What is the function of a glucose molecule in cellular respiration?
The correct answer and explanation is:
Glucose plays a central role in cellular respiration, which is the process by which cells convert nutrients into energy. The primary function of a glucose molecule in this process is to serve as the main fuel for the production of ATP (adenosine triphosphate), the energy currency of the cell. Glucose, a six-carbon sugar, undergoes a series of chemical reactions in three main stages: Glycolysis, the Krebs cycle (also called the citric acid cycle), and oxidative phosphorylation (electron transport chain and chemiosmosis).
- Glycolysis: In the first stage of cellular respiration, glucose is broken down in the cytoplasm into two molecules of pyruvate. This process occurs in the absence of oxygen (anaerobic) and produces a small amount of ATP and NADH. Glycolysis is essential because it begins the process of breaking down glucose, providing the cell with the necessary intermediates for further stages of respiration.
- Krebs Cycle: The pyruvate molecules produced in glycolysis are transported into the mitochondria, where they are further broken down into acetyl-CoA. This acetyl-CoA enters the Krebs cycle, where it is further oxidized to produce more high-energy molecules, such as NADH, FADH2, and ATP. During this cycle, carbon atoms from glucose are released as carbon dioxide.
- Oxidative Phosphorylation: The NADH and FADH2 produced in earlier stages carry electrons to the electron transport chain in the mitochondria, where they pass through a series of proteins, releasing energy used to pump protons (H+) across the mitochondrial membrane. This creates an electrochemical gradient, which drives the production of ATP through a process known as chemiosmosis. Oxygen is the final electron acceptor, combining with electrons and protons to form water.
Through these stages, glucose is fully oxidized to carbon dioxide and water, and in the process, a significant amount of ATP is generated, providing energy for cellular functions.