4 Functions of Mitochondria to Their Definition, Structure, and Role

Functions of Mitochondria – Mitochondria are often referred to as the powerhouse of the cell. They help convert the energy we take from food into energy that cells can use. But, there’s a lot more to mitochondria than energy production going on, Sinaumed’s.

Present in almost all types of human cells, mitochondria are essential for our survival. They produce most of the adenosine triphosphate (ATP), the energy in the catabolic pathway, aka the energy currency of the cell. Mitochondria are also involved in other tasks, such as signaling between cells and cell death, also known as apoptosis.

Through this sinaumedia article, we will study the function of mitochondria, their shape, structure, how they work, and their roles in life. Last but not least, we will also know about what happens when the mitochondria, the powerhouse of the cell, stop doing their jobs properly.

Mitochondria are round to oval shaped organelles found in the cells of almost all eukaryotic organisms. This component produces the energy known as ATP for cells through a series of chemical reactions.

In 1850, for the first time Kollicker observed and isolated mitochondria from cells. This could happen because of his observations on the striated muscle tissue of insects. At that time, he found granules with a free structure, and had no direct relationship with the internal structure of the cell.

In language, the term mitochondria itself comes from a combination of two words, namely Mito and Chodrion which respectively mean thread and granular.

The number of mitochondria per cell varies widely, Sinaumed’s. For example, in humans, erythrocytes (red blood cells) do not contain any mitochondria whereas liver cells and muscle cells may contain hundreds or thousands of these components. The only known eukaryotic organism lacking mitochondria is the oxymonas species Monocercomonoides .

Mitochondria are unlike any other cellular organelle. This is because they have two different membranes, a unique genome, and reproduce by binary fission. These features suggest that mitochondria share an evolutionary past with single-celled organisms.

Mitochondrial Function

The following are the functions of mitochondria as organelles that are part of this cell. Let’s get to know each other well!

Function of Mitochondria in Energy Production

The outer mitochondrial membrane is freely permeable by particles to small molecules and contains specialized channels capable of transporting large molecules. In contrast, the inner membrane is almost impenetrable so that only very small molecules can cross into the gel-like matrix that forms the central mass of the organelle.

This matrix contains the deoxyribonucleic acid (DNA) of the mitochondrial genome and the enzymes of the tricarboxylic acid (TCA) cycle, also known as the citric acid cycle or Krebs cycle, which metabolize nutrients into by-products that mitochondria can use for energy production.

Most of the ATP is produced in mitochondria through a series of reactions. Most of the energy production occurs in the folds or cristae of the inner membrane. Mitochondria convert the chemical energy from our food into forms of energy that cells can use. This process is called oxidative phosphorylation.

The Krebs cycle produces a chemical called NADH. NADH is the substance that enzymes embedded in cristae use to produce ATP. In the ATP molecule, chemical bonds bind energy and store it. When these chemical bonds are broken, energy can be used.

Other Mitochondrial Functions

Although the most well-known role of mitochondria is energy production, they also perform other important tasks. In fact, only about 3 percent of the genes needed to make mitochondria go into their energy production apparatus. Most are involved in other jobs that are specific to the cell type in which they are found.

Here are some other mitochondrial functions that are important for us to know.

1. Function of Mitochondria to Regulate Cell Death

Cell death which is also called apoptosis, is an essential part of life. When cells get old or damaged, they are cleaned and destroyed. It is in this case that mitochondria help decide which cells need to be destroyed.

This component releases cytochrome C which activates caspase , one of the main enzymes involved in cell destruction during apoptosis. In certain diseases such as cancer, there is a breakdown in normal apoptosis. This makes mitochondria considered to play a role in the disease.

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2. Function of Mitochondria to Store calcium

Calcium is essential for a number of processes. For example, releasing calcium back into cells can initiate the release of neurotransmitters from nerve cells or hormones from endocrine cells. Calcium is also needed for muscle function, fertilization, blood clotting, and so on. Other roles of calcium in cells include regulating cell metabolism, steroid synthesis, and hormone signaling

Because calcium is considered so important, cells regulate it tightly. Mitochondria, in this case, have the role of absorbing calcium ions and holding them quickly until the time when calcium is needed.

3. Function of Mitochondria for Heat Production

When we are cold, we shiver to stay warm. However, the body can also generate heat in other ways, one of which is by using a layer of so-called brown fat.

During a process called proton leakage, mitochondria can generate heat. This is known as non-shivering thermogenesis. Brown fat is found at the highest level of 5 percent in infants, when we are more susceptible to cold. The level slowly decreases with age.

Here are some additional mitochondrial functions:

  • Mitochondria have enzymes in liver cells. It works to detoxify ammonia.
  • Controls various cycles in the cell.
  • Building parts of hormones, such as estrogen or testosterone.
  • Supervise the process of differentiation, growth, and development in cells.
  • Where the processes of oxidative metabolism-cellular respiration occur.

Mitochondrial Structure

According to Sinaumed’s, what is the inside of the mitochondria, which looks oval and very small, like? Mitochondria, of course, still have several other components from the outside to the inside.

Mitochondria are small, often between 0.75 and 3 micrometers and are not visible under a microscope unless they are stained. Unlike other organelles (mini organs inside the cell), they have two membranes, an outer and an inner one. Each membrane has a different function.

Mitochondria are divided into different regions or compartments, each of which performs a different role. Some of the main regions of mitochondria include:

1. Outer membrane

As discussed earlier, small molecules can pass freely through the outer membrane. This outer covering includes proteins called porins, which form channels that allow proteins to cross. The outer membrane also houses a number of enzymes with various functions.

2. Intermembrane space

This is the area between the inner and outer membranes.

3. Inner membrane

This membrane holds proteins that serve several roles. There are no porins in the inner membrane, so this membrane is impermeable to most molecules that can only be from within special membrane transporters. Another fact, the inner membrane is where most of the ATP is made.

4. Cristae

It is an inner fold that increases the surface area of ​​the membrane thereby increasing the space available for chemical reactions.

5. Matrix

It is a space within the inner membrane that contains hundreds of enzymes, which are important in the production of ATP. Mitochondrial DNA is also stored here, Sinaumed’s.

The number of mitochondria varies depending on the type of cell. For example, mature red blood cells are completely devoid of mitochondria, while liver cells can have more than 2,000 of these organelles.

Cells with high energy requirements tend to have more mitochondria. Mitochondria take up about 40 percent of the cytoplasm in cardiac muscle cells.

Mitochondria are often described as oval-shaped organelles. However, they continue to divide (fission) and increase simultaneously (fusion). So, in fact, these organelles are linked together in an ever-changing network.

Also, in sperm cells, mitochondria rotate in the center and provide energy for tail movement.

Mitochondrial DNA

Although most of our DNA is stored in the nucleus of every cell, mitochondria have their own DNA sequence. Mitochondrial DNA aka mtDNA, interestingly, is more similar to bacterial DNA, Sinaumed’s.

Mitochondrial DNA or mtDNA stores instructions for a number of proteins and other supporting components in 37 genes.

The human genome stored in the nuclei of our cells contains about 3.3 billion base pairs, whereas mtDNA consists of less than 17,000. During reproduction, half of a child’s DNA comes from their father and half from their mother.

However, the child always receives mtDNA from the mother. For this reason, mtDNA has proven to be very useful for tracing genetic lines.

For example, mtDNA analysis has concluded that humans may have originated in Africa relatively recently, around 200,000 years ago, descended from a common ancestor known as the mitochondria of Eve.

Mitochondria and Human Evolution

Sinaumed’s, it seems that the mitochondria that we have can also trace our lineage to show traces of human evolution since our ancestors.

Maternal inheritance of mtDNA is important for research on human evolution and migration. This is because this allows the similarities inherited from generation to generation to be traced to a single ancestral line for several generations.

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Research has shown that fragments of the mitochondrial genome carried by all humans living today can be traced to an ancestor of single women who lived an estimated 150,000 to 200,000 years ago.

Scientists suspect that this woman lived among other women but a process of genetic drift (fluctuations in the frequency of genes that affect the genetic constitution of a small population) caused her mtDNA to randomly replace other women as the population evolved.

Variations in mtDNA that are inherited by successive human generations have helped researchers decipher the geographical origins as well as migration chronologies of different human populations.

For example, studies of the mitochondrial genome suggest that humans who migrated from Asia to the Americas 30,000 years ago may have been stranded in Beringia for 15,000 years before arriving on the American continent.

Mitochondria and Aging

Researchers have been investigating the relationship between mitochondrial dysfunction and aging for the past few years. There are a number of theories around aging and the mitochondrial free radical theory of aging has become popular over the last few decades.

The theory is that reactive oxygen species ( ROS) are produced in mitochondria, as a by-product of energy production. These highly charged particles damage proteins, fats, and even DNA.

The damage caused by these ROS results in damage to the functional parts of the mitochondria. When mitochondria no longer function properly, more ROS are produced and exacerbate the damage further.

Although a correlation has been found between mitochondrial activity and aging, not all scientists reach the same conclusion. Their exact role in the aging process is still unknown, Sinaumed’s.

The Role of Mitochondria in Disease

Mitochondrial DNA aka mtDNA is very susceptible to mutations. Mostly because it lacks any strong and common DNA repair mechanisms. In addition, mitochondria are the main site for the production of reactive oxygen species (ROS; or simply free radicals) because of their high tendency for aberrant release of free electrons.

While several different antioxidant proteins in mitochondria seek out and neutralize these molecules, some ROS can cause damage to mtDNA.

In addition, chemicals, certain infectious agents, and alcohol abuse can also damage mtDNA. In such instances, excessive ethanol intake saturates detoxifying enzymes, and causes highly reactive electrons to leak from the inner membrane into the cytoplasm or into the mitochondrial matrix. There, they combine with other molecules to form lots of radicals!

There are many mitochondrial diseases that are inherited or acquired without heredity. Many of them present at various age ranges and vary greatly in their clinical and molecular features.

The severity ranges from a relatively mild disease affecting only one organ to a debilitating and sometimes fatal disease affecting multiple organs.

Both inherited and non-inherited mitochondrial dysfunction are involved in diseases such as Alzheimer’s and Parkinson’s disease. The accumulation of mtDNA mutations throughout an organism’s life span is thought to play an important role in aging, as well as in the development of cancer and other diseases.

Mitochondria are also a major component of apoptosis (programmed cell death) which is routinely used to rid the body of cells that are no longer useful or functioning properly. If the mitochondria are not functioning so that it inhibits cell death, then this organelle contributes to the development of cancer.

Symptoms of Mitochondria Associated Diseases

If the mitochondria are dysfunctional or there is disease, there are several symptoms that we can feel. Although the symptoms of mitochondrial disease vary widely, they may include the following signs:

  • Loss of coordination and muscle weakness
  • Problems with vision or hearing
  • disability
  • Heart, liver, or kidney disease
  • Digestive problems
  • Neurological problems such as dementia

Diseases that involve some degree of mitochondrial dysfunction include the following conditions:

  1. Bipolar disorder
  2. Schizophrenia
  3. Chronic fatigue syndrome
  4. Huntington’s disease
  5. Diabetes
  6. autism


Apparently, mitochondria have a very important role in life and disease in us, Sinaumed’s. Before reading this article, what did you know about mitochondria? Its function is very crucial and important in various processes that maintain the body.

This organelle also has an interesting structure, its own DNA, aka mtDNA, and plays a role in many processes that occur in our bodies. Not only that, if the mitochondria are dysfunctional, aka not working properly, we can also feel certain symptoms, or even suffer from diseases related to this dysfunction.

Interesting, isn’t it, studying mitochondrial function? For Sinaumed’s who want to find out more about mitochondria, you can get recommended books at sinaumedia ! As #FriendsWithoutLimits, sinaumedia always provides the best products so you have #MoreWithReading information.