How do poisons and drugs affect cellular respiration?

Poisons and drugs can disrupt cellular respiration by inhibiting enzymes or blocking pathways involved in the process.

Cellular respiration is a vital process that occurs in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The process involves a series of metabolic reactions and is divided into four stages: glycolysis, the link reaction, the Krebs cycle, and the electron transport chain. Poisons and drugs can interfere with this process in various ways, leading to harmful effects on the organism.

Certain poisons, such as cyanide and carbon monoxide, can directly inhibit cellular respiration. Cyanide is a potent poison that binds to one of the proteins in the electron transport chain, preventing the transfer of electrons and the pumping of protons across the membrane. This stops the production of ATP, leading to a rapid depletion of energy in the cell. Carbon monoxide, on the other hand, binds to haemoglobin in red blood cells more readily than oxygen does, reducing the amount of oxygen that can be transported to cells for use in cellular respiration.

Drugs can also affect cellular respiration, although their effects can be more varied. Some drugs, such as antimycin A, act similarly to cyanide by inhibiting the electron transport chain. Others, like metformin, a common drug used to treat type 2 diabetes, inhibit the process of glycolysis. This reduces the amount of glucose that is broken down, thereby lowering blood sugar levels. However, this also means that less substrate is available for the later stages of cellular respiration, potentially affecting ATP production.

In addition, some substances can affect cellular respiration indirectly. For example, alcohol and other depressant drugs can slow down the nervous system, reducing the rate of respiration in cells. This can lead to a decrease in the overall rate of cellular respiration, as less oxygen is available for the process.

IB Biology Tutor Summary: Poisons and drugs disrupt the process by which cells turn food into energy, known as cellular respiration. They do this by blocking the steps required to produce ATP, the energy currency of cells. For example, cyanide stops energy production, carbon monoxide reduces oxygen for energy use, and some drugs interfere with glucose breakdown, affecting energy levels in various ways.