Chapter 5 Enzymes, Coenzyme and Energy

1. Chapter 5Enzymes, Coenzyme and Energy Biology 100 Spring 2009

2. Energy • All living things require energy. • Nutrients are one source of energy, as well as being molecules organisms require to grow, reproduce or repair • Biochemical reactions are the processes used for the formation, breakdown and rearrangement of molecules to provide organisms with energy

3. Activation Energy • Activation Energy is the required input of energy to make a reaction start

4. Catalyst • A catalyst is a chemical that speeds up the reaction but is not used up in the reaction • Lowers the activation energy needed to start a reaction • Is not used up during the reaction • Is unchanged after a reaction

5. Enzymes • Enzymes act as catalysts. Enzymes are proteins that speed up a rate of reaction • Found in cells throughout the body • Lowers activation energy • Enzymes will end in –ase • SPECIFIC!

6. Enzymes

7. How Enzymes Work • Each enzyme has a specific size and 3-D shape • Each enzyme is going to fit with a certain substrate (molecule enzyme connects to)

8. How Enzymes Work • When the enzyme and substrate are connected, it is known as enzyme-substrate complex • The binding site is where the enzyme physically attaches itself to the substrate • The active site is where the enzyme will cause a specific part of the substrate to change

10. Cofactors/Coenzynes • Some enzymes need an additional molecule to carry out the process • Cofactors are inorganic ions or organic molecules that serve an enzyme helpers • Coenzymes are organic molecules that function as a cofactor • May be certain amino acids, nitrogenous bases, and vitamins

11. Cofactors

12. Turnover Number • The number of molecules of substrate with which a single enzyme can react at a given time (ex. reactions/minute) is known as the turnover number • Can be quite large compared to uncatalyzed reeactions • Can depend on the environment

13. Environment • Temperature can have a huge impact on turnover rate • a higher temperate will increase the rate of molecular motion, to a certain extent • Too high of temperatures may cause the enzyme to change its shape, this is known as denaturing, where a protein structure is permanently changed

14. Environment • Optimum temperature is when the rate of formation of the enzyme-substrate complex is fastest

15. Environment • pH also affects the rate of enzyme-substrate complexes • Most enzymes have an optimum pH of around 7 (neutral) • However, some prefer acidic or basic conditions

16. Fig. 5.7, pg.103 Competition • Enzymatic competition is where there are several kinds of enzymes available to combine with the same kind of substrate molecule • The substrate acetyl can be acted upon by three different enzymes: citrate synthetase, fatty acid synthetase, and malate synthetase

17. Gene Regulator Proteins • Gene Regulator Proteins are chemical messengers that inform the genes of the cell’s need for enzymes • Gene-repressor proteins decrease protein production • Gene-activator proteins will increase protein production

18. Fig. 5.7, pg.103

19. Inhibitor • Inhibitor is a molecule that attaches itself to an enzyme and interferes with the enzymes ability to form an enzyme-substrate complex • Competitive Inhibition • Negative-Feedback Inhibition

20. Competitive Inhibition • In competitive inhibition an inhibitor has a shape that is closely resembling the normal substrate of an enzyme • Enzyme becomes ineffective

21. Negative-Feedback Inhibition • In negative-feedback inhibition is a process where the output of a system acts to oppose changes to the input of the system • Allosteric Regulation is the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site (a site other than the active site) http://highered.mcgraw-hill.com/olc/dl/120070/bio10.swf