What is the role of oxygen in aerobic respiration?
The role of oxygen in aerobic respiration is to act as the final electron acceptor in the electron transport chain. During aerobic respiration, glucose is broken down in the presence of oxygen to produce energy in the form of ATP (adenosine triphosphate), carbon dioxide, and water.
To understand the role of oxygen in aerobic respiration, let's break it down into steps:
1. Glycolysis: This is the first step of respiration, which occurs in the cytoplasm of cells. In this step, one molecule of glucose is converted into two molecules of pyruvate, producing a small amount of ATP. Oxygen is not directly involved in this step.
2. Pyruvate Decarboxylation: Next, each pyruvate molecule enters the mitochondria and undergoes decarboxylation, where one carbon is removed from each pyruvate, forming carbon dioxide. This step produces NADH (nicotinamide adenine dinucleotide) as a reduced electron carrier. Again, oxygen is not directly involved here.
3. Citric Acid Cycle (or Krebs cycle): In this step, the carbon dioxide released from previous steps is further broken down in the mitochondria. The carbon atoms are extracted and transferred to carrier molecules (NADH and FADH2) as high-energy electrons. This process generates more ATP, carbon dioxide, and more NADH and FADH2. Oxygen is still not directly involved.
4. Electron Transport Chain (ETC): This is the final step of aerobic respiration that takes place in the inner mitochondrial membrane. Here, the high-energy electrons from NADH and FADH2 are transported through a series of protein complexes, releasing energy. This energy is used to pump protons (H+) across the membrane, creating a concentration gradient. Finally, at the end of the electron transport chain, oxygen is required as the final electron acceptor.
Oxygen combines with the electrons and protons to form water (H2O), thereby removing the electrons from the electron transport chain and completing aerobic respiration. Without oxygen, the electron transport chain would not be able to function properly, and respiration would not proceed efficiently.
So, to summarize, oxygen's role in aerobic respiration is to serve as the final electron acceptor in the electron transport chain, allowing the process to generate ATP efficiently.