What is Adenosine Triphosphate? - Definition, Function & Structure

Instructor: Dominic Corsini
In this lesson, you'll find out why scientists refer to the molecule adenosine triphosphate (ATP) as energy currency. You'll also learn about the production, structure, and function of ATP through examples and illustrations. A brief quiz, complete with explanations of correct answers, follows the lesson.

Adenosine Triphosphate and Energy

A few years back, some friends and I started competing in local triathlons. One of the things we quickly learned was that our bodies needed to produce more adenosine triphosphate to be successful in these events. Adenosine triphosphate ATP is a high energy molecule that cells use to power their various functions. One such function is muscle cell contraction. For this reason, ATP is sometimes referred to as the energy currency of life.

At one point during our racing phase, we entered a 50-mile bike race. Now, at this time I'd never ridden 50 miles before, but I was young and foolish. So we went ahead without hesitation.

Cyclist using ATP
Cyclist Using ATP

The initial part of the ride went well, and I had plenty of energy and felt strong. However, as time past and the miles ticked away, I could feel myself tiring. At mile marker 42, I distinctly remember my legs being spent; I'd hit the proverbial wall. My muscle cells were unable to produce enough ATP to keep me moving quickly and I finished well behind my friends.

Powering Cells

So what happened during that race? Why couldn't I cover those final miles quickly? Part of the answer to these questions resides in my leg muscles, or more specifically, what's inside the cells of those leg muscles.

Inside our cells are small organelles called mitochondria. Organelles are specialized subunits within cells that perform specific functions. Mitochondria make up one such subunit that is responsible for producing cellular energy. Athletic training can increase the amount of mitochondria inside cells. For an endurance event, this increase is important because more mitochondria results in more energy production.

High Energy Molecules

What does it mean when we say mitochondria provide energy? What does this energy look like? Well, as we learned at the beginning of the lesson, cells provide energy in the form of adenosine triphosphate or ATP.

To release that energy, ATP breaks down into a lower form of energy called adenosine diphosphate (ADP). Below is an illustration of the process.

ATP breakdown

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