Answer:
cellular respiration.
Step-by-step explanation:
Cellular respiration is the metabolic process by which cells break down organic molecules, such as glucose, to release energy in the form of adenosine triphosphate (ATP). This process occurs in the presence of oxygen and is commonly divided into three main stages: glycolysis, the citric acid cycle (also known as the Krebs cycle), and oxidative phosphorylation (including the electron transport chain).
Here's a brief overview of these stages:
1. Glycolysis: This is the initial stage of cellular respiration, which takes place in the cytoplasm of the cell. During glycolysis, a molecule of glucose is broken down into two molecules of pyruvate. This process results in a small amount of ATP and electron carriers, such as NADH.
2. Citric Acid Cycle: Also known as the Krebs cycle, this stage takes place in the mitochondria. The pyruvate from glycolysis is further broken down, releasing carbon dioxide and generating additional ATP, electron carriers (NADH and FADH2), and other intermediate molecules.
3. Oxidative Phosphorylation: This stage occurs in the inner mitochondrial membrane. The electron carriers (NADH and FADH2) produced in the previous stages donate electrons to the electron transport chain. As the electrons move through the chain, energy is released, which is used to pump protons (H+) across the membrane. The flow of protons back across the membrane generates ATP through a process called chemiosmosis.
Overall, cellular respiration is the process that allows cells to extract energy from food molecules and convert it into ATP, which can be used as a direct source of energy for various cellular activities.