1. Enzymes Sections 5.1-5.9 in Concepts and Connections
We couldn’t live with out them!.....
And we die if they get messed up!

2. Chemical Reactions
Before we talk about enzymes…. We need to discuss chemical reactions.
A chemical reaction:
Involves rearrangement of atoms/bonds
Reactants are changed into products
Reactants are on the left
Products are on the right
Ex.
A B  C D
reactants products

3. Chemical Reactions There are four types of reactions: Synthesis
Decomposition
Single Replacement
Double Replacement

4. Practice: Identify reactants and products

5. Practice: Identify reactants, products and type of reaction

6. Practice: Identify reactants, products and type of reaction

7. Many molecules contain energy
Energy (E) is the capacity to do work.
Chemical energy is the potential energy of molecules.
This is the most important type of energy for living organisms
During photosynthesis sun E is stored as chemical E
This energy is used by organisms during cellular respiration.
Endergonic - chemical reaction that requires energy input
Ex. photosynthesis
Exergonic – chemical reaction that releases energy
Ex. Cellular respiration

8. Exergonic vs. Endergonic
Ex. Lighting gasoline Ex. Dissolving salt in water

9. The cell uses ATP as energy currency
Adenosine triphosphate (ATP) is the cell’s supply of energy.
ATP is like money in a checking account
Available right away wherever needed.
But only limited supply
ATP is a nucleotide

10. What is an enzyme? Known as a biological catalyst
Catalyst is something that speeds up a chemical reaction
Enzymes speed up reactions in living cells by lowering energy barriers
So reactions happen faster, and with less ATP

11. Enzymes LOWER Activation Energy
ACTIVATION ENERGY (EA) - the energy required for a reaction to begin
Energy
Uncatalysed reaction
Catalysed reaction
Reactants
Products
Progress of reaction

12. Imagine Jumping Beans (pg76)

13. Or building a snowman… on a hillside

14. Enzymes
Most essential reactions of metabolism occur quickly and precisely for the cell to survive.
The cell could die before it gets enough jumping beans or snowballs (cellular products)
Without enzymes, many metabolic reactions would occur too slowly to sustain life

15. Properties of Enzymes They are made of PROTEIN
Reusable - they are not changed by the reactions they speed up
They are specific - means that only one particular enzyme will work with one particular substrate

16. Shape is Essential! Like all proteins, enzymes have a unique
3-dimensial shape. (globular)
The shape determines which chemical reaction the enzyme catalyzes.
Each enzyme can only perform a few types of reactions
….. So there are thousands of enzymes in a cell!

17. Enzymes are specific!
Substrate – the substance that the enzyme works on
e.g. Amylase the substrate is starch
Product – the substance that is made by the reaction e.g. Breakdown of starch by Amylase the product is Maltose
Active site – the part of the enzyme that actually binds the substrate.
The shape of this pocket/groove determines what substrates an enzyme acts upon.

18. Enzymes are specific!
Each enzyme only catalyzes one, or a specific few types of reactions.
Enzymes are named using the suffix –ase
Examples:
Lipase – hydrolyzes (breaks down) lipids
Protease – hydrolyzes proteins (proteolysis)
Amylase – hydrolyzes starch
Sucrase – hydrolyzes sucrose into fructose and glucose
Catalase – decomposition of H202 into water and O2
ATP synthase – synthesizes ATP

19. CATALASE Found in animal and plant cells
Needed to speed up the breakdown of HYDROGEN PEROXIDE
Breaks it down to OXYGEN and WATER
The word equation for this looks like this
HYDROGEN PEROXIDE
OXYGEN AND WATER
HPCOW
CATALASE

20. CATALASE

21. Sucrase Found in small intestine Break down enzyme
Breaks SUCROSE down to GLUCOSE AND FRUCTOSE
Word equation looks like this
SUCROSE
GLUCOSE + FRUCTOSE
SUCRASE
SSGF

22. Sucrase

23. Amylase Found in saliva and in the pancreas Break down enzyme
Breaks STARCH down to MALTOSE
Word equation looks like this
STARCH
MALTOSE
AMYLASE
SAM

24. Amylase

25. Potato Phosphorylase Synthesis enzyme (puts together)
Builds Glucose-1-Phosphate molecules into Starch
The formation of starch is tested using iodine solution
Starch
Glucose-1-Phosphate
Phosphorylase
G1PPS

26. Potato Phosphorylase

27. More about Specific This means amylase will only breakdown starch
Catalase will only breakdown hydrogen peroxide
Amylase will NOT breakdown hydrogen peroxide
Catalase will NOT breakdown starch

28. Lock and Key
All enzymes have a special shaped area that fits onto their substrate
This area is called the ACTIVE SITE
This Active site will fit onto the substrate while the reaction takes place
Because it fits like a lock and key we call this the lock and key mechanism

29. enzyme substrate complex
Model of Lock and Key
substrate
products
enzyme substrate complex
active site
enzyme
enzyme – unchanged

30. Inducted Fit hypothesis
active site is empty
2. Sucrose enters…. “Induced fit” – enzyme changes shape and facilitates reaction
3. Substrate is converted to products glucose and fructose
4. The enzyme releases products and is unchanged
Sucrase, pg 77