1. Enzymes – The Amoeba Sisters

2. KEY CONCEPT Life depends on chemical reactions.

3. Bonds break and form during chemical reactions.
Chemical reactions change substances into different ones by breaking and forming chemical bonds.
Reactants are changed during a chemical reaction.
Products are made by a chemical reaction.

4. CO2 + H2O H2CO3 Carbonic Acid
Bond energy is the amount of energy that breaks a bond.
Energy is added to break bonds.
Energy is released when bonds form.
A reaction is at equilibrium when reactants and products form at the same rate.
CO2 + H2O H2CO3
Carbonic
Acid

5. Chemical reactions release or absorb energy.
Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction.
When a catalyst is present, less activation energy is needed.

6. Exothermic reactions release more energy than they absorb
Exothermic reactions release more energy than they absorb. EXIT – ENERGY OUT
Reactants have higher bond energies than products.
Excess energy is released by the reaction.

7. Endothermic reactions absorb more energy than they release. ENDO - INTO
Reactants have lower bond energies than products.
Energy is absorbed by the reaction to make up the difference.

8. Enzymes are catalysts for chemical reactions in living things
Enzymes are catalysts for chemical reactions in living things. They speed up chemical reactions.

9. Why are enzymes necessary?
Without enzymes, many important reactions would not occur.
Enzymes lower the activation energy of a reaction and thus allow the reaction to go faster.

10. Important Facts About Enzyme Structure
Enzymes are proteins.

11. More important facts about enzymes:
Enzymes are very specific for their function. Each enzyme has only one reaction to help.
They usually have “ase” endings that reflect what they work on. Ex – lipase breaks down lipids
Enzymes are not changed when they perform their function. They can be used over and over again.

12. How does the structure of an enzyme affect its function?
An enzyme’s structure allows only certain reactants (the substrate) to bind to the enzyme.
substrates (reactants)
enzyme
Substrates bind to an enzyme at certain places called active sites.

13. The lock-and-key model helps illustrate how enzymes function.
substrates brought together and held to enzyme by hydrogen bonds
bonds in substrates weakened
Substrates bind to an enzyme at certain places called active sites.
The enzyme brings substrates together and weakens their bonds.
The catalyzed reaction forms a product that is released from the enzyme.
enzyme video

14. Animation of enzyme action
The enzyme changes its shape when it binds to the substrate…called “induced fit model”.
Animation of enzyme action

15. Lock and Key versus Induced Fit Model?
Enzymes can change their shape to wrap around the substrate.
The lock and key model denotes a permanent shape for the enzyme which is not true even though enzymes are very specific for their substrates.

16. How enzymes become denatured
Changes in temperature and pH can affect the structure.
This is called denaturing.

17. Let’s review the properties of enzymes.
Enzymes are proteins. They act as catalysts, allowing chemical reactions to take place by lowering the amount of energy needed. They therefore speed up reactions or allow them to happen at low temperatures.
Some enzymes break down substances (e.g. digestive enzymes).
Some enzymes build up simple raw materials into more complex substances.
Enzymes are very specific. The lock and key hypothesis explains this using the idea that each enzyme has a specifically shaped active site.
enzyme properties

18. Bet you didn’t know…
Cellulase is the major industrial enzyme used to soften and fade jeans.
Cellulase speeds up the break-down of cellulose, which is present in jeans as the main component of cotton and other natural plant fibers.

19. Hydrogen Peroxide is poisonous to cells!
Our lab
Catalase – the enzyme
Catalase is found in all cells. It catalyzes the breakdown of hydrogen peroxide into water and oxygen.
Hydrogen Peroxide is poisonous to cells!
catalase
2H2 O H2 O + O2

20. How will you know if the reaction occurs?

21. We will check how the following factors affect the action of catalase?
Temperature pH

22. What will be our source of catalase?
Potato cells
The purple dots are iodine-
stained starch granules.

23. What will we measure to indicate a reaction has occurred?
OXYGEN
2H2 O H2 O + O2

24. How will we measure this?