.

Physiological Consequences

The combination of reduced oxygen-carrying capacity and impaired oxygen release leads to tissue hypoxia—a condition where tissues are deprived of adequate oxygen. This has widespread effects on the body:

1. Neurological Effects:

The brain is highly sensitive to oxygen deprivation. Symptoms of \(CO\) poisoning often start with headache, dizziness, confusion, and can progress to seizures, loss of consciousness, and even coma.

2. Cardiovascular Effects:

The heart, which requires a constant supply of oxygen to function properly, can suffer from arrhythmias, myocardial ischemia, and eventually cardiac arrest.

3. Muscular and Systemic Effects:

Muscle weakness, fatigue, and general malaise are common. Severe cases can lead to multi-organ failure and death if not treated promptly.

Treatment: Immediate treatment for \(CO\) poisoning is crucial:

1. Removal from Exposure:

The first step is to remove the individual from the \(CO\) source to stop further exposure.

2. Oxygen Therapy:

Administering 100% oxygen via a mask or mechanical ventilation helps to displace \(CO\) from hemoglobin, although this process can take several hours. In severe cases, hyperbaric oxygen therapy may be used, where the patient breathes pure oxygen in a pressurized chamber. This increases the rate at which \(CO\) is removed from hemoglobin and tissues.

Summary

The reason why a person dies in an atmosphere of carbon monoxide is because: It combines with the hemoglobin of the blood making it incapable of absorbing oxygen.

By binding to hemoglobin, \(CO\) prevents oxygen transport and release, leading to tissue hypoxia, organ failure, and ultimately death if not treated promptly.