Why are mitochondria called the powerhouse of the cell?

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Why are mitochondria called the powerhouse of the cell?

Mitochondria are generally known as the “powerhouse” of the cell because these are the site for the oxidation of foodstuff in Presence of Oxygen and supply energy to the cell for the completion of innumerable cell activities.

The various chemical events taking place during the breakdown of food and the production of energy are collectively discussed under the metabolic pathway for the respiratory cycle.

The respiratory cycle or the metabolic pathway is separated into the following phases or pathways.

  1. Glycolysis or anaerobic respiration –  Embden-Meyerhoef Parnas pathway.
  2. Oxidative  decarboxylation
  3. Krebs cycle or Aerobic respiration in mitochondria or tricarboxylic acid cycle or citric acid cycle.
  4. Electron transport system or respiratory chain.
  5. Oxidative phosphorylation. 

Diagram of Mitochondria –

mitochondria called the powerhouse of the cell
Mitochondrion in section

Energetics of Cellular respiration

The Energy Released During Each Cycle –

  1. Glycolysis –
  • From one molecule of glucose, two molecules of pyruvic Acid are formed.
  • 2 ATP molecules are used While 4 ATP molecules are formed. therefore there is a net gain of 2 ATP molecules.
  • 2H+  atoms are formed. These are accepted by NAD which changes into N A D H + .2H+ and is transferred to ETS.

2. Oxidative decarboxylation –

On entering mitochondria the pyruvic acid molecule releases one molecule of CO2 and changes into acetic acid. This is called decarboxylation. Acetic acid is combined with coenzyme A  and forms acetyl coenzyme-A.  During this process, 2H is released which is accepted by NAD  forming NADH + H+.NADH Transfer them to the electron transport system.

3. Krebs tricarboxylic acid cycle (TCA ) –

  • 2H Are released during dehydrogenation-I of isocitric acid into oxalo succinic acid.
  • 2H are released during dehydrogenation-II of ketoglutaric acid into succinyl-CoA.
  • 1 ATP by phosphorylation of ADP when succinyl-CoA separates into succinic acid and CoA and GDP are phosphorylated to GTP phosphorylate which transfers ~P to ADP.
  • 2H is released during dehydrogenation-III when malic acid changes into fumaric acid.
  • 2H is released during dehydrogenation-IV when malic acid changes to oxaloacetic acid.

Thus During the Krebs cycle, 4 pairs of hydrogen atoms are produced which are carried to ETS for the release and transport of ATP.

4. Transport of H+ ions along the respiratory chain –

While moving down along the complex of the respiratory chain 2H atoms release electrons and get oxidised to form water.

5. Oxidative phosphorylation –

Electrons released during the transport of h along ETS  are accepted by the electron acceptor of ETS  and passed on to F0– F1 Complex where ADP is phosphorylated into energy-rich ATP molecules. 2H molecules produce 3 ATP.

Important Question Answer –

  1. Name the cell type in which mitochondria are absent.

Ans – RBC

2. Who coined the term ‘mitochondria’?

Ans – Benda in 1897.

3. Name the organism which possesses only one mitochondrion.

Ans – In Microsomonas.

4. Which cells possess the highest number of mitochondria?

Ans – In the flight muscles of insects.

5. What is the role of elementary particles?

Ans – It forms a proton-translocating channel and acts as a proton carrier.

6. Where are the enzymes of the respiratory or ETS system located in mitochondria?

Ans – Inner mitochondrial membrane.

7. For which structure, the name bioplast was used by Altman?

Ans – For mitochondria.

8. What type of ribosomes are found in mitochondria?

Ans – 70S ribosomes.

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