Enzymes

1. Enzymes Proteins that make reactions happen

2. Metabolism Metabolism: the complete set of chemical reactions occurring in cells • Anabolism: using energy to build macromolecules • Catabolism: releasing energy by the enzymatic breakdown of macromolecules • Energy Coupling: Energy released by the breakdown of a molecule is used to fuel the creation of another

3. Energy • Potential: stored energy • Ex. Bowling ball held overhead • The ability to cause change • Kinetic: energy at work • Ex. Bowling ball falling to the ground • The occurrence of change

4. Chemical Reaction • The formation and breaking of covalent bonds between atoms

5. Reaction Energy • Endothermic rxn: requires energy input A + B + Energy -> AB • Exothermic rxn: releases excess free energy as heat AB -> A + B+ Energy

6. Exothermic: Releases Energy

7. Activation Energy • Energy required to destabilize chemical bonds and initiate a chemical reaction • Supplied by ATP

8. Endothermic: Absorbs energy

10. ATP Adenosine Tri-phosphate • Similar to a nucleotide but with 3 phosphate groups • Used as energy currency for cells • Energy is released when unstable third phosphate is released • ATP is created during cellular respiration

11. ATP

12. ATP Structure

13. ATP releases usable energy by transferring a phosphate group By coupling an exothermic reaction (the release of a phosphate from ATP) with an endothermic reactions (the acceptance of the phosphate by an enzyme) cells can transfer energy between molecules to perform work

14. Enzyme • A protein • Lowers the activation energy of a reaction (catalyst) • Can be reused • Typically uses ATP for the energy it requires

16. Substrate • An organic molecule that will undergo a reaction when paired with an appropriate enzyme

17. Enzyme + Substrate

18. Active Site • The location on an enzyme where the substrate binds

19. Enzyme-Substrate Complex

20. Substrate Specificity • A particular enzyme can only bind with a particular substrate due to complementation of 3-dimensional configurations

21. Enzymes can break or form bonds for substrates

22. Substrate + Enzyme = Product + Enzyme

23. Develop lactose free milk • Sweeten yogurt • Smoother ice cream • Speed cottage cheese production • Some people lack lactase • Glucose sweeter than lactose • Lactose makes gritty ice cream • Bacteria ferment monomers more quickly Industrial Uses Why?

24. Enzyme Mechanisms • Induced Fit • Enzyme and substrate both slightly change 3-D structure to fit together • Lock and Key • Substrate and enzyme fit perfectly together

25. Enzyme Mechanisms

26. Induced Fit

27. Induced Fit

28. Inhibition • The process by which enzymatic activity is reduced or halted by the presence of an inhibitory molecule that binds to the enzyme.

29. Inhibition • Non-competitive • Inhibitory molecule binds to another site (allosteric site) on enzyme, changing the 3-D shape of the enzyme so a substrate cannot bind to the active site • Competitive • Inhibitory molecule binds directly to the active site, preventing substrate-enzyme complex

30. Competitive Inhibition

31. Why competitive?Whichever is more highly concentrated (substrate/inhibitor) wins

32. Non-competitive Inhibition

33. Allosteric Regulation • Non-competitive inhibition is an example of allosteric regulation • Occurs when a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site. • Can result in stimulation or inhibition of enzyme activity.

34. Enzyme Summary

35. Biochemical Pathways • Enzymes work together in sequence or in cycles to catalyze a whole series of reactions • The product of one reaction becomes the substrate for the next

37. End Product Inhibition • The end product of a biochemical pathway serves as a non-competitive inhibitor to the enzyme responsible for initiating the pathway • Also known as feedback inhibition

38. End Product Inhibition