Understanding Enzymes: Role, Activation Energy, and Factors Affecting Activity

1. Enzymes

2. Target #13- I can describe an enzyme • Reactions, like those in photosynthesis are a part of a metabolic pathway, a series of linked reactions • Enzymes are a type of protein that functions to speed up chemical reactions • Ex: Rubisco from the Calvin Cycle • Are also known as a catalyst • Contributes to the rate of the reaction, but is not a reactant or product

4. Target #14- I can explain Activation energy • Some energy must be absorbed by the reactants in any chemical reaction • Activation Energy: the amount of energy that needs to be absorbed for a chemical reaction to start

5. Active Site: the surface depressions where the enzyme and substrate connects • Substrate: the molecule on which the enzyme acts • Has to fit into the active site of the enzyme • Temporarily bind to enzymes at specific places called activate sites • Like a lock-and-key Target #15- I can describe the Pieces associated with enzyme activity

6. Target #16- I can differentiate between the two models describing enzyme activity • Induced-Fit Model • Binding to a substrate may cause the enzyme to change shape slightly in order to fit • Each enzyme’s active site is shaped so that only a certain substrate molecule will fit • Lock-and-Key Model • Substrates exactly fit the active site of their corresponding enzyme • Enzymes bring substrate molecules close together • Enzymes decrease the activation energy needed and a chemical reaction can occur

8. Target #17- I can explain the factors that affect enzyme activity • The rate of enzymatic activity is dependent upon several factors • Substrate concentration • Generally, the higher the amount of substrate, the higher the rate of activity • Has a maximum rate of productivity • Temperature & pH • As the temperature rises, so does the rate of enzymatic activity • Has a maximum rate of productivity • Rate of enzyme activity decreases eventually due to the enzyme becoming denatured • Causes the enzyme to change shape, and no longer functions • Perferred pH varies according to the enzyme • Most require a neutral pH

9. Enzyme activation • Not all enzymes are needed at all times • Can be activated by adding or removing phosphates, or by adding or removing parts of the protein • Enzyme Inhibition • Occurs when the substrate is unable to bind to the active site of an enzyme • Activity is regulated by feedback inhibition • As the products of the reactions are used up, enzyme activity increases and inhibition decreases • Enzyme Cofactors • Some enzymes need an inorganic ion, like copper metal, called a cofactor • Some enzymes need an organic molecule, like vitamins, called a coenzyme Target #17- cont.