Adenosine triphosphate

Adenosine triphosphate, or ATP, is a very important chemical compound found in all living things. It helps give energy to cells so they can do their jobs, like making muscles move, sending messages through nerves, and building new chemicals. Because it provides energy for so many processes, ATP is often called the "molecular unit of currency" for energy transfer inside cells.

When cells need energy, ATP changes into smaller molecules called adenosine diphosphate (ADP) or adenosine monophosphate (AMP). Later, through processes like oxidative phosphorylation or substrate-level phosphorylation, ATP is made again so it can be used once more.

ATP is also a building block for DNA and RNA, the molecules that carry instructions for life. Every day, an adult human body recycles about 50 kilograms of ATP.

From a chemistry point of view, ATP is made of three parts: a base called adenine, a sugar called ribose, and a chain of three phosphate groups. This structure lets ATP store and release energy exactly where and when a cell needs it.

Structure

ATP is made up of three parts: a sugar, a special base called adenine, and a group of three phosphates linked together. The adenine attaches to the sugar, and the sugar holds the three phosphates. In the body, ATP can lose one or two of these phosphates, turning into ADP or AMP.

ATP can also bind to certain metals, especially magnesium. This binding helps ATP work with proteins in the cell and is important for many of ATP’s jobs.

Chemical properties

ATP can be found as colorless solids. It stays stable in water when the pH level is between 6.8 and 7.4, but breaks down quickly at more extreme pH levels. In living cells, there is much more ATP than a similar energy molecule called ADP, which helps cells do important work.

Reactive aspects

When ATP breaks down into smaller parts, it releases energy that cells can use to do work. This process is very important for all living things. The amount of energy released depends on the conditions inside the cell and can vary slightly.

The presence of certain minerals, like magnesium, can also affect how much energy is released when ATP breaks down. This shows how closely linked the chemistry of life is to the tiny details of molecular interactions.

Main article: Standard state

Production from AMP and ADP

Production, aerobic conditions

In our bodies, a typical amount of ATP is between 1–10 micromoles per gram of muscle tissue. ATP can be made in several ways, but three main paths in cells with a nucleus are: (1) glycolysis, (2) the citric acid cycle/oxidative phosphorylation, and (3) beta-oxidation. When we break down glucose completely, we can make about 30 ATP molecules from each glucose.

Most ATP in cells that need oxygen is made in the mitochondria, tiny parts inside cells that help turn food into energy.

Glycolysis

In glycolysis, glucose is turned into a simpler molecule called pyruvate. This process makes two ATP molecules and also creates two molecules of NADH, which can help make more ATP later.

Glycolysis has two parts. In the first part, we spend one ATP to get ready, and in the second part, we make two ATP molecules back. Overall, we make a net of two ATP molecules.

Citric acid cycle

In the mitochondrion, pyruvate is changed into a two-carbon piece that goes through the citric acid cycle. Each turn of this cycle makes energy carriers like NADH and FADH₂, which help make more ATP.

Beta oxidation

When we break down fats, each cycle makes one NADH and one FADH₂, which help make ATP through the citric acid cycle and oxidative phosphorylation.

Ketosis

When we don’t have enough glucose, our body can use ketone bodies for energy, making ATP in the mitochondria.

Production, anaerobic conditions

When there’s no oxygen, cells can still make ATP through fermentation. For example, breaking down glucose can make ATP and lactic acid.

ATP production during photosynthesis

In plants, ATP is made in the chloroplast using light energy in a process called photophosphorylation.

ATP recycling

Our bodies recycle ATP many times each day. The total amount of ATP in our bodies stays about the same, but each ATP molecule is used and recycled around 1000–1500 times daily.

Biochemical functions

ATP is like energy money for cells. When cells need energy, ATP can lose one of its parts to become ADP, releasing energy to power important jobs like moving muscles or sending signals in the brain.

ATP also helps cells talk to each other and build important molecules like DNA and RNA. It even helps muscles contract by giving energy to proteins that pull on each other to make movement possible.

Abiogenic origins

Scientists have found ways to make a molecule called acetyl phosphate, which is a helper for making ATP—the energy carrier in our cells. They can create it from another chemical called thioacetate under certain conditions, like normal air temperature and slightly basic water. However, acetyl phosphate doesn’t last as long when it gets warmer or more alkaline. It can help gather and stabilize another molecule called AMP and might help link smaller molecules together, especially on surfaces of minerals. Importantly, acetyl phosphate can turn ADP into ATP, which could be why all living things use ATP for their energy needs.

ATP analogues

Scientists use special versions of ATP, called ATP analogs, to study how cells use energy. These analogs help researchers see how proteins interact with ATP. One common analog replaces an oxygen atom in ATP with a sulfur atom, making it harder for enzymes to break down. This helps scientists understand the steps in energy use inside cells. However, scientists must be careful when using these analogs because some enzymes might still break them down under certain conditions.

Medical use

ATP can be given directly into the bloodstream to help treat certain heart problems. This method is used when doctors need to quickly support the heart’s health and function.

History

ATP was discovered in 1929 by Karl Lohmann and also by Cyrus Fiske and Yellapragada Subba Rao, who were both working with muscle tissue. Later, in 1941, Fritz Albert Lipmann suggested that ATP helps move energy between different processes inside cells.

In 1948, Alexander Todd made ATP in a lab and won a Nobel Prize in Chemistry in 1957 for this work. Other scientists, like Peter Dennis Mitchell, Paul D. Boyer, John E. Walker, and Jens C. Skou, also won Nobel Prizes for their important discoveries about how ATP is made and works in our cells.