1. CH. 6 (Unit H) Metabolism : Energy and Enzymes

2. Forms of Energy These forms of energy are important to life: chemical
radiant (examples: heat, light)
mechanical
electrical
Energy can be transformed from one form to another.
CHEMICAL energy is the energy contained in the chemical bonds of molecules. It is the main energy form we are interested in studying
when it comes to Biology

3. Laws of Thermodynamics
1st law: Energy cannot be created or destroyed.
Energy can be converted from one form to another. The sum of the energy before the conversion is equal to the sum of the energy after the conversion.
Example: A light bulb converts electrical energy to light energy and heat energy. Fluorescent bulbs produce more light energy than incandescent bulbs because they produce less heat.
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
300 J J  100 J J J

4. Laws of Thermodynamics
2nd law: Some usable energy dissipates (leaves) during transformations and is lost as heat.
During changes from one form of energy to another, some usable energy dissipates, usually as heat. The amount of remaining usable energy therefore decreases.

5. Categories of Metabolic (cellular) Reactions
1. ANABOLIC
2. CATABOLIC

6. Energy is required to form bonds – ANABOLIC Reactions (endothermic/endergonic)
Atoms or molecules
Energy
+ Energy
Larger molecule
The energy that was used to form the bonds is now stored in the bonds of this molecule.
Example: Taking amino acids and building them into a protein. Synthesis requires energy input 8

7. Substrates (Reactants)
Anabolic Reactions
Products
Anabolic reactions consume energy. ENDERGONIC or ENDOTHERMIC
Energy Supplied
Substrates (Reactants)
Energy Released 9
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8. Energy is released when bonds are broken – CATABOLIC Reactions (Exothermic/exergonic)
Larger macromolecules are hydrolyzed to give rise to smaller monomers. Energy is released.
Example : When the body take triglycerides and breaks them into Glycerol and Three Fatty Acids 8
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9. Energy is released when bonds are broken.
When bonds break, energy is released. It may be in a form such as heat or light or it may be transferred to another molecule. 8
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10. Catabolic Reactions Energy Supplied Substrate (Reactant)
Catabolic reactions release energy. EXERGONIC EXOTHERMIC
Energy Released
When bonds are broken, energy is released. 10
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11. Video Clip – Endothermic vs Exothermic

12. Catabolic and Anabolic Reactions
The energy-producing reactions within cells generally involve the breakdown of complex organic compounds to simpler compounds. These reactions release energy and are called catabolic reactions.
Anabolic reactions are those that consume energy while synthesizing compounds.
ATP produced by catabolic reactions provides the energy for anabolic reactions. Anabolic and catabolic reactions are therefore coupled (they work together) through the use of ATP.
Diagram: next slide

13. Catabolic and Anabolic Reactions
An anabolic reaction
A catabolic reaction
ATP
ADP + Pi
Energy
Catabolic and Anabolic Reactions 8
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14. ENTROPY Calculation G = Eproducts - Ereactants
Entropy = is a mathematically-defined thermodynamic quantity that helps to account for the flow of energy through a thermodynamic process such as a chemical reaction
G = Eproducts - Ereactants
Example : if Reactants have 500 Joules of usable energy but your products end up only having 200 Joules of usable energy. Then 300 Joules were released.
According to the example: G = Eproducts - Ereactants
So 300 J – 500 J = Joules. A negative number indicates a exothermic/exergonic reaction

15. Go Over Ch. 6 Worksheet
Question #11
Then we will see why
ENZYMES
Are so important

16. Rate of Reaction
Reactions with enzymes are up to 10 billion times faster than those without enzymes.
Enzymes typically react with between 1 and 10,000 molecules per second. Fast enzymes catalyze up to 500,000 molecules per second.
Substrate concentration, enzyme concentration, Temperature, and pH  affect the rate of enzyme reactions.
They increase reaction rate by lowering the amount of Ea required!

17. Enzymes in Action – video clip
Enzymes in Action – video clip

18. Enzymes
Catalysts are substances that speed up chemical reactions.  Organic catalysts (contain carbon) are called enzymes.
Enzymes are specific for one particular reaction or group of related reactions.
Many reactions cannot occur without the correct enzyme present.
They are often named by adding “ASE" to the name of the substrate. Example: Dehydrogenases are enzymes that remove hydrogen. – Helicase, Maltase, DNA Polymerase, Reverse Transcriptase etc.

19. Metabolic reactions use enzymes

20. 1 3 2 Enzymes Menu Enzymes are organic catalysts. Substrate
Active Site
Enzyme
Product
Enzyme-Substrate Complex 3 2
Enzyme 15
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21. Cofactors
Many enzymes require a cofactor to assist in the reaction.  These "assistants" are nonprotein and may be metal ions such as magnesium (Mg++), potassium (K+), and calcium (Ca++). 
The cofactors bind to the enzyme and participate in the reaction by removing electrons, protons , or chemical groups from the substrate.

22. Coenzymes Cofactors that are organic molecules are coenzymes.
Coenzymes are usually vitamins.

23. Coenzymes Coenzyme Coenzymes are cofactors that are non protein.
They bind to the enzyme and also participate in the reaction by carrying electrons or hydrogen atoms.

24. STOP For the day

25. How do Enzymes Speed Up Reaction Rate ??
Activation Energy
In either kind of reaction, additional energy must be supplied to start the reaction. This energy is called “Activation Energy.
Energy Supplied
Activation Energy
Energy Released 21
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26. Enzymes Lower Activation Energy
Enzymes lower the amount of activation energy needed for a reaction.
Enzymes Lower Activation Energy
Activation energy without enzyme
Energy Supplied
Activation energy
with enzyme
Energy Released 22
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27. TWO THEORIES ON HOW AN ENZYME BONDS WITH ITS SUBSTRATE
Induced Fit Theory
Locak and Key Theory

28. Induced Fit Theory – Most current
The substrate molecule does not fit exactly in the active site. This induces a change in the enzymes conformation (shape) to make a closer fit.
After the reaction, the products are released and the enzyme returns to its normal shape.
Only a small amount of enzyme is needed because they can be used repeatedly.

29. Lock and Key Theory
The older theory of how enzymes work was that the enzyme has an already perfect active site shape for that particular substrate. Just like
only the perfect key will fit the complimenting lock

30. When studying enzymes in upcoming units remember to watch your S. T. E
When studying enzymes in upcoming units remember to watch your S.T.E.P.P s
P = pH – OPTIMAL pH
P = PRODUCT NAME
E = ENZYME NAME
T = OPTIMAL TEMERATURE
S = SUBSTRATE NAME

31. Metabolic Pathways
Metabolism refers to the chemical reactions that occur within cells.
Reactions occur in a sequence and a specific enzyme catalyzes each step.

32. Metabolic Pathways A B C D E F enzyme 1 enzyme 2 enzyme 3 enzyme 4
Notice that C can produce either D or F. This substrate has two different enzymes that work on it.
Metabolic Pathways
A B C D E
enzyme 1 enzyme 2 enzyme 3 enzyme 4
Enzymes are very specific. In this case enzyme 1 will catalyze the conversion of A to B only. F
enzyme 5 4

33. A B C D Feedback Inhibition
The goal of this hypothetical metabolic pathway is to produce chemical D from A.
A B C D
enzyme 1
enzyme 2
enzyme 3
B and C are intermediates.
The next several slides will show how feedback inhibition regulates the amount of D produced.
Enzyme regulation by negative feedback inhibition is similar to the thermostat example. As an enzyme's product accumulates, it turns off the enzyme just as heat causes a thermostat to turn off the production of heat. 34

34. X X A B C D X Feedback Inhibition
C and D will decrease because B is needed to produce C and C is needed to produce D. X
The amount of B in the cell will decrease if enzyme 1 is inhibited.
A B C D X
enzyme 1
enzyme 2
enzyme 3
Enzyme 1 is structured in a way that causes it to interact with D. When the amount of D increases, the enzyme stops functioning. 35

35. A B C D B X X X C D Feedback Inhibition
B, C, and D can now be synthesized.
A B C D B X X X C D
enzyme 1
enzyme 2
enzyme 3
When the amount of D drops, enzyme 1 will no longer be inhibited by it. 39

36. A B C D X Feedback Inhibition enzyme 1 enzyme 2 enzyme 3
As D begins to increase, it inhibits enzyme 1 again and the cycle repeats itself. 42

37. The End