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Med’11 Biochemistry Enzymes

What are enzymes? Biological catalysts They permit reactions to “go” at conditions that the body can tolerate and can process millions of molecules every second They are very specific – react with one or only a few types of molecules (substrates)
How do enzymes increase the reaction rates? By providing an alternate, easier pathway for a reaction and lowering activation energy barrier
What is the transition state? Unstable arrangement of atoms in which chemical bonds are in the process of being formed or broken
Define activation energy. The energy required to reach the transition state from the ground state of the reactants
Formation of ES (raises/lessens) energy of S by bringing reactants together? Raises
Enzymes _____ the transition state. Stabilize
What is a prosthetic group? Coenzyme or cofactor covalently linked or bound non-covalently very tightly to an enzyme
What is a substrate? The molecule acted upon by the enzyme to form product
What is the product? The substance that is produced by the action of the enzyme
What is an apoenzyme? The protein portion of the enzyme which is catalytically inactive
What is a coenzyme? An additional component to the enzyme to function properly . Organic or organo-metallic molecule that assists an enzyme
What is a cofactor? An additional component to the enzyme to function properly Usually a metal ion or small organic molecule that is needed to activate the apoenzyme
What is an active site? A particular arrangement of amino acids side-chain in the polypeptide, specific to bind a specific substrate, also contains the machinery involved in catalyzing the reaction
True or False: Enzymes are huge proteins, and all of the enzyme is used in the reaction. False - Only a small part is involved in the reaction
What are the 2 components of the active site? Binding Site Catalytic Site
Enzymes are biological catalysts. They increase the rate of chemical reactions by: A. Raising the activation energy B. Temporarily increasing the temperature C. Covalently binding the substrate D. Lowering the activation energy D Lowering the activation energy
What is a holoenzyme? Holoenzyme: The apoenzyme + cofactor or prosthetic group
What is a proenzyme (zymogen)? inactive precursor form of some enzymes (e.g. many digestive enzymes) that will be activated by cleavage of a specific peptide in its structure
What is an allosteric site? A region of enzyme molecules (not at the active site) where small molecules bind & effect a change in the activity of the active site by change in the conformation of the enzyme.
Compare between enzymes and inorganic catalysts their natures. Enzymes: Proteins Inorganic Catalysts: Usually metals
Compare between enzymes and inorganic catalysts their effects of heat. Enzymes: Heat labile Inorganic Catalysts: Heat stable
Compare between enzymes and inorganic catalysts their molecular weights. Enzymes: High Inorganic Catalysts: Low
Compare between enzymes and inorganic catalysts their dialysis. Enzymes: Non-dialysable Inorganic Catalysts: Dialyasble
Compare between enzymes and inorganic catalysts their reversibility. Enzymes: Most reactions are reversible Inorganic Catalysts: Irreversible
Compare between enzymes and inorganic catalysts their specificity. Enzymes: All highly specific Inorganic Catalysts: Non-specific
What is the nomenclature of enzymes based on? How it reacts Add –ase ending
What is the basis of enzyme classification? Based on type of reaction
What are the different classifications of enzymes? Lyases break C-O, C-C or C-N bonds Isomerases rearrange functional groups Ligases join two molecules
What are the types of enzyme specificity? Absolute -Reacts with a single substrate Relative (linkage) specificity-Catalyze a specific combination of bonds Group specificity-Work with similar molecules with the same functional grp Stereochemical specificity-Work with the proper D- or L
What is a ribozyme? RNA enzyme
List the activities of ribozymes. Cleavage and rejoining of oligonucleotide substrate Cleavage of DNA phosphodiester bonds Cleavage of RNA at sequence-specific sites Hydrolysis of esters Formation of peptide bonds between amino acid
Created by: Salma O
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