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ENERGY
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Energy capacity to perform work
done when objects are moved against opposing forces & things move in directions in which they would not have moved if left alone body needs energy cells are biggest users of energy in the body need energy to make complex molecules from monomer building blocks-anabolic reactions need energy to break down macromolecules- catabolic reactions to obtain energy to do all of the activities they need to do everyday
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First Law of Thermodynamics
energy cannot be destroyed nor created energy can be converted from one form to another plants convert energy in sunlight into chemical energy that life forms can use to perform activities of life
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Forms of Energy Kinetic energy energy of motion Potential energy
stored energy an object has as a result of its locomotion or structure
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Forms of Energy
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Energy Conversions energy can be converted from one type into another
cannot be created or destroyed can’t use energy over & over because each time there is energy transfer some energy becomes unusable
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Second Law of Thermodynamics
energy conversions generate heat kinetic energy from random movement of atoms & molecules difficult to reuse to perform work lost to surroundings energy of aimless molecular movement measure of disorder or randomness amount of disorder in a system is entropy Second Law of Thermodynamics energy conversions increase entropy in a system & reduce order
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Energy Flow energy flows into our ecosystem as sunlight
kinetic energy (from sun) is transformed into chemical energy-potential energy of food & fuels by photosynthesis
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Energy Flow animals consume food products to provide ATP or energy for cells to perform work
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Endergonic Reactions yield potential energy require input of energy
products acquire more energy than reactants energy is stored in covalent bonds of products photosynthesis is an endergonic reaction
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Exergonic Reactions release energy
reactions begin with reactants whose covalent bonds contain more energy than those in products & release energy to the environment occur in cells of body cellular respiration oxygen is used to convert chemical energy stored in fuel molecules (glucose) to chemical energy (ATP) cell uses to carry on its processes Glucose + O2 CO2 + H2O
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ATP-Adenosine Triphosphate
provides energy for cellular work consists of adenine nitrogenous base ribose five carbon sugar called adenosine 3 PO4 groups attached-triphosphate part phosphate bonds are unstable can be easily broken by hydrolysis in exergonic reactions each PO4 group released from ATP yields 7Kcal of energy one phosphate group removed ATPADP + pi + 7Kcal of energy adenosine diphosphate + inorganic phosphate + energy another phosphate removed AMP + pi + 7Kcal of energy adenosine monophosphate
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Cellular Metabolism every working cell in body performs exergonic & endergonic reactions sum-cellular metabolism energy released from exergonic reactions is used to drive endergonic reactions energy coupling ATP functions in energy coupling
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Energy Coupling
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Factors in Chemical Reactions
many molecules in body store tremendous amount of potential energy do not spontaneously break down into smaller components to initiate reactions reactants need to overcome an energy barrier amount of energy that a compound must absorb before a chemical reaction can begin-activation energy requires a catalyst something to speed rate of a reaction
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Enzymes speed rate of reactions lower activation energy
globular proteins names typically end in –ase each has a unique 3-D shape shape determines which reactions enzyme can catalyze
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Enzymes specific reactant for specific enzyme-substrate
fits into specific area-active site once product forms enzyme detaches from active site free to start another reaction
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Enzyme Action
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Saturation Limit reaction rate is proportional to concentration of substrate & concentration of enzyme enzyme must meet with specific amount of substrate before catalysis can begin higher substrate concentrations more frequently encountered by enzyme when substrate concentrations are high enough so every enzyme molecule is cycling through its reaction sequence at top speed further increase in substrate concentration will not effect rate of reaction unless more enzyme is added substrate concentration at which rate of a reaction is maximum is saturation limit
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Regulation of Enzymatic Reactions
many variables turn enzymes on & off to control reaction rates enzymes are proteins protein shapes can be changed by the environment Temperature Salt concentration pH
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Regulators of Enzymatic Activity
Cofactors important in enzyme function ions or molecules that bind to an enzyme before substrate can bind allows enzymes to be active sometimes & inactive at other times several important inorganic cofactors-zinc, iron & copper organic cofactors are coenzymes most made from vitamins or are vitamins
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Inhibition of Enzymatic Activity
chemicals that interfere with enzyme function are inhibitors competitive inhibitors fit into active sites so real substrate cannot noncompetitive inhibitors bind at sites other than active site changes enzyme’s shape causes active site to no longer recognize substrate
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Inhibition Reversible inhibitors Irreversible inhibitors
can serve a regulatory function turn enzyme on when needed turn it off when not Irreversible inhibitors kill enzyme function poisons block metabolic processes that are essential to survival
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Irreversible Inhibition
Penicillin inhibits enzymes in bacteria needed to make cells walls since humans do not have this enzyme penicillin can be used to kill the bug without effecting human cells
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