Does Cellular Respiration Occur In The Mitochondria? 7 Facts

Respiration is a continuing process that occurs all the time in all living organisms for providing energy. Let us find out if cellular respiration occurs in mitochondria.

Mitochondria are where cellular respiration occurs and it is divided into two types. Not all type of cellular respiration happens in mitochondria. Mitochondria is restricted only to aerobic respiration.

Let us discuss more about cellular respiration in mitochondria, when and why it occurs only in mitochondria and many more detailed facts around it.

What is the purpose of cellular respiration?

Cellular respiration is a biologically regulated process. Let us find out the purpose behind cellular respiration.

Some of the important purposes of cellular respiration are given below:

  • The main purpose of cellular respiration is biological oxidation of organic substances inside of living cells that is enzymatically controlled to obtain energy. 
  • For both immediate use and short-term storage, energy is released in separate steps.
  • Several biochemicals can be synthesized using intermediates of cellular respiration.
  • Energy is required for all bodily mechanical processes and a majority of living things make energy through a process called cellular respiration in their mitochondria.

When does cellular respiration happen in the mitochondria?

Cellular respiration is a continuous process in the living organisms. Let us get to know when it happens in mitochondria.

Cellular respiration in mitochondria occurs when pyruvate from glycolysis enters the matrix of mitochondria. The process is known as Krebs Cycle or citric acid cycle.

The substrates so formed in the Krebs cycle is acetyl CoA. Oxaloacetate is the acceptor molecule which combines with acetyl CoA in presence of enzyme citrate synthetase. The product so formed is six carbon compound citrate. The series of eight reaction occurs in the Krebs cycle with the help of different enzymes present in the mitochondria.

Why does cellular respiration happen in the mitochondria?

Mitochondria is a semi-autonomous organelle and can function on its own. Let us explore why it happens in mitochondria.

The main reason for cellular respiration to occur in mitochondria is that mitochondria is the power house of the cell as it releases energy in small steps and can be used immediately as required by the cell or it can store temporarily.

Mitochondrial inner membrane has foldings in a finger shaped projections called cristae. These cristae helps in increasing the surface area so that, mitochondria can produce more ATP molecules required for cellular respiration.

What is the role of mitochondria in cellular respiration?

Cellular respiration can occur with or without the involvement of oxygen. Let us discover the actual role played by mitochondria in cellular respiration.

Mitochondria plays a crucial role in cellular respiration by producing large amount of ATP. All the necessary enzymes are present in mitochondrial matrix and inner membrane for the oxidation of substrate to produce energy.

Only aerobic respiration takes place inside the mitochondria. Mitochondria produces higher number of ATP in cellular respiration. However, the final step of aerobic respiration which involves release of protons and electrons from reduced coenzymes also takes place in the inner membrane of mitochondria.

Does all phases of cellular respiration occur in mitochondria?

There are two phases of cellular respiration. Let us find out which phase occur in mitochondria.

All phases of cellular respiration does not occur in mitochondria. Cellular respiration occurs in two steps. Glycolysis is the first step of cellular respiration that occurs in cytosol. While, the second phase of cellular respiration occurs in the mitochondrial matrix.

What are the benefits of cellular respiration?

Continuous process of cellular respiration provides many benefits to cell and organisms. Let us explore what kind of benefits are obtained from cellular respiration.

The benefits of cellular respiration are given below:

  • It helps in the oxidation of organic substances and in return releases energy.
  • Several biochemicals can be synthesized using intermediates formed during cellular respiration.
  • The majority of respiratory energy is released as heat and lost, with just about half of it being retained for cell function.
  • Being able to instantly access any amount of energy because the trapping of ATP is very advantageous during cellular respiration.
  • Since ATP is transferable throughout the cell, energy can be made available from the site of cellular respiration
  • It is not necessary for the cell to immediately use all of the respiratory energy. Therefore, energy wastage is kept to a minimum.

Which phase of cellular respiration does not occur in the mitochondria?

There are two phases of cellular respiration. Let us find out which phase do not happen in mitochondria.

Glycolysis phase of cellular respiration does not occur in mitochondria. Glycolysis is the first stage of cellular respiration that brings about the breakdown of glucose to two pyruvate molecules, two hydrogen ions, and two ATP molecules which are produced when glucose is broken down or split in the cytosol.

When hydrogen ions react with NAD, NADH is the result. NAD are electron carriers that aid in the synthesis of ATP. Then, pyruvate and NADH molecules are sent to the mitochondria.

How many steps are there in cellular respiration?

There are several stages to cellular respiration. Let us explore the number of steps in cellular respiration in more depth.

There are three main steps in cellular respiration. These are:

  • Glycolysis
  • Citric acid cycle or Tricarboxylic acid cycle or Krebs cycle
  • Terminal Oxidation or Oxidative phosphorylation


In the cytoplasm, where this metabolic process takes place, glucose is first converted into the three-carbon compound pyruvate. Both aerobic and anaerobic circumstances might result in it.

Krebs cycle

Pyruvate so formed enters the mitochondrial matrix where oxidation of pyruvate takes place. Acetyl-CoA joins a four-carbon oxaloacetate to create the six-carbon citrate, which starts the TCA cycle. It is restricted to aerobic conditions.

Oxidative phosphorylation

In this pathway ,a proton gradient is produced by a sequence of redox reactions driven by energetic electrons that pump protons across the membrane. Together, they provide an electrochemical gradient.

The last electron acceptor, O2, combines with protons at the conclusion of the electron transport chain to create water (H2O). In the meantime, protons are moved back into the mitochondrial matrix by ATP synthase to produce ATP.


To sum up this post, we can say that the mitochondria are where cellular respiration occurs. Cellular respiration is divided into three stages: glycolysis, the Krebs cycle, and oxidative phosphorylation. Glycolysis occurs in cytosol while krebs cycle takes place in mitochondrial matrix and terminal oxidation happens at inner mitochondrial membrane. However, second phase generates higher amount of ATP than any other phases.

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