Mitochondria – NCERT Class 11 Biology: Important notes for NEET 2022

There is a topic with the topic mitochondria in the NEET 2022 Syllabus of Biology. NCERT Class 11 Biology chapter on mitochondria is one of the most important topics concerning the NEET 2022 Important Chapters. Hence, preparing the topic well in Class 11 Biology will be a smart step for NEET-UG 2022. So here in this article, we will learn every possible detail related to mitochondria prescribed in NCERT Class 11. To prepare well regarding the topic, students can refer to the NCERT Solutions for Class 11 Biology, Biology Concepts, and NCERT Solutions for Class 10 Science for basic and advanced facts regarding the topic. The topic of mitochondria is also very relevant in exams like CUCET Preparation, NTSE, KVPY, and Olympiad.

Introduction to mitochondria

Recognized as the “powerhouse of the cell”, mitochondria are the dual membrane-bound organelle originally found in maximum eukaryotic organisms. They are usually found inside the cytoplasm, and their necessary function is to act as the digestive system of the cell body. Mitochondria are formed with two words, mito, which means thread, and chondroitin, which means granule. In scientific words, that was described and compiled by a German pathologist in the year 1890 named Richard Altman. 

Mitochondria are a semi-autonomous system with hollow sac-type structures pressing in all eukaryotes except the mature RBCs of mammals and sieve ducts of the phloem. There are several more names through which Mitochondria are also known. They are as follows: chondrocytes, plastosomes, chondrioplast, plasmosomes and plastchondriane. Mitochondria is the key part of breaking down food and nutrients to create molecules filled with energy for the cell in the form of ATP. Mitochondria is also the processor of several activities that involve cellular respiration in many biochemical procedures.

Discoveries data

1. Kolliker made the first observation in the year 1880. The observation was noticed in the strained muscles of an insect in a granule form, and he named it ‘sarcosomes’.
2. The second observation was recorded in 1882 by the scientist Flemming who named the thread-like structure ‘Fila’.
3. The third observation was mentioned in 1890 when the scientist Altman named the structure ‘Bioplast’. 
4. C. Benda was the one who termed the structure as mitochondria in the year 1890.
5. F. Meves made the fifth observation in the year 1904 by noticing mitochondria in plants with the name Nymphea.
6. The sixth observation was regarding the role played by the mitochondria in respiration.
7. The scientists duo Bensley and Hoerr worked on isolating the structure (mitochondrial) from the liver cells. The process was done in the year 1934.
8. Seekevitz was the scientist who described mitochondria as the ” powerhouse of the cell”.
9. Nass and Afzelius were the scientist duo who first observed mitochondria in the DNA of humans. They discovered the fact in 1965.

Also See: NCERT Solutions for Class 11 Biology | NEET Biology Syllabus

Size of mitochondria

According to past experiments conducted, the average size of mitochondria is between 0.75 and 3 μm in the area but varies significantly in size and structure. In detail, 0.51.00 μm where the length is 110 μm. The smallest size of mitochondria can be found in yeast cells which measure 1 μm, and the possible largest size of mitochondria can be found in oocytes of Rana pipiens which is around 2040 μm measurement.

Diagram of mitochondria

Mitochondria can be seen bound by a dual membrane-bound separated by a peri mitochondrial area of 6 to 10 nm wide. There are various parts in mitochondria that can be recognised as: 

• Granules
• Matrix
• Deoxyribonucleic acid (also known as DNA in short)
• Ribosome
• ATP Synthase Particle
• Cristae
• Inner Membrane
• Outer Membrane
• Intermembrane Space

Structure Description of Mitochondria

The number of mitochondria present in a cell can differ widely in the organism, tissue, and cell type. In a mature red blood cell, there are no mitochondria, whereas, in a liver cell, there can be more than 2000. The mitochondrion is organised in cavities that help carry out various specialised purposes. These compartments or regions include granules, matrix, deoxyribonucleic acid (also known as DNA), ribosome, ATP synthase particle, cristae, inner membrane, outer membrane, intermembrane space.

• Outer membrane-: The outer membrane of mitochondria, which is surrounded by the entire organelle, is 60 to 75 angstroms (Å) thick, which is recognised as peri mitochondrial space. It retains a protein-to-phospholipid ratio similar to that of the cell membrane. This area is filled with enzymes necessary for the oxidation of fats and pyruvic acid. When the outer membrane structure present in Mitochondria is omitted, the next structure is known as mitoplast. Several sessile particles attached to the outer membrane are recognised as ‘subunits of persons’.
• Inter membrane space-The area between the inner and outer membrane is known as the intermembrane space. This space is filled with small molecules known as ions and sugars, as the outer membrane enclosing it is porous to these molecules. It is also recognised as peri mitochondrial space. The protein configuration of this area is different from the other protein components of the cytosol. One protein that can be recognised in the intermembrane space is cytochrome.
• Inner membrane-: The inner membrane of the mitochondria consists of proteins that help in carrying out various functions in the system. This membrane also retains enzymes that are necessary for the process of catalysing, which is necessary for the procedure of ATP formation. It also has proteins that help perform the electron transport chain redox reactions. This inner membrane is porous to various components like carbon dioxide, oxygen and water. This membrane is the foundational site for the formation of ATP. The folds present in this membrane of mitochondria are known as ‘cristae’ which help in increasing the surface area.
• Cristae- The various folds present in the inner membrane of the mitochondria are known as ‘cristae’. Cristae are present to help the membrane increase the surface area needed to create ATP molecules in the membrane. The larger and wider the surface, the more area to help carry out the cell’s functions. On the surface of cristae, there are some structures attached to the surface known as exosomes which help in aiding the osmosis of the ions. Cristae is also necessary for the other chemical reactions that happen in the mitochondria’s inner membrane.
• Matrix-: The fluid structure that consists of various components like ribosomes, proteins, enzymes, genomic DNA and tRNA that is present in the space in the inner membrane of the mitochondria apart from cristae is known as matrix. Due to the existence of all the genetic materials Matrix is present in, the mitochondria can synthesise its protein and RNA. The synthesis process of ATP will remain incomplete without the present enzymes in the matrix, which help in processing the most important chemical chains and cycles.

Enzymes present in mitochondria

There are many enzymes present in the mitochondria, which also help in carrying out various processes and chemical cycles. Numerous enzymes are present in various parts of the mitochondria, such as in the outer membrane, the inner membrane, peri mitochondrial space and the inner matrix.

Chemical composition

The scientist known as Cohn is the one who designed and proposed the chemical composition of the mitochondria. According to him-

• The protein composition in the mitochondria is from 65 to 70 percent.
• Lipids are present in 25 to 39 percent, of which 90 percent consist of phospholipids and 10 percent of several components like cholesterol and Vit. E and some more.
• The composition of RNA in the mitochondria is about 5 to 7 percent, whereas DNA composition lies between 2 to 5 percent.
• Matrix present in mitochondria has numerous catabolic enzymes such as cytochrome oxidases and reductases, several fatty acid oxidases, transaminases, and many other components that are also a part of the chemical composition of the mitochondria.

Functions of mitochondria

Mitochondria is already known as the powerhouse of the house, and its most important function is to produce energy in the cell through oxidative phosphorylation. The power generator helps generate power through nutrients by turning them into the form of ATP through the oxidation process. Mitochondria also plays a role in carrying out cellular metabolism, also known as another important function. Along with it, several more functions are performed by the powerhouse, mitochondria. 

• Energy Conversion- Mitochondria’s most important and dominant role in the cell. Many proteins and enzymes reproduce the production of ATP by the oxidation process. Components like Pyruvate Glucose and NADH produced by cytosol are responsible for oxidation. 
• Electron Transport Chain- Another process of the mitochondria is to transfer electrons. The electrons from the components like FADH2 and NADH are transferred to oxygen, hydrogen and an energy-rich molecule. All the processes are held in several steps with the help of the electron transport chain. Both NADH and FADH2 are produced in the matrix.
• Storage of Calcium ions- One of the functions of the mitochondria is to store the calcium ions present in the cell. The concentration of free ions of calcium can trigger an order of reactions and is also important for signal transduction in the cell structure. To operate all processes, mitochondria can store the ions of calcium, which contributes to the homeostasis of calcium in the cells.
• Mitochondria also help in the regulation of the potential in the membrane.
• Mitochondria also produce Apoptosis, which is known as a programmed cell death function.
• Steroid synthesis is also operated with the help of mitochondria.
• Several functions are performed by the mitochondria but in the specific types of the cells, such as detoxifying ammonia from the liver cell with the help of enzymes. Mutation in any gene can result in mitochondrial diseases.

Conclusion

Here is the whole story of the powerhouse of the cells. It can be estimated that mitochondria are a part of the cell that can’t be ignored because it holds a very powerful spot in various processes such as reading energy during respiration, generating energy in the form of ATP, helping in electron transportation, preventing from the mitochondrial diseases, regulating calcium ions and much more other important functions. 

The existence of mitochondria is dependent on the metabolic activities occurring in the cell. The collective name of a mitochondrial cell is known as self-replicating organelles present in DNA. Mitochondria is a vast and strong, suggestive topic for NEET 2022 preparation tips, NTSE exam, KVPY Exam, and Olympiad Exam. Preparing it with experts and subject materials like Lakhmir Singh Solutions, Important Concepts, or for more guidance on NEET, one can Find Aakash Coaching Institute Near You.

FAQs

1. What is the percentage of chemical composition in the mitochondria?

Several components are responsible for the final chemical composition of the mitochondria. They are – The protein composition in the mitochondria is from 65 to 70 percent lipids are present in the composition of 25 to 39 percent, of which 90 percent consist of phospholipids and 10 percent of several components like cholesterol and vitamin E and some more. Composition If RNA in the mitochondria is about 5 to 7 percent, whereas DNA composition lies between 2 to 5 percent. Matrix present in mitochondria has numerous catabolic enzymes such as cytochrome oxidases and reductases, several fatty acid oxidases, transaminases, and many other components that are also a part of the chemical composition of the mitochondria.

2. Why are mitochondria known as the powerhouse of the cell?

Cells need a high amount of energy to perform their function properly. Mitochondria help the cell by breaking down the food into a simple form of energy through which cells can perform the rest of the process without any breakage. This is the reason why mitochondria are known as powerhouses.

3. What is the meaning of mitochondria, and who discovered the name?

In scientific words, the name Mitochondria was described and compiled by a German pathologist in 1890 named Richard Altman. Mitochondria are formed with two words, Mito, which means thread, and Chondria, which means granule.

4. What can be the possible consequences of the lack of mitochondria in animal cells?

Lack of mitochondria can impact a lot on the human body. There will be no source or less source of energy form in ATP, breakage of muscles tissues and bones, issues like organ failure, diseases like Alpers disease, Kearns-Sayre syndrome, and Barth syndrome can infect the body.