Problem 15 Most of the ATP produced during ... [FREE SOLUTION] (2024)

Short Answer

Glycolysis

Glycolysis is the first step in cellular respiration. This process takes place in the cytoplasm of the cell. During glycolysis, one molecule of glucose (a six-carbon sugar) is broken down into two molecules of pyruvate (a three-carbon compound). This breakdown releases energy, which is used to produce a small amount of ATP. Specifically, glycolysis produces 2 ATP molecules per glucose molecule through substrate-level phosphorylation. Glycolysis also produces 2 NADH molecules, which are used later in the electron transport chain.

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, occurs in the mitochondria. Each pyruvate molecule from glycolysis is converted into Acetyl-CoA, which enters the citric acid cycle. The main purpose of the citric acid cycle is to produce high-energy electron carriers (NADH and FADH2) that will be used in the electron transport chain. Additionally, the cycle produces 2 ATP molecules per glucose molecule through substrate-level phosphorylation. The citric acid cycle also releases carbon dioxide as a waste product.

Electron Transport Chain

The electron transport chain (ETC) is located in the inner mitochondrial membrane. This is where most of the ATP during cellular respiration is produced. High-energy electrons from NADH and FADH2 (produced during glycolysis and the citric acid cycle) are transferred through a series of proteins. As electrons move through the ETC, energy is released and used to pump protons across the membrane, creating a gradient. This gradient drives the production of ATP through oxidative phosphorylation. The electron transport chain produces about 34 ATP molecules per glucose molecule.

Anaerobic Respiration

Anaerobic respiration occurs when oxygen is not available. In this process, cells rely on glycolysis for ATP production, followed by fermentation to regenerate NAD+. Lactate fermentation (in animals) and alcoholic fermentation (in yeast) are common types. Both processes produce very little ATP compared to aerobic respiration. For instance, fermentation yields only 2 ATP molecules per glucose molecule. Anaerobic pathways are less efficient than aerobic pathways because they do not use the electron transport chain.

Oxidative Phosphorylation

Oxidative phosphorylation is the final stage of cellular respiration and occurs in the mitochondria. This process is driven by the electron transport chain. The energy released from electrons moving through the ETC creates a proton gradient across the mitochondrial membrane. ATP synthase, an enzyme, uses this proton gradient to synthesize ATP from ADP and inorganic phosphate. Oxidative phosphorylation is responsible for producing the majority of ATP in cellular respiration, generating approximately 34 ATP molecules from one glucose molecule.