What is Adenosine Triphosphate (ATP)?

Although an understanding of biology is not essential to raising plants or animals, it can make the process even more enjoyable than it already is.  Biology can help us interpret the phenomena that we see and experience every day.  It can also help us think up creative solutions for the challenges that we face.

So for you science addicts out there….

Adenosine triphosphate (ATP) is critical to life, as we shall see in a moment.  It is part of the process of photosynthesis, and it keeps animals alive.  Before we get into the nuts and bolts of ATP and its functions, however, a description is in order.

ATP is made up of two parts.  The first is adenosine, which is a nitrogen base linked to a sugar molecule.  Adenosine is often found in combination with phosphate groups.  This brings us to the second part of ATP: three molecules of phosphoric acid.

The bonds between the three phosphates are unique.  They are frequently called “high-energy” bonds, which is something of a misnomer.  It is true that a useful amount of energy is released when the bonds are broken, but ATP represents a type of compromise.  Some level of energy is sacrificed in favor of an easily renewable energy source.

Where ATP Comes From

In plants, ATP is formed by the chloroplasts, the parts of the cell which contain chlorophyll and carry out photosynthesis.  As chlorophyll is exposed to light, a chemical reaction begins which provides energy for the production of ATP.

In animals, ATP is produced primarily in two ways:

  1. Glycolysis: Digestible nutrients, such as fats and carbohydrates, are broken down into simpler products that the body can use.  These products include glucose and glycerol.  The cells then break these substances down still further.  One of the results is ATP.
  2. Oxidative phosphorylation: Oxidative phosphorylation is a complex chemical reaction that occurs in the mitochondria, tiny cylindrical objects in the cells sometimes referred to as “power plants.”  Mitochondria contain enzymes that combine adenosine diphosphate (ADP) with one more phosphoric acid molecule to form ATP.  As you might have guessed, ADP is very similar to ATP; the missing phosphoric acid molecule is the only difference between the two.  But this slight difference is exactly what gives the latter its power.

How ATP Works

What is ATP?

Suppose that a cell needs to use ATP for energy.  What happens?

There are a few things that we need to know about the properties of ATP.  For one thing, it is water-soluble.  For another thing, it is rather unstable.  The phosphate groups are bonded together with negatively charged oxygen, and thus tend to repel each other.  In a water solution, ATP will tend to deteriorate into ADP and phosphate because the latter substances are far more stable.  It is when this change occurs that energy is released.  Because ATP is unstable, it is not used for energy storage, but rather for energy transport.

Here is the process of using ATP in a nutshell:

  1. A water molecule comes between the unstable bonds of ATP.
  2. One of the phosphoric acid molecules breaks off.
  3. Energy is released.
  4. The result is the two stable products ADP and phosphate.

As we have seen, ADP and phosphate can later be recombined by the mitochondria, making ATP a useful renewable energy source.

The power of ATP is used in many critical functions in plants and animals:

  • Assembling DNA.
  • Regulating cellular osmosis.
  • Constructing proteins.
  • Fueling the immune system.
  • Maintaining the metabolism.
  • Regulating body temperature.
  • Controlling muscle contraction.
  • Sending nerve impulses, such as pain and taste.
  • Even glowing in the dark (think fungus and fireflies).

In short, just about anything that requires energy requires ATP.

Practical Applications

The subject of ATP is very complex.  The explanation above just touched on the most critical points.

Still, ATP is worth investigating, since it is so essential to both plant and animal health.  By understanding this topic, we can begin to understand the importance of a number of other factors, such as the need for water and the various sources of energy in feedstuffs.  ATP is a key part of the field of nutrition.