1 Enzymes section 2.4

1. A chemical reaction is the process of making or breaking the chemical bonds that link atoms. 2. When the bonds are broken, energy is released. The release of energy is called an exergonic reaction 2

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3. When the reaction requires energy it is called an endergonic reaction 4

Comparison of Exergonic & Endergonic 5

4. All the chemical reactions taken together are called METABOLISM. 5. The energy needed to start a chemical reaction is called activation energy. 6. Cellular reactions can occur quickly at low temperatures because of enzymes. 6

7 What Are Enzymes? Proteins that can speed up a chemical reaction and lower the activation energy needed 7. Most enzymes are Proteins that can speed up a chemical reaction and lower the activation energy needed Catalyst 8. Enzymes act as Catalyst, which make a reaction go faster but without themselves being used up

8 8. continued catalyze A. Are specific for what they will catalyze Reusable B. Are Reusable ase C. End in –ase-Sucrase-Lactase-Maltase

9 9. How do enzymes Work? weakening bonds lowers Enzymes work by weakening bonds which lowers activation energy

10Enzymes Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme

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12 Enzyme-Substrate Complex substrate. 10. The molecule on which the enzyme acts is called the substrate. Enzyme Substrate Joins

Substrates and enzyme active sites must fit together to correctly work Enzyme Substrate Active Site

Part II. These are known as enzymes or catalystsThere are chemicals (or substances) that can change the speed of chemical reactions. These are known as enzymes or catalysts. 1. Enzymes are biological catalyst 1. Enzymes are biological catalyst that change the speed of chemical reactions without themselves being changed at the end of the reaction. 14

2. Properties of Enzymes a. Enzymes are made of proteins b.They speed up chemical reactions inside the cell c.They are needed only in small amounts. They remain unchanged after each reaction and can therefore be reused. d.Each enzyme can only work on one chemical reaction. They are substrate specific. Substrate is the chemical that the enzyme is working on. 15

16 III. Factors Affecting Enzyme Activity A-Temperature B- pH C- Concentrations D- Cofactors & Coenzymes

17 A. Temperature i.At very low temperatures, enzymes are inactive. ii. The activity of enzymes increase when the temperature increases iii. Each enzyme has a special temperature that they are most active. This is the optimum temperature

Temperature cont….. iv.When the temperature is too high, the enzymes are destroyed or denatured. –Most enzymes like near neutral pH (6 to 8) and near normal body temperature 18

B. Effect of pH on Enzyme i.Different enzymes work best at different pH. The pH that makes the enzyme most active is known as the optimum pH ii.If the pH is very high or very low, enzymes can be denatured. 19

C. Concentration A. Concentration of Substrate i.When substrate concentration increases, the speed of the reaction increases B.Concentration of Enzyme i. The higher the concentration of enzyme, the faster the speed of the reaction 20

21 D. Cofactors and Coenzymes Inorganic substances (zinc, iron) vitamins enzymatic activityInorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity. Example :Example : Ironhemoglobin oxygen Iron must be present in hemoglobin in order for it to pick up oxygen.

22 Lock and Key Model As an enzyme works, it combines with it substrate and converts it to products.