Enzymes Living organisms are dependent on chemical reactions to survive. These chemical reactions happen TOO SLOWLY or require TOO MUCH ENERGY for us to survive. To make these reactions possible, we use special proteins called ENZYMES! Enzyme

What does an Enzyme do? 1. Enzymes act as biological catalysts to speed up reactions in living things. 2. Enzymes speed up these reactions by LOWERING the ACTIVATION ENERGY of the reaction. 3. Enzymes can BUILD things UP or BREAK things DOWN. biological catalyst LIVING things speed up reactions

How does an Enzyme work? Think of a LOCK and a KEY!! 1. Enzymes are very SPECIFIC. This means they only work on ONE type of SUBSTRATE. Think of a LOCK and a KEY!!

Active Site Every enzyme has something called an ACTIVE SITE. This is where the SUBSTRATE attaches to the enzyme so the reaction can occur. If the active site and substrate don’t fit, the reaction can’t occur.

Reusable? When the reaction has occurred, the PRODUCTS leave the enzyme. The enzyme, which has NOT BEEN CHANGED during the reaction, can be used OVER and OVER AGAIN!

Factors Affecting Enzyme Activity 1. Concentration – If there is a higher concentration of enzyme or substrate, then there is a greater chance of collisions between the two, therefore the reaction rate will INCREASE!!

Factors Affecting Enzyme Activity 2. Temperature - Most enzymes work best in your body at 37°C. If the temperature gets much higher than that, the enzyme will change shape, and the substrate will no longer fit into the active site. This is called DENATURING.

Why 37°C Because that is your normal body temperature… 98.6°F or 37°C

Factors Affecting Enzyme Activity 3. pH – Just like temperature, enzymes will only work at specific pH’s. If the pH is too high or too low, the enzyme will DENATURE.

pH Most human enzymes function best at about a pH of 7…why? That is the pH of MOST parts of the human body Stomach enzymes function best at about a pH of 2…why? That is the pH of the human stomach, thanks to stomach acid

Enzyme Animation http://www.lpscience.fatcow.com/jwanamaker/animations/Enzyme%20activity.html