Enzymes are biological catalysts. A catalyst is a substance that lowers the activation energy needed to make a reaction run. The catalyst is not altered during the reaction in any way. Enzymes are essential to life. If it weren't for enzymes, some life-sustaining reactions would take thousands of years to complete by themselves!
Enzymes are truly amazing for a few reasons. First of all, each enzyme is reaction-specific. An enzyme can only catalyze one type of reaction, but it can catalyze it forwards and backwards. Also, it is reusable, since it doesn't get altered in the reaction.
Enzymes are said to be working according to the lock-and-key theory, pictured below (although the process itself is much more complex):
Time for a few definitions. The active site is the place on the enzyme where the reaction occurs (the place onto which the reactants attach themselves). The enzyme then alters its shape a little to fit the substrate (products) snugly. When the products are in the active site, the whole thing (enzyme and the substrate) is called the enzyme-substrate complex. Afterwards, the products leave the active site. The reason why enzymes are so efficient is because they successfully put both products in the same place (active site), and without the enzyme, the probability of those molecules colliding is much lower.
Sometimes, a molecule that is not a substrate goes into the active site of the enzyme, disabling it from catalyzing reactions. This molecule is called an inhibitor. Many inhibitors are neurotransmitters that control impulses.
Proteins
- Amino acids
- Protein structure
- Enzymes