Enzymes

1. Enzymes

2. Chemical Reactions • A chemical reaction is a process that changes one set of chemicals into another set of chemicals. • Some chemical reactions occur slowly, such as the combination of iron and oxygen to form an iron oxide called rust.

3. Chemical Reactions • Other reactions occur quickly. For example, when hydrogen gas is ignited in the presence of oxygen, the reaction is rapid and explosive. • The elements or compounds that enter into a chemical reaction are known as reactants. • The elements or compounds produced by a chemical reaction are known as products. NaOH + HCl NaCl + H2O Reactants Products

4. Energy in Reactions • Energy is released or absorbed whenever chemical bonds form or are broken. • Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy.

5. Energy in Reactions • In order to stay alive, organisms need to carry out reactions that require energy. • Every organism must have a source of energy to carry out chemical reactions. • Plants get their energy from the sun. • Animals get their energy from eating plants or other animals.

6. What is activation energy? • Chemical reactions that release energy do not always occur spontaneously. • Chemists call the energy that is needed to get a reaction started the activation energy.

7. Activation Energy • Some chemical reactions that make life possible are too slow or have activation energies that are too high to make them practical for living tissue. • If this is so, than how are these chemical reactions made possible so that life can exist? • We have special proteins called enzymes!

8. Reminders About Proteins • Building blocks are amino acids. • There are 20 different amino acids found in nature. • Different combinations of amino acids create many different types of proteins. • This sequence of amino acids is called a protein’s primary structure. • The folding or coiling of the polypeptide chain is called the secondary structure. • The tertiary structure is the complete, three-dimensional arrangement. • Proteins with multiple polypeptide chains are said to have a quaternary structure.

9. What Are Enzymes? • Most enzymes are Proteins • Act as Catalyst to accelerates a reaction • Structure determines function • Not permanently changed in the process

10. Enzymes • Are specific for what they will catalyze • AreReusable • End in –ase -Sucrase -Lactase -Maltase

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

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

14. Enzyme-Substrate Complex Enzyme The substance (reactant) an enzyme acts on is the substrate Joins Substrate

15. Active Site Enzyme • A areaof an enzyme molecule which binds to the substrate. Active Site Substrate

16. What Affects Enzyme Activity? • Three factors: 1. Environmental Conditions 2. Cofactors and Coenzymes 3. Enzyme Inhibitors

17. 1. Environmental Conditions 1. Extreme Temperatures are the most dangerous - high tempsmay denature (unfold) the enzyme. 2. pH (most like 6 - 8 pH near neutral) 3. Ionic concentration (salt ions)

18. 2. Cofactors and Coenzymes • Inorganic substances (zinc, iron)andvitamins (respectively) are sometimes need for proper enzymatic activity. • Example: Iron must be present in the quaternary structure-hemoglobin in order for it to pick up oxygen.

19. Enzymes play essential roles in: Enzymes play essential roles in: • regulating chemical pathways. • making material that cells need. • releasing energy. • transferring information.

20. An Enzyme-Catalyzed Reaction