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

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CH. 6 (Unit H) Metabolism Energy and Enzymes
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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.
• Energy that is stored is called potential energy.

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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 200 J ? 100 J 100 J 300 J
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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.
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Energy is required to form bonds ANABOLIC
Reactions (endothermic/endergonic)
Atoms or molecules
Example Taking amino acids and building them
into a protein. Synthesis requires energy input
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Anabolic Reactions
Products
Energy Supplied
Substrates(Reactants)
Energy Released
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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
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Energy is released when bonds are broken.
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Catabolic Reactions
Energy Supplied
Substrate(Reactant)
Energy Released
When bonds are broken, energy is released.
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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

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Catabolic and Anabolic Reactions
An anabolic reaction A catabolic
reaction
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ENTROPY Calculation
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 - 200 Joules. A
negative number indicates a exothermic/exergonic
reaction
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One very important energy storing and releasing
molecule is ATP
3 phosphate groups
Base (adenine)
A
Sugar (ribose)
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ATP Stores Energy
A
ATP
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ATP is Recycled In the ATP CYCLE

• ATP (Adenosine Triphosphate) is an
  energy-containing molecule used to supply the
  cell with energy. The energy used to produce ATP
  comes from glucose or other high-energy
  compounds.
• ATP is continuously produced and consumed as
  illustrated below.
• ADP Pi Energy ? ATP H2O(Note Pi
  phosphate group)

ATP
Energy
Energy (from glucose or other high-energy
compounds)
ADP Pi
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ATP
The ATP Cycle can be coupled to drive other
anabolic reactions, or coupled with catabolic
reactions to form ATP from ADP P.
In this diagram, energy from breaking bonds in
this molecule is used to form ATP.
ATP
ADP Pi
Energy
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ATP
The energy in ATP can be used to form bonds in
other molecules.
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ATP (Adenosine Triphosphate)
NH2
Base (adenine)
C
N
N
C
CH
HC
C
N
N
O- O- O-
O P O P O P O
CH2
O
-
C
C
O O O
H H
C
H
C
C
OH OH
3 phosphate groups
Ribose
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METABOLISM THE SUM OF ALL THE ANABOLIC AND
CATABOLIC REACTIONS THAT TAKE PLACE INSIDE ALL
THE CELLS OF AN ORGANISM. - The rate of these
reactions gives rise to ones METABOLIC RATE
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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.

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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!

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Metabolic reactions use enzymes
A high-energy molecule (substrate) is used to
transfer a phosphate group to ADP to form ATP.
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Enzymes
Substrate

• Enzymes are organic catalysts.

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Active Site
Enzyme
Product
Enzyme-Substrate Complex
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2
Enzyme
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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.

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Coenzymes

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

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Vitamins are Coenzymes

• Vitamin Coenzyme Name
• Niacin NAD
• B2 (riboflavin) FAD
• B1 (thiamine) Thiamine pyrophosphate
• Pantothenic acid Coenzyme A (CoA)
• B12 Cobamide coenzymes

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Coenzymes
Coenzyme
Enzyme

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

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Activation Energy
Energy Supplied
Activation Energy
Energy Released
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Activation Energy
Energy Supplied
Activation Energy
Energy Released
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Enzymes Lower Activation Energy
Activation energy without enzyme
Energy Supplied
Activation energy with enzyme
Energy Released
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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
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Induced Fit Theory Most current

• An enzyme-substrate complex forms when the
  enzymes active site binds with the substrate
  like a key fitting a lock.
• 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.

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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
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Metabolic Pathways

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

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Metabolic Pathways
A B C
D E
enzyme 1 enzyme 2 enzyme 3 enzyme 4
F
enzyme 5
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A Cyclic Metabolic Pathway
In this pathway, substrate A enters the
reaction. After several steps, product E is
produced.
A
B
A F ? B B ? C ? D D ? F E
F
C
D
E
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Feedback Inhibition
A B C D
enzyme 1
enzyme 2
enzyme 3
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.
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Feedback Inhibition
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.
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Feedback Inhibition
A B C D
X
X
X
C
D
enzyme 1
enzyme 2
enzyme 3
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Feedback Inhibition
A B C D
X
enzyme 1
enzyme 2
enzyme 3
As D begins to increase, it inhibits enzyme 1
again and the cycle repeats itself.
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The End