Does Glycolysis Occur In The Mitochondria? 5 Facts

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Glycolysis is a process in which the sugars are being utilized by the living being. Let us see in detail if glycolysis occurs in mitochondria or not.

Glycolysis does not occur in mitochondria. Glycolysis occurs inside the cytoplasm or to be more precise the cytosol which is the space where the glycolysis process takes place. Cytosol is a jelly-like liquid  substance that is present inside the cytoplasmic membrane.

Cytosol is rich in soluble amino acids, molecules and ions. Cytosol is also moist rich which aids in the tonicity, it has lots of enzymes, lipids and nucleic acids for support. This articles briefly explains on the glycolysis process and the role of mitochondria in glycolysis process.

What is glycolysis?

Glycolysis holds a very significant stand among all the biochemical processes that happens inside the system. Now let us see how this glycolysis process takes places.

Glycolysis is a biochemical process in which the simple sugar molecule or the glucose molecule is split or lysed into further simpler units so that they can be utilized by the living being. Hence, glucose molecules are split into simpler forms for the utilization process and is called glycolysis.

The products of the glycolysis are pyruvate molecules ( 2 numbers) along with ATP (Adenosine triphosphate), NADH (nicotinamide adenine dinucleotide) and water molecules.

C6H12O6 + 6O2 → 6CO2 + 6H2O + Chemical Energy (in ATP)

Why does glycolysis not occur in mitochondria?

In order to understand why glycolysis does not occur in mitochondria we need to know why it occurs in cytosol. Let us see in detail.

Glycolysis does not occur in mitochondria because glycolysis is a process which requires lots of enzymes and organic molecules that are not in mitochondria and also mitochondria is an anabolic component so they work collectively for other mechanisms.

Cytosol is the membranous space inside the cell, which has nutrients that is specific for glycolysis and this is why the glycolysis happens inside the cytosol.

Where does glycolysis occur?

Glycolysis requires more enzymes, water, lipids, minerals and ions to process. Let us have a deeper view to understand where it happens.

Glycolysis takes place inside the cytosol as that is the space where all the required materials are being available to work on. Cytosol is the semi solid matrix-like fluid that is rich in enzymes, water, lipids, minerals and ions. Therefore, glycolysis occurs inside the cytosol.

The living system is very much adapted to the utilization of ATP molecules. So taking it directly as complex carbohydrates like starch or any polysaccharide or even simple sugars like glucose is difficult. By the process of glycolysis, the sugar molecules are absorbed and utilized even better.

Does glycolysis require mitochondria?

Mitochondria produces various enzymes that aid in most cellular mechanisms so let us see what is their role in the glycolysis process.

Glycolysis requires mitochondria in order to liberate the carbon-di-oxide and water molecule during the process as the mitochondrial enzymes only can oxidize the fatty molecules and hydrolyze the sugar bond in the carbohydrate (sugar) molecule.

Mitochondria extracts the energy from the food that is ingested by the cell through the process of cellular respiration called the oxidative phosphorylation and this is how mitochondria plays a small but important role in glycolysis.

Which processes occur inside the mitochondria?

The mitochondria houses many complex mechanisms. Below we can find the different functions performed by the mitochondria.

  • The primary energy molecule, Adenosine tri phosphate (ATP) is synthesized in the mitochondria.
  • The electron transport chain occurs in mitochondria in which a sequence of 4 polypeptide complexes combine with the oxidation and reduction reaction which produces a gradient of electrochemistry, which is called the oxidative phosphorylation.
  • The citric acid cycle happens inside the matrix of mitochondria which is called the process of oxidative metabolism.
  • Apoptosis which is otherwise called the programmed cell death takes place inside the matrix of the mitochondria.
  • The ability in the maintenance of calcium ions in each cell is regulated by the mitochondria thus called the process as calcium homeostasis.
  • The tonicity of calcium ions and their interaction and signaling is communicated by the mitochondria.
  • The oxidation and reduction homeostasis is maintained by the mitochondria.
  • The mitochondria has an inner membrane called the inner mitochondrial membrane or the IMM is the location where the steroid synthesis is being initiated.
  • Acetyl CoA, NADH (Nicotinamide adenine dinucleotide), FADH (Flavin adenine dinucleotide) is being generated by the mitochondrial fatty acids through beta oxidation.
  • The hormone signaling is performed inside the matrix of the mitochondria.
  • The Heme molecule is synthesized inside the mitochondria
  • Ion potential across membranes commonly known in the tonicity process is maintained by the mitochondria organelle.

The overview of the glycolysis process:

Let us see the complete glycolysis process in a simple theoretical way.

Step- 1:

The initiation of the glycolysis takes place, let’s see the first step in detail now.

The partial oxidation of glucose produces two molecules of pyruvate. In the preparation phase, ATP is consumed, and in the payoff phase, ATP is produced. A net yield of 2 ATPs and 2 NADH is obtained.

Step- 2:

The transformation of glycose into simple products are given below.

Six molecules of 6C glucose are converted to two molecules of 3C pyruvate through ten enzymatic reactions.

Glycolysis
Glucose to pyruvate
Image credits- Wikimedia

Step- 3:

Generation of ATP is performed in this stage. Let’s have a detailed look now.

A three-step process is used to phosphorylate glucose to fructose-1,6-bisphosphate, which is then broken down into 3C compounds G3P (Glyceraldehyde-3-phosphate) and DHAP (Dihydroxyacetone phosphate). In this case, G3P is generated. ATP is used in this phase.

Step- 4:

The end product is being formed here in this step let’s see in detail.

A second phase, energy capturing, takes place. It takes five steps to convert G3P to pyruvate. Two NADH molecules are formed and four ATP molecules are formed.

Step- 5:

The final step in which the dissociation of the glycolyze complex and the final products enters into other reaction which is given in detail below.

The pyruvate formed by aerobic respiration in eukaryotes enters mitochondria, where it undergoes oxidative decarboxylation to form acetyl CoA, which enters the Krebs cycle or citric acid cycle. This reaction occurs in the cytosol of aerobic prokaryotes.

The anaerobic process converts pyruvate into lactate, for example, in muscles, or acetaldehyde, which is converted into ethanol and CO2 in bacteria and yeast.

Conclusion:

To conclude this article, we have discussed the glycolysis process and where it occurs and also we saw the reason behind why the glycolysis does not happen in mitochondria. The contents in the cytosol and their components are the highlights in this  glycolysis process.

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