Metabolic Pathways
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Linked reactions, one reaction leads to
-E another
Enzyme – organic catalyst (speeds chemical
reaction)
Ribozymes – made of RNA, not proteins,
biological catalyst (RNA/protein synthesis)
Substrates – reactants in reaction, act on
enzymes
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Activation energy – energy needed to start a
reaction
Enzymes lower the amount of activation
needed in a reaction
Active site – area on enzyme that the
substrate binds to.
Induced fit model- enzyme complex
undergoes a slight change in shape
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Degradative reactions – substrate broken down
Synthesis reaction – substrates combine, larger
product
Enzymes are not used up in the reaction, available to
bind to another substrate.
Reactions require specific enzymes
Enzymes are sometimes named for their substrates,
usually end in -ase
Factors that affect speed of enzyme
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Substrate concentration
Temperature and pH – leads to denaturing
Enzyme concentration
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Cofactors – inorganic ion (copper,zinc or iron)
Coenzymes - nonprotein organic molecule
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Vitamins
Enzyme Inhibition
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Inhibitor binds to enzyme
Usually reversible
Feedback inhibition – final product of
pathway inhibits a reaction
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Competitive inhibition – substrate and
competitor bind, only substrate produces
Noncompetitive inhibition – inhibitor attaches
to allosteric site, enzymes changes shape
Redox reactions
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Permits flow of energy to all living things
Oxidation – loss of electrons
Reduction – gain of electrons
Photosynthesis – H+’s, transferred with e’s
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coenzyme NADP+ - NADPH
Cellular respiration –
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Coenzyme NAD+ - NADH (accepts 2e’s and
H+)
Cont’d redox reaction examples
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Electron Transport Chain
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Series of membrane-bound carriers, pass e’s from one
carrier to another.
Photosynthesis/thylakoid membrane
Cellular respiration/cristae – inner membrane of mito.
ATP Production
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ATP synthase complexes – carrier proteins and enzymes
Chemiosmosis – production of ATP due to H+ gradient
across a membrane