Enzymes: Part 2

1. Enzymes: Part 2

2. Enzyme Activity can be affected by: • General environmental factors, such as temperature, pH, salt concentration, etc. • Chemicals that specifically influence the enzyme See a movie Choose narrated http://www.desktopfotos.de/Downloads/melt_cd.jpg http://www.nealbrownstudio.com/adm/photo/163_nb_fried_egg.jpg

3. TEMPERATURE & ENZYME ACTIVITY Each enzyme has an optimal temperature at which it can function (Usually near body temp) http://www.animated-gifs.eu/meteo-thermometers/001.htm

4. http://www.uic.edu/classes/bios/bios100/lectures/chemistry.htmhttp://www.uic.edu/classes/bios/bios100/lectures/chemistry.htm Increasing temperature increases the rate of an enzyme-catalyzed reaction up to a point. Above a certain temperature, activity begins to decline because the enzyme begins to denature.

5. pH and ENZYME ACTIVITYEach enzyme has an optimal pH at which it can function

6. http://www.wissensdrang.com/media/wis9r.gif COFACTORS= non-protein enzyme helpers • EX: Zinc, iron, copper COENZYMES= organic enzyme helpers • Ex: vitamins http://www.elmhurst.edu/~chm/vchembook/595FADcoq.html

7. SUBSTRATE CONCENTRATION & ENZYME ACTIVITY ← V MAX Adding substrate increases activity up to a point

8. REGULATION OF ENZYME PATHWAYS • GENE REGULATIONcell switches on or off the genes that code for specific enzymes

9. REGULATION OF ENZYME PATHWAYS • FEEDBACK INHIBITIONend product of a pathway interacts with and “turns off” an enzyme earlier in pathway • prevents a cell from wasting chemical resources by synthesizing more product than is needed FEEDBACK INHIBITION

10. A A Negative feedback Enzyme 1 Enzyme 1 B B Enzyme 2 C C Enzyme 3 D D D D D D D D D D D NEGATIVE FEEDBACK • An accumulation of an end product slows the process that produces that product Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway

11. W W Enzyme 4 Enzyme 4 Positivefeedback X X Enzyme 5 Enzyme 5 Y Y Enzyme 6 Enzyme 6 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z POSITIVE FEEDBACK (less common) • The end product speeds up production EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.

12. REGULATION OF ENZYME ACTIVITY • ALLOSTERIC REGULATIONprotein’s function at one site is affected by binding of a regulatory molecule at another site • Allosteric regulation can inhibit or stimulate an enzyme’s activity Allosteric enzyme inhibition http://bio.winona.edu/berg/ANIMTNS/allostan.gif

13. SOME ALLOSTERIC ENZYMES HAVE MULTIPLE SUBUNITS • Each enzyme has active and inactive forms • The binding of an ACTIVATOR stabilizes the active form • The binding of an INHIBITOR stabilizes the inactive form

14. Binding of one substrate molecule to active site of one subunit locks all subunits in active conformation. Substrate Inactive form Stabilized active form Cooperativity another type of allosteric activation

15. COOPERATIVITY= form of allosteric regulation that can amplify enzyme activity Binding of one substrate to active site of one subunit locks all subunits in active conformation

16. Enzyme Inhibitors COMPETITIVE inhibitor REVERSIBLE; Mimics substrate and competes with substrate for active site on enzyme ENZYMEANIMATION

17. Enzyme Inhibitors NONCOMPETITIVE inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective ENZYMEANIMATION