1. Enzymes
What, how, why, what

2. Prior Learning From GCSE what can you remember about Enzymes
Hopefully you got
Biological catalysts, proteins, specific shape, active site, substrate,

3. What are ENZYMES
Biological catalysts – so they speed up the reaction whilst not being used up themselves.
They are made of PROTEIN and are GLOBULAR (so are folded and have a 3d shape)
Folding is due to two things
Sequence – what Amino Acid is where
Bonding – there are four types, ionic, disulphide, hydrophobic/hydrophilic interactions, hydrogen bonds
Look at the white board!

4. Enzyme Facts There are two types of two types!
Simple GCSE types – Catabolic, anabolic enzymes one breaks and one breaks can you guess which is which?
Correct Anabolic makes catabolic makes….
Now AS level types –
Intracellular (inside cells) so for example catalase (more about that next week)
Extracellular (outside cells) for example digestive enzymes like trypsin, pepsin or amylase.

5. Why does they work?
First GCSE revision – what affects the rate of reaction?
Temperature
Concentration
Surface area
Catalyst
Does anyone know why catalysts work?
They lower activation energy!

6. A Bit of Detail So, so far we know the following
Biological catalysts, Protein, Specific shape, Lowers activation energy
But how they do what do they do?
Simple
If joining the enzyme holds the two bits (molecules) together to overcome any repulsion
If splitting it puts a strain on the bonds and they break easily (see hydrolysis reactions)

7. Shape matters
Indeed it does – the enzyme and substrate have to match to start with.
So if the protein strand is not right then the shape isn’t right then the substrate won’t bind
Example – Fabrys disease – lipases are not made properly and they build up in the kidney heart and other organs.
All because the enzyme can’t do this

8. Two models
First lock and key model – substrate fits like a hand in a glove – look at white board!!
Second model – like the first but a bit different
Induced fit – a bit like tight jeans! A little bit of movement is needed makes the enzyme substrate relationship even more specific!

9. SO

10. Quick Recap So far we have covered the following:
Enzyme structure – 1, 2, 3, 4
Enzyme action – lock and key and induced fit (more useful and accurate)
Types of enzymes (intra and extra)
And factors affecting their action conc of enzyme and substrate
What enzymes actually do!

11. SO

12. Factors affecting enzymes
First rate of reaction revision:
Temperature
Concentration
Surface area
Catalysts

13. Factors affecting enzyme performance
Temperature
Concentration pH
Enzyme structure

14. Graphs and limiting factors
Temperature – increases rate due to increased collisions then after optimum the enzyme structure breaks down
pH – Either side of optimum pH the H+ and OH- ions interrupt the tertiary structure and this changes the active site
Concentration of enzyme and substrate – Both increase until a plateau is reached then the reaction is limited due to not enough substrate or the active sites being Occupied

15. Denaturation and occupied sites
IMPORTANT
Enzyme structure breaking down leads to DENATURING, not breaking – it is a specific thing that needs to be explained specifically!!!
Additionally – when an enzyme controlled reaction hits a limiting factor that is the enzyme it is because the active sites are OCCUPIED not USED UP – think of it like seats on a bus

16. IMPORTANT!!!! Temperature – increasing it increases rate of reaction
Temperature coefficient or Q10 is a value for the reaction that shows how much the rate increases when you increase the temperature by 10oC
At temperatures before optimum if the Q10 is 2 then the rate doubles for 10oC increase
A value of 3 will triple the rate
Most enzymes are at 2

17. Calculate Tangent
Worksheet!
Practice Questions

18. Cofactors and inhibition
These are two different things
One stops and one makes it work, can you figure out which is which?!?!?!?
Correct cofactors – help
Inhibitors – no help

19. Cofactors
Two types
Inorganic – the help the substrate and enzyme bond but are not changed or used in any way
Example Cl- for amylase
Organic – They are called coenzymes and participate in the reaction and are changed by it (second substrate) they also recycle
Example Vitamins e.g. NAD is derived from vitamin B3
When a cofactor is bound to the enzyme it is known as a prosthetic group e.g. Zn ions on carbonic anhydrase

20. Inhibition
Again two types Competitive and Non competitive On white boards draw what you think this means.

21. Correct Competitive – hit the active site
Non competitive hit somewhere else (allosteric site)
We then move into permanent (non reversible) and non permanent (reversible)
That is all to do with the bonding – if it is strong covalent bonds no removal, if ionic or H then they can be removed
Try the questions on page 110 of text book

22. Special inhibition End product inhibition
E.g. phospofructokinase an enzyme used in production of ATP lots of ATP inhibit it’s production – makes sense really
Enzyme inhibition – inactive precursors e.g. pepsin/pensinogen

23. Questions Can you explain the structure of enzymes
Explain how enzymes work
Outline all the factors that can affect enzyme function
Describe what a cofactor is and how they influence enzyme action
Outline an example of when an enzyme is inhibited in the body