1. 2.5 Enzymes KEY CONCEPT Enzymes are catalysts for chemical reactions in living things.

2. 2.5 Enzymes A catalyst lowers activation energy. Catalysts are substances that speed up chemical reactions. –decrease activation energy –increase reaction rate

3. 2.5 Enzymes Enzymes allow chemical reactions to occur under tightly controlled conditions. Enzymes are catalysts in living things. –Enzymes are needed for almost all processes. –Most enzymes are proteins. –Enzymes end with an –ASE ending. Catalase is an enzyme used to break down Hydrogen Peroxide (H 2 O 2 )  H 2 O 2 is a toxic by-product of many normal metabolic processes.  To prevent damage, it must be quickly converted into other, less dangerous substances. 2 H 2 O 2 → 2 H 2 O + O 2

4. 2.5 Enzymes Disruptions in homeostasis can prevent enzymes from functioning. –Enzymes function best in a small range of conditions. –Changes in temperature and pH can break hydrogen bonds and change the shape of the enzyme. –An enzyme that looses its shape and therefore its ability to perform its function has DENATURED –An enzyme’s function depends on its structure.

5. 2.5 Enzymes What is a fever? A fever, or pyrexia, is a rise in internal body temperature to levels that are above normal. Average body temperature is about 98.6°F or 37°C, and temperatures above 100.4°F or 38°C are considered to be a fever. A fever is a defense mechanism to ward off a preceived bacterial or viral attack.

6. 2.5 Enzymes Why is a high fever dangerous? A fever of 105°F or 41°C is considered deadly. When the temperature of the body exceeds 105°F or 41°C enzymes begin to denature rapidly. The result is a loss of homeostasis in the body. WHEN HOMEOSTASIS IS NOT MAINTAINED IN THE BODY THE END RESULT IS DEATH!

7. 2.5 Enzymes An enzyme’s structure allows only certain reactants to bind to the enzyme. –substrates –active site substrates (reactants) enzyme Substrates bind to an enzyme at certain places called active sites.

8. 2.5 Enzymes The lock-and-key model helps illustrate how enzymes function. –substrates brought together –bonds in substrates weakened Substrates bind to an enzyme at certain places called active sites. The enzyme brings substrates together and weakens their bonds. The catalyzed reaction forms a product that is released from the enzyme.