Section 2-4 & 2-5 “Chemical Reactions & Enzymes” Write everything that is underlined

2.4 Chemical Reactions / 2.5 Enzymes California State Standards The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept:The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. As a basis for understanding this concept: –Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings

2.4 Chemical Reactions / 2.5 Enzymes Section 2-4 KEY CONCEPT: Life depends on chemical reactions.

2.4 Chemical Reactions / 2.5 Enzymes Bonds break and form during chemical reactions Chemical reactions change substances into different ones by breaking and forming chemical bondsChemical reactions change substances into different ones by breaking and forming chemical bonds –Reactants are changed during a chemical reaction (the starting chemicals) –Products are made by a chemical reaction

2.4 Chemical Reactions / 2.5 Enzymes Chemical reactions release or absorb energy. Activation energy is the amount of energy needed to start a chemical reactionActivation energy is the amount of energy needed to start a chemical reaction

2.4 Chemical Reactions / 2.5 Enzymes Exothermic reactions release energyExothermic reactions release energy

2.4 Chemical Reactions / 2.5 Enzymes Endothermic reactions absorb (use) energyEndothermic reactions absorb (use) energy

2.4 Chemical Reactions / 2.5 Enzymes Section 2-5 KEY CONCEPT: Enzymes are catalysts for chemical reactions in living things.

2.4 Chemical Reactions / 2.5 Enzymes I. Catalysts 1. A catalyst lowers activation energy. Catalysts are substances that speed up chemical reactions.Catalysts are substances that speed up chemical reactions. –decrease activation energy –increase reaction rate

2.4 Chemical Reactions / 2.5 Enzymes II. Enzymes A. Enzymes are catalysts in living things. A. Enzymes are catalysts in living things. –Enzymes are needed for almost all processes –Most enzymes are proteins.

2.4 Chemical Reactions / 2.5 Enzymes B. Homeostasis disruptions can prevent enzymes from functioning. –Definition: -Homeostasis: Regulation and maintenance of constant internal conditions in an organism. –Enzymes function best in a small range of conditions. –Changes in temperature and pH can break hydrogen bonds. C. An enzyme’s function depends on its structure.

2.4 Chemical Reactions / 2.5 Enzymes An enzyme’s structure allows only certain reactants to bind to the enzyme.An enzyme’s structure allows only certain reactants to bind to the enzyme. Substrates bind to an enzyme on its active sites substrates (reactants) enzyme

2.4 Chemical Reactions / 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.