First Five

1. First Five • Define and give an example of: • Carbohydrate • Lipid • Protein • Nucleic Acid

2. Enzymes

3. Major Characteristics of Enzymes • Enzymes are special proteins present in the cytoplasm of all cells • They help speed up the chemical reactions in cells • There are hundreds of different kinds of enzymes, but each enzyme only speeds up one reaction.

4. Enzymes For example, glucose and fructose might join up slowly to form sucrose glucose- -fructose With the right enzyme present, the reaction happens faster glucose- -fructose

5. Enzyme Action • Enzymes are large proteins • like all proteins, each enzyme molecule has a certain shape • the shape determines which reaction the enzyme can speed up • In speeding up the reaction, the enzyme combines temporarily with a substrate • substrate: any substance an enzyme acts on

6. substrate A substrate B The substrate molecules fit the shape of the enzyme enzyme

7. STAGE 1

8. two substrates combine temporarily with enzyme STAGE 2 the enzyme joins the two substrates together

9. enzyme unchanged and ready for next reaction new compound released by enzyme STAGE 3

10. Different Types of Enzyme Reactions • Enzymes can • join substrates together • break a substrate apart

11. the shape of the substrate molecule fits the enzyme shape A ‘breaking-down’ reaction this is called the active site of the enzyme STAGE 1

12. A ‘breaking-down’ reaction substrate combines temporarily with enzyme A ‘breaking-down’ reaction enzyme will break molecule here STAGE 2

13. A ‘breaking-down’ reaction substrate splits and separates from enzyme STAGE 3

14. Final break-down products enzyme ready for next reaction end-products STAGE 3

15. Properties of Enzymes • Enzymes can act on only one type of substrate • Enzymes always produce the same end-products. • Enzymes are not used up in the reaction. • They return to their original state after the reaction.

16. this substrate this substrate Enzymes can act on only one type of substrate cannot combine with this enzyme cannot combine with this enzyme

17. Properties of Enzymes • Enzymes – like any protein – are denatured by heat or some chemicals. • Denaturing changes the shape of a protein • For an enzyme, this means that it can no longer combine with the substrate. • Each enzyme works best at a particular temperature and pH (acidity or alkalinity) • These are referred to as the optimal temperature and optimal pH

18. enzyme denatured by heat denatured enzyme cannot combine with substrate Because enzymes are proteins, they are denatured by heat or some chemicals enzyme + substrate

19. ENZYME ACTION 1 E glucose molecules 1. A glucose molecule combines with the active site on the enzyme phosphorylase

20. E 2 A region of the active site is still available

21. part of starch molecule E 3 One end of a growing starch molecule combines with the glucose molecule at the active site

22. E 4 The growing starch molecule breaks free from the enzyme phosphorylasewhich is now free to repeat the reaction

23. 1 1 E 2 E part of starch molecule glucose molecules E 3 E E E 4 Enzyme action

24. Enzymes Reading • Read the text individually • Mark the text as you read: • Answer the summary questions in your journal. • Put all answers into your own words. • Finish as homework. Due Tuesday