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

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: 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

Section 2-4 KEY CONCEPT: Life depends on chemical reactions.

Bonds break and form during chemical reactions Chemical 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

Chemical reactions release or absorb energy. Activation energy is the amount of energy needed to start a chemical reaction

Exothermic reactions release energy

Endothermic reactions absorb (use) energy

Section 2-5 KEY CONCEPT: Enzymes are catalysts for chemical reactions in living things.

I. Catalysts 1. A catalyst lowers activation energy. Catalysts are substances that speed up chemical reactions. decrease activation energy increase reaction rate

II. Enzymes A. Enzymes are catalysts in living things. Enzymes are needed for almost all processes Most enzymes are proteins.

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.

Substrates bind to an enzyme on its active sites An enzyme’s structure allows only certain reactants to bind to the enzyme. substrates (reactants) enzyme Substrates bind to an enzyme on its active sites

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.