Enzymes Metabolism and Enzymatic Reactions

Metabolism All living things need energy This energy is used by organisms to develop, grown and reproduce Energy is used in chemical reactions to perform this development, growth and reproduction. METABOLISM is the sum of all the biochemical reactions that occur in a cell.

The energy-producing reactions within cells generally involve the breakdown of complex organic compounds to simpler compounds. These reactions release energy and are called catabolic reactions. Anabolic reactions are those that consume energy while synthesizing compounds. ATP produced by catabolic reactions provides the energy for anabolic reactions. Anabolic and catabolic reactions are therefore coupled (they work together) through the use of ATP.

ATPADP + P i Energy Menu An anabolic reaction A catabolic reaction Catabolic and Anabolic Reactions

Metabolic reactions have – REACTANTS, which are the substances that participate in a reaction, and – PRODUCTS, which are the resulting substances A+B→C+D Within cells many reactions are often linked together to create the products a cell needs from the reactants it is able to acquire. These chains of reactions are called METABOLIC PATHWAYS. A→B→C→D→E→F→G In this process the products from one reaction become the reactants for the next reaction.

6 F A B C D E Metabolic pathways can branch so that a product like D can become the reactant in two different types of reactions

7 Enzymes enzyme 1enzyme 2enzyme 3enzyme 4 F enzyme 5 A B C D E ENZYMES are protein molecules that help to sped up, or catalyze, a specific reaction. The enzyme causes the reactants in a reaction to associate with each other so that they will react to for the products.

Substrate Enzyme Active Site Enzyme-Substrate Complex Product Enzyme Reactants in an enzymatic reaction are called SUBSTRATES. An enzyme brings substrates together to speed up their reaction. Menu

Many enzymes require another non-protein piece to function properly – APOENZYME: protein portion of the enzyme. It’s shape is what gives it the ability to only run a single type of reaction – COENZYME/COFACTOR: non-protein portion. The portion that binds to the enzyme and then carries a chemical group or electron of one or both reactants.

Apoprotein + Coenzyme(s) = Holoenzyme (Haloenzyme)

11 Cofactors Many enzymes require a cofactor to assist in the reaction. These "assistants" are nonprotein and may be metal ions such as magnesium (Mg++), potassium (K+), and calcium (Ca++). The cofactors bind to the enzyme and participate in the reaction by removing electrons, protons, or chemical groups from the substrate.

12 Coenzymes Cofactors that are organic molecules are coenzymes. Coenzymes are usually vitamins. VitaminCoenzyme Name NiacinNAD + B 2 (riboflavin)FAD B 1 (thiamine)Thiamine pyrophosphate Pantothenic acidCoenzyme A (CoA) B 12 Cobamide coenzymes

13 Coenzymes are cofactors that are not protein. They bind to the enzyme and also participate in the reaction by carrying electrons or hydrogen atoms. Enzyme Coenzyme

Activation Energy Many reactions won’t occur unless there is an input of energy added to start the reaction This ACTIVATION ENERGY causes the first reactant molecules to collide with enough force to react. They release energy which drives further reactions. In the lab this is often achieved by adding heat to increase the number of collisions that occur. Activation energy is often shown by the symbol (E a ).

Enzymes catalyze (speed up) reactions by lowering the activation energy (Ea) required to get the reaction started. They do this by bringing the substrates closer together so they are able to react more easily.

16 Enzymes Lower Activation Energy Energy Supplied Energy Released Activation energy without enzyme Activation energy with enzyme Enzymes lower the amount of activation energy needed for a reaction. Menu

Because enzymes are made up of proteins they require a specific substrate at a specific temperature and a specific pH to work properly. S.T.E.P.P – S= SUBSTRATE (what substrate does it work on?) – T= TEMPERATURE (at what temp does it work?) – E= ENZYME (what is the name of the enzyme?) – P=pH (at what pH does it work best? – P=PRODUCT (what new chemical products form?)