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23 Cards in this Set
- Front
- Back
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Two important points about how enzymes support life.
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(1)they efficiently accelerate chemical reactions
(2) with a high degree of specificity |
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Define cofactor.
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inorganic ions (trace nutrients, vitamins, metals) that are required by some enzymes for their catalytic activity.
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Define coenzyme.
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complex organic or metallo-organic molecules that are required by some enzymes for their catalytic activity
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Define prosthetic group.
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A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein
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Define holoenzyme.
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the complete, catalytically active enzyme complex together with its bound coenzyme and/or metal ions.
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Define apoenzyme/apoprotein.
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the protein part of the enzyme without cofactors or prosthetic groups. It is catalytically inactive.
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define active site.
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area on an enzyme containing the amino acid side chains that are involved in catalyzing the reaction.
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Define substrate.
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The molecule that is bound in the active site and is acted on by the enzyme to form the product.
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What do the oxidoreductases do?
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Transfer electrons (hydride ions or H atoms)
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What do transferases do?
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They group transfer reactions.
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What do hydrolases do?
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They hydrolyze reactions (transfer functional groups to water)
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What do lyases do?
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The add groups to double bonds or form double bonds by removal of groups
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What do isomerases do?
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They transfer groups within molecules to yield isomeric forms.
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What do ligases do?
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They form C-C, C-S, C-O, and C-N bonds by condensation reactions coupled to ATP cleavage.
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Bottom line with enzymes (three big points).
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(1) high degree of specificity
(2) enzymes are proteins (with few exceptions) (3) enzymes are classified according to the type of reaction that they catalyze |
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Name two distinguishing features of an enzyme-catalyzed reaction.
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(1) the reaction only takes place within the confines of a pocket called the ACTIVE SITE.
(2) The molecule bound selectively to the active site and acted upon by the enzyme is called a SUBSTRATE. |
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T/F: enzymes affect the position and direction of equilibrium.
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false.
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What controls the speed of reaction?
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The reaction energy path controls the reaction speed.
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Name two ways rate of reactions can be increased.
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(1) raising the temperature, thereby increasing the number of molecules with sufficient energy to overcome the energy barrier
(2) lowering the activation energy: adding an enzyme. |
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What is the 'rate-limiting step'?
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When several steps occur in a reaction, the overall rate is determined by the step with the highest activation energy. This step is the rate-limiting step. It limits the throughput of the reaction.
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What are enzyme inhibitors?
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Molecular agents that interfere with catalysts, slowing or halting enzymatic reactions.
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what is the relationship between the activation energy and the rate of reaction?
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a higher activation energy corresponds to a slower reaction
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how do enzymes decrease activation energy?
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Enzymes decrease the activation energy by forming enzyme-substrate (ES) complexes and enzyme-product (EP) complexes). It accelerates the interconversion of S and P; this is a bidirectional catalyzing reaction. The reaction reaches the equilibrium point must faster, but the final equilibrium point is unaffected.
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