Difference Between Glycolysis and Krebs Cycle

Main Difference

Glycolysis and Krebs cycle are the pathways in biochemistry. Both of them are of great importance. Glycolysis is the breakdown of glucose into pyruvic acid by the help of an enzyme. It comes in the metabolism of carbohydrates. In glycolysis 2 NADH and 4 ATP are formed, and 2 ATP are utilized, so the energetic of glycolysis are 8 ATP molecules. On the other hand, Krebs cycle is the sequence of reactions in living organisms using oxygen and producing water and CO2 as by-products and forming ATP molecules. Moreover, Krebs cycle is the primary cycle for oxidation of carbohydrates, lipids, and proteins. In Krebs cycle, 3 NADH, 1 FADH, and 1 GTP are produced and no ATP is utilized. Thus the energetics of Krebs cycle are 12 ATP molecules.

Comparison Chart

GlycolysisKrebs Cycle
Main FunctionGlycolysis is concerned with carbohydrate metabolism.Krebs cycle is the primary cycle for oxidation of carbohydrates, lipids, and proteins.
FormationIn glycolysis 2 NADH and 4 ATP are formed, and 2 ATP are utilized, so the energetics of glycolysis is 8 ATP molecules.In Krebs cycle, 3 NADH, 1 FADH, and 1 GTP are produced, and no ATP is utilized. Thus the energetics of Krebs cycle are 12 ATP molecules.
ReactionIt is a straight chain reaction.It is a cyclic reaction.
EnzymesGlycolysis has different enzymes as phospho hexo isomerase, Hexokinase, Aldolase, Dehydrogenase, Kinase, Mutase, and Enolase.Krebs cycle has different enzymes as pyruvate dehydrogenase, citrate synthase, Aconitase, Isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, Succinyl synthase, Succinyl dehydrogenase, Fumarase and Malic dehydrogenase.

What is Glycolysis?

It is one of the metabolisms of carbohydrates. In this, the breakdown of glucose takes place resulting in the formation of pyruvic acid. Glycolysis is the series of reactions that includes different enzymes in it; these oxidize six carbon sugar (glucose) into three carbon compound pyruvic acid with is related to the production of ATP molecules. Glycolysis has total nine steps in which 1st, 3rd, and 9th steps are irreversible.

These steps are as follows:

  • Glucose converts into glucose six phosphates.
  • Glucose 6 phosphates into fructose six
  • Fructose 6 Phosphate into fructose 1, six bisphosphates.
  • Fructose 1, six bisphosphates into glyceraldehyde three phosphate and dihydroxyacetone phosphate.
  • Glyceraldehyde three phosphate and dihydroxyacetone phosphate into 1, three bits phosphoglyceric acids.
  • Three phosphoglyceric acids into three phosphoglyceric acids.
  • Three phosphoglyceric acids into two phosphoglyceric acids.
  • Two phosphoglyceric acids into phosphoenol pyruvic acid.
  • Phosphoenol pyruvic acid into pyruvic acid.

Enzymes involved in these steps are phospho hexo isomerase and Aldolase that are used in the 2nd and 4th step of this process respectively. Glycolysis is of two types; one is aerobic glycolysis, and the other is anaerobic glycolysis. In aerobic glycolysis, 2 NADH and 4 ATP are formed, and 2 ATP are utilized, so the energetics of glycolysis are 8 ATP molecules, while in anaerobic glycolysis, 2 NADH and 4 ATP are formed and 2 ATP 2 NADH are utilized, so the energetics of anaerobic glycolysis are 2 ATP molecules.

What is Krebs Cycle?

Krebs cycle is also called citric acid cycle. Krebs cycle is the sequence of reactions in living organisms using oxygen and producing water and CO2 as by-products and forming ATP molecules. Moreover, Krebs cycle is the primary cycle for oxidation of carbohydrates, lipids, and proteins. In Kreb cycle, 3 NADH, 1 FADH, and 1 GTP are produced and no ATP is utilized. Thus the energetics of Kreb cycle are 12 ATP molecules.

The process of Krebs Cycle has following steps:

  • Pyruvic acid combines with Ach and oxaloacetic acid to form citric acid.
  • Citric acid into cis-aconitic acid.
  • Cis-Aconitic acid into isocitric
  • Iso-Citric acid into alpha-ketoglutarate.
  • Alpha-Ketoglutarate into succinyl-CoA.
  • succinyl-CoA into succinic acid.
  • Succinic acid into fumaric acid.
  • Fumaric acid into malic acid.
  • Malic acid into oxaloacetic acid.
  • Oxaloacetic acid combines back with pyruvic acid, and Ach and cycle go

Enzymes involved in the steps above are pyruvate dehydrogenase, citrate synthase, Isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, Succinyl synthase, Succinyl dehydrogenase, and Malic dehydrogenase.

Glycolysis vs. Kerbs cycle

  • Glycolysis is concerned with carbohydrate metabolism while Krebs cycle is the primary cycle for oxidation of carbohydrates, lipids, and proteins.
  • In glycolysis 2 NADH and 4 ATP are formed, and 2 ATP are utilized, so the energetics of glycolysis are 8 ATP molecules, whereas in Krebs cycle, 3 NADH, 1 FADH, and 1 GTP are produced, and no ATP is utilized. Thus the energetics of Krebs cycle are 12 ATP molecules.
  • Glycolysis is a straight chain reaction while curbs cycle is a cyclic response.
  • Glycolysis has different enzymes as phospho hexo isomerase, Hexokinase, Aldolase, Dehydrogenase, Kinase, Mutase and Enolase and contrary to this; Krebs cycle has different enzymes as pyruvate dehydrogenase, citrate synthase, Aconitase, Isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, Succinyl synthase, Succinyl dehydrogenase, Fumarase, and Malic dehydrogenase.

Comparison Video

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Aimie Carlson is an English language enthusiast who loves writing and has a master degree in English literature. Follow her on Twitter at @AimieCarlson

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