Chemical Reactions & Enzymes Sections 2.4 and 2.5

Metabolism (Greek: “change”): The sum of all chemical processes that occur within a living organism. catabolic: “breaks things down” anabolic: “builds things up”

Chemical reactions change substances into different substances by breaking and reforming chemical bonds. Reactants Products Bond energy: the amount of energy needed to break and form bonds between atoms.

The amount of energy released relative to the amount absorbed determines whether a chemical reaction is exothermic or endothermic. Let’s have a different look…

Exothermic: Notice: There is more energy in the reactants than the products

Endothermic: Notice: There is less energy in the reactants than the products

Activation Energy: The amount of energy needed to start a chemical reaction. Did you notice the “hump” in both of the pervious chemical reactions?

Chemical reactions in living things are unable to proceed fast enough on their own to support the myriad of life processes.

…that is the job of a catalyst ! Catalyst: Any substance that speeds up the rate of a chemical reaction by lowering the activation energy. Enzyme: Organic catalysts (usually proteins). Speed of the rate of chemical reactions in living organisms.

Enzyme controlled chemical reaction:

Enzyme Property I: Enzyme do not change (chemically and physically) in a chemical reaction, therefore enzyme can be reused.

Enzyme Property II: Enzymes are proteins. Therefore, enzymes have a specific 3-dimensional shape. This property explains: – Substrate specific (lock-and-key model) – Active site

Enzyme Property III: Like all proteins, enzymes denature (change shape) under extreme heat or extreme acidic environments.

Liver Lab: 2H 2 O 2 2H 2 O + O2 catalase Test tube:Tube Contents:Fizz: 1H 2 O + MnO 2 0 2H 2 O 2 + MnO H 2 O 2 + piece of liver+++ 4H 2 O 2 + ground liver++++ 5H 2 O 2 + cooked liver+ 6H 2 O 2 + cooked MnO H 2 O 2 + liver in acid0 8H 2 O 2 + piece of potato+