chapter 8 an introduction to metabolism the totality of an organism’s chemical reactions is called...
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CHAPTER 8 AN INTRODUCTION TO
METABOLISM
• The totality of an organism’s chemical reactions is called _______________.
• A cell’s ______________ is an elaborate road map of the chemical reaction.
1. The chemistry of life is organized into _______________________
Fig. 6.1
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• Enzymes selectively _____________ each step.
• _____________ pathways __________ energy by breaking down complex molecules to simpler compounds.
• _________________ pathways __________ energy to build complicated molecules from simpler compounds.
• _________________- the study of how organisms manage their energy resources.
Some terms
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• Energy - the capacity to do ________ ( to move or rearrange matter).
• __________ energy is the energy of _________.
• Objects in motion, photons, and heat are examples.
• ___________ energy is the energy that matter ______________because of its location or structure.
• Chemical energy is a form of potential energy in molecules because of the arrangement of atoms.
2. Organisms transform _________
• Cellular respiration and other catabolic pathways unleash energy stored in ________ and other complex molecules.
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• _________________ is the study of energy transformations.
• A_________ system- isolated from its surroundings
• Example- liquid in a thermos
• An _____ system - energy (and often matter) can be transferred between the system and _______________.
3. The energy transformations of life are subject to two laws of __________________
•Organisms are ______ systems.
•They _________ energy - light or chemical energy in organic molecules - and _________ heat and metabolic waste products.
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• The first law of ____________________ -energy cannot be created or destroyed.
• It can be transferred and transformed
• Plants transform light to __________ energy; they do not __________ energy.
•The second law of ______________________ -every energy transformation must make the universe more ________________.
•__________ - a measure of _______, or randomness.
•Increased randomness = increased ___________
•Living cells convert organized energy to heat.
•Organisms are__________ of low entropy in an increasingly random universe.
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4. Organisms live at the expense of _____ ___________
• _________________ (G) - portions of a system’s energy that is able to perform work (temperature constant)
Fig. 8.5 Diffusion Chemical Reactions
ExamplesHigh G
Low GWork
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4. Organisms live at the expense of _____ __________• ____________ (G) - portions of a system’s energy that is
able to perform work (temperature constant)
Fig. 8.5 Diffusion Chemical Reactions
ExamplesHigh G
Low GWork
Gravity
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• ______________reaction - ___________ of free energy and G is ___________
Fig. 8.6a
Cellular respiration:
•C6H12O6 + 6O2 -> 6CO2 + 6H2O
•G = ______________
•Thus, 686 kcal are available to do ______
Reactants
Products
Example:
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• ______________ reaction - ___________ free energy from its surroundings.
• _________ energy,
• G is_______________
• reactions are non-
spontaneous.
Fig. 8.6b
• Photosynthesis
• Delta G = _______ kcal / mol.
•A cell that has reached metabolic ________________ has a G = 0 and is dead!
Reactants
Products
Example:
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5. Cellular work is powered by ____ - couples __________ and ___________ reactions
• ATP (adenosine triphosphate) is a ___________ consisting of:
Fig. 6.8a
2..
1.
3.
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ATP is converted to ADP via hydrolysis
G = -7.3 kcal/mol.
• This energy is “captured” by transferring the phosphate group to another molecule.
Fig. 8.10
Fig. 8.9
Result = overall Gis ______, reaction is ___________
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• ________________, an endergonic process, requires an investment of energy: G = _________
Fig. 8.12
•Over 10 million ATPs are consumed and regenerated per second per cell.
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• A _________ changes the rate of a reaction without being ____________ by the reaction.
• An ____________ is a catalytic protein.
• Enzymes regulate the movement of molecules through ________________________.
6. Enzymes ___________ metabolic reactions by ___________ energy barriers
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• ______________________ is the amount of energy necessary to push the reactants over an energy barrier.
This difference is the G.
This is the the energy of activation (EA)
Fig. 8.14
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Enzymes _______ the EA.
Fig. 8.15
Enzymes do not ________ G.
•It hastens reactions that would occur eventually.
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• A ________ is a reactant which binds to an enzyme.
• Example: Sucrase - enzyme that binds to sucrose and breaks the disaccharide into fructose and glucose.
7. Enzymes are ___________ specific
Substrate Enzyme Products
The specificity of an enzyme is due to the fit between the ___________ and that of the substrate.
Fig. 8.16
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• What holds a substrate in the active site?
• Answer- _________ ______________ ______.
• What catalyzes the substrate to a product?
• Answer- __________ of a few amino acids on the _________
8. The active site is an enzyme’s ________ __________
Fig. 8.17
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• A single enzyme molecule can catalyze __________ of reactions a second.
• Enzymes are ____________ by the reaction and are reusable.
• Most metabolic enzymes can catalyze a reaction in both the __________ and __________ direction.
Some enzyme factoids-
What affects the rate of reaction?• • • • •
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1.___________ concentration.
• At low substrate concentrations:
• There is a limit to how fast a reaction can occur.
• At high substrate concentrations, the active sites on all enzymes are engaged, called __________________.
What affects the rate of reaction?
[S] = Rate
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2. Temperature (T).
• at some point heat ______________ protein
• Each enzyme has an _______________ temperature.
Fig. 8.18a
What affects the rate of reaction?
T = Rate
Rea
ctio
n r
ate
Temperature (oC)
Most enzymesThermophilic
enzyme
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3. pH
• influences _______ and therefore reaction rate
• each enzyme has an optimal pH.
• This falls between pH _____ for most enzymes.
• Exceptions include digestive enzymes in the stomach: these are most active at _____
Fig. 8.18b
What affects the rate of reaction?
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4. ____________
• Non-protein _________ for enzyme activity.
• Includes _________ molecules (e.g. zinc, iron, and copper) .
• Organic cofactors, ____________, include vitamins or molecules derived from vitamins.
5. ____________ • covalent interaction (often irreversible) or ionic
(reversible) with enzymes..
• If the inhibitor binds to the same site as the substrate, then it _______ substrate binding via _________________________.
• If the inhibitor binds somewhere other than the active site, it blocks substrate binding via _________________________
What affects the rate of reaction?
Fig. 8-19
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• Some molecules bind weakly to a ____________ site ( a specific receptor on the enzyme that is not the active site).
9. Metabolic control often depends on _________________ regulation
•Can inhibit or stimulate enzyme activity.
•Most allosterically regulated enzymes contain multiple polypeptide chains.
• Some allosteric regulators ___________; Other regulators _____________.
Fig. 8.20
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• __________________ - a metabolic pathway is turned off by its end product.
Fig. 8.21
•In enzymes with multiple _________________, binding by a substrate to one active site stabilizes favorable conformational changes at all other subunits, a process called ___________________.
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• A team of enzymes for several steps of a metabolic pathway may be assembled together as a ______________________________.
• The product from the first can then pass quickly to the next enzyme until the final _____________ is released.
10. The _________________ of enzymes within a cell helps order metabolism