Enzymes

Enzymes

To understand how enzymesProteins that speed up chemical reactions in the body. participate in reactions, we should review some terms first.  I know this example is silly. I’m a visual learner. This is a great visual for understanding how reactions proceed.  In both situations here we’re going to start with the reactants or the raw materials which are these dry frogs.  As our reaction proceeds, each frog will jump into the waterThe universal solvent essential for life.. It will become a product. In this case, it is a wet frog.   Think of the word product; it’s what’s produced.  In math you have 2 * 2 equals 4 and 4 is the product.  In order to get our dry frogs to become wet frogs there is a barrier to this reaction.  That barrier is called the activation energyThe minimum amount of energy required to start a chemical reaction..  Activation energyThe capacity to do work or cause change. is what is needed to be overcome in order to get the reaction started.  In our picture, the activation energy is the pile of rocks. The frogs have to jump over this pile of rocks in order to get the reaction started.  This is very important: enzymes do not contribute activation energy.  They lower the activation energy that’s required to start the reaction and therefore they lower the barrier to the reaction.  Think about all the different ways you can start a fire.  Some are really easy like a lighter and some are a little bit more difficult like rubbing 2 sticks together.  Your method is the barrier to the reaction. A better method means you will start your fire more quickly.

Enzyme Action

Because enzymes are proteinsLarge molecules made of amino acids with various functions in the body., they have very specific shapes.  One area on an enzyme is called the active siteThe specific region of an enzyme where a substrate binds and a reaction occurs..  This is the place where a substance known as a substrate can bind to the enzyme.  The active site has a shape that fits the substrate specifically. It works like a lock and key.  Because enzymes are proteins and have again that specific shape, they are not multitaskers.  The enzyme lactase will work only with lactoseA disaccharide sugar found in milk. as its substrate. Similarly, the enzyme sucrase will work only with sucrose as its substrate. Likewise, the enzyme urease will work only with urea as its substrate.  As you can see -ase is a common ending among enzymes.  When enzyme and substrate bind they are believed to have an induced fit resulting from the very specific shapes.  This specificity means that if you lose your lactase enzyme, no one else will step up and do the job.  Bummer.

This diagram here is the story of how an enzyme can help catalyze an anabolic reaction.  I could have easily made this picture to be a catabolic reaction because enzymes can catalyze whatever reaction you have.  This picture tells a story from left to right.  Glucose and fructose are substrates that bind to the active sites on this enzyme sucrase.  An anabolic reactions occurs, covalently bonding glucoseA simple sugar that is the main source of energy for cells. to fructose to create sucrose.  Sucrose is released from the enzyme and the enzyme is ready to be used again. 

Activation Energy

When many people hear the word enzyme, they immediately think of the word catalyst.  I think of cupid. Cupid facilitates two people falling in love by shooting one of them in the butt with an arrow.  Regardless of where the arrow hits, cupid is increasing the rate at which 2 people fall in love.  Enzymes increase the rate of reactions.  If you were to ingest a hamburger, it would get exposed to your digestive enzymes. The hamburger would break down much more quickly. In contrast, leaving it on the counter top would allow it to just rot.  Actually, there’s fungus in every environment.  Overtime the hamburger will inevitably get colonized by fungus. This colonization will expose the hamburger and the bread to fungal digestive enzymes. The enzymes will break it down at a rate that can support the life of the fungus.