1. Energy and Chemical Reactions
Energy can be stored or released in chemical reactions.
In a chemical reaction bonds in molecules are broken between atoms and new ones are formed.
In this process one or more substances are produced.
Thousands of chemical reactions are occurring in your cells every second.
When energy (heat) is added to a raw egg atoms and molecules and atoms are rearranged in egg. You notice that clear part of the egg becomes white.

2. Energy and Chemical Reactions
Energy - Capacity of doing work; the ability to change or to move matter.
Activation Energy - the amount of energy required to start a chemical reaction.

3. Energy and Chemical Reactions
BIO BIT
The production of light in bioluminescent organisms results from the conversion of chemical energy to light energy. Bioluminescence is found among some insects, mollusks, fish, ctenophores (comb jellies) and annelid worms. Some of the most dramatic light-producing creatures are found in marine environments.  Bioluminescence should not be confused with fluorescence, in which light from an outside source is stored and re-emitted.

4. Energy and Chemical Reactions
A potential energy diagram displayed here presents relative potential energies ("internal" energies) of the chemicals believed to take part in the overall chemical reaction.
When molecules have enough energy to collide effectively chemist say they form an Activated complex.
The activated complex is placed at the top of the activation energy "hill".

5. Energy and Chemical Reactions
Since reactions can be either exothermic or endothermic we have two general forms of this diagram.
(a) In an exothermic reaction energy is given off: heat/ light. Reactants have more energy then products
(b) In an endothermic reaction energy is absorbed: Icepacks. Products have more energy then Reactants.

6. Energy and Chemical Reactions
Enzymes - substance that speeds up a chemical reaction.
Active Sites – site on an enzyme that attaches to a substrate.

7. Energy and Chemical Reactions
The activation energy is the extra energy needed to help the reactants to form into the products.
We represent this activation energy as a hill between the reactants and products. The size of the hill is determined by the nature of the reactants involved.
The presence of enzyme lowers the hill and allows for reactants to be turned into products easier than without the enzyme.

8. Energy and Chemical Reactions
Another Way of Looking at an Enzyme Catalyzed Reaction
The picture is an analogous way of thinking of how enzymes work. The enzyme lowers the EA barrier so the reactants can become products easier.

9. Energy and Chemical Reactions
A glucose molecule approaches an enzyme and enters its active site.
The conformation (shape) of the enzyme changes slightly so that no other substance can enter the active site while the enzyme is working on the glucose.
In this example the substrate is broken down into two products.
Observe how the shape of the active site is almost a perfect for the substrate that the enzyme acts on.
Biochemists refer to this as specificity. For every substrate(s) there is one enzyme.

10. Energy and Chemical Reactions
In an enzyme catalyzed reactions the substrate attaches to the enzyme at its active site.
In the active site the substrate and the enzyme interact to form a complex that reduces the activation energy needed for the reaction to occur, making it more likely for a reaction to proceed.
The enzyme, upon completion of the reaction releases the new product(s) from its active site.
The freed up enzyme is now capable of repeating the process on a new substrate(s).

11. Energy and Chemical Reactions
Enzyme Animations
(Two reactants, one product)
(Change in Conformation)
(Energy Diagram)
(Activation Energy)
(Orientation and Collisions)
(In active site)
(Pathway)
(Allosteric Enzyme)

12. Energy and Chemical Reactions
Example of Enzyme Activity
Digestion

13. Energy and Chemical Reactions
BIO BIT
Why do some laundry detergents contain enzymes?
Enzymes breakdown carbohydrates and proteins in common foods and blood - making the stains easier to remove. The enzymes are purified form mutant bacteria that can tolerate the high temperatures and alkaline conditions required for cleaning fabrics.

14. Energy and Chemical Reactions
Two Models for Explaining how Enzymes Work on Their Substrate
Lock – and – Key Model
The specific action of an enzyme with a single substrate can be explained using a Lock and Key analogy. In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).
Induced – Fit Model
The induced-fit theory assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible. This explains why certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much. Only the proper substrate is capable of inducing the proper alignment of the active site.

15. Energy and Chemical Reactions
Lock and Key Theory:

16. Energy and Chemical Reactions
Induced Fit Theory:

17. Energy and Chemical Reactions
Directions: Identify; the enzyme, the substrate, the reactants, and the products.
Enzyme:
Substrate(s):
Reactants:
Products:
Enzyme:
Substrate(s):
Reactants:
Products:

18. Energy and Chemical Reactions
Directions: Identify; the enzyme, the substrate, the reactants, and the products.
Enzyme: Carbonic anhydrase
Substrate(s): CO2 and H2O
Reactants: CO2 and H2O
Products: H+ and HCO3-
Enzyme: Catalase (peroxidase)
Substrate(s): H2O2
Reactants: H2O2
Products: O2 and H2O

19. Energy and Chemical Reactions
Directions: Identify; the enzyme, the substrate, the reactants, and the products.
Enzyme:
Substrate(s):
Reactants:
Products:

20. Energy and Chemical Reactions
Directions: Identify; the enzyme, the substrate, the reactants, and the products.
Enzyme: Amylase
Substrate(s): Amylose + (water)
Reactants: Amylose + Water
Products: Maltose

21. Energy and Chemical Reactions
A change in pH can also affect enzyme activity.
Each enzyme has an optimal pH range that helps maintain its normal configuration in an environment which it operates.
A change in pH can alter the tertiary or quaternary structure of a protein. A denatured protein can not combine with a substrate.

22. Energy and Chemical Reactions
A higher temperature generally results in an increase in enzyme activity.
If the temperature rises beyond a certain point, however, the enzyme activity eventually levels out and then declines rapidly because the enzyme is denatured by heat.
The enzyme shape changes during denaturation and can not catalyze the reaction.

23. Energy and Chemical Reactions
IEC Classification of Enzymes
 Group Name
 Type of Reaction Catalyzed
 Oxidases or Dehydrogenases
 Oxidation-reduction reactions
 Transferases
Transfer of functional groups
 Hydrolases
Hydrolysis reactions
 Lyases
Addition to double bonds or its reverse
 Isomerases
Isomerization reactions
 Ligases or Synthetases
Formation of bonds with ATP cleavage
Honors

24. Energy and Chemical Reactions
Enzyme Regulation
Competitive Inhibition -The inhibitor chemical and substrate both bind to the active site. Binding of the inhibitor prevents substrate binding.
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25. Energy and Chemical Reactions
Enzyme Regulation
Allosteric regulation is the regulation of an enzyme binding an effector molecule at the enzyme's allosteric site (that is, a site other than the enzyme's active site).
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26. Energy and Chemical Reactions
Enzyme Regulation
As the final product in a chemical pathway increases in concentration it will inhibit the first enzyme in the chemical pathway.
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27. Energy and Chemical Reactions
Enzyme Regulation
Effectors that enhance the protein's activity are referred to as allosteric activators.
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28. Energy and Chemical Reactions
Enzyme Regulation
Effectors that decrease the protein's activation are called allosteric inhibitors.
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29. Energy and Chemical Reactions
Enzyme Regulation
Noncompetitive Inhibition - Inhibitor and substrate bind to different sites. Binding distorts the enzyme and decreases the likelihood of substrate binding.
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30. Energy and Chemical Reactions
Michaelis-Menten equation describes the kinetics (rate) of many enzymes.
The speed V means the number of reactions per second that are catalyzed by an enzyme.
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31. Energy and Chemical Reactions
To determine the maximum rate of an enzyme mediated reaction, the substrate concentration ([S]) is increased until a constant rate of product formation is achieved.
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32. Energy and Chemical Reactions
Enzyme to Substrate Ratio
If there is a high concentration of Enzyme and low concentration of Substrate the reaction will proceed at a fast rate.
If there is a low concentration of Enzyme and high concentration of Substrate the reaction will proceed at a slow rate.