Question

What is the end product of glycolysis?

Short answer

The end products of glycolysis are two pyruvate molecules, two ATP molecules, and two NADH molecules.

Step-by-step solution

Understand Glycolysis

Glycolysis is a metabolic pathway that breaks down glucose to extract energy for cellular metabolism. It is the first step in cellular respiration, occurring in the cytoplasm of the cell.

Glycolysis Phases

Glycolysis has two main phases: the energy investment phase and the energy payoff phase. In the energy investment phase, two ATP molecules are used to modify glucose. In the energy payoff phase, four ATP molecules are produced, along with two NADH molecules.

Final Products

At the end of glycolysis, one molecule of glucose (a six-carbon molecule) is split into two molecules of pyruvate (a three-carbon molecule). Additionally, a net gain of two ATP molecules and two NADH molecules are produced.

Summary

To sum up, glycolysis breaks down one molecule of glucose into two molecules of pyruvate, with a net production of two ATP molecules and two NADH molecules.

Key concepts

metabolic pathway

A metabolic pathway is a series of chemical reactions within a cell. These reactions are connected; the product of one reaction becomes the substrate for the next. Glycolysis is one such metabolic pathway. It begins with glucose, a six-carbon molecule, and through a series of steps, converts it into pyruvate, which is a three-carbon molecule.
Glycolysis occurs in nearly all living organisms and takes place in the cytoplasm of the cell. It is one of the most ancient metabolic pathways, thought to have evolved over a billion years ago. The pathway involves 10 enzyme-catalyzed reactions, divided into two phases: the energy investment phase and the energy payoff phase.

ATP production

ATP, or Adenosine Triphosphate, is the energy currency of the cell. During glycolysis, ATP production occurs primarily in the energy payoff phase.
In the energy investment phase, the cell uses 2 ATP molecules to phosphorylate glucose, preparing it for later steps. In the energy payoff phase, these phosphorylated molecules are converted into pyruvate, producing 4 ATP molecules. Because 2 ATP were invested at the start, the net gain is 2 ATP per glucose molecule.
This ATP is used for various cellular functions, providing energy for processes such as muscle contraction, protein synthesis, and cell division.

pyruvate formation

Pyruvate formation happens in the final steps of glycolysis. As a glucose molecule is broken down and modified, it eventually results in two molecules of pyruvate. Pyruvate is a crucial molecule in cellular metabolism.
Each molecule of glucose produces two pyruvate molecules, each of which contains three carbon atoms. Pyruvate can then be used in several ways, depending on the cell's needs and the presence of oxygen:

• In the presence of oxygen, pyruvate enters the mitochondria and is further broken down in the citric acid cycle.
• Without oxygen, pyruvate can undergo fermentation to produce lactate in animals or ethanol in plants and yeast.

The formation of pyruvate is essential for these subsequent pathways that continue to extract energy from food.

NADH

NADH, or Nicotinamide Adenine Dinucleotide (in its reduced form), plays a vital role in cellular respiration. During glycolysis, NAD⁺ molecules accept electrons, becoming NADH. Specifically, 2 NAD⁺ molecules are reduced to 2 NADH molecules for each glucose molecule processed.
NADH functions as an electron carrier, transporting electrons to the electron transport chain in the mitochondria. There, these electrons help produce a large amount of ATP through oxidative phosphorylation. Each NADH molecule can contribute to the formation of up to 3 ATP molecules, highlighting its importance in energy production.
Thus, NADH generated during glycolysis is a key player in the broader context of cellular respiration and energy generation.