Introduction
What does it mean to have energy? Well, think about how you feel when you wake up in the morning. If you have lots of energy, that probably means you feel awake, ready to go, and able to do what needs to be done during the day. If you have no energy (maybe because you didn’t get your eight hours of sleep), then you may not feel like getting out of bed, moving around, or doing the things you need to do.
While this definition of energy is an everyday one, not a scientific one, it actually has a lot in common with the more formal definition of energy (and can give you a helpful way to remember it). Specifically, energy is defined as the ability to do work – which, for biology purposes, can be thought of as the ability to cause some kind of change. Energy can take many different forms: for instance, we’re all familiar with light, heat, and electrical energy.
Here, we’ll look at some types of energy that are particularly important in biological systems, including kinetic energy (the energy of motion), potential energy (energy due to position or structure), and chemical energy (the potential energy of chemical bonds). Energy is never lost, but it can be converted from one of these forms to another.
Kinetic energy
When an object is in motion, there is energy associated with that object. Why should that be the case? Moving objects are capable of causing a change, or, put differently, of doing work. For example, think of a wrecking ball. Even a slow-moving wrecking ball can do a lot of damage to another object, such as an empty house. However, a wrecking ball that is not moving does not do any work (does not knock in any buildings).