Difference Between Glycolysis and Krebs Cycle

Respiration is an essential process that occurs in all living beings in which oxygen is utilised and carbon dioxide is released from the body. The mechanism of cellular respiration involves the following mechanism:

  • Glycolysis – Partial breakdown of Glucose to Pyruvic acid (Anaerobic)
  • Krebs Cycle – Complete oxidation of Pyruvate to release Carbon dioxide (Aerobic respiration)
  • Electron Transport system – Oxidation of NADH and FADH2 to generate ATP

Here, in the article, let us discuss the difference between the Krebs Cycle and glycolysis but first let us take a look at what each of these terms means.

Glycolysis – It is an anaerobic process, which occurs in the cytoplasm of the cell. In glycolysis, partial oxidation of glucose occurs, which yields two molecules of pyruvic acid.

Krebs Cycle – It is an aerobic process that takes place in the mitochondria of the cell. It gives Carbon dioxide after complete oxidation of pyruvic acid formed during glycolysis.

Given below in a tabular column are the differences between glycolysis and Krebs Cycle.

Also Read: TCA Cycle

Glycolysis vs Krebs Cycle


Glycolysis Krebs Cycle
It is the first step of respiration yielding two molecules of pyruvic acid after the partial breakdown of a glucose molecule in a set of enzymatic processes Krebs Cycle is the second step of aerobic respiration in which pyruvate is oxidised completely into inorganic substances forming carbon dioxide
Occurs in all the living organisms Occurs in aerobes
Occurs inside the cytoplasm Occurs inside the mitochondria
No carbon dioxide evolved Carbon dioxide evolved
Oxygen not required for glycolysis Oxygen is required for Krebs Cycle
Four ATP molecules are produced in the glycolysis for each glucose molecule One ATP or GTP molecule is produced by substrate-level phosphorylation in each turn of the Kreb’s cycle
Consumes 2 molecules of ATP for initial phosphorylation of substance molecules Doesn’t consume ATP
 Net gain of two molecules of ATP and two molecules of NADH gained for every molecule of glucose broken down  Each turn of the Krebs cycle yields three molecules of NADH and two molecules of FADH2
Occurs as a linear sequence Occurs as a cyclic sequence

Both glycolysis and the Krebs cycle are enzyme-mediated and are under constant regulation based on the energy requirement of the cell/organism. The rates of these processes vary under various conditions such as the well-fed state, fasting state, exercised state and starvation state.

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