What is the energy produced by the mitochondria?

What is the energy produced by the mitochondria?

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I know that the mitochondria is basically the power house of the body, it consumes amino acids, fatty acids, glucose, etc and oxygen.

When these molecules meet up in a enzyme, a series of reactions happen (Krebs cicle) which end up in CO2, H20 and energy.

Then the enzyme and later mitochondria will release its energy which will be stored in ATP molecules.

My question is what is this energy?

ATP is a form of chemical energy. Hydrolysis of the third phosphate group produces quite a bit of energy:

ΔG° = −30.5 kJ/mol (−7.3 kcal/mol)

ATP is used in a variety of cellular processes, from signal transduction to biosynthetic reactions, motility, and cell division.

An interesting bonus fact: an adult human body only contains about 250 grams of ATP at any one time, but turns over its entire body weight in ATP during the course of a single day.

The use of the energy in ATP is quite complex. Since my college days our knowledge of how ATP is used has broadened considerably.

Let's look first at the role of ATP in the sodium-potassium pump. This pump uses roughly 20% of the ATP your body produces, even more if you are a couch potato. ATP powers this process by attaching its terminal phosphate group to the pump. The phosphate group is highly charged. Its attachment pulls and tugs on some regions of the pump and repels other regions due to the fact that many of the amino acids comprising the pump are polar or charged. These electrical, magnetic-like, interactions change the shape of the pump. This causes sodium ions to be pumped outside the cell even though they are more plentiful there. When the phosphate is released, the pump returns to its original shape bringing in potassium ions and reloading sodium. It is this pumping action that, among other things, provides the energy for messages in nerve and muscle cells (action potentials).

Probably the important energy use of ATP is this. Many of the reactions your body needs are uphill battles. That is, there is more energy in the substances we wish to produce (products) than in the substances which we must use for raw materials (reactants). So, the ATP attaches its phosphate to the reactant. This raises the energy in the reactant making it now have more energy (more unstable) than the product we wish to produce. The reaction now becomes "downhill" and can proceed naturally ("spontaneously") without holding a bunsen burner under your bottom. This concept is termed "coupled reactions" where we take the "downhill" breaking down of ATP and use it to power the "uphill" production of a requires substance.

There are two principal reasons a molecule becomes more energetic when a phosphate is attached. It is now more complex. Complexity increases instability, a consequence of the laws of thermodynamics. Another reason is that the highly charged phosphate creates stress in the molecule due to electrical interactions with other parts of the molecule.

Here's an image (mine) to show the concept of coupled reactions:

You seem to have misunderstood energy as some sort of substance which is produced as a product of cellular respiration like CO2 or H2O then released into the bonds of ATP molecules. Remembering that it is not a substance and that it is transferred(and not made) by the breaking and formation of bonds in the process of respiration should help clear that out.

Mitochondria and Aging (CER)

  • Contributed by Shannan Muskopf
  • High School Biology Instructor at Granite City School District
  • Sourced from Biology Corner

Aristotle believed that we possess a finite amount of some &ldquovital substance.&rdquo When that substance is consumed, we die. The idea was based on the principle that if you use something long enough, it will eventually wear out. Some philosophers even argued that each person had only a finite, predetermined number of breaths or heartbeats and that once they were used, you would die. Biologists have always been curious about what causes aging and death, and solving that riddle may be the key to longer lifespans and better quality of life. Scientists proposed a new hypothesis based on this old idea of a &ldquovital substance,&rdquo that energy consumption limits longevity. In other words, an organism's metabolic rate determines its lifespan.

As we age, the mitochondria become larger and less numerous, and sometimes develop abnormalities with their structure. Experiments performed on mice shows that increased levels of mitochondrial mutations are related to a variety of age related changes, such as osteoporosis, hair loss, and weight reduction. The &ldquoMitochondrial Theory of Aging&rdquo posits that the accumulation of damage to the DNA of a mitochondria leads to aging in humans and animals.

Mitochondria are unique in that they are the only organelle in animal cells that possess their own DNA, referred to as mtDNA, which is separate from the DNA in the cell nucleus. When a cell divides, the mitochondria divide independently, and new mitochondria are passed to the new cells. New daughter created through mitosis are identical to the original cell but may contain mitochondria that have new mutations. Every new cell division has the possibility of resulted in mutations within the cell&rsquos nucleus and within the mtDNA.

How are mitochondria and metabolic rate related?

Metabolic rate refers to the amount of energy that is used by an organism to maintain life processes. On a cellular level, the mitochondria use oxygen to convert food (glucose) to an energy storing molecule called adenosine triphosphate, or just ATP. This process is called cellular respiration. The ATP produced in this reaction is then used by the cell to maintain homeostasis and ensure that the cell and body function normally.

Why is mitochondria known as the ‘energy currency of the cell’?

Why is mitochondria known as the ‘energy currency of the cell’, discuss.

Nehal Rathi

Mitochondria are double-membraned organelles. The mitochondria is know as “energy currency of the cell” or “the power house of the cell” because it produces ATP. ATP stands for adenosine triphosphate, it is a type of energy that is released. They contain their own own ribosomes and dna. It helps in cellular respiration because of production of ATP in this cell. ATP is produced by consuming glucose and other nutrients.

Mitochondria uses oxygen and as a by product it releases carbon dioxide. In fact after every breath a human inhales oxygen and the carbon dioxide which is released out of the body is by the product of the cell. One human can have one single large mitochondria or even thousands of small mitochondria. It also stores calcium as it a very important part of our body it helps in the functioning of our muscles fertilisation, blood Clotting etc. Size of one mitochondria is generally 1-10 micrometers in length.

ATP is also a very good source of energy for our body. they have a power to recycle them. It is produced it plants, animals and humans. It can be used in Endothermic and exothermic processes. When a cell in our body becomes old or broken they have to be cleared away and destroyed so that new cells can be formed. Mitochondria play as very important role as it decides which cells is suppose to be removed and destroyed.

Mitochondria plays a very important role as in absorbs the calcium, irons, and store in until it is needed to out body. Mitochondria is also helpful to produce heat in our body it can use a tissue called brown fat which can be used to generate heat. Brown fat is found at its highest level in infants and it slowly reduces as one persons age increases. These are the reasons by why it is called “energy currency of the cell”.

Other Organelles

In addition to the nucleus, eukaryotic cells have many other organelles, including ribosomes and mitochondria. Ribosomes are present in all cells.


Ribosomes are small organelles and are the sites of protein synthesis (or assembly). They are made of ribosomal protein and ribosomal RNA, and are found in both eukaryotic and prokaryotic cells. Unlike other organelles, ribosomes are not surrounded by a membrane. Each ribosome has two parts, a large and a small subunit, as shown in Figure below. The subunits are attached to one another. Ribosomes can be found alone or in groups within the cytoplasm. Some ribosomes are attached to the endoplasmic reticulum (ER) (as shown in Figure below), and others are attached to the nuclear envelope.

The two subunits that make up a ribosome, small organelles that are intercellular protein factories.

Ribozymes are RNA molecules that catalyze chemical reactions, such as translation.Translation is the process of ordering the amino acids in the assembly of a protein, and translation will be discussed more in another concept. Briefly, the ribosomes interact with other RNA molecules to make chains of amino acids called polypeptide chains, due to the peptide bond that forms between individual amino acids. Polypeptide chains are built from the genetic instructions held within a messenger RNA (mRNA) molecule. Polypeptide chains that are made on the rough ER (discussed below) are inserted directly into the ER and then are transported to their various cellular destinations. Ribosomes on the rough ER usually produce proteins that are destined for the cell membrane.

Ribosomes are found in both eukaryotic and prokaryotic cells. Ribosomes are not surrounded by a membrane. The other organelles found in eukaryotic cells are surrounded by a membrane.


A mitochondrion (mitochondria, plural), is a membrane-enclosed organelle that is found in most eukaryotic cells. Mitochondria are called the "power plants" of the cell because they are the sites of cellular respiration, where they use energy from organic compounds to make ATP (adenosine triphosphate). ATP is the cell's energy source that is used for such things such as movement and cell division. Some ATP is made in the cytosol of the cell, but most of it is made inside mitochondria. The number of mitochondria in a cell depends on the cell&rsquos energy needs. For example, active human muscle cells may have thousands of mitochondria, while less active red blood cells do not have any.

(a): Electron micrograph of a single mitochondrion, within which you can see many cristae. Mitochondria range from 1 to 10 &mum in size. (b): This model of a mitochondrion shows the organized arrangement of the inner and outer membranes, the protein matrix, and the folded inner mitochondrial membranes.

As Figure above (a) and (b) show, a mitochondrion has two phospholipid membranes. The smooth outer membrane separates the mitochondrion from the cytosol. The inner membrane has many folds, called cristae. The fluid-filled inside of the mitochondrion, called matrix, is where most of the cell&rsquos ATP is made.

Although most of a cell's DNA is contained in the cell nucleus, mitochondria have their own DNA. Mitochondria are able to reproduce asexually, and scientists think that they are descended from prokaryotes. According to the endosymbiotic theory, mitochondria were once free-living prokaryotes that infected or were engulfed by ancient eukaryotic cells. The invading prokaryotes were protected inside the eukaryotic host cell, and in turn the prokaryote supplied extra ATP to its host.

Bringing new energy to mitochondria research

Tiny mitochondria in our cells turn oxygen and nutrients into usable energy in a process called respiration. This process is essential for powering our cells, and yet in spite of its importance many of the finer details of how it happens remain unknown. One long-standing mystery is how a molecule called nicotinamide adenine dinucleotide (NAD), which plays a big part in respiration and metabolism, gets into the mitochondria in humans and other animals. Mitochondria use NAD in order to produce adenosine triphosphate (ATP), the energy supply molecules used throughout the cell. Researchers knew the identities of the molecules that transport NAD from the wider cell into the mitochondria of yeast and plants, but had not found the animal equivalent—in fact, there was some debate over whether one even existed or whether animal cells used other methods altogether.

Now, research from postdoctoral researcher Nora Kory in Whitehead Institute Member David Sabatini’s lab may end the debate. In a paper published in Science Advances on September 9, the researchers show that the missing human NAD transporter is likely the protein MCART1. This discovery not only answers a longstanding question about a vital cellular process, but may contribute to research on aging—during which cells’ NAD levels drop—as well as research on diseases that involve certain mitochondrial dysfunctions, for which cells with broken NAD transporters could be an experimental model.

“I find it striking that mitochondria play such an important role in metabolism in the cell, which in turn plays a huge role in health and disease, but we still don’t understand how all of the molecules involved get in and out of mitochondria. It was exciting to fill in a piece of that puzzle.” Kory says.


Kory did not set out to find the long sought-after transport molecule. Rather, she was trying to better understand mitochondrial respiration by mapping the genes involved. She was comparing gene essentiality profiles, which show how important a gene is to different processes in a cell—the more co-essential two genes are, the more likely they are to be involved in the same cellular process—and one gene stood out: MCART1, also known as SLC25A51. It was highly correlated to other genes involved in mitochondrial respiration, and belonged to a family of genes known to code for transporters, yet its function was unknown. The protein coded for by MCART1 clearly played an important role, so Kory decided to figure out what that was as her research progressed, she realized she had found the missing NAD transporter.

Kory and colleagues applied a common approach to determine MCART1’s function: inactivate the gene in cells, and see what breaks down in its absence. This approach is like troubleshooting a machine if you cut a wire in your car and the headlights stop working, but everything else is fine, then that wire was probably linked to the headlights. When the researchers removed MCART1, the cells exhibited much lower oxygen consumption, reduced respiration and ATP production, and reliance on other, far less efficient means of ATP production—exactly what you’d expect to see if the inactivated gene was needed for respiration. Moreover, the biggest change that the researchers observed in cells without MCART1 was reduced levels of NAD in the mitochondria, while NAD levels in the wider cell remained the same, which they quantified using experiments previously developed in the lab. The researchers confirmed that MCART1 is essential for NAD transport into isolated mitochondria and overabundance of MCART1 caused an increased uptake.

“It’s very satisfying when our lab returns to the techniques that we have developed in order to make new findings such as identifying this important protein,” says Sabatini, who is also a professor of biology at Massachusetts Institute of Technology and an investigator with the Howard Hughes Medical Institute.

The evidence supports that the protein MCART1 is itself the transport channel. However, it is possible that the protein may play some other essential contributing role to transportation, or that it combines with other molecules to do its job. To strengthen the case for MCART1 as the transporter, the researchers showed that MCART1 and the known yeast NAD transport could be switched out for each other in both human and yeast cells, suggesting an equivalent function. Still, further experiments are needed to determine the precise mechanism of transport.

A serendipitous case of synchronous discovery reinforces Kory’s findings. A paper by other researchers published on the same day in the journal Nature also put forth that MCART1 is the missing NAD transporter, based on a completely different set of evidence. Combined, the papers provide an even more compelling case.

“It was nice to see how our different approaches complemented each other, and led to the same conclusion,” Kory says.

Understanding how NAD gets into the mitochondria opens up new questions about the details of mitochondrial respiration. Kory will shortly be leaving Sabatini’s lab to open her own lab at the Harvard T.H. Chan School of Public Health, where she intended to continue investigating the role of the mitochondria’s NAD supply in metabolism and signaling.

David Sabatini’s primary affiliation is with Whitehead Institute for Biomedical Research, where his laboratory is located and all his research is conducted. He is also a Howard Hughes Medical Institute investigator and a professor of biology at Massachusetts Institute of Technology.

Kory, N., et al. (2020). MCART1/SLC25A51 is required for mitochondrial NAD transport. Science Advances. doi:10.1126/sciadv.abe5310

Luongo, T. S., et al. (2020). SLC25A51 is a mammalian mitochondrial NAD+ transporter. Nature. doi:10.1038/s41586-020-2741-7

Mitochondrial Parts

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Like all other cell organelles, mitochondria is also a membrane enclosed cell organelle, contained in the cytosol (intracellular fluid) of eukaryotic cells (cells that contain a nucleus). The structure is constituted of the following parts:

Outer membrane

This is constituted of a semi permeable phospholipid bilayer, made of porins (protein structures). This layer is permeable to ions, ATP (adenosine triphosphate), ADP (adenosine diphosphate) and nutrient molecules.

Inner membrane

This is a complex but permeable membrane made of complex molecules of electron transport system, ATP synthetase complex and transport proteins. This layer allows oxygen, water and carbon dioxide.


Cristae are shelf like folds in inner membrane. They help in expansion of the inner cell membrane structure when there is a need for more space to accommodate more molecules of mitochondrial DNA.

Intermembrane space

This is the space between outer membrane and inner membrane. Intermembrane space is primarily responsible for oxidative phosphorylation.

Cytoplasmic matrix

Cytoplasmic matrix contains the DNA molecules (responsible for cellular respiration), enzymes (responsible for citric acid cycle reactions), dissolved gases (like oxygen, carbon dioxide), recyclable intermediates (serve as energy shuttles) and water.


The mitochondria perform most important functions such as oxidation, dehydrogenation, oxidative phosphorylation and respiratory chain of the cell. Their structure and enzymatic system are fully adapted for their different functions.

They are the actual respiratory organs of the cells where the foodstuffs, i.e., carbohydrates and fats are completely oxidised into CO2 and H2O. During the biological oxidation of the carbohydrates and fats large amount of energy is released which is utilized by the mitochondria for synthesis of the energy rich compound known as adenosine triphosphate or ATP.

Because mitochondria synthesize energy rich compound ATP, they are also known as “power houses” of the cell. In animal cells mitochondria produce 95 per cent of ATP molecules remaining 5 per cent is being produced during anaerobic respiration outside the mitochondria. In plant cells, ATP is also produced by the chloroplasts.

Adenosine triphosphate or ATP:

The ATP consists of a purine base adenine, a pentose sugar ribose and three molecules of the phosphoric acids .The adenine and ribose sugar collectively constitute the nucleoside adenosine which by having one, two or three phosphate groups forms the adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) respectively.

In ATP the last phosphate group is linked with ADP by a special bond known as “energy rich bond” because when the last phosphate group of the ATP is released the large amount of energy is released.Recently, besides ATP, certain other energy rich chemical compounds have been found to be active in the cellular metabolism.

These are cytosine triphosphate (CTP), uridine triphosphate (UTP) and guanosine triphosphate (GTP). These compounds, however, derive the energy from the ATP by nucleoside diphosphokinases. The energy for the production of ATP or other energy rich molecules is produced during the breakdown of food molecules including carbohydrates, fats and proteins (catabolic and exergonic activities).


The carbohydrates enter in the cell in the form of monosaccharides such as glucose or glycogen. These hexose sugars are first broken down into 3-carbon compound (pyruvic acid) by a series of chemical reactions known by many enzymes.

The pyruvic acid enters in the mitochondria for its complete oxidation into CO2 and water. The reactions which involve in the oxidation of glucose into CO2 and water are known to form the metabolic pathways and they can be grouped under the following heads:

(i) Glycolysis or Embden-Meyerhof pathways (EMP) or Embden-Meyerhof-Parnas pathways (EMPP)

(ii) Oxidative decarboxylation

(iii) Krebs cycle citric acid cycle or tricarboxylic acid cycle

(iv) Respiratory chain and oxidative phosphorylation.


Besides the ATP production, mitochondria serve the following important functions in animals:

Heat production or thermiogenesis:

In some mammals, especially young animals and hibernating species, there is a specialized tissue called brown fat. This tissue, typically located between the shoulder blades, is especially important in temperature regulation it produces large quantities of body heat necessary for arousal from hibernation. The colour of brown fat comes from its high concentration of mitochondria, which are sparse in ordinary fat cells.

The mitochondria appear to catalyze electron transport in the usual way but are much less efficient at producing ATP. Hence, a higher than usual fraction of the oxidatively released energy is converted directly to heat (called non-shivering thermiogenesis).

Biosynthetic or anabolic activities:

Mitochondria also perform certain biosynthetic or anabolic functions. Mitochondria contain DNA and the machinery needed for protein synthesis. Therefore, they can make less than a dozen different proteins. The proteins so far identified are subunits of the ATPase, portions of the reductase responsible for transfer of electrons from Co Q to the iron of Cyt c, and three of the seven subunits in cytochrome oxidase.

Accumulation of Ca2+ and phosphate:

In the mitochondria of osteoblasts present in tissues undergoing calcification large amount of Ca2+ and phosphate (PO4¯ ) tend to accumulate. In them microcrystalline, electrone-dense deposits may become visible. Sometimes, the mitochondria assume storage function, e.g., the mitochondria of ovum store large amounts of yolk proteins and transform into yolk platelets


Cell Biology: Organelle Structure and Function

David E. Sadava – 1993

Essential Cell Biology

Bruce Alberts, ‎Dennis Bray, ‎Karen Hopkin – 2013

All About Mitochondria

Mitochondria are essential components of nearly all cells in the body. These organelles are the powerhouses for cells, providing energy to carry out biochemical reactions and other cellular processes. Mitochondria make energy for cells from the chemical energy stored in the food we eat.

Where are mitochondria found?

Mitochondria are found in all body cells, with the exception of a few. There are usually multiple mitochondria found in one cell, depending upon the function of that type of cell. Mitochondria are located in the cytoplasm of cells along with other organelles of the cell.

How did mitochondria come about?

This question has been raised due to many characteristics shared by mitochondria and other single cellular living organisms. For example, mitochondria are the only organelles in the cell which contain their own DNA, as well as their own protein making machinery. Researched has shed light on the possibility of a theory known as endosymbiosis.
When life first began on our planet, single celled organisms produced energy in a way that was highly inefficient (anaerobic respiration, meaning without oxygen) compared to what most multi-cellular organisms use today (aerobic respiration, using oxygen). Through evolutionary time, plants came about and were able to produce oxygen in the atmosphere giving rise to aerobic respiration which produced energy in a highly efficient manner. The theory of endosymbiosis suggests that mitochondria were once free living organisms on their own that used aerobic respiration. Larger anaerobic cells simply engulfed these aerobic mitochondria to use their energy, giving rise to complex cells we find today such as those in our bodies.

Timeline of Mitochondrial Disease

The area of mitochondrial medicine is extremely new, and therefore ever expanding. The discovery of most mitochondrial diseases actually only occurred within the last 30 years. The timeline below shows some important milestones in the history of mitochondrial medicine:

1962 – The first case of suspected mitochondrial disease occurs where a woman has an extremely fast and efficient metabolism, and mitochondria that were larger in size and number in her muscle tissue
1962 – Chemical staining is applied to mitochondria, to identify any observable changes in mitochondria under a microscope
1975 – First case of MELAS is described
1981 – The mitochondrial genome is mapped
1982 – Scientific papers are published regarding Kearns-Sayre Syndrome and MERRF
1984 – First scientific paper published about MELAS
1991 – Biochemical and molecular analysis of tissue samples from patients becomes commercially available

How is energy made?

Our food contains the building blocks of life known as macromolecules, namely carbohydrates, proteins and fats. The energy stored in the molecular bonds of these molecules is converted into a usable energy source in the body known as ATP. ATP is the only energy currency that can be used in our bodies. This concept is analogous to energy from power plants entering our homes. Similar to macromolecules, there are many sources of energy including hydro, wind, nuclear etc. Although the sources are different, the energy that enters our homes is almost always converted to electricity to power various devices, similar to how only ATP in our cells is used to carry out cellular functions.
The actual production of ATP is quite a complex process. The inner membrane of the mitochondrion is what is responsible for mass energy production.

Specifically, five proteins form a chain on the inner mitochondrial membrane known as the respiratory chain that transfers energy (in the form of an electron) along these five proteins until it becomes ATP. This is shown in the animation below.

The Mitochondria produces energy in a cell, but how does this energy actually work?

More specifically, I would like to know how the energy is used to do cell functions. I am taking biology, and we are doing cells, but nobody can really explain this.

I'm certain somebody else will come along and give a more detailed (and maybe more accurate) explanation soon enough, but I miss talking about this stuff, so I'll respond anyway.

The energy your class is talking about is ATP, often considered the fuel for the cell. It's been a long time since I've taken a Biology class, but I do remember the Krebs (or citric acid cycle) being the focus in discussions on what the mitochondria does (though it does a lot more than just that). The end product of of the Krebs cycle is, of course, ATP.

Now, ATP isn't the most complicated molecule out there. It's an adenine molecule (one of the bases in DNA and RNA), with a sugar molecule attached (ribose, as in, deoxy-ribo-nucleic acid), and a chain of phosphates attached to that. It's the chain of phosphates that's really relevant here they're where the energy comes from. They're chained through what's called a phosphoanhydride bond. ATP has three of these phosphates (adenosine triphosphate), and two of these phosphoanhydride bonds. ADP has two (di) phosphates, and one remaining phosphoanhydride bond – ADP itself can be used as fuel, too.

See, those phosphoanhydride bonds are referred to as "high energy." They're not terribly unstable – they don't just want to react to whatever comes their way – but they are weak. Those phosphates would really prefer not to be bonded, but a lot of energy was put into them to make them bond anyway. So when an ATP molecule meets up with the right enzyme, the enzyme uses that molecule (and whatever else it needs to) to perform its task. These enzymes are incredibly complex molecules which ATP will react with, but the enzyme channels that "energy" (a chain reaction of molecules shifting based on what they prefer and how much energy there is. ) to creating other changes in other molecules in the cell.

I could get into more depth on the topic of energy – which is more along the lines of what I've been studying lately – but I'm guessing this is enough for you.

Oh, and in addition, that ATP, once used up and turned into AMP, is incredibly crucial to DNA synthesis. The remaining phosphate and sugar become part of the DNA backbone, and the adenosine becomes the adenosine base in the DNA strand. Of course, all of this is regulated by a huge factory of enzymes!

I hope that's about what you wanted.

edit: Im_That_1_Guy makes a good point below about ATP production, if anyone was bothered by my focus on the Krebs cycle.

As for the DNA synthesis thing, I shouldn't have included any of that at all. I had this nagging thought in my head that it's a different sugar and I would remember if AMP and dATP/dNTPs were the same, which I ignored. With the help of Wikipedia, I've now managed to thoroughly confuse myself, and I don't have the time to look up and clarify to myself and on here how exactly that bit works.

And yes, when I said ATP is "used up" I was referring to the following use of ADP, as well.

What is the function of mitochondria?

Mitochondria are the 'powerhouses' of the eukaryotic cell. These organelles are the sites of cellular respiration, the metabolic process that generates energy from carbohydrates in the cell. The energy produced is in the form of ATP, the energy carrier molecule.

Mitochondria are physically adapted to this task:

- ​Double membrane: ​The outer membrane controls entry and exit of material into the organelle. The inner membrane is folded to form structures called the cristae:

- ​Cristae​: shelf-like extensions of the inner membrane. They have a large surface area for enzymes that carry out reactions in respiration to attach to.

- Matrix : ​the material that fills space inside the inner membrane of the mitochondria. It contains protein, lipids and traces of DNA so that mitochondria can produce their own proteins. Enzymes involved in respiration are also contained within the matrix.