HESI A2 Biology Practice Test

Glycolysis is the process that breaks down glucose to produce energy. This metabolic pathway occurs in the cytoplasm of cells and consists of a series of enzymatic reactions that convert one molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon compound). During this process, a small amount of energy is released in the form of ATP (adenosine triphosphate), which is the primary energy carrier in cells. Additionally, glycolysis generates reduced electron carriers, such as NADH, which can be used in further stages of cellular respiration to yield even more ATP.

In contrast, fermentation is an anaerobic process that occurs after glycolysis when oxygen is not present, allowing for the recycling of NADH but not a full oxidation of glucose to produce as much energy as possible. Photosynthesis, on the other hand, is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose, rather than breaking it down. Chemiosmosis refers to the movement of ions across a selectively permeable membrane, specifically in the context of generating ATP in mitochondria during oxidative phosphorylation, and is not directly involved in the initial breakdown of glucose.