Question

The number of molecules of pyruvic acid formed from one molecule of glucose at the end of glycolysis is (a) 1 (b) 2 (c) 3 (d) 4

Short answer

The number of molecules of pyruvic acid formed from one molecule of glucose at the end of glycolysis is 2.

Step-by-step solution

Understand Glycolysis

Glycolysis is a metabolic pathway in which one glucose molecule (C6) is splitted into two pyruvic acid molecules (C3). This is a ten-step process that occurs in the cytoplasm of the cell.

Apply Knowledge to Question

Since one glucose molecule is needed to produce two pyruvic acid molecules in glycolysis, the number of pyruvic acid molecules formed from one glucose molecule at the end of glycolysis is 2.

Key concepts

Glycolysis

Glycolysis is the first major step of carbohydrate metabolism, which plays a pivotal role in the process of energy production. It begins with a single six-carbon molecule of glucose and ends with the production of two three-carbon molecules of pyruvic acid. During this anaerobic process, which does not require oxygen, a series of ten enzyme-catalyzed reactions occur in the cytoplasm of the cell.

The key phases of glycolysis can be divided into two main stages: the energy investment phase and the energy payoff phase. In the initial phase, two ATP molecules are used to modify glucose and create a compound that can be readily broken down in later steps. The second phase is where the energy is harvested, resulting in the production of four ATP molecules, two NADH molecules, and two pyruvic acid molecules.

This net gain of two ATP molecules per glucose molecule illustrates the efficiency of glycolysis in extracting energy, even in the absence of oxygen. The pyruvic acid generated is then ready for further processing in the cell's metabolism, either entering the anaerobic fermentation pathway or continuing into the aerobic Krebs cycle if oxygen is present.

Metabolic pathways

Metabolic pathways are series of chemical reactions that occur within a biological cell, governed by specific enzymes. These biochemical pathways are highly regulated and are key to maintaining homeostasis in the body. They are essentially the roads of the cell's metabolic map, with each pathway functioning as a route to synthesize or break down molecules necessary for life.

Glycolysis is one such metabolic pathway, and it serves as a crucial junction connecting several different metabolic routes. Following glycolysis, pyruvic acid is a metabolic crossroad molecule; it can either undergo fermentation to be converted into lactate or ethanol, or it can be transformed into acetyl-CoA to enter the aerobic Krebs cycle for further energy extraction.

Understanding these pathways allows us to appreciate the efficiency and adaptability of cellular processes, as they can radically alter their function based on the energy needs of the cell and the availability of oxygen. Metabolic pathways are not standalone - they're interlinked to form an intricate network that supports the cell's dynamic functions.

Glucose metabolism

Glucose metabolism is fundamental to life, serving as the primary source of energy for most organisms. It encompasses the entire process of glucose conversion, from the point of entry into the body through to its final usage or storage. Glycolysis is the first stage of this metabolic process after glucose enters a cell.

From glycolysis, we see two pivotal pathways diverge: aerobic and anaerobic metabolism. In aerobic conditions, where oxygen is plentiful, pyruvic acid enters the mitochondria of cells to be converted into acetyl-CoA and fully oxidized in the Krebs cycle, eventually leading to ATP production through the electron transport chain. In anaerobic conditions, such as in muscle cells during intense exercise, pyruvic acid is fermented into lactate, allowing glycolysis to continue but producing less energy.

The elegance of glucose metabolism lies in its versatility; the body can store glucose as glycogen, convert it to fat, or immediately use it for energy, ensuring that cells receive a constant supply of ATP to perform every function, from muscle contraction to neural activity.