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Mitochondria

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Introduction

MVSAT 2024

Mitochondria is the powerhouse of the cell, which produces energy. It is a membrane-bound organelle, present in the cytoplasm of the cell of Eukaryotic organisms which synthesizes energy molecules in the form of ATP, which is used by the cell. Hypothetically mitochondria are believed to have originated as prokaryotic cells like bacteria. They were capable of oxidative mechanisms. Over the course of evolution, they started living as endosymbionts inside the cell of prokaryotes. Mitochondria have fragments of genetic information in the form of DNA and can multiply on their own by division.


In this article, we discuss a very important biological concept that is Mitochondria. The students after reading the note will be able to explain the very concept of Mitochondrial. Following are the concepts being covered - 


What is a Mitochondrion?

A mitochondrion is a double membrane-bound organelle, which is found in the cytoplasm of most of the cells of most Eukaryotic organisms. This little center for energy generation digests the nutrients and releases chemical energy in the cell in the form of ATP- Adenosine Triphosphate. Apart from generating ATP molecules, the mitochondria also regulate cell growth and cell death, it signals the cells and generates heat. It plays a major role in cellular respiration. Anaerobic fermentation is another process by which ATP is generated in the body but anaerobic fermentation does not take place in mitochondria. Mitochondria necessarily need oxygen and glucose to generate ATP. The energy generated through this process is more than the energy generated by anaerobic fermentation.


Structure of Mitochondria

Mitochondria in animals are round or oval and are bound by a double membrane. These membranes are composed of phospholipid bilayers and proteins. The different parts of mitochondria in animal cells are:

  • Outer Membrane- The outer membrane keeps the inner organelles intact and in place. It is made up of protein and phospholipid bilayer. The outer membrane contains the enzymes involved in various activities. This layer is also permeable to macromolecules so that ions, ATP, ADP, etc. can easily pass through this membrane.

  • Inter Membrane Space- The space between the outer membrane and inner membrane is the intermembrane space. This space also consists of small molecules like ions and sugars, as the outer membrane surrounding it is permeable to these molecules.

  • Inner Membrane- The inner membrane of the mitochondria is made up of proteins that carry out different functions. It also has enzymes necessary which catalyzes processes necessary in the production of ATP. The inner mitochondrial membrane is permeable to oxygen, carbon dioxide, and water. The inner mitochondrial membrane is the fundamental site of ATP generation. The inner mitochondrial membrane has several folds in it called Cristae, to increase the surface area.

  • Cristae- The inner membrane of mitochondria is folded into several folds. These folds are called cristae. The cristae increase the surface area inside the mitochondrial membrane to generate ATP molecules efficiently. The larger the surface, the more the space to carry out cell functions. The surface of the cristae has exosomes attached to it, which aids the osmosis of ions. A lot of chemical reactions occur in the inner membrane on the surface of the cristae.

  • Matrix- The space in the inner membrane apart from the cristae in the Matrix. It is fluidic and contains proteins, ribosomes, enzymes, tRNA, and genomic DNA. Due to the presence of genetic material, the Mitochondrial Matrix can synthesize its RNA and proteins. The synthesis of ATP would be incomplete without the enzymes of the matrix which aid the most important chemical cycles. 


Functions of Mitochondria

The prime function of mitochondria is to produce energy. It is the power generation plant where the nutrients turn into ATP by a chemical process. The other major role played by mitochondria is carrying out cellular metabolism. Through cellular metabolism, three major processes are carried.

  1. Conversion of food into energy

  2. Conversion of food into molecules that are essential for the body like proteins, carbohydrates, etc.

  3. Eliminations of the wastes.

Mitochondria is also responsible for cell growth and multiplication. When there’s too much strain on an organ, performing a specific task, mitochondria multiply on their own to carry out their purpose more efficiently. It also plays a major role in apoptosis or cellular suicide. During apoptosis, a cell does not die of an injury but a series of chemical reactions leading to the elimination of the cell.


It is also responsible for homeostasis by heat production. It happened by the process of mitochondrial uncoupling, wherein the re-entered protons in the matrix are not converted to ATP. It stores calcium ions thus helping cell signaling. Free calcium regulates a series of chemical reactions in the cell and thus, mitochondria regulate cell signaling.

Apart from these, mitochondria regulate cell differentiation and cell senescence or the cessation of cell division.


Facts about Mitochondria

Mitochondria are colorless organelles; therefore, they cannot be seen under a microscope unless they are dyed. So, it was Richard Altman who used and dyed, and observed these organelles under a microscope and explained that these structures are the basic units of cellular activity. In 1898, Carl Benda coined the term ‘Mitochondria’ for these organelles.


Red Blood Cells or RBCs lack mitochondria. As RBC uses none of the oxygen which they transport in the body, they do not possess mitochondria. Instead, they derive energy from a different chemical process called glycolysis. Mitochondria have a lot of features common with bacteria.

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FAQs on Mitochondria

1. Why is Mitochondria called the Powerhouse of the cell?

Cells need a lot of energy to carry on their function. And Mitochondria are tiny organelles that break down the food into simpler substances which in turn helps in prodigy energy. Mitochondria are present in the cells and provide them the energy by breaking the food. The energy produced by breaking the food is used by the cells For this simple reason, Mitochondria is considered as the  Powerhouse of the cell.

2. What consequences does a human body have to face if the mitochondria stop working?

When the Mitochondria will stop working the human body will face the following consequences -   

  • There will be no or less conversion of food into ATP ( Adenosine triphosphate).

  • The muscles which require more ATP will start getting weaker.

  • There would be a reduction in body strength and power.

  • There would be easy breakage of bones and muscles tissues.

  • It can even cause an organ to fail.

  • The person can have Alpers disease, Barth syndrome, and Kearns-Sayre syndrome.

  • Thus, the Mitochondria are one of the most significant parts of the human body.

3. What is the functional role of Mitochondria?

Mitochondria has the following functional role to play in a human body - 

  • Act as the storehouse of calcium.

  • Helps in cell signaling.

  • Promotes cell growth and their multiplication.

  • It also regulated the metabolic activity of the cells.

  • Causes apoptosis or programmed cell death.

  • Build certain parts of blood and hormones like testosterone and estrogen.

More functions are being discussed in detail by the experts at Vedantu. Students can refer to the free PDF of notes or can watch the video lectures.

4. What is Cristae in the topic of Mitochondria?

The inner membrane of Mitochondria has a complex structure, it has many folds placed as layers one over the other, this layered structure is called the Cristae. It helps in increasing the surface area inside an organelle and also aids in the production of ATP molecules. Such similar concepts are explained by the subject experts in detail on the website and the mobile app of Vedantu.

5. Why do RBCs lack mitochondria?

One of the many functions of RBCs is to carry oxygen throughout the body. However, while doing this, it does not use up any oxygen on its own. Rather it follows a simple process of generating energy from glucose molecules by a chemical process called glycolysis. Therefore, RBCs neither need mitochondria nor possess them.


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