Question

Identify each of the following as a six-carbon or a three-carbon compound and arrange them in the order in which they occur in glycolysis: a. 3 -phosphoglycerate b. pyruvate c. glucose-6-phosphate d. glucose e. fructose- 1,6 -bisphosphate

Short answer

Glucose, Glucose-6-phosphate, Fructose-1,6-bisphosphate, 3-Phosphoglycerate, Pyruvate

Step-by-step solution

Identify the six-carbon compounds

Six-carbon compounds in glycolysis include glucose, glucose-6-phosphate, and fructose-1,6-bisphosphate. These molecules initially have six carbon atoms.

Identify the three-carbon compounds

Three-carbon compounds include 3-phosphoglycerate and pyruvate. These are the products of the split of six-carbon molecules.

Arrange compounds in the order of occurrence in glycolysis

1. Glucose (six-carbon) 2. Glucose-6-phosphate (six-carbon) 3. Fructose-1,6-bisphosphate (six-carbon) 4. 3-Phosphoglycerate (three-carbon) 5. Pyruvate (three-carbon)

Key concepts

Six-carbon compounds

In the glycolysis pathway, six-carbon compounds play a significant role in the initial stages. These compounds have six carbon atoms in their structure, providing a starting point for the breakdown of glucose into energy. The major six-carbon compounds in glycolysis include:

• Glucose: The primary sugar molecule that serves as the initial substrate in glycolysis.
• Glucose-6-phosphate: Formed from glucose through phosphorylation by the enzyme hexokinase.
• Fructose-1,6-bisphosphate: Produced by the phosphorylation of fructose-6-phosphate and considered a key intermediate in glycolysis.

Each of these compounds undergoes various enzymatic reactions, leading to the production of energy and the eventual splitting into smaller molecules.

Three-carbon compounds

As glycolysis progresses, the six-carbon compounds are split into three-carbon compounds. These smaller molecules are crucial for extracting energy from glucose and are involved in the later stages of glycolysis. The three-carbon compounds in glycolysis include:

• 3-Phosphoglycerate: A molecule formed from 1,3-bisphosphoglycerate during the energy-yielding phase of glycolysis.
• Pyruvate: The end product of glycolysis, which can enter further metabolic pathways like the citric acid cycle for additional energy production.

These three-carbon compounds, derived from the breakdown of six-carbon molecules, help convert chemical energy into ATP, the cell's primary energy currency.

Metabolic order

Glycolysis follows a specific sequence known as metabolic order, where each compound gets transformed step by step. Understanding this order is crucial for grasping how cells derive energy from glucose. Here are the key steps in metabolic order during glycolysis:

• First, glucose (a six-carbon compound) is phosphorylated to form glucose-6-phosphate.
• This is then converted into fructose-6-phosphate, followed by phosphorylation to create fructose-1,6-bisphosphate.
• The six-carbon fructose-1,6-bisphosphate is split into two three-carbon molecules, including 3-phosphoglycerate.
• Finally, 3-phosphoglycerate is converted into pyruvate, concluding the glycolysis pathway.

This ordered sequence ensures a controlled release of energy, which cells can capture efficiently.