1. Enzymes

2. Enzymes (Image from: http://www-news. uchicago. edu/releases/06/061011
proteins produced by cells
biological catalysts
speed up chemical reactions without being consumed
This enzyme is the insulin-degrading enzyme, control of which might help to sure Alzheimer’s disease.

3. Activation Energy (EA) (Image from: http://drmccarthysciencehgms
all chemical reactions require an initial input of energy, called activation energy (EA)
Recall collision theory from Grade 10 Science

4. Enzymes and EA (Image from: http://www. glogster. com/glog. php

5. Activation Energy
enzymes increase the rate of a reaction by lowering the activation energy (EA)
How?

6. What are enzymes?
enzymes are globular proteins that act on substrates (reactants)
substrates bind to specific sites (active sites) on enzymes, creating the enzyme-substrate complex

7. Enzyme-Substrate Complex (Image from: http://kentsimmons. uwinnipeg

8. Induced-Fit Model (Image from: http://chsweb. lr. k12. nj
in the “induced-fit” model, the enzyme alters shape to better “fit” substrate
“lock and key” model
Interactions between functional groups of enzyme & substrate cause enzyme to alter shape to better fit substrate

9. And then what? weak bonds form between substrate and enzyme
enzyme provides proper orientation of substrate(s)
enzyme puts strain on bonds of substrate(s), making them easier to break

10. Example: Sucrase Image from: http://awesomebiology. wikispaces

11. What do these enzymes do?
lactase
breaks down lactose (sugar found in milk)
ATPase
Breaks off a phosphate group from ATP, resulting in ADP, an inorganic phosphate, and energy
amylase
breaks down starch (in saliva & intestine)

12. What about this one? ATP synthase
synthesizes ATP from ADP and inorganic phosphate

13. Animation Activation Energy & Enzymes:

14. Factors Affecting Enzyme Activity
temperature pH
substrate concentration
enzyme concentration
presence of cofactors or coenzymes
Increasing the substrate concentration increases the reaction rate to a certain point. Once the enzymes are saturated with substrate, the concentration of enzyme becomes the limiting factor.
Protein (enzyme) folding depends on interactions between amino acid side (R) groups, some that are acidic or basic. Each protein (enzyme) has an optimal pH at which they fold correctly.
Temperature – At high temperatures, enzymes become denatured and don’t function. At low temperatures, enzymes are too rigid to catalyse a reaction. Enzymes usually function best at body temperature (37C in humans).

15. Cofactors and Coenzymes
some enzymes require cofactors to function as catalysts
cofactors are non-protein molecules or inorganic ions
coenzymes are organic cofactors
Cofactors: Zn, Fe ions, etc.
Coenzymes: NAD, FAD, CoA, etc. 15

16. Coenzymes (Image from: http://en. wikibooks16

17. Enzyme Regulation 17

18. Competitive Inhibition18

19. Competitive Inhibition
competitive inhibitors
have a similar structure to the substrate
bind to the enzyme’s active site and block the substrate from binding. 19

20. Allosteric Regulation
some enzymes have allosteric sites (receptor sites away from the active site)
allosteric sites can bind substances that inhibit or stimulate an enzyme’s activity 20

21. Allosteric Regulation21

22. Allosteric Regulation
allosteric activators promote the action of the enzyme
allosteric inhibitors prevent the action of the enzyme by changing the 3-D structure so that the substrate(s) can no longer bind to the active site (i.e. non-competitive inhibition) 22

23. Feedback Inhibition (Image from: http://classes. midlandstech
can be used to regulate multi-step metabolic pathways
the end product of a metabolic pathway acts as an allosteric inhibitor of the first enzyme of the pathway 23

24. Commercial Uses of Enzymes (Image from: http://housewares
detergents
cheese
lactose-free dairy proucts
corn & wheat syrup sweeteners
etc.
Starch-processing into glucose through enzyme-catalyzed hydrolysis
Cheese manufacturing involves enzymes called proteases (rennet) and lipases
Dairy products without lactose.
Detergents often contain proteases and amylases to remove protein and carbohydrate stains.