1. Add to your concept map
Write all the key words from last lesson – leave some space so you can add more in coming lessons (2 word trigger meaning with it)
Join different word – write how they are joint on the line ....
Induced fit
Activation energy
Orientation
Affinity
Metabolism – chemical reactions
2 types
Catabolism –breakdown , energy made

2. Regulation of metabolic pathways by the action of enzymes

3. How does your body prevent “burnout”?
Clue 

4. Gene Expression of Enzymes
Some metabolic pathways are only required to operate under certain circumstance
Prevent wasted resources by “switching on/off” of genes that code for the enzymes controlling each of the stages

5. Learning Outcomes
Control by gene expression - give an example of lactose metabolism being switched by presence/absence of lactose (Lac-operon proposed by Jacob-Monod)
Control by signalling molecules (adranalin)
Control by inhibitors or competitors

6. Genes & Escherichia Coli (E.Coli)
E.Coli preferred food source is glucose
Lactose is disaccharide made up of glucose and galactose.
E.Coli has gene for β-glactosidase which digests lactose to glucose and galactose
Gene for β-glactosidase in E.Coli on switched on when lactose present – off usually by the repressor upstream of lac operon
Process of switch on is called enzyme induction -

7. Operon consists of; Regulator consists of;
1 or more (3 here) structural genes which code for enzyme
operator region controls switching on/off of
Promoter site for RNA polymerase to bind to
Regulator consists of;
Promoter site for RNA polymerase to bind to
Gene for making repressor protein
phET Animation

8. When lactose present
Up to 4:40mins

9. Gene action hypothesis was put forward by Jacob-Monod
Confirmed by many experimental experiments – one of which you will complete next lesson .....
Jacob, Monod & Lwoff
© NobelPrize.org

10. Regulation by signal molecules
Intracellular Signals ;Lactose is an example of a signal molecule from the cells environment
Extracellular Signals; Epinephrine (Adrenalin)is also a signal molecule – this time outside the liver cells (in blood stream by adrenal glands) – but it triggers conversion of glucose from stored glycogen in liver cells.

11. Regulation by inhibitors
2 types;
Competitive inhibitors
Non-competitive inhibitors
Compete for the active site
Directly compete
Overcome by increasing substrate concentration
Attached to non-active site (allosteric), but this changes the shape of the enzyme molecule.
Indirect change
Not overcome

12. As shown below, the competitive inhibitor can be challenged by increasing the substrate concentration – as more enzyme sites will contain substrate not inhibitor. No effect on non-competitive inhibitor when substrate concentration is increased.

13. 1 Enzyme many active sites ...
Some enzymes have several polypeptide subunits with their own active sites.
Can be either active or inactive
Can change shape if regulator molecule (reg) bound to allosteric (non- active site)
If reg activato rthe enzyme active and enzyme activity stimulated, rate of reaction
If reg non-competitive inhibitor then inactive state and no enzyme activity rate of reaction

14. Regulation by products
Final method of regulation is by end-product feedback inhibition
Guess what you think it is – tell your partner
Come up with a collaborative idea

15. End-product Feedback Inhibition
The end product acts as an inhibitor, feedback to the pathway.
This is then binds to an earlier enzyme that catalyses the reaction earlier in pathway
The end product then inhibits this enzyme
Causing the slowing down of conversions
Called negative feedback control; finely tuned in order not to accumulate intermediates/final products and prevent wasteful conversions!
The control of metabolic pathways by feedback inhibition where an end product binds to an enzyme that catalyses a reaction early in the pathway.

16. Demonstrate your knowledge
Use the cards and place them into different categories – you choose categories!
Metabolic pathways are controlled by the presence or absence of particular enzymes.
Enzymes always act individually.
Competitive inhibition can be reversed by increasing the substrate concentration.

17. Review Complete this extended response in 20 minutes;
Describe the 'induced fit' model for enzyme activity and explain how enzyme activity may be regulated.

18. Swap with someone on another table and peer assess Use the markscheme .....

19. b-galactosidase

20. b-galactosidase

21. Competitive inhibition

22. Non-competitive inhibition

23. Non-competitive inhibition

24. Effect of [substrate] Competitive inhibitor Non-competitive inhibitor
Increasing [substrate] displaces inhibitor from active site
Non-competitive inhibitor
Increasing [substrate] has little or no effect on enzyme activity

25. Method Carry out reaction
Without inhibitor at low [S] (ONPG)
In presence of inhibitor
Galactose
Iodine
[I] chosen to completely inhibit reaction and look at increasing [S]

26. Colorimeter
Direction
of Beam
R = Reference T = Test

27. 1 2 - 1.0 0.25 0.75 3 0.5 4 5 Cuvette No 20% galactose in buffer (cm3)
ONPG stock solution (cm3)
Buffer
(cm3)
ONPG x 20 dilution
Absorbance 1 2 -
1.0
0.25
0.75 3
0.5 4 5

28. I = Galactose (steps 6-7) Prepare test tubes
Each tube contains 2 cm3 galactose (I)
Tubes 1 – 5 contain increasing [S]
NOTE – diluted (x 20) ONPG into tube 1, ONPG stock and buffer into tubes 2 – 5
Mix, place in cuvette  colorimeter, reference colorimeter
Return to test tube
Add 0.5 cm3 diluted enzyme, start timer & mix, add to cuvette, read Absorbance after 2 min

29. Step 10
Add buffer and diluted (x 20) ONPG to test tube, mix and reference colorimeter
Add 0.5 cm3 diluted enzyme, start timer, mix read in colorimeter after 2 min
Compare with results after step 5.

30. Step 10
Mix diluted buffer and diluted ONPG in test tube, zero colorimeter
Add diluted enzyme
Read absorbance after two minutes
Compare with results after step 5.

31. Results

32. Results