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MCAT Bio. Chem Ch. 2

Enzymes Biological catalysts that are unchanged by the reactions they catalyze and are reusable.
Note About Enzymes And Their Reactions Each enzyme catalyzes a single reaction or type of reaction with high specificity.
Oxidoreductases Catalyze oxidations-reduction reactions that involve the transfer of electrons.
Transferases Move a functional group from one molecule to another molecule.
Hydrolases Catalyze cleavage with the addition of water.
Lyases Catalyze cleavage without the addition of water and without the transfer of electrons. The reverse reaction (synthesis) is more important biologically.
Isomerases Catalyze the interconversion of isomers, which include constitutional isomers and stereoisomers.
Ligases Join two large biomolecules, often of the same type.
Exergonic Reactions Release energy, Delta G is negative
What Enzymes Do In Biological Reactions They lower the activation energy required for the reactions
Note About Enzymes and Delta G and Delta H They do not alter free energy (Delta G) or enthalpy (Delta H), they change the rate at which equilibrium is reached (kinetics).
How Enzymes Act They stabilize the transition state to provide a favorable micro environment or bond with substrate molecules.
Active Site Site of catalysis.
Lock And Key Theory / Induced Fit Model Hypothesizes that the enzyme and substrate are exactly complementary.
Induced Fit Model Hypothesizes that the enzyme and substrate undergo conformational changes to interact fully.
Cofactors Metal cations that are required by some enzymes
Coenzymes Small organic molecules that are required by some enzymes.
Saturation Kinetics As substrate conc. increases, the reaction rate does as well until a max. value is reached
Michaelis-Menten Plot Represents saturation kinetics as a hyperbola
Lineweaver-Burk Represents saturation kinetics as a line
Note On How Enzymes Can Be Compared by their Km and vmax values
Km Michaelis-Menten Constant, which is the substrate conc. at which the enzyme is functioning at half of its max. velocity.
Cooperative Enzymes Display a sigmoidal curve because of the change in activity with substrate binding.
Temp and pH Effects On Enzyme Activity Changes in temp and pH result in denaturing an enzyme and loss of activity due to loss of secondary, tertiary, or quaternary structure
Note About Salinity's Impact On Enzymes Salinity can impact the action of enzymes.
Feedback Inhibition Regulatory mechanism in which the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway.
Reversible Inhibition The ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment
Competitive Inhibition Results when the inhibitor is similar to substrate and binds at the active site. This can be overcome by adding substrate. vmax is unchanged, Km increases.
Noncompetitive Inhibition Results when the inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex. vmax is decreased, Km is unchanged.
Mixed Inhibition Results when the inhibitor binds with unequal affinity to the enzyme and the enzyme-substrate complex. vmax is decreased, Km is increased or decreased depending on if the inhibitor has higher affinity for the enzyme or enzyme-substrate complex.
Uncompetitive Inhibition Results when the inhibitor binds only with the enzyme-substrate complex. Km and vmax both decrease.
Irreversible Inhibition Alters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently. New enzyme molecules must be synthesized for the reaction to occur again.
Allosteric Sites Sites of an enzyme that can be occupied by activators which increase either affinity or enzymatic turnover.
Phosphorylation Covalent modification with phosphate that can alter the activity or selectivity of enzymes.
Glycosylation Covalent modification with carbohydrate that can alter the activity or selectivity of enzymes.
Zymogens Secreted in an inactive form and are activated by cleavage.
Created by: SamB91
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