Energy and enzymes

This course is a part of AP®︎ Biology, a 38-course Topic series from Khan Academy.

You, like other living systems, are an amazing energy transformer. As you move your eyes to read these words, your body is busily converting chemical energy from your lunch into kinetic energy and thermal energy (heat). Learn more about how biological energy transfers work, as well as how protein machines called enzymes direct metabolic traffic through your cells.

This course contains 6 segments:

Energy in metabolism

Can you feel the energy flowing through your body? The answer may be no (unless you’ve had something caffeinated recently), but it’s true: energy is constantly being transformed in your body. Learn about different types of energy and how they’re interconverted, and discover the metabolic “traffic” that takes place in each of your cells.

Laws of thermodynamics

Although it might be fun to be exempt from the laws of physics (flying, anyone?), it turns out that cells and organisms are in fact subject to these laws, just like any other type of matter. Learn more about the laws of thermodynamics and how they relate to energy transfers in biological systems.

Free energy

Unsure whether a chemical reaction will be spontaneous (take place without added energy)? Gibbs free energy to the rescue! Learn about the Gibbs free energy change (ΔG) and how it can be used to predict reaction spontaneity.

ATP and reaction coupling

You may have heard ATP described as the “energy currency” of a cell. But what exactly does that mean? Learn more about how ATP stores energy and how its breakdown (hydrolysis) powers energy-requiring reactions in a cell.

Introduction to enzymes

Every second of the day, tiny molecular machines called enzymes are working away busily inside your cells, catalyzing and directing the chemical reactions that keep you alive. Learn more about how enzymes speed up reactions and direct metabolic “traffic” in cells.

Enzyme regulation

Enzymes may control chemical reactions, but what controls enzymes? As it turns out, enzymes can be turned “on” or “off” by a wide range of molecules, some found normally in cells and others added from the outside. Learn about different types of enzyme regulators, which include nerve gas, HIV drugs, and the end products of metabolic pathways.