Proteins that control chemical reactions in our cells. Enzymes Proteins that control chemical reactions in our cells.

Enzyme Basics Every cell has thousands of different kinds of enzymes in it. Each enzyme controls only one chemical reaction – that’s why we need so many different kinds. Most enzymes are proteins (made of amino acids) – but not all proteins are enzymes. All enzymes act as catalysts  molecules that speed up chemical reactions. Many enzyme names tell what they do, and they often end in “-ase” (e.g., lactase splits lactose sugar, protease digests proteins, DNA polymerase builds DNA, phoshorylase adds phosphate to other molecules…) Some enzymes split molecules apart - they use hydrolysis, and are called catabolic enzymes. Other enzymes build bigger molecules by dehydration synthesis – they are known as anabolic enzymes.

Enzyme Vocab “Substrates” are the molecules that react with the enzyme The “active site” is the part of an enzyme that bonds with the substrates The “products” are the new molecules made by the enzyme active site

Lock & Key Model of Enzyme Action Enzymes can be compared to a key that is able to open a lock, because only the key with the right shape will work on the matching lock. An enzyme’s structure allows only certain substrates to bind to the enzyme, so the enzyme only acts on specific molecules (the enzyme lactase will break down lactose, but it will not work on sucrose). The lock and key model has four steps that can be drawn like this….

Lock & Key Model of Enzyme Action Substrate Lock & Key = a perfect fit! Active Site Enzyme Step Two: Enzyme bonds with substrate at the active site Step One: molecules floating in cytoplasm Products Step Four: Enzyme releases products, and returns to its original shape so it can act again on another substrate with the right shape Step Three: Enzyme changes substrate (splitting it, in this example)