Chemical Reactions, Energy, and Enzymes

Chemical Reactions A process that changes one set of chemicals into another set of chemicals Two parts in a chemical reaction:

Chemical Reactions A process that changes one set of chemicals into another set of chemicals Two parts in a chemical reaction: 1) reactant—the element or compound that enters a chemical reaction

Chemical Reactions A process that changes one set of chemicals into another set of chemicals Two parts in a chemical reaction: reactant—the element or compound that enters a chemical reaction products—the elements or compounds produced by a chemical reaction

H2CO3 → CO2 + H20 Chemical Reactions Chemical reaction always involved the breaking of bonds in reactants and formation of new bonds in products. Examples: CO2 + H2O → H2CO3 H2CO3 → CO2 + H20

Energy Energy in reactions—is either released or absorbed whenever chemical bonds form or are broken Energy releasing reactions occur spontaneously. Energy absorbing reactions cannot occur without a source of energy

Exergonic Reactions—release energy

Endergonic Reactions—absorb energy

Two types of Energy Potential Energy energy of position “stored energy” Kinetic Energy energy of motion used by organisms

Energy During a chemical reaction, bonds break, energy is released, and potential energy is converted to kinetic energy to be used by cells to do work!!!

Activation Energy Activation energy is the minimum amount of energy needed to start a chemical reaction

Enzymes biological protein catalysts Catalyst—a substance that speeds up the rate of a chemical reaction by lowering a chemical reaction’s activation energy Most enzymes end with ---ase Ex. Maltase, sucrase, lactase What carbohydrates do you think these enzymes help digest?

Enzymes Each chemical reaction in a living system requires an enzyme Enzymes control the rate of a chemical reaction.

Enzyme Action—page 52

Enzyme Action provides a site where reactants can be brought together in order to reduce energy for a reaction Substrate—the reactant of enzyme catalyzed reactions i.e. the substance the enzyme is working on

Enzyme-Substrate Complex The enzyme + the substrate

Enzyme-Substrate Complex

Lock and Key Model Think that an enzyme as a key that fits only one lock. The “lock” is a specific molecule(substrate) The “ key” is the enzyme. The place where the enzyme joins the substrate is the active site. When they join it is called the Enzyme-substrate complex.

Lock and Key Model

Induced Fit Model A modified version of Lock and Key Model Enzyme’s active site and the substrate do not need to fit exactly. The shape of the enzyme slightly changes—making the enzyme and substrate fit more exactly. The enzyme is a “flexible” key.

Induced Fit Model

Coenzymes Non-protein helper molecules Help enzymes bind to the substrate Many are made from vitamin molecules They are reusable and needed in small amounts

Inhibitors Compounds that block active sites. Can also distort the shape of substrate so enzymes won’t function properly

Denaturation Occurs when proteins are heated Changes the shape of their molecules to distort and no longer function Cannot work as an enzyme Often occurs with foods that contain protein

Factors that affect enzyme activity Temperature pH value Enzyme concentration Substrate concentration

Important roles of Enzyme Activity Regulating chemical pathways Making materials that cells need Transferring information