1. Enzymes What do you know already? What are they?
Where do substrates bind? Factors affecting enzymes and how?

2. What are they?
Biological Catalysts: Speed up reaction rates of chemical reactions in cells. These are called metabolic reactions

3. Enzymes are globular proteins
Proteins are made up of single units called amino acids linked together to form a polypeptide chain
One amino acid. The R group is a variable group that differs in different amino acids
Globular proteins are Compact, Spherical, Soluble molecules

4. Enzymes are tertiary structure proteins
These have a specific 3D shape. Why is this important in enzymes?
Tertiary Structure is dependent on the bonds that form between R groups of an amino acid as the polypeptide chain folds.
These bonds are disulphide bridges, hydrogen bonds, ionic bonds, hydrophobic interactions.
These bonds give the enzyme a very precise 3D shape

5. Activation energy: The energy needed for a reaction to happen
Enzymes lower the ACTIVATION ENERGY to make a reaction happen
So reactions can happen at a lower temperature i.e. body temperature

6. How do they Work? ONLY in solution Lock and Key hypothesis –
Emil Fischer (1894)
Each enzyme has a specific and different shape

7. Lock and Key Hypothesis
Active site region
Complementary shape to substrate
Enzyme and substrate successfully collide
Substrate binds to active site
Forms enzyme-substrate complex
Reaction takes place  products formed
Enzyme used again collides with next substrate

8. The lock and key hypothesis

9. NB enzymes don’t always break things down!

10. Factors Affecting enzyme activity

11. Temperature Frying eggs animation
Hydrogen bonds break, tertiary structure changes, active site changes shape. Substrate no longer fits
(Low temps inactivate enzymes)
The rate of reaction doubles for each 10°C rise until the optimum is reached

12. pH The range of pH over which an enzyme can work is NARROW.
Changes in pH affect ionic and hydrogen bonds
Small deviations from the optimum
are reversible and inactivate the enzyme
Large deviations cause denaturation.
The narrow optimum pH will vary
between different enzymes

13. Enzyme concentration
e.g. Substrate concentration

14. Substrate Concentration
All the active sites are
full all of the time
Reaction is at its maximum unless more enzyme is added (Vmax)
Substrate concentration limits the reaction rate

15. Enzymes re-cap: On a whiteboard…
What do you know NOW? What are enzymes?
Where do substrates bind? Factors affecting enzymes and how?
DRAW GRAPHS AND USE KEY WORDS