Written by Lawrence Barquilla

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

The mitochondria’s major role is to generate ATP or adenosine triphosphate. ATP is the cell’s primary energy source and is utilized for reactions. Cellular respiration produces ATP.

The mitochondrion (plural: mitochondria) is an organelle found in all eukaryotic cells. It is popularly known as the cell’s “powerhouse,” and its primary function is to produce energy for the body.

You will learn throughout this article about the powers of the cell’s powerhouse. You will also identify the key roles this organelle plays in the body’s normal physiology.

What is the major goal of cellular respiration?

Cellular respiration is the process of which the major goal is to produce ATP. This process occurs in the mitochondria of cells. Cellular respiration is an integral process. It is where the cells convert nutrients into usable energy in the form of ATP. Thus, the mitochondria sustain life.

The process of cellular respiration is a series of metabolic pathways. In these pathways, glucose and organic molecules break down to produce ATP. This occurs in three main stages as follows.

1. Glycolysis

This involves splitting one molecule of glucose into two molecules of pyruvate. It is the process of splitting a 6-carbon sugar into a 3-carbon sugar. This process generates a net gain of 2 ATP molecules. The method of substrate-level phosphorylation produces these 2 ATP molecules.

Alongside the ATP produced, electron carriers such as NADH molecules are also produced. These will be needed in the later stages of the process. Additionally, this stage occurs in the cytoplasm. Later on, the products will move into the mitochondria for further processing.

• Citric Acid Cycle

The pyruvate molecules from glycolysis now enter the mitochondria. Each of the 2 pyruvate molecules is converted into acetyl-CoA. The products then enter the citric acid cycle afterward. During this stage, ATP is not produced.

However, 2 GTP are produced, which function similarly to that of ATP. GTP stands for guanosine triphosphate. GTP is equal to 1 ATP per 1 GTP molecule produced.

Additionally, the products are electron carriers. These include NADH and FADH2, as well as carbon dioxide, which are waste products. These products will move into the next few steps of the process.

• Oxidative Phosphorylation

This is the final stage in the process of cellular respiration. It takes place in the inner mitochondrial membrane. The electron transport chain makes use of the electrons from the electron carriers.

From the previous steps, NADH and FADH2 serve as the electron carriers of the system. The electron carriers create a proton gradient. This proton gradient allows for the electron transport chain to operate. Additionally, this gradient is what drives the synthesis of ATP.

As electrons are transferred from the carriers, a proton gradient across the inner mitochondrial membrane is created. Once the electrons enter back into the mitochondrial matrix, they pass through the ATP synthase. As they pass through the enzyme, ATP is generated.

This step produces the most ATP among the stages. A total of 28 to 34 ATP molecules are produced.

Which cell in the human body does not have mitochondria?

The erythrocytes, commonly known as the red blood cells, are the only cells in the body that do not contain mitochondria. These erythrocytes not only lack the mitochondria but also lack other cell organelles, one of which is the nucleus.

Red blood cells function primarily to carry oxygen throughout the entire body. Thus, having the adaptation of losing the mitochondria allows for maximized oxygen transport.

By removing this specific organelle, the red blood cells can accommodate more hemoglobin. Once more hemoglobin is accommodated, more oxygen can be transported from the lungs to the tissues to the cells of the body.

Another point to look at is the shape and structure of red blood cells. They have a biconcave shape, which allows for an increased surface area for gas exchange. By removing the mitochondria and other organelles, the red blood cells are able to maximize the space.

Without the mitochondria, you may start to wonder how red blood cells produce energy for their own use. Well, they still have a reliable source of energy through the process of anaerobic respiration.

Anaerobic respiration involves metabolizing glucose through glycolysis. This is to generate ATP without the need for oxygen. Although possible, this is not as efficient as cellular or aerobic respiration. Anaerobic respiration is not as efficient in ATP generation.

Regardless, it enables red blood cells to attain energy. It is important to have an energy source as they carry and transport oxygen through the body.

Overall, having no mitochondria comes to be more beneficial for red blood cells. It is a crucial adaptation that improves their ability to carry oxygen efficiently. This interesting adaptation is what maintains the oxygen concentration at a healthy level.

Which organ contains the most mitochondria?

The heart is the organ that is most abundant in the amount of mitochondria. As the heart is in a continuous state of function, it needs significantly more energy than other organs of the body.

The heart holds the highest number of mitochondria. It amounts to about one-third or 30% of the total cardiac cell volume. The high mitochondrial density enables the heart to generate the needed amount of energy. This energy sustains the rhythmic contractions of the heart.

To help sustain the function of the heart, more ATP is needed. The heart beats about 100,000 times in one day. This activity requires a large amount of energy. As such, the need for more ATP is addressed by having more mitochondria in the cell itself.

The mitochondrial count is also high among other high-energy demanding organs. This includes your liver and skeletal muscles.

The liver is responsible for a lot of functions. It includes detoxification, protein synthesis, and regulation of biochemical reactions. Thus, hepatocytes need more ATP to enable the liver to function efficiently.

The skeletal muscles require a substantial amount of energy for contraction and movement. The more we move our bodies, the more energy is needed. The more active we are, the more mitochondria are required in order to produce more energy.

This all boils down to the fact that as the cells become more active, more energy is needed. In order to keep up with the increased need for energy, more mitochondria are required.

How many mitochondria does a human have?

By a general estimate, humans can have around 1000 mitochondria per cell. As such, the total mitochondria of a human being can be estimated to reach around 100 trillion mitochondria. The sum of all the mitochondria in each possible cell of the human body.

Mitochondrial density varies across different cell types. As you have learned earlier, some cells need more, while some don’t need the mitochondria at all.

By approximation, the diverse activities, functions, and processes a human being undergoes require a ton of energy supplied by the 100 trillion mitochondria everywhere.

What foods repair mitochondria?

Numerous scientists worldwide have recorded mitochondrial damage. As such, researchers discovered that this degradation is reversible. This can be done through food intake that supports and restores mitochondrial function.

1. Antioxidants

Antioxidants are good to combat the presence of free radicals. Free radicals are harmful to the cells and can damage the mitochondria even more. As such, antioxidants are a great way to combat the presence of risky free radicals.

Blueberries and other berries, in general, are packed with antioxidants. Pomegranate seeds have also been found to be high in antioxidants. They are also high in fiber, vitamin C, and potassium.

• B Vitamins

B vitamins work as co-enzymes. These help start up the mitochondrial engines to synthesize energy. These B vitamins are cofactors for many enzymes in the mitochondrial energy metabolism.

For optimal function of the mitochondria, adequate amounts of B vitamins and other vitamins must be observed. Beef is a great and complete source of B vitamins. Additionally, it contains healthy amounts of omega-3 fats.

• Sulfur

Sulfur compounds play a role in mitochondrial dynamics. They also contain antioxidant properties that reduce oxidative stress in the cell.

Sulfur can be sourced from broccoli and broccoli sprouts. They have far higher concentrations of sulfur in broccoli than among other vegetables.

• Fats

Fats in the mitochondria are used as part of a protective membrane. A diet comprised of high-quality fats and oils is essential to ensure a healthy mitochondrion.

Familiar healthy fat sources include olive oil, Butter, and Salmon. Olive oil is rich in phytonutrients that combat free radical damage efficiently. Butter, in healthy moderation, serves as a good source of fat-soluble vitamins.

Fatty fish such as salmon are high in essential omega-3 fatty acids. This helps support mitochondrial function as well as reduce inflammation.

• Magnesium

Magnesium is a mineral that performs numerous functions on a daily basis. The mitochondria depend on magnesium as it is a vital cofactor. Magnesium is involved in glycolysis, cell respiration, and transmembrane transport.

As such, magnesium is in avocados and spinach. Avocados are high in magnesium content as well as their monounsaturated fat. Spinach, along with most common green leafy vegetables, contains high and healthy amounts of magnesium.

It is essential to look at your diet and try to incorporate such examples into your meals. By doing so, you are able to support mitochondrial repair. You are also able to enhance your overall cellular energy turnover. This eventually leads to better health and lifestyle outcomes.

What happens if the mitochondria stop working?

Once the mitochondria stop working, a range of health issues collectively known as mitochondrial dysfunction can occur.

As you may have learned, the mitochondria serve an integral function in sustaining life. Once the mitochondria stop working, the cell will bear the consequences as follows.

1. Energy Deficiency

ATP production now happens at a much slower rate. It results in a significantly lesser turnover.

Aside from cellular respiration, there are also other means of producing ATP in the body. It can occur through beta-oxidation, ketosis, protein catabolism, and anaerobic metabolism. The problem here is that these are not as efficient as the mitochondria in ATP synthesis.

When the body functions continue, the lack of energy will cause a significant imbalance. An imbalance between the production and expenditure of ATP. Thus, an energy deficiency.

• Organ Defects and Dysfunction

Earlier, you have learned that some organs contain more mitochondria than others. This is because of their functions. Some require them to have more mitochondria and generate more energy.

As such, the inhibition of ATP production can lead to severe damage and complications to the heart, skeletal muscles, and kidneys, for instance. The effects can span a range of disorders that overall impair the body’s normal functioning.

• Metabolic Disorders

Metabolic disorders result from mitochondrial dysfunction, and these include mainly diabetes and obesity.

If the body continues to consume the daily food and nutrient intake, the inability to produce the same amount of energy causes an imbalance. This imbalance is between energy production and use leads to a defective metabolism.

Other diseases of a metabolic nature are type 2 diabetes, dyslipidemia, and cardiovascular diseases.

Overall, the mitochondria prove to be the cell’s powerhouse. Not just the cell but the entire body system’s powerhouse. All of the essential functions depend on ATP, and the mitochondria serve to produce as much ATP as needed. Without these important organelles, life would be put to a halt as we deal with its consequences. As such, keeping your body healthy lies at the forefront of ensuring that your organs, tissues organelles, and cells function efficiently.

References:

Bhatti, J. S., Bhatti, G. K., & Reddy, P. H. (2016). Mitochondrial dysfunction and oxidative stress in metabolic disorders — A step towards mitochondria based therapeutic strategies.

Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 1863(5), 1066–1077. https://doi.org/10.1016/j.bbadis.2016.11.010

Brand, M. D., Orr, A. L., I.V. Perevoshchikova, & Quinlan, C. L. (2013). The role of mitochondrial function and cellular bioenergetics in aging and disease. British Journal of Dermatology, 169, 1–8. https://doi.org/10.1111/bjd.12208

Cox, A. (2019). Top 9 Foods You Need to Boost Your Mitochondria – Institute for Restorative Health. Institute for Restorative Health. https://instituteforrestorativehealth.com/2019/07/09/top-9-foods-you-need-to-boost-your- mitochondria/ health.com/2019/07/09/top-9-foods-you-need-to-boost-your-mitochondria/

Hashiguchi, K., & Qiu-Mei Zhang-Akiyama. (2009). Establishment of Human Cell Lines Lacking Mitochondrial DNA. Methods in Molecular Biology, 383–391. https://doi.org/10.1007/978-1-59745-521-3_23

Li, A., Shami, G. J., Griffiths, L., Lal, S., Irving, H., & Braet, F. (2023). Giant mitochondria in cardiomyocytes: cellular architecture in health and disease. Basic Research in Cardiology, 118(1). https://doi.org/10.1007/s00395-023-01011-3

Mouna Habbane, Montoya, J., Taha Rhouda, Yousra Sbaoui, Driss Radallah, & Emperador, S. (2021). Human Mitochondrial DNA: Particularities and Diseases. Biomedicines, 9(10), 1364–1364. https://doi.org/10.3390/biomedicines9101364

Rogers, K. (2009, January 19). Mitochondrion | Definition, Function, Structure, & Facts.

Encyclopedia Britannica. https://www.britannica.com/science/mitochondrion

Zhang, Z., Cheng, J., Xu, F., Chen, Y., Du, J., Yuan, M., Zhu, F., Xu, X., & Yuan, S. (2011). Red blood cell extrudes the nucleus and mitochondria against oxidative stress. IUBMB Life, 63(7), 560–565. https://doi.org/10.1002/iub.490