Enzymes are biological catalysts Enzymes are proteins that: Increase the rate of reaction by lowering the energy of activation. Catalyze nearly all.
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Enzymes are biological catalysts Enzymes are proteins that: Increase the rate of reaction by lowering the energy of activation. Catalyze nearly all the chemical reactions taking place in the cells of the body. Have unique three-dimentional shapes that fit the shapes of reactants.
The name of an enzyme : Usually ends in –ase. Identify the reacting substance. Ex: sucrase catalyzes the reaction of sucrose. Describes the function of the enzyme. Ex: oxidases catalyze oxidation. Could be a common name, particularly for the digestion enzymes such as pepsin and trypsin.
Examples lactose To react with lactose. lactase carboxylpyruvate To remove carboxyl from pyruvate. pyruvate decarboxylase -ase ending whatwith what with orhow it reacts +
The active site: Is a region within an enzyme that fits the shape of molecules called substrates. Contains amino acid R groups that align and bind the substrate. Release products when the reaction is complete.
The proper fit of a substrate (S) in an active site forms an enzyme-substrate (ES) complex. E + S ES Within the (ES) complex, the reaction occurs to convert substrate to Product (P). ES E + P The products which are no longer attracted to the active site, are released. Overall substrate is converted to products. E + S ES E + P
Enzymes may recognize and catalyze: A single substrate. A group of similar substrates. A particular type of bond.
Classification of Enzymes Enzymes are classified by the reaction they catalyze. ClassType of Reactions catalyzed OxidoreductasesOxidation-reduction TransferasesTransfer groups of atoms Hydrolases Hydrolysis LyasesAdd atoms/remove atoms to or from a double bond IsomerasesRearrange atoms LigasesUse ATP to combine small molecules
Lock and key model In the lock and key model of enzyme action: The active site have a rigid shape. Only substrates with the matching shape can fit. The substrate is a key that fits the lock of the active site.
Induced fit model In the induced fit model: The active site is flexible, not rigid. The shape of the enzyme active site and substrate adjust to maximum the fit, which improve catalysis. There is a greater range of substrate specificity.
Classification of Enzymes Oxidoreductases catalyze redox reactions –Reductases –Oxidases Transferases transfer a group from one molecule to another –Transaminases catalyze transfer of an amino group –Kinases transfer a phosphate group
Classification of Enzymes Hydrolases cleave bonds by adding water –Phosphatases –Peptidases –Lipases Lyases catalyze removal of groups to form double bonds or the reverse break double bonds –Decarboxylases –Synthases
Classification of Enzymes Isomerases catalyze intramolecular rearrangements –Epimerases –Mutases Ligases catalyze a reaction in which a C-C, C-S, C-O, or C-N bond is made or broken