Where does my energy come from?

adenosine triphosphate

The energy in our body is generated in the form of a molecule called adenosine triphosphate, or ATP, which powers all your bodily functions and reactions.

The ATP molecule contains chemical bonds that store energy. When these bonds are broken, energy is released and this is used to power your body. It may be easier to think of adenosine triphosphate as a battery that gets charged, and once the ATP is charged, it sets off a spark of energy that can be used throughout the body.

What is adenosine triphosphate (ATP)?

The ATP molecule is one of the most important molecules existing in our body. It is designed to provide a large amount of energy for a wide variety of processes. Known as the ‘energy currency of life,’ adenosine triphosphate can store and transport the energy we need to do just about everything that we do. Essentially all metabolic functions of living cells require energy for operation and obtain it directly from stored ATP.

The body can only store a small amount of ATP, and during exercise these stores are quickly used up, especially when energy demands on the body are high. This means that ATP needs to be constantly produced during exercise. Your body has a number of processes it uses to do this – the predominant one used depends on the type, intensity and duration of exercise.

The amount of ATP that the body produces depends on the energy source (i.e. fat, carbohydrate) being broken down. Fat (triacyglycerol) is the preferred source of fuel for resting muscle and can cover the demands for low to moderate intensity exercise. During high intensity exercise, carbohydrate becomes the predominant source of energy. In addition, the rate of adenosine triphosphate produced is higher from carbohydrate than fat, therefore you should aim to start exercise with your glycogen stores fully topped up.

The science of adenosine triphosphate

Our food contains the energy that our body needs to make adenosine triphosphate, and it can be used directly from the food source or else the food is stored as fat and then used later. ATP is used and recycled constantly in the body, beginning as either ADP (adenosine diphosphate) or AMP (adenosine monophosphate) before having either one or two phosphate molecules added to it.

This process happens in the mitochondria-a small organelle that exists inside of the cells of the body and that are often known as the body's energy factory. The ADP/AMP and phosphate is carried into the mitochondria from the cytosol-the fluid that fills the cell, and ATP is later passed back out. This process is incredibly rapid as particularly active cells (such as muscle cells) may need more than 2 million molecules of ATP every single second, and they would not have sufficient to to last for more than a second or two.

Therefore the more active cells have more of these mitochondria within them, sometimes thousands in the one cell and they are constantly busy recycling the adenosine triphosphate. The ATP is 'spent' when the bonds between the phosphate groups and the rest of the molecule are broken, releasing the large amount of energy that what invested in it during its creation. It is therefore more appropriate to consider it to be a converter rather than a store-it converts chemical energy stores such as food or fat, into usable energy that our cells needs and also carries that energy to the place it is to be used. In a single day, a body may create more than its own weight in adenosine triphosphate.

Respiration-a process called the Krebs cycle that gives us energy as outlined above, is not the only use for ATP in the body. However it serves other essential purposes too, for instance being a constituents of RNA chains and in a reduced form it is also included in DNA-the building block of life.

It is required for the filament shortening that allows muscles to contract, and is an essential component of certain intracellular and extracellular signaling processes. However you look at it, this multipurpose molecule is incredibly versatile and essential to life as we know it.

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