Chemical Reactions in Cells Energetics, Enzymes and Metabolic Reactions.
Energy, Chemical Reactions, and Enzymes
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Transcript of Energy, Chemical Reactions, and Enzymes
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Energy,
Chemical Reactions,
and
Enzymes
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Energy• the ability to move or change matter
– found in many forms
– can be converted from one form into another
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Chemical Reactions• process that changes one set of
chemicals into another
• always involves changes in the chemical bonds that join the atoms in the compounds
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Chemical Reactions• reactants
– substances that enter into a chemical reaction
– found on the left side of the arrow• products
– substances produced by the chemical reaction
– found on the right side of the arrow
H2CO3H2OCO2+
carbon dioxide plus water forms carbonic acid
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Energy in Reactions• some chemical reactions release
energy and others absorb energy
• energy changes are an important factor in determining whether a reaction will occur
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Exothermic• chemical reaction that releases energy
– C → A + B + Energy
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Endothermic• chemical reaction that needs to absorb
energy to begin– A + B + Energy → C
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Energy in Reactions• Label each of the following
reactions as either:
– Energy-Releasing Reaction
or
– Energy-Absorbing Reaction
(from Holt Biology, pg. 39)
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Use the location of the REACTANTS and PRODUCTS to help.
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Energy in Reactions
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Energy in Reactions
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Activation Energy• energy needed to start a chemical
reaction– ex: spark plug in an engine
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Enzymes• enzymes are biological catalysts
– catalyst• substances that reduce the activation energy of
a chemical reaction• reducing activation energy allows the reaction
to occur more frequently and faster
Hydrolysis of Sucrose by SucraseMcGraw - Hill
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Enzymes & Activation Energy
Reaction pathwaywithout enzyme
Activation energywithout enzyme
Activationenergywith enzymeReaction pathway
with enzyme
Reactants
Products
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What type of macromolecule are most enzymes?
• enzymes are proteins• these proteins enzymes increase the
speed of chemical reactions– some enzymes break molecules apart
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What type of macromolecule are most enzymes?
• enzymes are proteins• these proteins enzymes increase the
speed of chemical reactions– some enzymes break molecules apart– other enzymes put molecules together
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What type of macromoleculeare enzymes?
• enzymes are proteins• these proteins enzymes increase the
speed of chemical reactions– some enzymes break molecules apart– other enzymes put molecules together– do not get used up in a chemical reaction
• help maintain homeostasis
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Substrate
• substance on which an enzyme acts during a chemical reaction
• substrate = reactants
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Active Site• the location on an enzyme that attaches to a
substrate
How Enzymes WorkMcGraw - Hill
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Enzyme Specificity• enzymes are specific because only its substrate
fits into its active site– enzymes are similar to a lock and key
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Enzyme Efficiency• work well only within a certain set of conditions
– changes in conditions like pH and temperature can change the shape of the protein
– when the substrate no longer fits the active site, the enzyme will not work• the “lock and key” no longer fit in one another
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Example• lactase is an enzyme that breaks down milk
sugar (lactose) lactase
lactose glucose + galactose
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Why is lactase written above the arrow and not included in the chemical equation?
• because enzymes (like lactase) are not used up in chemical reactions– they can be re-used over and over again for the same type
of reaction
lactaselactose glucose + galactose