1. ENZYMES and Activation Energy
OR: Why don’t you burn up in flames when you eat!
Refer to Enzyme Demo
Ask the students to answer this question.

2. What is Energy?
Energy is the ability to cause matter to move or change.
All life processes are driven by energy
Where does all energy come from?
There are many forms of energy, not all are light. Ex: mechanical, chemical, thermal, nuclear.
Without energy, you do not function.
Energy comes from the sun. – Where have they seen this before?

3. Chemical Reactions
When bonds are broken and reformed to make different substances.
EX:
Reactants Products
C6H12O6 + 6O2 6CO2 + 6H2O
Remember, energy is stored in the bonds of the compounds.
Reactants are also called raw materials – They need to know this term.
Have them tell you the reactants and products of the above equation.

4. What is Metabolism?
Metabolism is the sum of all chemical reactions in your body
- Metabolism is basically two components
Breaking down foods for energy
Building new compounds to make you
Ask the kids what they know about metabolism.
Then show the notes.
Metabolism is the sum of all chemical reactions in your body – it is what allows you to function.
Breaking down foods for energy – breaking the bonds in the compounds
Building new compounds to make you – carbs, lipids, proteins
You are what you eat because the food you eat is broken down and the products are then used to make new compounds. Ex:Hot dog for lunch, body breaks it into monomers (ask them what this term is), then rebuilds the monomers into you. So you are nothing more than recycled hot dog parts!
Literally, you are what you eat!

5. What is needed to start a reaction?
Activation energy
Energy absorbed
Activation Energy: energy required to get a reaction started
Point out the high amount of energy needed with reaction in graph.
The activation energy on the graph comes in when you click the mouse – the purpose is to get the answer from them first. – Remember enzyme demo
reactant
Energy released
Products

6. What is a Catalyst?
A catalyst is anything that lowers activation energy
There are basically two kinds:
1. Organic
2. Inorganic
Ask question before notes.
A catalyst is anything that lowers activation energy
They can be organic or inorganic - living or non-living
Organic catalysts are called enzymes
Organic catalysts are called Enzymes

7. Why is the activation energy lower?
Energy absorbed
Energy released
reactant
Products
Activation energy
Because a catalyst was used.
Catalyst: anything that lowers activation energy
Point out that the amount of energy has been significantly lowered

8. Comparing Reactions
Which line would represent a reaction without an enzyme present?
With an enzyme present?
Energy absorbed
Reactant
Products
Energy released

9. How Do Enzymes Work? Enzymes work like a lock and key.
Specific enzymes work with specific substrates.
enzyme
Use the analogy of enzymes as a lock and key.
Explain that substrates are reactants.
Substrate (key) must fit exactly into the active site of and enzyme (lock), just like only specific keys fit certain locks.
substrate

10. How Do Enzymes Work?
Each substrate fits into the enzyme’s active site.
Then the enzyme controls chemical reaction.
Substrate is also the reactant in a chemical reaction.
Enzymes are not used up in the reaction.

11. Induced Fit The reactant an enzyme acts on is called the substrate
Enzyme binds to substrate at the active site to initiate rxn

13. Enzymes aren’t used up Enzymes are not changed by the reaction
used only temporarily
re-used again for the same reaction with other molecules
very little enzyme needed to help in many reactions
substrate
product
active site
enzyme

14. Enzymes can be affected by:
Temperature:
pH:
Concentration: 3 7 5 9 11 13
Neutral
Battery Acid
Bleach
Blood (7.5)
Temperature: all enzymes have an optimal temp they work best at
pH: acidity/alkalinity can increase or decrease the function of an enzyme
Concentration: Increasing the concentration of the enzyme can increase the rate of the chemical reaction

15. Order of amino acids Wrong order = wrong shape = can’t do its job! DNA
folded protein
chain of amino acids
DNA
right shape!
folded protein
chain of amino acids
DNA
wrong shape!

16. Temperature Optimum temperature Raise temperature (boiling)
Effect on rates of enzyme activity
Optimum temperature
greatest number of collisions between enzyme & substrate
human enzymes
35°- 40°C (body temp = 37°C)
Raise temperature (boiling)
denature protein = unfold = lose shape
Lower temperature T°
molecules move slower
fewer collisions between enzyme & substrate

17. Temperature human enzymes reaction rate temperature 37°
What’s happening here?!
37°
reaction rate
temperature

18. How do cold-blooded creatures do it?
Enzymes work within narrow temperature ranges. Ectotherms, like snakes, do not use their metabolism extensively to regulate body temperature. Their body temperature is significantly influenced by environmental temperature. Desert reptiles can experience body temperature fluctuations of ~40°C (that’s a ~100°F span!).
What mechanism has evolved to allow their metabolic pathways to continue to function across that wide temperature span?

19. pH Effect on rates of enzyme activity
changes in pH changes protein shape
most human enzymes = pH 6-8
depends on where in body
pepsin (stomach) = pH 3
trypsin (small intestines) = pH 8

20. pH stomach pepsin intestines trypsin reaction rate pH 1 2 3 4 5 6 7 8
What’s happening here?!
reaction rate 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH

21. Concentration
Concentration is how much of something there is in a particular area.
Rate is how fast a reaction occurs.

22. Increasing enzyme concentration

23. ATP stores Energy ATP ADP
ATP is the special carrier molecule that stores energy available for cell use.
ATP
energy
energy
Adenosine Triphosphate – three phosphates, and as energy is released a phosphate is broken off. As energy is stored, a phosphate is added. P P
ADP
ATP is the energy currency of the cell; the energy source for all cell functions.