Glycolysis — Science definition

A cytosolic pathway converting glucose to pyruvate with a net gain of two ATP per glucose.

Where it is taught

In use

Glycolysis in the cytosol yields pyruvate and a net two ATP per glucose.

Cellular Respiration

Questions using glycolysis

Problem 1

How many ATP molecules does glycolysis produce as a NET gain from one glucose?
Answer and explanation

2 ATP

Glycolysis makes 4 ATP but spends 2 to get started, for a net gain of 2 ATP.

Problem 2

Using model yields of 30 ATP per glucose aerobically and 2 from glycolysis supported by fermentation, how many times as much ATP is obtained aerobically?
Answer and explanation

15 times

30 ÷ 2 = 15 under the stated model.

Problem 3

Why can fermentation help glycolysis continue when oxygen-dependent pathways are unavailable? Show the reasoning, not just the conclusion.
Hints

Atoms and energy must be accounted for separately.

Answer and explanation

It regenerates NAD⁺ needed for glycolysis, with products depending on the organism/pathway.

Problem 4

Fermentation can keep glycolysis supplied with a required carrierFermentation can keep glycolysis supplied with a required carrierGlycolysisuses NAD⁺Fermentationregenerates NAD⁺Net glycolytic ATP in the supplied glucose model: 2 ATP.Fermentation supports carrier recycling, not a second large ATP yield.
Original carrier-recycling abstraction; the two-ATP count belongs to the stated glycolysis model, not every anaerobic process.
Interpret the supplied visual. What would limit ongoing glycolysis if the needed oxidized carrier were not regenerated?
Answer and explanation

The carrier supply would become insufficient; regeneration enables continued pathway flow under suitable conditions.

NAD⁺ is an electron carrier used in glycolysis, becoming reduced NADH. Fermentation regenerates NAD⁺ by transferring electrons to selected organic products, allowing glycolysis to continue under suitable conditions. In the simple glucose-to-glycolysis account, the net ATP yield is two per glucose; the fermentation conversion is not an additional large ATP-producing electron-transport system. Different fermentation pathways produce different materials, such as lactate or ethanol plus CO₂. “Anaerobic” does not name one identical pathway for every organism.

The carrier supply would become insufficient; regeneration enables continued pathway flow under suitable conditions.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

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