Chemical Reactions & Enzymes 2-4 Chemical Reactions & Enzymes

A chemical reaction is a change in which one or more substances are converted into new substances. A + B C + D The substances that will be reacting together are called reactants. The substances that are produced are called products.

Chemical reactions where the reactants release energy, often occurs almost instantly. 2H2 + O2 → 2H2O Burning hydrogen gas Oxygen gas Water Exothermic reaction Chemical reactions where you have to add energy to the reactants will not happen unless you add energy to it. Burning hydrogen gas Oxygen gas Water 2H2O → 2H2 + O2 Endothermic reaction

So how much ENERGY does it take to start a chemical reaction? Energy is used to create chemical reactions no matter which method is used. Energy + Energy changes into… or forms. C A B Reactants Products You have to put energy into the equation to get a reaction to work So how much ENERGY does it take to start a chemical reaction?

The amount of ENERGY needed to start a chemical reaction is called the ACTIVATION ENERGY If not enough energy is added, the ball cannot reach the Activation Energy level and there is NO REACTION. If enough energy is added, the ball reaches the Activation energy level and the Chemical Reaction Occurs

Chemical A Chemical C Chemical B (Reactant) Activation energy Chemical B (Product) (Reactant) When the reaction occurs, ENERGY is RELEASED because the ENERGY is changing forms.

Energy Released B A Product

ENZYMES

(which breaks down proteins like in a steak that you eat) ENZYMES are proteins that help speed up a chemical reaction. Another word for this (speed up reaction) is called CATALYST A great example of an enzyme is in your stomach with the enzyme Pepsin. (which breaks down proteins like in a steak that you eat)

When you eat, your food is still too big to digest properly. Your stomach can’t absorb the food this way

Your stomach releases an ENZYME called PEPSIN, which breaks down the food proteins into small monomers which the body absorbs for energy.

If you didn’t have this enzyme, the stomach acids would take days for it to dissolve the food into smaller pieces. What happens if you don’t eat for days? 1. You’re sluggish / no energy 2. Body systems start to shut down 3. Leads to illness

How does it do it? – It lowers the So the enzyme PEPSIN, speeds up the chemical breakdown of proteins in our food. How does it do it? – It lowers the ACTIVATION ENERGY

Energy Released B A Product Remember this?

Pepsin lowers the activation level like this. Energy Released B A You don’t need as much energy!!!

ENZYMES: Speed up a reaction Lower Activation Energy. Are reusable? Yes, enzymes can be used over an over and over like re-chargeable batteries. Let’s look at the enzyme “Pepsin” up close…

The reactant it attaches to is called a *SUBSTRATE* Pepsin attaches one of the reactants (protein) The reactant it attaches to is called a *SUBSTRATE* Where it attaches is called the “Active Site” Substrate (protein) Active site Pepsin PEPSIN

Note how the curves fit perfectly together… Pepsin is very specific for one Substrate only! (Just like only 1 key can fit a lock) All enzymes are specific Note how the curves fit perfectly together… Substrate PEPSIN Pepsin

Enzyme-Substrate Complex When the enzyme and substrate join together, it gets a new name called the: Enzyme-Substrate Complex Substrate Pepsin PEPSIN PEPSIN This is when the chemical reaction occurs!

Notice that the lock & key curves are the same, yet the chemical reaction makes the new products in that same space. Pepsin

After the chemical reaction, the new Products (proteins) are made and the Pepsin looks for more Substrate to break down. Pepsin

The Process Simplified… Pepsin Pepsin Pepsin + + Enzyme + Substrate Enzyme Enzyme + Product(s) SubstrateComplex E + S ESC E + P

Since enzymes are specific for a certain substrate, there are many enzymes in your body. Enzymes were originally named with a “-in” ending (Pepsin). Later on, scientist started naming the enzymes with a “-ase” ending Since Carbohydrate sugars are named with a “-ose” ending, there is a enzyme that is specific for each one.

SUGAR NAME ENZYME NAME Lactose Lactase Sucrose Sucrase Maltose Maltase What I want you to remember from this is: Sugars – have “ose” endings Enzymes – have “ase” endings

What could cause enzymes not to work properly? When an enzyme doesn’t work properly it is said to be Denatured - the active sites on an enzyme change in shape, therefore unabling the enzyme to lock up with a substrate Pepsin

Causes of Denaturation are: 1. Too high of Acid or Base (pH) in your body 2. Temperature differences (hot / cold) fever, chills Pepsin 3. Lack of Water / Oxygen

One of the most important reactions in your body involves the enzyme Catalase. Catalase turns the cell waste product of Hydrogen Peroxide (H2O2) into Water and Oxygen gas. The reaction is: 2H2O2 ----> 2H2O + O2 (fix) Hydrogen Peroxide ----> Water Oxygen Gas