Chemical Reactions and Enzymes Section 2.4

Chemical Reaction Review Reactions involve changes in the chemical bonds of substances. Mass and energy are conserved. Reaction rates vary. (rusting vs. combustion) Reactants and products

Energy in Reactions Some chemical reactions release energy (exothermic) in the form of heat, light, and sound. – Exothermic reactions can to be spontaneous. Example: cell respiration Some reactions absorb energy (endothermic). – Endothermic reactions will not occur without a source of energy. Example: photosynthesis Exothermic reaction Endothermic reaction

Enzymes Enzymes are proteins that act as biological catalysts which speed up chemical reactions that take place in cells. Without enzymes, some biological processes would happen too slowly to maintain homeostasis. Enzymes are very specific, generally catalyzing only one chemical reaction, from which the name of the enzyme is derived.

Enzyme Substrates Substrates are the reactants of enzyme catalyzed reactions. Substrates bind to a site on the enzyme called the active site. The fit is so precise that the active site is compared to a lock and key.

Enzyme Regulation Temperature, pH, and regulatory molecules can affect the activity of enzymes. The enzyme can become denatured. What is an inhibitor? How can inhibitors change enzyme activity?