Enzymes

Amino Acid Basic Structure

Primary Structure

Secondary Structure

Tertiary Structure

Quaternary Structure

Yeast

Sucrase

Human/Bacterial/Bacterial Mg

Catalase- H 2 O 2 -> O 2 + H 2 0

Catalase Lab Intro: What is catalase / function/structure Structure of proteins Overview of Lab- pH, Temperature, substrate Organism used in Lab Problem- write as a class Hypothesis- write as a class Procedure- See Vernier Biology Manual- 6B » Enzyme Action: Testing Catalase Activity

HOW ENZYMES FUNCTION Enzymes speed up the cell’s chemical reactions by lowering energy barriers

–For a chemical reaction to begin Reactants must absorb some energy, called the energy of activation Figure 5.5A E A barrier Reactants Products 12 Enzyme

–A protein catalyst called an enzyme Can decrease the energy of activation needed to begin a reaction Figure 5.5B Reactants E A without enzyme E A with enzyme Net change in energy Products Energy Progress of the reaction

A specific enzyme catalyzes each cellular reaction –Enzymes have unique three-dimensional shapes That determine which chemical reactions occur in a cell

Figure 5.6 Enzyme (sucrase) Glucose Fructose Active site Substrate (sucrose) H2OH2O 1 Enzyme available with empty active site 2 Substrate binds to enzyme with induced fit 4 Products are released 3 Substrate is converted to products –The catalytic cycle of an enzyme

5.7 The cellular environment affects enzyme activity –Temperature, salt concentration, and pH influence enzyme activity –Some enzymes require nonprotein cofactors Such as metal ions or organic molecules called coenzymes

Enzyme inhibitors block enzyme action –Inhibitors interfere with an enzyme’s activity

–A competitive inhibitor Takes the place of a substrate in the active site –A noncompetitive inhibitor Alters an enzyme’s function by changing its shape Figure 5.8 Substrate Enzyme Active site Normal binding of substrate Enzyme inhibition Noncompetitive inhibitor Competitive inhibitor