Cellular location: Where are the enzymes of glycolysis found within a eukaryotic cell?

Introduction / Context:
Subcellular localization of pathways influences regulation and metabolite channeling. Glycolysis supplies ATP and intermediates for biosynthesis and links to mitochondrial respiration or fermentation depending on oxygen availability.

Given Data / Assumptions:

• Eukaryotic cells compartmentalize metabolism.
• Glycolysis converts glucose to pyruvate.
• Mitochondria carry out the citric acid cycle and oxidative phosphorylation.

Concept / Approach:
Glycolytic enzymes (e.g., hexokinase, phosphofructokinase, pyruvate kinase) reside in the cytosol. Pyruvate is then transported into mitochondria for oxidation (aerobic conditions) or converted to lactate in the cytosol (anaerobic conditions). This spatial separation allows rapid ATP generation near cellular processes and efficient handoff to mitochondrial metabolism.

Step-by-Step Solution:
Identify pathway: glucose → pyruvate (glycolysis).Recall localization: cytosolic enzymes catalyze each step.Select the cytosol as the correct compartment.

Verification / Alternative check:
Biochemical fractionation places glycolytic activities in the cytosolic fraction; mitochondrial matrix assays lack these enzymes but host pyruvate dehydrogenase and TCA enzymes.

Why Other Options Are Wrong:

• Intermembrane space / mitochondrial matrix: Host respiration, not glycolysis.
• Plasma membrane / ER lumen: Not primary sites for glycolytic enzyme sets.

Common Pitfalls:
Confusing pyruvate metabolism (mitochondria) with glycolysis itself (cytosol).

Final Answer:
Cytosol.