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Do you think of yourself as the peaceful, laid-back type? Think again. Every second of your life is a standoff of epic proportions. In fact, your body is trying to defy some of the most fundamental laws of physics right now. "But wait," you ask, "Shmoop, why are we talking about physics in a biology unit?"
Because, whether or not you would like to admit it, physics and chemistry are so intimately connected to biology—ooh la la!—that it is impossible to understand biology without learning about physics and chemistry, too. Therefore, young Jedis, before we get into the nitty gritty of the epic standoff between your life and a world craving disorder, we must step back for a second and discuss some physics basics. It will prepare you well for what is to come. (Really, though, we knew you'd had enough chemistry from the last unit, and physics was the only other topic we could plausibly throw in here to increase the suspense of the good stuff that comes later on. Kidding, kidding. Maybe.)
You know all about energy. Energy is what you never have enough of, what power companies provide you with and charge you lots for, and what politicians ramble on and on about. All of that is correct, but for now, you need to familiarize yourself with the physics-based definition of energy.
Here it is:
Energy is defined as the capacity to work, or rather, the capacity to create change.
What is work? Work is defined as what happens when energy is transferred from one system to another. In the physical sense, if we have two objects, and the first object transfers energy to the second object, the first object is said to have done work on the second object.
Back to energy. There are many different types of energy:
Kinetic energy is the energy that an object has because of its movement, while thermal energy, or heat, is released when you burn wood in a bonfire (yum, s'mores).
Potential energy is used to describe "unused" energy that has the ability to accomplish work but currently isn’t. A good example of potential energy is an object that has the ability to do work because of its position in the gravitational field.
Pretend you are at Disneyland, or Disney World (count us in; we can be packed in under 30 minutes, and if you bring the tickets, we'll bring our savant-like knowledge of hidden Mickey locations). Picture yourself in the railroad car on the Big Thunder Mountain Railroad ride. Clankity-clank-clank-clank-clank, and you are soon at the top of the hill at the start. You know that second where you know you are about to go down, and the fun is about to begin? At that exact moment, the train has a lot of potential energy because gravity will soon get to work, speeding you downhill and through the rock formations and caverns of the mine.
Another example of potential energy is a rock that has been pulled back in a slingshot. Or, better yet, a bird in a slingshot, pointed at some green pigs with eggs under blocks of wood and rocks. How did we create such a scenario? Beats us. Either way, that little red birdie is full of potential energy before he is shot through the air.
We will talk about energy in more depth later, but the important concept to grab here is that energy is the workhorse of change.
You have probably heard that ATP is the "energy currency" in the cell. How is the potential energy stored in ATP? As it turns out, the ability to release the phosphate group at the end of ATP is what makes it so high in energy.