At molecular level, why do many organisms need oxygen to survive?
At the molecular level, many organisms require oxygen to survive because it is essential for a process called aerobic respiration. Aerobic respiration is a series of biochemical reactions that occur within the cells of organisms to generate energy for various cellular activities. Here is an explanation of the process and why oxygen is necessary:
1. Aerobic respiration:
Aerobic respiration involves the breakdown of organic molecules (such as glucose) in the presence of oxygen to produce energy in the form of ATP (adenosine triphosphate). ATP is the energy currency of cells and is required for various biological processes.
2. Oxygen as the final electron acceptor:
During the process of aerobic respiration, the organic molecules are broken down through a series of chemical reactions in a process called the electron transport chain. In this chain, electrons are passed from one molecule to another until they ultimately reach molecular oxygen (O2), which acts as the final electron acceptor. Oxygen combines with these electrons and protons to form water (H2O).
3. ATP production:
As the electrons flow through the electron transport chain, they release energy, which is used to pump protons (H+) across a membrane. This creates a concentration gradient of protons, which drives the production of ATP through a protein complex called ATP synthase. Oxygen's role as the final electron acceptor is crucial for this process, as it allows the continuous flow of electrons, creating a steady supply of usable energy in the form of ATP.
4. Alternative energy sources:
While oxygen is the most efficient electron acceptor, some organisms can survive in environments with low oxygen levels or even absence of oxygen. These organisms can utilize alternative energy sources or perform alternative forms of respiration, such as anaerobic respiration or fermentation. Anaerobic respiration uses other electron acceptors like sulfate or nitrate, while fermentation does not involve electron transport chain and uses organic molecules as the final electron acceptor.
In summary, oxygen is vital for many organisms at the molecular level because it serves as the final electron acceptor in aerobic respiration, allowing the efficient production of ATP, which is essential for cellular functions and survival.